Feeding rumen-protected methionine during the peripartum period improved milk fat content and reduced the culling rate of Holstein cows in a commercial herd

Researchers have reported the benefits of feeding rumen-protected methionine (RPM) during the peripartum on the health parameters of dairy cows. Rumen-protected Met has reportedly improved milk yield, milk components, and liver health, but the literature is scarce on its effects in commercial herds. Therefore, we aimed to determine the effects of feeding RPM (Smartamine M, Adisseo Inc., Antony, France) prepartum (8 g/cow per day) and postpartum (15 g/cow per day) on performance, metabolic profile, and culling rate of Holstein cows in a commercial herd. One hundred sixty-six (n = 166) Holstein cows, 58 nulliparous and 108 parous, were randomly assigned to 1 of 2 dietary treatments, consisting of TMR top-dressed with RPM (RPMet; 2.35% and 2.24% Met of MP for close-up and fresh cows, respectively) or without (control [CON] 2.03% and 1.89% Met of MP for close-up and fresh cows, respectively), fed from 21 ± 6 d prepartum until 16 ± 5 d postpartum. From 17 DIM until dry-off, all cows received RPMet. Daily milk yield was recorded, and milk samples were collected in the first and second weeks after calving to determine their composition. Blood samples were collected before the morning feeding on -14, -7, +1, +7, and +14 d relative to calving. Mortality and morbidity were recorded during the first 60 DIM. Cows supplemented with RPMet had greater milk yield during the first 16 DIM (31.76 vs. 30.37 kg/d; SEM = 1.04, respectively), and had greater milk fat content (4.45 vs. 4.10%; SEM = 0.11, respectively), but not milk total protein (3.47 vs. 3.39%; SEM = 0.04, respectively) and casein contents (2.74 vs. 2.66%; SEM = 0.04, respectively) than CON cows. Cows in RPMet had increased plasma Met concentrations than cows in CON (24.9 vs. 21.0 µmol/L; SEM = 1.2, respectively). Although morbidity was similar between treatments, the culling rate from calving until 60 DIM was lower for RPMet cows than for CON cows (2.4% vs. 12.1%; SEM = 0.02). In conclusion, cows receiving RPMet have greater milk yield, improved milk fat content, and a lower culling rate at 60 DIM than CON cows.

Systematic review and meta-analysis of dairy cow responses to rumen-protected methionine supplementation before and after calving

Balancing dairy cow diets for AA is an effective strategy to reduce dietary CP concentration, maintain levels of productivity, and increase nitrogen use efficiency. Most studies evaluating supplemental rumen-protected Met (sRPMet) focus on cows in established lactation; however, there is an increasing body of evidence suggesting that initiating sRPMet feeding to transition dairy cows is beneficial to production, reproduction, and health. Therefore, the objective of this study was to evaluate the effects of feeding sRPMet before and after calving through meta-analysis on pre- and postpartum performance and selected metabolic parameter responses. A literature search was conducted for published papers reporting on the effects of feeding sRPMet starting before parturition and continuing through early lactation, resulting in 21 publications with 40 treatment comparisons. Studies provided sRPMet both before (average of 8.20 [±2.94 SD] g of metabolizable sRPMet/d, which began at 19.3 [±4.23 SD] d before calving) and after calving (10.53 [±3.30 SD] g of metabolizable sRPMet/d for an average of 85.9 [±38.36 SD] DIM). Prepartum DMI and pre- and postpartum BW and BCS were unaffected by sRPMet. In contrast, postpartum DMI, milk yield, milk fat and true protein yield, and milk fat and true protein concentration were increased by sRPMet. Most production responses to sRPMet declined as lactation progressed where the predicted response in milk fat and true protein yield was 118 and 92 g/d at 21 DIM, respectively. Postpartum circulating metabolites were unaffected by sRPMet; however, the sample sizes for these analyses were much lower than for production responses. This meta-analysis indicates that feeding sRPMet before and after calving results in increased productivity beyond that which would be expected by providing sRPMet in established lactation alone.

Reducing dietary protein and supplementation with starch or rumen-protected methionine and its effect on performance and nitrogen efficiency in dairy cows fed a red clover and grass silage-based diet

The increasing cost of milk production, in association with tighter manure N application regulations and challenges associated with ammonia emissions in many countries, has increased interest in feeding lower crude protein (CP) diets based on legume silages. Most studies have focused on alfalfa silage, and little information is available on low-CP diets based on red clover silage. Our objectives were to examine the effects of dietary CP content and supplementing a low-CP diet with dietary starch or rumen-protected Met (RPMet) on the performance, metabolism, and nitrogen use efficiency (NUE; milk N output/N intake) in dairy cows fed a red clover and grass silage-based diet. A total of 56 Holstein-Friesian dairy cows were blocked and randomly allocated to 1 of 4 diets over a 14-wk feeding period. Diets were based on red clover and grass silages at a ratio of 50:50 on a dry matter (DM) basis and were fed as a total mixed ration, with a 53:47 ratio of forage to concentrate (DM basis). The diets were formulated to supply a similar metabolizable protein (MP) content, and had a CP concentration of either 175 g/kg DM (control [CON]) or 150 g/kg DM (low-protein [LP]), or LP supplemented with either additional barley as a source of starch (LPSt; +64 g/kg DM) or RPMet (LPM; +0.3 g/100 g MP). At the end of the 14-wk feeding period, 20 cows (5 per treatment) continued to be fed the same diets for a further 6 d, and total urine output and fecal samples were collected. We observed that dietary treatment did not affect DM intake, with a mean of 21.5 kg/d; however, we also observed an interaction between diet and week with intake being highest in cows fed LPSt in wk 4 and CON in wk 9 and 14. Mean milk yield, 4% fat-corrected milk, and energy-corrected milk were not altered by treatment. Similarly, we found no effect of dietary treatment on milk fat, protein, or lactose content. In contrast, milk and plasma urea concentrations were highest in cows fed CON. The concentration of blood plasma β-hydroxybutyrate was highest in cows receiving LPM and lowest in LPSt. Apparent NUE was 28.6% in cows fed CON and was higher in cows fed any of the low-protein diets (LP, LPSt, or LPM), with a mean value of 34.2%. The sum of milk fatty acids with a chain length below C16:0 was also highest in cows fed CON. We observed that dietary treatment did not affect the apparent whole-tract nutrient digestibility of organic matter, N, neutral detergent fiber, and acid detergent fiber, with mean values of 0.785, 0.659, 0.660, and 0.651 kg/kg respectively, but urinary N excretion was approximately 60 g/d lower in cows fed the low-CP diets compared with CON. We conclude that reducing the CP content of red clover and grass silage-based diets from 175 to 150 g/kg DM while maintaining MP supply did not affect performance, but reduced the urinary N excretion and improved NUE, and that supplementing additional starch or RPMet had little further effect.

Effects of rumen-encapsulated methionine and lysine supplementation and low dietary protein on nitrogen efficiency and lactation performance of dairy cows

Low crude protein (CP) diets might be fed to dairy cows without affecting productivity if the balance of absorbed AA were improved, which would decrease the environmental effect of dairy farms. The aim of this study was to investigate the effects of supplementing ruminally protected Lys (RPL) and Met (RPM) at 2 levels of dietary CP on nutrient intake, milk production, milk composition, milk N efficiency (MNE), and plasma concentrations of AA in lactating Holstein cows and to evaluate these effects against the predictions of the new NASEM (2021) model. Fifteen multiparous cows were used in a replicated 3 × 3 Latin square design with 21-d periods. The 3 treatments were (1) a high-protein (HP) basal diet containing 16.4% CP (metabolizable protein [MP] balance of -130 g/d; 95% of target values), (2) a medium-protein diet containing 15% CP plus RPL (60 g/cow per day) and RPM (25 g/cow per day; MPLM; MP balance of -314 g/d; 87% of target values), and (3) a low-protein diet containing 13.6% CP plus RPL (60 g/cow per day) and RPM (25 g/cow per day; LPLM; MP balance of -479 g/d; 80% of target values). Dry matter intake was less for cows fed MPLM and LPLM diets compared with those fed the HP diet. Compared with the HP diet, the intake of CP, neutral detergent fiber, acid detergent fiber, and organic matter, but not starch, was lower for cows fed MPLM and LPLM diets. Milk production and composition were not affected by MPLM or LPLM diets relative to the HP diet. Milk urea N concentrations were reduced for the MPLM and LPLM diets compared with the HP diet, indicating that providing a low-protein diet supplemented with rumen-protected AA led to greater N efficiency. There was no significant effect of treatment on plasma AA concentrations except for proline, which significantly increased for the MPLM treatment compared with the other 2 treatments. Overall, the results supported the concept that milk performance might be maintained when feeding lactating dairy cows with low CP diets if the absorbed AA balance is maintained through RPL and RPM feeding. Further investigations are needed to evaluate responses over a longer time period with consideration of all AA rather than on the more aggregated MP and the ratio between Lys and Met.

Valine and nonessential amino acids affect bidirectional transport rates of leucine and isoleucine in bovine mammary epithelial cells

A more complete understanding of the mechanisms controlling AA transport in mammary glands of dairy cattle will help identify solutions to increase nitrogen feeding efficiency on farms. It was hypothesized that Ala, Gln, and Gly (NEAAG), which are actively transported into cells and exchanged for all branched-chain AA (BCAA), may stimulate transport of BCAA, and that Val may antagonize transport of the other BCAA due to transporter competition. Thus, we evaluated the effects of varying concentrations of NEAAG and Val on transport and metabolism of the BCAA Ala, Met, Phe, and Thr by bovine mammary epithelial cells. Primary cultures of bovine mammary epithelial cells were assigned to treatments of low (70% of mean in vivo plasma concentrations of lactating dairy cows) and high (200%) concentrations of Val and NEAAG (LVal and LNEAAG, HVal and HNEAAG, respectively) in a 2 × 2 factorial design. Cells were preloaded with treatment media containing [15N]-labeled AA for 24 h. The [15N]-labeled media were replaced with treatment media containing [13C]-labeled AA. Media and cells were harvested from plates at 0, 0.5, 1, 5, 15, 30, 60, and 240 min after application of the [13C]-labeled AA and assessed for [15N]- and [13C]-AA label concentrations. The data were used to derive transport, transamination, irreversible loss, and protein-synthesis fluxes. All Val fluxes, except synthesis of rapidly exchanging tissue protein, increased with the HVal treatment. Interestingly, the rapidly exchanging tissue protein, transamination, and irreversible-loss rate constants decreased with HVal, indicating that the significant flux increases were primarily driven by mass action with the cells resisting the flux increases by downregulating activity. However, the decreases could also reflect saturation of processes that would drive down the mass-action rate constants. This is supported by decreases in the same rate constants for Ile and Leu with HVal. This could be due to either competition for shared transamination and oxidation reactions or a reduction in enzymatic activity. Also, NEAAG did not affect Val fluxes, but influx and efflux rate constants increased for both Val and Leu with HNEAAG, indicating an activating substrate effect. Overall, AA transport rates generally responded concordantly with extracellular concentrations, indicating the transporters are not substrate-saturated within the in vivo range. However, BCAA transamination and oxidation enzymes may be approaching saturation within in vivo ranges. In addition, System L transport activity appeared to be stimulated by as much as 75% with high intracellular concentrations of Ala, Gln, and Gly. High concentrations of Val antagonized transport activity of Ile and Leu by 68% and 15%, respectively, indicating competitive inhibition, but this was only observable at HNEAAG concentrations. The exchange transporters of System L transport 8 of the essential AA that make up approximately 40% of milk protein, so better understanding this transporter is an important step for increased efficiency.

Methionine Supplementation Alleviates the Germ Cell Apoptosis Increased by Maternal Caffeine Intake in a C. elegans Model

Caffeine (1,3,7-trimethylxanthine) is a widely consumed bioactive substance worldwide. Our recent study showed that a reduction in both reproduction and yolk protein production (vitellogenesis) caused by caffeine intake were improved by vitamin B12 supplementation, which is an essential co-factor in methionine metabolism. In the current study, we investigated the role of methionine in the reproduction of caffeine-ingested animals (CIAs). We assessed the effect of methionine metabolism on CIAs and found that caffeine intake decreased both methionine levels and essential enzymes related to the methionine cycle. Furthermore, we found that the caffeine-induced impairment of methionine metabolism decreased vitellogenesis and increased germ cell apoptosis in an LIN-35/RB-dependent manner. Interestingly, the increased germ cell apoptosis was restored to normal levels by methionine supplementation in CIAs. These results indicate that methionine supplementation plays a beneficial role in germ cell health and offspring development by regulating vitellogenesis.

Vitamin B12 Supplementation Improves Oocyte Development by Modulating Mitochondria and Yolk Protein in a Caffeine-Ingested Caenorhabditis elegans Model

Vitamin B12 is an essential cofactor involved in the function of two enzymes: cytosolic methionine synthase and mitochondrial methylmalonic-CoA mutase. In our previous studies, caffeine (1,3,7-trimethylxanthine), the most popular bioactivator, was shown to reduce yolk protein (vitellogenin) and fertility in a Caenorhabditis elegans model. Based on the previous finding that methionine supplementation increases vitellogenesis in C. elegans, we investigated the role of vitamin B12 in methionine-mediated vitellogenesis during oogenesis in caffeine-ingested animals (CIA). Vitamin B12 supplementation improved vitellogenesis and reduced oxidative stress by decreasing mitochondrial function in CIA. Furthermore, the decreased number of developing oocytes and high levels of reactive oxygen species in oocytes from CIA were recovered with vitamin B12 supplementation through a reduction in mitochondrial stress, which increased vitellogenesis. Taken together, vitamin B12 supplementation can reverse the negative effects of caffeine intake by enhancing methionine-mediated vitellogenesis and oocyte development by reducing mitochondrial stress.

Relationships between dietary rumen-protected lysine and methionine with the lactational performance of dairy cows - A meta-analysis

OBJECTIVE

Our objective was to examine the relationships of supplemental rumen-protected lysine (RPL) or lysine + methionine (RPLM) on lactational performance, plasma amino acids (AA) concentration, and nitrogen use efficiency of lactating dairy cows by using a meta-analysis approach.

METHODS

A total of 56 articles comprising 77 experiments with either RPL or RPLM supplementation were selected and analyzed using a mixed model methodology by considering the treatments and other potential covariates as fixed effects and different experiments as random effects.

RESULTS

In early lactating cows, milk yield was linearly increased by RPL (β1 = 0.013; p<0.001) and RPLM (β1 = 0.014; p<0.028) but 3.5% fat-corrected milk (FCM) and energy-corrected milk (ECM) (kg/d) was increased by only RPL. RPL and RPLM did not affect dry matter intake (DMI) but positively increased (p<0.05) dairy efficiency (Milk yield/DMI and ECM/DMI). As a percentage, milk fat, protein, and lactose were unchanged by RPL or RPLM but the yield of all components was increased (p<0.05) by feeding RPL while only milk protein was increased by feeding RPLM. Plasma Lys concentration was linearly increased (p<0.05) with increasing supplemental RPL while plasma Met increased (p<0.05) by RPLM supplementation. The increase in plasma Lys had a strong linear relationship (R2 = 0.693 in the RPL dataset and R2 = 0.769 in the RPLM dataset) on milk protein synthesis (g/d) during early lactation. Nitrogen metabolism parameters were not affected by feeding RPL or RPLM, either top-dress or when supplemented to deficient diets. Lactation performance did not differ between AA-deficient or AA-adequate diets in response to RPL or RPLM supplementation.

CONCLUSION

RPL or RPLM showed a positive linear relationship on the lactational performance of dairy cows whereas greater improvement effects were observed during early lactation. Supplementing RPL or RPLM is recommended on deficient-AA diet but not on adequate-AA diet.

Lactational performance effects of supplemental histidine in dairy cows: A meta-analysis

The objective of this meta-analysis was to examine the effects of supplemental His on lactational performance, plasma His concentration and efficiency of utilization of digestible His (EffHis) in dairy cows. The meta-analysis was performed on data from 17 studies published in peer-reviewed journals between 1999 and 2022. Five publications reported data from 2 separate experiments, which were included in the analyses as separate studies, therefore resulting in a total of 22 studies. In 10 studies, His was supplemented as rumen-protected (RP) His; in 1 study, 2 basal diets with different dHis levels were fed; and in the remaining experiments, free His was infused into the abomasum (4 studies), the jugular vein (3 studies) or deleted from a mixture of postruminally infused AA (4 studies). The main forages in the diets were corn silage in 14 and grass silage in 8 studies. If not reported in the publications, the supplies of dietary CP, metabolizable protein (MP), net energy of lactation, and digestible His (dHis) were estimated using NRC (2001). An initial meta-analysis was performed to test the standard mean difference (SMD; raw mean difference of treatment and control means divided by the pooled standard deviation of the means), that is, effect size, and the corresponding 95% confidence interval (CI) in production parameters between His-supplemented groups versus control. Further, regression analyses were also conducted to examine and compare the relationships between several response variables and dHis supply. Across studies, His supplementation increased plasma His concentration (SMD = 1.39; 95% CI: 1.17-1.61), as well as DMI (SMD = 0.240; 95% CI: 0.051-0.429) and milk yield (MY; SMD = 0.667; 95% CI: 0.468-0.866), respectively. Further, milk true protein concentration (MTP; SMD = 0.236; 95% CI: 0.046-0.425) and milk true protein yield (MTPY; SMD = 0.581; 95% CI: 0.387-0.776) were increased by His supplementation. Notably, the increase in MTP concentration and MTPY were 3.9 and 1.3 times greater for studies with MP-deficient (according to NRC 2001) diets compared with studies with MP-adequate diets. The regression analyses revealed that production parameters (DMI, MY, and MTPY) responded in a nonlinear manner to increasing His supply. Further, we detected a difference in the magnitude of change in MTPY and plasma His concentration with the level of His supply and between His supplementation methods, being greater for infused His compared with RPHis. Lastly, a linear and negative relationship between EffHis and the ratio of total digestible His to net energy for lactation supply was observed, indicating an important interaction between dHis and energy supply and EffHis (i.e., utilization of dHis to support protein export). Overall, these analyses confirm His as an important AA in dairy cattle nutrition.

Influence of Cobalt Source, Folic Acid, and Rumen-Protected Methionine on Performance, Metabolism, and Liver Tissue One-Carbon Metabolism Biomarkers in Peripartal Holstein Cows

Vitamin B₁₂ plays a role in the remethylation of homocysteine to Met, which then serves as a substrate for Met adenosyltransferase (MAT) to synthesize S-adenosylmethionine (SAM). We investigated effects of feeding two cobalt sources [Co-glucoheptonate (CoPro) or CoPectin, Zinpro Corp.], an experimental ruminally-available source of folic acid (FOA), and rumen-protected Met (RPM) on performance and hepatic one-carbon metabolism in peripartal Holstein cows. From -30 to 30 d around calving, 72 multiparous cows were randomly allocated to: CoPro, CoPro + FOA, CoPectin + FOA, or CoPectin + FOA + RPM. The Co treatments delivered 1 mg Co/kg of DM (CoPro or CoPectin), each FOA group received 50 mg/d FOA, and RPM was fed at 0.09% of DM intake (DMI). Milk yield and DMI were not affected. Compared with other groups, the percentage of milk protein was greater after the second week of lactation in CoPectin + FOA + RPM. Compared with CoPro or CoPro + FOA, feeding CoPectin + FOA or CoPectin + FOA + RPM led to a greater activity of MAT at 7 to 15 d postcalving. For betaine-homocysteine S-methyltransferase, CoPro together with CoPectin + FOA + RPM cows had greater activity at 7 and 15 d than CoPro + FOA. Overall, supplying FOA with CoPectin or CoPectin plus RPM may enhance S-adenosylmethionine synthesis via MAT in the liver after parturition. As such, these nutrients may impact methylation reactions and liver function.

Processed fava bean as a substitute for rapeseed meal with or without rumen-protected methionine supplement in grass silage-based dairy cow diets

Fava bean offers a sustainable home-grown protein source for dairy cows, but fava bean protein is extensively degraded in the rumen and has low Met concentration. We studied the effects of protein supplementation and source on milk production, rumen fermentation, N use, and mammary AA utilization. The treatments were unsupplemented control diet, and isonitrogenously given rapeseed meal (RSM), processed (dehulled, flaked, and heated) fava bean without (TFB) or with rumen-protected (RP) Met (TFB+). All diets consisted of 50% grass silage and 50% cereal-based concentrate including studied protein supplement. The control diet had 15% of crude protein and protein-supplemented diets 18%. Rumen-protected Met in TFB+ corresponded to 15 g/d of Met absorbed in the small intestine. Experimental design was a replicated 4 × 4 Latin square with 3-wk periods. The experiment was conducted using 12 multiparous mid-lactation Nordic Red cows, of which 4 were rumen cannulated. Protein supplementation increased dry matter intake (DMI), and milk (31.9 vs. 30.7 kg/d) and milk component yields. Substituting RSM with TFB or TFB+ decreased DMI and AA intake but increased starch intake. There were no differences in milk yield or composition between RSM diet and TFB diets. Rumen-protected Met did not affect DMI, or milk or milk component yields but increased milk protein concentration in comparison to TFB. There were no differences in rumen fermentation except for increased ammonium-N concentration with the protein-supplemented diets. Nitrogen-use efficiency for milk production was lower for the supplemented diets versus control diet but tended to be greater for TFB and TFB+ versus RSM. Protein supplementation increased plasma essential AA concentration but there were no differences between TFB diets and RSM. Rumen-protected Met clearly increased plasma Met concentration (30.8 vs. 18.2 µmol/L) but did not affect other AA. Absence of differences between RSM and TFB in milk production together with limited effects of RP Met suggest that TFB is a potential alternative protein source for dairy cattle.

Effects of Sodium Nitrate and Coated Methionine on Lactation Performance, Rumen Fermentation Characteristics, Amino Acid Metabolism, and Microbial Communities in Lactating Buffaloes

Sodium nitrate is used as a non-protein nitrogen supplement while methionine is considered as a common methionine additive for ruminants. This study investigated the effects of sodium nitrate and coated methionine supplementation on milk yield, milk composition, rumen fermentation parameters, amino acid composition, and rumen microbial communities in lactating buffaloes. Forty mid-lactation multiparous Murrah buffaloes within the initial days in milk (DIM) = 180.83 ± 56.78 d, milk yield = 7.63 ± 0.19 kg, body weight = 645 ± 25 kg were selected and randomly allocated into four groups (N = 10). All of animals received the same total mixed ratio (TMR) diet. Furthermore, the groups were divided into the control group (CON), 70 g/d sodium nitrate group (SN), 15 g/d palmitate coated L-methionine group (MET), and 70 g/d sodium nitrate +15 g/d palmitate coated L-methionine group (SN+MET). The experiment lasted for six weeks, including two weeks of adaption. The results showed that most rumen-free amino acids, total essential amino acids, and total amino acids in Group SN increased (p < 0.05), while the dry matter intake (DMI) and rumen acetate, propionate, valerate, and total volatile fatty acids (TVFA) in Group MET decreased (p < 0.05). However, there was no significant difference in milk yield, milk protein, milk fat, lactose, total solid content, and sodium nitrate residue in milk among groups (p > 0.05). Group SN+MET had a decreased rumen propionate and valerate (p < 0.05), while increasing the Ace, Chao, and Simpson indices of alpha diversity of rumen bacteria. Proteobacteria and Actinobacteriota were significantly increased (p < 0.05) in Group SN+MET, but Bacteroidota, and Spirochaetota were decreased (p < 0.05). In addition, Group SN+MET also increased the relative abundance of Acinetobacter, Lactococcus, Microbacterium, Chryseobacterium, and Klebsiella, which were positively correlated with cysteine and negatively correlated with rumen acetate, propionate, valerate, and TVFA. Rikenellaceae_RC9_gut_group was identified as a biomarker in Group SN. Norank_f__UCG-011 was identified as a biomarker in Group MET. Acinetobacter, Kurthia, Bacillus, and Corynebacterium were identified as biomarkers in Group SN+MET. In conclusion, sodium nitrate increased rumen free amino acids, while methionine decreased dry matter intake (DMI) and rumen volatile fatty acids. The combined use of sodium nitrate and methionine enriched the species abundance of microorganisms in the rumen and affected the composition of microorganisms in the rumen. However, sodium nitrate, methionine, and their combination had no significant effect on the milk yield and milk composition. It was suggested that the combined use of sodium nitrate and methionine in buffalo production was more beneficial.

Implications of supplementing mid-lactation multiparous Holstein cows fed high by-product low-forage diets with rumen-protected methionine and lysine in a commercial dairy

Supplementation of rumen-protected amino acids may improve dairy cow performance but few studies have evaluated the implications of supplementing low-forage diets. Our objective was to evaluate the effects of supplementing rumen-protected methionine (Met) and lysine (Lys) on milk production and composition as well as on mammary gland health of mid-lactating Holstein cows from a commercial dairy farm feeding a high by-product low-forage diet. A total of 314 multiparous cows were randomly assigned to control (CON; 107 g of dry distillers' grains) or rumen-protected Met and Lys (RPML; 107 g dry distillers' grains + 107 g of RPML). All study cows were grouped in a single dry-lot pen and fed the same total mixed ration diet twice a day for a total of 7 weeks. Treatments were top-dressed on the total mix ration immediately after morning delivery with 107 g of dry distillers' grains for 1 week (adaptation period) and then with CON and RPML treatments for 6 weeks. Blood samples were taken from a subset of 22 cows per treatment to determine plasma AA (d 0 and 14) and plasma urea nitrogen and minerals (d 0, 14, and 42). Milk yield and clinical mastitis cases were recorded daily, and milk components were determined bi-weekly. Body condition score change was evaluated from d 0 to 42 of the study. Milk yield and components were analyzed by multiple linear regression. Treatment effects were evaluated at the cow level considering parity and milk yield and composition taken at baseline as a covariate in the models. Clinical mastitis risk was assessed by Poisson regression. Plasma Met increased (26.9 vs 36.0 µmol/L), Lys tended to increase (102.5 vs 121.1 µmol/L), and Ca increased (2.39 vs 2.46 mmol/L) with RPML supplementation. Cows supplemented with RPML had higher milk yield (45.4 vs 46.0 kg/d) and a lower risk of clinical mastitis (risk ratio = 0.39; 95% CI = 0.17-0.90) compared to CON cows. Milk components yield and concentrations, somatic cell count, body condition score change, plasma urea nitrogen, and plasma minerals other than Ca were not affected by RPML supplementation. Results suggest that RPML supplementation increases milk yield and decreases the risk of clinical mastitis in mid-lactation cows fed a high by-product low-forage diet. Further studies are needed to clarify the biological mechanisms for mammary gland responses to RPML supplementation.

Effects of rumen-protected methionine supplementation on production performance, apparent digestibility, blood parameters, and ruminal fermentation of lactating Holstein dairy cows

This study aimed to evaluate the effects of reducing dietary CP and supplementing rumen protected-methionine (RPM) on production performance, blood parameters, digestibility of nutrients or ruminal fermentation in lactating Holstein dairy cows. A total of 96 lactating cows were randomly assigned to 1 of 2 treatments: a diet containing 17.3% CP without RPM (control group; CON; n = 49) or a diet containing 16.4% CP and supplemented with 15.0 g/d of RPM (treatment group; RPM; n = 47). No effect was observed in the RPM group on milk yield, milk composition and digestibility of nutrients. The results of blood parameters showed that cows in the RPM group exhibited lower blood urea nitrogen concentration than in CON group. Rumen microbial crude protein (MCP) was higher in the RPM group compared to the CON group. Ruminal volatile fatty acid (VFA) concentrations were not different between treatments except for butyrate and isovalerate, which were higher in the RPM group than the CON group 2 h after feeding. In conclusion, reducing dietary CP with RPM supplementation did not limit milk yield, milk composition or digestibility of nutrients, but could improve nitrogen utilization, synthesis of MCP and partially increase VFA production 2 h after feeding cows.

Rumen-protected zinc–methionine dietary inclusion alters dairy cow performances, and oxidative and inflammatory status under long-term environmental heat stress

Dairy cows are susceptible to heat stress due to the levels of milk production and feed intake. Dietary supplemental amino acids, particularly rate-limiting amino acids, for example, methionine (Met), may alleviate the potential negative consequences. Zinc (Zn) is beneficial to the immune system and mammary gland development during heat stress. We investigated the impact of a source of a rumen-protected Zn-Met complex (Loprotin, Kaesler Nutrition GmbH, Cuxhaven, Germany) in high-producing Holstein cows during a long-term environmental heat stress period. A total of 62 multiparous lactating Holstein cows were allocated in a completely randomized design to two dietary treatments, namely, basal diet without (control) and basal diet with the supplemental Zn-Met complex (RPZM) at 0.131% of diet DM. Cows in the RPZM group had higher energy-corrected milk (46.71 vs. 52.85 ± 1.72 kg/d for control and RPZM groups, respectively) as well as milk fat and protein concentration (27.28 vs. 32.80 ± 1.82 and 30.13 vs. 31.03 ± 0.25 g/kg for control and RPZM groups, respectively). The Zn-Met complex supplemented cows had lower haptoglobin and IL-1B concentration than the control (267 vs. 240 ± 10.53 mcg/mL and 76.8 vs. 60.0 ± 3.4 ng/L for control and RPZM groups, respectively). RPZM supplementation resulted in better oxidative status, indicated by higher total antioxidant status and lower malondialdehyde concentrations (0.62 vs. 0.68 ± 0.02 mmol/L and 2.01 vs. 1.76 ± 0.15 nmol/L for control and RPZM groups, respectively). Overall, the results from this study showed that RPZM dietary inclusion could maintain milk production and milk composition of animals during periods of heat stress. Enhanced performance of animals upon Zn-Met complex supplementation could be partly due to improved oxidative and immune status.

In situ and in vitro evaluation of the bioavailability of rumen-protected methionine with coating prototypes

Rumen protected amino acids are supplements that can enhance ruminal performance, yet the coating designed to protect the amino acids might also lead to different effects. Methionine is an essential methyl donor to synthesize protein, and little data exists on the effects of coating materials on its bioavailability. The purpose of this study was to estimate the effect of rumen-protected methionine (RPM) coatings with different ratios of acrylic resin IV (AR), ethyl cellulose (EC), and a mixture of AR and EC (AREC). Fifteen RPMs were prepared according to a single factor design, with 5 proportions each of AR, EC, and AREC to DL-methionine (DL-Met). Twelve hybrid small-tailed Han sheep with rumen fistula were utilized to evaluate in situ escape of RPMs, followed by in vitro abomasum-intestinal release of the RPMs. The results showed a regular variation in both ruminal disappearance and gastrointestinal release of RPMs with different coating prototypes and retention time. The RPMs that were EC and AREC coated presented high bioavailability compared to those with AR. Bioavailability of RPMs was optimal with the 2:20 AREC: DL-Met ratio, when the proportion of AR:EC is 1:1. Additionally, RPMs with a 1:3 ratio of AR:EC confirmed the optimum effect for the RPM of 2:20 AREC: DL-Met. In conclusion, an RPM with a lower AREC ratio coating can achieve better bioavailability and is synergistic to those with EC and AR.

Methionine Supplementation during Pregnancy of Goats Improves Kids' Birth Weight, Body Mass Index, and Postnatal Growth Pattern

The last third of gestation is a period of high energy and protein demand for the dam to support fetal growth and the following onset of lactation. Methionine is an essential amino acid that contributes to protein formation, fetal development, and milk synthesis; thus, is likely to have positive effects on the weight and size of the newborn and, afterward, milk yield and milk composition, which may improve growth patterns of the progeny. To test these hypotheses, we used 60 pregnant multiparous Alpine goats with similar live weights and gestational ages (~Day 100 of pregnancy; Mean ± SD; 1410 ± 14 days old and 50.4 ± 6.6 kg) and were separated into two groups: control and supplemented with the delivery. Treatments were T-MET (n = 30; received 1% herbal methionine Optimethione® dry matter based on from Day 100 of the pregnancy to delivery) or T-CTL (n = 30; served as the control and did not receive methionine). The methionine powder provided individual supplementation and was adjusted every week as the live weight and dry matter intake changed. At birth, the weight, body mass index (BMI), birth type, and sex of the kids were determined. Subsequently, the progeny was weighed weekly up to weaning. Two weeks after parturition, the milk composition was recorded weekly, and the milk yield was recorded monthly. The maternal live weight at the start (Mean ± SEM; T-CTL: 50.5 ± 1.1 vs. T-MET: 50.3 ± 1.3 kg) and end (T-CTL: 54.2 ± 1.3 vs. T-MET: 52.8 ± 1.4 kg) of the experiment did not differ statistically among treatments (p > 0.05); however, daily live weight changes tended to differ between groups (T-CTL: 73 ± 10 vs. T-MET: 51 ± 7 g day−1; p = 0.06). The birth weight (T-CTL: 3.1 ± 0.1 vs. T-MET: 3.5 ± 0.1 kg; p < 0.001), daily live weight change (T-CTL: 121 ± 6 vs. T-MET: 141 ± 6 g day−1; p < 0.01), and weaning weight (T-CTL: 8.3 ± 0.2 vs. T-MET: 9.3 ± 0.3 kg; p < 0.01) differed between treatments. The BMI at birth (T-CTL: 0.28 ± 0.01 vs. T-MET: 0.3 ± 0.01 units kg m−2; p < 0.01) and at weaning (T-CTL: 0.85 ± 0.1 kg vs. T-MET: 1.00 ± 0.06 units kg m−2; p < 0.05) differed between treatments. Milk components (protein, fat, lactose, and solids non-fat) and milk yield were similar between treatments (p > 0.05). It is concluded that the inclusion of methionine in the maternal goat diet during the last third of gestation increases the birth and growth variables of the progeny but without significant influence on the milk yield and composition.

Feasibility of Supplying Ruminally Protected Lysine and Methionine to Periparturient Dairy Cows on the Efficiency of Subsequent Lactation

The objective of this study was to evaluate the effects of supplying ruminally protected Lys (RPL) and ruminally protected Met (RPM) to transition cows' diets on the efficiency of subsequent lactation. A total of 120 prepartum Holstein cows were assigned into four treatments blocked by the anticipated calving date, previous lactation milk yield, number of lactations, and body condition score and fed either RPL, RPM, or the combination (RPML) or control diet (CON) throughout the transition period (3 weeks before till 3 weeks after calving). From 22 to 150 days in milk (DIM), all animals (100 cows) were fed a combination of RPM and RPL (0.17% RPM and 0.41% RPL of DM; n = 25 cows/treatment) as follows; CON–RPML, RPM–RPML, RPL–RPML, and RPML–RPML. Milk production and dry matter intake (DMI) were measured daily; milk and blood samples were taken at 21, 30, 60, 90, 120, and 150 DIM. Supplemented amino acids (AA) were mixed with the premix and added to the total mixed ration during the experiment. DMI (p &lt; 0.001) and energy-corrected milk (ECM, p = 0.04) were higher for cows that were fed RPML–RPML than other cows. Compared with CON–RPML, yields of milk total protein, lactose, and nitrogen efficiency were increased (p &lt; 0.01), whereas milk urea nitrogen (MUN; p = 0.002) was decreased for other treatments. However, supplemental AA did not affect milk lactose percentage, fat yield, feed efficiency, or serum total protein concentration (p &gt; 0.10). Transition cows that consumed AA had a greater peak of milk yield (p &lt; 0.01), as well as quickly reached the peak of milk (p &lt; 0.004). There were differences in β-hydroxybutyrate concentration during the early lactation, with a lower level for AA groups (p &lt; 0.05), and the difference faded with the progression of lactation (p &gt; 0.10). Fertility efficiency as measured by pregnancy rate was improved by supplemental AA during the perinatal period (p &lt; 0.05). In conclusion, transition cows consumed RPM and RPL, increased post-calving DMI, milk production, milk protein yield, nitrogen efficiency, and improved fertility performance.

Effect of Post-Ruminal Casein Infusion on Milk Yield, Milk Composition, and Efficiency of Nitrogen Use in Dairy Cows

Adequate supply of amino acids can improve the efficiency of nitrogen use. Casein is the predominant milk protein, and its supplementation can improve milk protein synthesis and nitrogen efficiency. We evaluated the effects of post-ruminal supplementation of casein on milk yield and composition and whole-body protein deposition. Two ruminally cannulated Holstein dairy cows (599 kg) were used in a switch-back design, and treatments were an abomasal infusion of 0 or 400 g/day casein. Cows were fed a diet consisting of corn silage, alfalfa hay, wet corn gluten feed, whole cottonseed, and grain mix, and they received 320 g/day dextrose via abomasal infusion to increase energy:metabolizable protein. The experiment used three 8-day periods. Milk, urine, and feces samples were collected to evaluate milk production, milk composition, and nitrogen retention. Abomasal casein infusion increased (p < 0.01) milk protein percentage and milk urea nitrogen. Nitrogen retention (p = 0.03) and urinary N excretion (p < 0.001) were increased and fecal N excretion (p < 0.001) was decreased by casein infusion. Results suggest casein stimulated protein deposition and altered nitrogen use in lactating dairy cattle. Adaptation periods of 4 days were appropriate for evaluating responses to casein supplementation. Our data provide elements that can aid the design of future experiments.

Harnessing the Value of Rumen Protected Amino Acids to Enhance Animal Performance – A Review

In general, higher mammals need nine amino acids (AA) in their diets as building blocks to synthesize proteins while ruminants can produce some of them through the synthesis of microbial proteins. Diet is utilized by ruminal microorganisms to synthesize microbial protein (MCP) which is digested in the small intestine (SI). Although protein and amino acid requirements in ruminants are subject to microbial protein synthesis, it is not enough for optimal daily production. Therefore, there is a current trend towards supplementing amino acids in ruminant diets. In the rumen, free amino acids can be degraded by rumen bacteria, therefore, the AAs need to be supplemented in a protected form to be stable in the rumen and absorbable post-ruminal for metabolic purposes. The main site of amino acid absorption is the small intestine (SI), and there is a need to keep AA from ruminal degradation and direct them to absorption sites. Several approaches have been suggested by feed scientists to decrease this problem such as defaunation and debacterization of the rumen against amino acid-fermenting fungi and bacteria, inhibitors or antagonists of vitamin B6 enzymes, diet composition and also protecting AA from rumen degradation. A number of studies have evaluated the roles of amino acids concerning their effects on milk yield, growth, digestibility, feed intake and efficiency of nitrogen utilization of ruminants. The focus of this review was on experimental and research studies about AAs in feedstuff, metabolism, supplementing amino acids for ruminants and the current trends of using rumen protected amino acids.

Effects of supplemental lysine and methionine on performance of nursing Awassi ewes fed two levels of dietary protein

The objective of this study was to investigate the effects of rumen-protected lysine (RPL) and methionine (RPM) supplementation on production performance of nursing ewes fed two levels of dietary protein. Individually housed Awassi ewes (n = 34) nursing single lambs were randomly assigned (2 × 2 factorial design) to one of four dietary treatments with two levels of protein (170 or 151 g/kg; HP or MP) and two levels of RPL and RPM (0 or 8.5 plus 4 g/day/ewe of RPL and RPM, respectively; no or yes). The trial lasted for 5 weeks. Ewes fed the MP diets had (P < 0.01) lower protein intake compared to those fed the HP diets. Intake of other nutrients and milk composition were not significantly (P > 0.13) affected by dietary treatments. Ewes fed the MPYES diet produced more (P < 0.05) milk compared to those fed the MPNO and HPYES diets and tended (P = 0.08) to be more than the HPNO diet. Additionally, milk composition yields for the MPYES diet were significantly (P < 0.05) more than the HPYES diets and tended (P ≤ 0.10) to be more than the MPNO and HPNO diets. Milk efficiency was highest (P < 0.05) for the MPYES diet. Final BW, total gain, and growth rate of lambs were greater when their dams were fed the MPYES diet compared to MPNO and HPNO diets. Under our conditions, decreasing dietary protein from 170 to 151 g/kg did not negatively affect the performance of ewes and their lambs. Supplemental RPL and RPM were beneficial for ewes fed diets containing 151 g/kg, but not 170, protein.

Lactational performance of dairy cows in response to supplementing N-acetyl-l-methionine as source of rumen-protected methionine

The objective of this experiment was to evaluate the effects of supplementing a rumen-protected source of Met, N-acetyl-l-methionine (NALM), on lactational performance and nitrogen metabolism in early- to mid-lactation dairy cows. Sixty multiparous Holstein dairy cows in early lactation (27 ± 4.3 d in milk, SD) were assigned to 4 treatments in a randomized complete block design. Cows were blocked by actual milk yield. Treatments were as follows: (1) no NALM (control); (2) 15 g/d of NALM (NALM15); (3) 30 g/d of NALM (NALM30); and (4) 45 g/d of NALM (NALM45). Diets were formulated using a Cornell Net Carbohydrate and Protein System (CNCPS) v.6.5 model software to meet or exceed nutritional requirements of lactating dairy cows producing 42 kg/d of milk and to undersupply metabolizable Met (control) or supply incremental amounts of NALM. The digestible Met (dMet) supply for control, NALM15, NALM30, and NALM45 were 54.7, 59.8, 64.7, and 72.2 g/d, respectively. The supply of dMet was 88, 94, 104, and 115% of dMet requirement for control, NALM15, NALM30, and NALM45, respectively. Milk yield data were collected, dry matter intake (DMI) was measured daily, and milk samples were collected twice per week for 22 wk. Blood, ruminal fluid, urine, and fecal samples were collected during the covariate period and during wk 4, 8, and 16. Data were analyzed using the GLIMMIX procedure of SAS (SAS Institute) using covariates in the model for all variables except body weight. Linear, quadratic, and cubic contrasts were also tested. Treatments did not affect DMI, milk yield, and milk component concentration and yield; however, feed efficiency expressed as milk yield per DMI and 3.5% fat-corrected milk per DMI were quadratically affected, with greater response observed for NALM15 and NALM30 compared with control. Acetate proportion linearly increased, whereas propionate proportion linearly decreased with NALM supplementation. Blood urea nitrogen linearly decreased with NALM supplementation. Total plasma essential AA concentrations were quadratically affected, as greater values were observed for control and NALM45 than other treatments. Plasma Met concentration was quadratically affected as lower levels were observed with NALM15, whereas Met concentrations increased with NALM45 compared with control. Nitrogen utilization efficiency and apparent total-tract nutrient digestibility were not affected by treatment. Supplementation of NALM at 15 or 30 g/head per day resulted in the greatest improvements in feed efficiency without affecting N metabolism of early- to mid-lactation dairy cows.

Production effects and bioavailability of N-acetyl-l-methionine in lactating dairy cows

Two experiments were conducted to investigate the production effects of N-acetyl-l-methionine (NALM; experiment 1) and to estimate its bioavailability (BA) and rumen escape (RE; experiment 2), respectively, in lactating dairy cows. In experiment 1, 18 multiparous Holstein cows were used in a replicated, 3 × 3 Latin square design experiment with three 28-d periods. Treatments were (1) basal diet estimated to supply 45 g/d digestible Met (dMet) or 1.47% of metabolizable protein (MP; control), (2) basal diet top-dressed with 32 g/d of NALM to achieve dMet supply of 2.2% of MP, and (3) basal diet top-dressed with 56 g/d of NALM to achieve dMet supply of 2.6% of MP. The NALM treatments supplied estimated 17 and 29 g/d dMet from NALM, respectively, based on manufacturer's specifications. In experiment 2, 4 rumen-cannulated lactating Holstein cows were used in a 4 × 4 Latin square design experiment with four 12-d periods. A 12-d period for baseline data collection and 4 d for determination of RE of NALM preceded the Latin square experiment. For determination of RE, 30 g of NALM were dosed into the rumen simultaneously with Cr-EDTA (used as a rumen fluid kinetics marker) and samples of ruminal contents were collected at 0 (before dosing), 1, 2, 4, 6, 8, 10, 14, 18, and 24 h after dosing. Rumen escape of NALM was calculated using the estimated passage rate based on the measured Cr rate of disappearance. Bioavailability of abomasally dosed NALM was determined using the area under the curve of plasma Met concentration technique. Two doses of l-Met (providing 7.5 and 15 g of dMet) and 2 doses of NALM (11.2 and 14.4 g dMet) were separately pulse-dosed into the abomasum of the cows and blood was collected from the jugular vein for Met concentration analysis at 0 (before dosing), 1, 2, 4, 6, 8, 10, 12, 14, 18, and 24 h after dosing. Supplementation of NALM did not affect DMI, milk yield, feed efficiency, or milk protein and lactose concentrations and yields in experiment 1. Milk fat concentration and energy-corrected milk yield decreased linearly with NALM dose. Plasma Met concentration was not affected by NALM dose. The estimated relative BA of abomasally dosed NALM (experiment 2) was 50% when dosed at 14.4 g/cow (11.2 g/d dMet from NALM) and 24% when dosed at 28.8 g/cow (14.4 g/d dMet from NALM). The estimated RE of NALM was 19% based on the measured k_p of Cr at 11%/h. The total availability of ingested NALM was estimated at 9.5% for the lower NALM dose when taking into account RE (19%) and bioavailability in the small intestine (50%). Overall, NALM supplementation to mid-lactation dairy cows fed a MP-adequate basal diet below NRC (2001) recommendations (45 g/d or 1.47% Met of MP) decreased milk fat and energy-corrected milk yields but did not affect milk or milk true protein yields. Further evaluation of BA of NALM at different doses is warranted. In addition, intestinal conversion of NALM to Met needs additional investigation to establish a possible saturation of the enzyme aminoacylase I at higher NALM doses.

Multi-omics revealed the effects of rumen-protected methionine on the nutrient profile of milk in dairy cows

Cow's milk is a highly-nutritious dairy product part of human diet worldwide. Rumen-protected methionine (RPM) is widely used to improve lactation performance of dairy cows, but understanding of the effects of RPM on milk nutrients composition are still limited. In this study, twenty mid-lactating dairy cows were supplemented with 20 gm/day RPM for 8 weeks to investigate the responses of milk nutritional composition to RPM. Metabolomics was applied for analyzing milk metabolites and 16S rRNA gene sequencing was used for analysis of rumen microbial composition. Milk fat content and yield were significantly increased after RPM supplementation. Totally 443 compounds belonging to 15 classes were identified, among which 15 metabolites were significantly changed. The functional nutrient α-ketoglutaric acid were significantly increased in the milk after RPM supplementation. We found 48 significantly differing bacterial genera in the rumen after supplementing RPM. Multi-omics integrated analysis revealed the higher abundance of Acetobacter, unclassified_f_Lachnospiraceae and Saccharofermentan contributed to the improved milk fat. In addition, the enriched abundance of Thermoactinomyces, Asteroleplasma, and Saccharofermentan showed positive correlations with higher α-ketoglutaric acid of milk. Our results uncover the metabolomic fingerprint and the key functional metabolites in the milk after supplementing RPM in dairy cows, as well as the key rumen bacteria associated with them. These findings provide novel insights into the development of functional dairy products that enriched the functional nutrient α-ketoglutaric acid or high milk fat.

Replacing Soybean Meal with Distillers Dried Grains with Solubles plus Rumen-Protected Lysine and Methionine: Effects on Growth Performance, Nutrients Digestion, Rumen Fermentation, and Serum Parameters in Hu Sheep

Simple Summary

Improving the economic benefits and precise nutrient supply are hotspots of the sheep breeding industry. Evaluation of the production performance, the rumen fermentation, and blood metabolism indexes found that replacement of soybean meal with distillers dried grains with solubles in a diet with adequate metabolizable protein and amino acids (lysine and methionine) could maintain the normal growth performance of Hu sheep. The comprehensive evaluation results provide a reference for reducing production costs, improving production efficiency, and decreasing the nitrogen excretion of the sheep breeding industry. Besides, the study will help in the development of low-protein diets with amino acid balance for sheep.

Abstract

(1) Background: we investigated the influence of dietary soybean meal (SBM) replaced with distillers dried grains with solubles (DDGS) plus rumen-protected (RP) lysine and methionine on the growth performance, nutrients digestion, rumen fermentation, and serum parameters of Hu sheep. (2) Methods: ninety Hu sheep were allocated to five groups: the control group (CON) which received the SBM diet, the DDGS group (NSM), the DDGS diet with RP lysine group (DRPL), the DDGS diet with RP methionine group (DRPM), and the DDGS diet with a mixture of RP lysine and methionine group (DRPLM). (3) Results: Final BW and carcass weight of the DRPLM and CON groups were greater (p ≤ 0.05) compared to NSM, DRPL, and DRPM groups. The DRPLM group tended to increase the dry matter intake (DMI, p = 0.06), average daily gain (ADG, p = 0.06), dressing percentage (p = 0.07), and tail fat weight (p = 0.09). The DRPLM group had increased (p ≤ 0.05) apparent digestibility and had altered ruminal fermentation characteristics. (4) Conclusions: replacement of SBM with DDGS in a diet with adequate metabolizable protein and by-pass amino acids (lysine and methionine) could maintain the growth performance of Hu sheep.

Amino Acids Supplementation for the Milk and Milk Protein Production of Dairy Cows

Simple Summary

The composition of milk not only has nutritional implications, but is also directly related to the income of dairy producers. As regards milk’s composition, concerns around milk protein have emerged from the increased consumption of casein products. The synthesis of proteins in milk is a highly complex and high-cost process, because the conversion efficiency of dietary protein to milk protein is very low in dairy cows. Thus, some studies have increased milk protein by using protein supplements or a single amino acid (AA) supply. AAs are the building blocks of protein, and can also stimulate the protein synthetic pathway. This review mainly concerns the use of AAs for producing milk protein in high-producing dairy cows, particularly with methionine, lysine, and histidine. Understanding the mechanisms of AAs will help to promote milk protein synthesis in the dairy industry.

Abstract

As the preference of consumers for casein products has increased, the protein content of milk from dairy cows is drawing more attention. Protein synthesis in the milk of dairy cows requires a proper supply of dietary protein. High protein supplementation may help to produce more milk protein, but residues in feces and urine cause environmental pollution and increase production costs. As such, previous studies have focused on protein supplements and amino acid (AA) supply. This review concerns AA nutrition for enhancing milk protein in dairy cows, and mainly focuses on three AAs: methionine, lysine, and histidine. AA supplementation for promoting protein synthesis is related to the mammalian target of rapamycin (mTOR) complex and its downstream pathways. Each AA has different stimulating effects on the mTOR translation initiation pathway, and thus manifests different milk protein yields. This review will expand our understanding of AA nutrition and the involved pathways in relation to the synthesis of milk protein in dairy cows.

Economic and environmental effects of revised metabolizable protein and amino acid recommendations on Canadian dairy farms

The objective of this research was to evaluate the potential economic and environmental effects of the formulation model used to balance dairy rations for metabolizable protein (MP) or 3 essential AA (EAA: His, Lys, and Met) in 3 regions of Canada with different farming systems. The Maritimes, Central Canada, and the Prairies reference dairy farms averaged 63, 71, 144 mature cows per herd and 135, 95, 255 ha of land, respectively. Using N-CyCLES, a whole-farm linear program model, dairy rations were balanced for (1) MP, based on National Research Council (NRC) requirements (MP_2001); (2) MP plus Lys and Met, based on NRC (AA_2001); (3) MP (MP_Rev); or (4) for His, Lys, and Met (AA_Rev), both based on a revised factorial approach revisiting both supply and requirements of MP and EAA. Energy was balanced to meet requirements based on NRC (2001). Assuming the requirements were met within each approach, it was considered that milk yield and composition were not affected by the type of formulation. Given the assumptions of the study, when compared with MP_2001 formulation, balancing dairy rations using the AA_Rev approach reduced calculated farm N balance by 3.8%, on average from 12.71 to 12.24 g/kg of fat- and protein-corrected milk; it also enhanced farm net income by 4.5%, from 19.00 to 19.70 $CAN/100 kg of fat- and protein-corrected milk, by reducing inclusion of protein concentrate in dairy rations. Calculated animal N efficiency was on average 4.3% higher with AA_Rev than with MP_2001 for mid-lactation cows. This gain in N efficiency would result in a reduction in N₂O emission by manure, contributing to a partial decrease of total greenhouse gas emission by 1.7%, through a reduction of N excreted in manure. With the AA_2001 formulation, farm N balance was 1% higher than with MP_2001 formulation while reducing farm net income by 6.4%, due to the need to purchase rumen-protected AA, with no effect on total greenhouse gas emission. Both MP formulations lead to fairly similar outputs. The AA_Rev formulation also indicated that His might be a co-limiting AA with Met in dairy rations balanced with ingredients usually included in Canadian dairy rations. Given the assumptions of the study, balancing dairy rations for 3 EAA (His, Lys, and Met) rather than MP, has some potential positive effects on Canadian dairy farms by increasing net incomes through a reduction of crude protein supply, leading to a decreased environmental effect.

Dietary supplementation with N-carbamoylglutamate initiated from the prepartum stage improves lactation performance of postpartum dairy cows

The objective of this study was to investigate the effects of supplementing N-carbamoylglutamate (NCG), an Arg enhancer, on amino acid (AA) supply and utilization and productive performance of early-lactating dairy cows. Thirty multiparous Chinese Holstein dairy cows were randomly divided into control (CON, n = 15) and NCG (CON diet supplemented with NCG at 20 g/d per cow, n = 15) groups at 4 wk before calving. Diets were offered individually in tie-stalls, and NCG was supplemented by top-dress feeding onto total mixed ration for the NCG group. The experiment lasted until wk 10 after calving. Dry matter intake tended to be higher (P = 0.06), and yields of milk (P < 0.01), milk protein (P < 0.01), and milk fat (P < 0.01) were higher in the NCG-cows than in the CON-cows. Plasma activities of aspartate aminotransferase (P < 0.01), alanine aminotransferase (P = 0.03), and plasma level of β-hydroxybutyrate (P = 0.04) were lower in the NCG-cows than in the CON-cows, whereas plasma glucose (P = 0.05) and nitric oxide (NO, P < 0.01) concentrations were higher. Coccygeal vein concentrations of Cys (P < 0.01), Pro (P < 0.01), Tyr (P = 0.05), most essential AA except Thr and His (P < 0.01), total essential AA (P < 0.01), and total AA (P < 0.01) were higher in the NCG-cows than in the CON-cows. The arterial supply of all AA was greater in the NCG-cows than in the CON-cows. The NCG-cows had higher mammary plasma flow of AA (P = 0.04) and clearance rate of Cys (P < 0.01), Pro (P < 0.01) and Asp (P < 0.01), and higher ratios of uptake to output of Met (P = 0.05), Lys (P < 0.01), Cys (P = 0.01), Pro (P = 0.03), and Asp (P = 0.01). In summary, addition of NCG initiated from the prepartum period improved the lactation performance of postpartum dairy cows, which might attribute to greater Arg and NO concentrations, as well as improved AA supply and utilization, liver function, and feed intake in these cows.

Effects of rumen-protected methionine supplementation on the performance of high production dairy cows in the tropics

Increasing methionine availability in dairy cow diets during the first third of lactation may enhance their performance and health. The aim of this study was to determine the effect of supplementing rumen-protected methionine (Smartamine® M, SM) in a lactation diet with protein and energy levels calculated according to the literature. Seventy-six multiparous Holstein cows (39.1 ± 6.8 kg of milk/d and 65 ± 28 DIM) were assigned to 1 of 2 dietary treatments (38/treatment) according to a randomized complete block design with a 2-wk (covariate) and 10-wk experimental period. Treatments were a basal diet (CON; 3.77 Lys:1Met); and CON + 23 g SM (2.97 Lys:1 Met). Individual milk samples were taken every 2 weeks to determine milk composition. Blood was collected from 24 cows on d+30 d to measure plasma AA levels. Body weight and body condition score (BCS) were measured at the beginning and the end of the experiment. The SM diet promoted higher milk yield (41.7 vs. 40.1 kg/d; P = 0.03). Energy-corrected milk yield (41.0 vs. 38.0 kg/d), milk protein yield (1.30 vs. 1.18 kg/d), milk protein (3.14% vs. 2.97%) and casein (2.39% vs. 2.28%) were also different (P < 0.01) as well as milk fat yield (1.42 vs. 1.29 kg/d; P = 0.02). A trend (P = 0.06) for higher milk fat % (3.41% vs. 3.21%) was observed. Both diets resulted in similar body weight, but CON-fed cows tended (P = 0.08) to have higher BCS. Higher plasma methionine levels were determined with SM compared with CON (29.6 vs. 18.4 μM; P < 0.01), but lysine and histidine were not different. Dietary supplementation of RPM improved productive performance by increasing milk yield and milk components yields, suggesting better dietary AA utilization when Met levels are adjusted in Lys-adequate lactation diets.

Effects of feeding rumen-protected methionine pre- and postpartum in multiparous Holstein cows: Lactation performance and plasma amino acid concentrations

Objectives were to evaluate the effect of feeding rumen-protected methionine (RPM) in pre- and postpartum total mix ration (TMR) on lactation performance and plasma AA concentrations in dairy cows. A total of 470 multiparous Holstein cows [235 cows at University of Wisconsin (UW) and 235 cows at Cornell University (CU)] were enrolled approximately 4 wk before parturition, housed in close-up dry cow and replicated lactation pens. Pens were randomly assigned to treatment diets (pre- and postpartum, respectively): UW control (CON) diet = 2.30 and 2.09% of Met as percentage of metabolizable protein (MP) and RPM diet = 2.83 and 2.58% of Met as MP; CU CON = 2.22 and 2.19% of Met as percentage of MP, and CU RPM = 2.85 and 2.65% of Met as percentage of MP. Treatments were evaluated until 112 ± 3 d in milk (DIM). Milk yield was recorded daily. Milk samples were collected at wk 1 and 2 of lactation, and then every other week, and analyzed for milk composition. For lactation pens, dry matter intake (DMI) was recorded daily. Body weight and body condition score were determined from 4 ± 3 DIM and parturition until 39 ± 3 and 49 DIM, respectively. Plasma AA concentrations were evaluated within 3 h after feeding during the periparturient period [d -7 (±4), 0, 7 (±1), 14 (±1), and 21 (±1); n = 225]. In addition, plasma AA concentrations were evaluated (every 3 h for 24 h) after feeding in cows at 76 ± 8 DIM (n = 16) and within 3 h after feeding in cows at 80 ± 3 DIM (n = 72). The RPM treatment had no effect on DMI (27.9 vs. 28.0 kg/d) or milk yield (48.7 vs. 49.2 kg/d) for RPM and CON, respectively. Cows fed the RPM treatment had increased milk protein concentration (3.07 vs. 2.95%) and yield (1.48 vs. 1.43 kg/d), and milk fat concentration (3.87 vs. 3.77%), although milk fat yield did not differ. Plasma Met concentrations tended to be greater for cows fed RPM at 7 d before parturition (25.9 vs. 22.9 µM), did not differ at parturition (22.0 vs. 20.4 µM), and were increased on d 7 (31.0 vs. 21.2 µM) and remained greater with consistent concentrations until d 21 postpartum (d 14: 30.5 vs. 19.0 µM; d 21: 31.0 vs. 17.8 µM). However, feeding RPM decreased Leu, Val, Asn, and Ser (d 7, 14, and 21) and Tyr (d 14). At a later stage in lactation, plasma Met was increased for RPM cows (34.4 vs. 16.7 µM) consistently throughout the day, with no changes in other AA. Substantial variation was detected for plasma Met concentration (range: RPM = 8.9-63.3 µM; CON = 7.8-28.8 µM) among cows [coefficient of variation (CV) > 28%] and within cow during the day (CV: 10.5-27.1%). In conclusion, feeding RPM increased plasma Met concentration and improved lactation performance via increased milk protein production.

Effect of protein level and methionine supplementation on dairy cows during the transition period

Cows experience a significant negative protein balance during the first 30 d of lactation. Given the functional effects of AA on health, especially in challenging periods such as calving, higher levels of protein and specific AA in the diet may act to improve health and feed intake. The response of dairy cows to 3 protein supplementation strategies during the transition period and through the first 45 d in milk was evaluated. The final data set had 39 Holstein cows blocked based on parity (primiparous vs. multiparous) and expected calving and randomly assigned within each block to one of 3 dietary treatments: low protein (LP), high protein (HP), or high protein plus rumen-protected methionine (HPM). Treatments were offered from d -18 ± 5 to 45 d relative to parturition. Pre- and postpartum diets were formulated for high metabolizable protein (MP) supply from soybean meal, and HP and HPM provided higher MP balance than LP. Preplanned contrasts were LP versus HP+HPM and HP versus HPM. Significance was declared at P ≤ 0.05 and trends at 0.05 <P ≤ 0.10. Cows fed HP and HPM had greater fry matter intake (DMI) prepartum than LP (+2 kg/d), and there was a trend for greater DMI with HPM than with HP (+1.6 kg/d). Body weight and condition score before and after calving did not differ among treatments. High protein (HP and HPM) tended to increase milk yield during the first 45 d of lactation (+1.75 kg/d), increased milk lactose content and urea-N in milk and plasma, tended to increase blood BHB 14 d postpartum, and tended to reduce milk/DMI compared with LP. Blood concentrations of calcium at calving and of glucose, and nonesterified fatty acids pre- and postpartum did not differ. High protein induced lower concentration of plasma IL-1 at calving and lowered blood lymphocytes 21 d postpartum, suggestive of a reduced inflammatory status compared with LP. The concentrations of IL-10, tumor necrosis factor alpha, and other hemogram variables did not differ among treatments. Addition of rumen-protected methionine to the HP diet did not alter milk yield but increased fat and total solids concentrations. The rumen-protected methionine had no effect on blood metabolites and immunity markers, with the exception of increased pre-partum insulin concentrations. The data indicate that dairy cows around calving respond positively to an increase in the supply of MP and to rumen-protected methionine supplementation of the HP diet by increasing intake and improving immune status.

Methionine precursor effects on lactation performance of dairy cows fed raw or heated soybeans

Two experiments were conducted to evaluate the effect of isopropyl ester of 2-hydroxy-4-(methylthio) butanoic acid (HMBi) on lactation performance of dairy cows. Experiment 1 evaluated the effect of HMBi in diets with 15.3% crude protein (CP) and with different proportions of rumen-degradable and undegradable protein. Variation in rumen-degradable and undegradable protein was achieved by replacing raw with heated soybeans. Experiment 2 was an on-farm trial to evaluate HMBi with a large number of observations and using a farm-formulated diet (17.2% CP). In experiment 1, 20 Holsteins at 100 ± 41 d in milk were allocated to 5 replicated 4 × 4 Latin squares with 21-d periods. Treatments were formed by a 2 × 2 factorial arrangement of raw or heated soybeans with or without HMBi. Paper capsules with HMBi were orally administered twice daily to each cow. Dosage of HMBi was 7.6 g of digestible Met/cow per day. There was no interaction between soybean type and HMBi. Heat-treated soybeans increased the yields of milk, protein, fat, and lactose, and reduced urea N in milk and plasma (PUN) compared with raw soybeans. Rumen microbial yield, dry matter intake (DMI), and the total-tract apparent digestibility of nutrients did not differ between soybean types. There was no evidence for HMBi-driven effects on DMI, milk and components yield, or diet digestibility. Urinary purine derivative excretion and PUN concentration were reduced in HMBi-fed cows compared with cows fed diets without HMBi. In experiment 2, 294 Holstein cows were blocked by parity and milk yield, and randomly assigned to HMBi (8.9 g of digestible Met/cow per day) or control. The final data set had 234 cows (215 ± 105 days in milk; 96 primiparous and 138 multiparous; 114 on control and 120 on HMBi) housed in 4 freestall groups (1 group/treatment per parity). The freestall group was the experimental unit for DMI, diet and orts composition, and feed availability. The HMBi supplement was top dressed for 28 d on the first daily meal of each cow, immediately after feed delivery of the same batch of feed to all 4 freestall groups (3 times per day). Sample collection and feed analysis occurred during the last 5 d. Spot urine samples and blood samples from each cow were obtained for analysis of the urinary allantoin to creatinine ratio and PUN. Feed availability, the contents of CP and neutral detergent fiber in diets and orts, and DMI did not differ. Cows fed with HMBi had greater milk protein yield and concentration compared with control and had no change in milk fat and lactose. Rumen microbial yield was greater and PUN was lower in HMBi-fed cows compared with control. In experiment 1, HMBi decreased rumen microbial yield and did not affect lactation performance, but it increased ruminal microbial yield and the secretion of milk protein in experiment 2. These results suggest that lactation response to HMBi may be partially mediated by ruminal events. Heated soybeans increased the efficiency of N utilization and the yields of milk, protein, fat, and lactose, but did not interact with HMBi supplementation.

Effect of rumen-protected methionine supplementation to beef cows during the periconception period on performance of cows, calves, and subsequent offspring

Maternal nutrition affects the development of the fetus and postnatal performance of the calf. Methionine may play a critical role in developmental programming and is likely deficient in beef cows fed low-quality forage. The objective of this study was to determine the effect of metabolizable methionine supply to lactating beef cows during the periconception period on performance of cows, calves, and subsequent offspring. This project involved two consecutive production cycles commencing at calving in which dietary treatments were fed to cows during the periconception period along with measurements on cows and initial calves in Production Cycle 1, and measurements on subsequent calves in Production Cycle 2. Brangus-Angus crossbred lactating beef cows (N = 108; age = 6.4 (2.8) year) were stratified by previous calving date and assigned to one of three supplements: (1) control, molasses plus urea at 2.72 kg/day as fed, (2) fishmeal, 2.27 kg/day molasses plus urea plus 0.33 kg/day as fed of fishmeal, and (3) methionine, 2.72 kg/day of molasses plus urea plus 9.5 g/day of 2-hydroxy-4-(methylthio)-butanoic acid. Cows were fed supplements and low-quality limpograss (Hemarthria altissima) hay while grazing dormant bahiagrass (Paspalum notatum Flüggé) pastures during the 115-day periconception period from December 2014 to April 2015 in Production Cycle 1 only. Body weight change and milk yield of cows were measured during the periconception period in Production Cycle 1. Body weight of calves was measured at birth and weaning in both production cycles. Following weaning in Production Cycle 2, eight subsequent steer calves per treatment were individually housed for a 42-day metabolism experiment. Treatment did not affect (P > 0.10) BW change of cows, but cows fed methionine tended (P = 0.09) to produce more energy-corrected milk than control and fishmeal. Treatment did not affect (P > 0.10) 205-day adjusted weaning weight of calves in either production cycle. During the metabolism experiment, subsequent calves from dams fed fishmeal and methionine gained faster (P < 0.05) and had greater (P < 0.05) gain:feed than control calves. Methionine calves tended (P = 0.06) to have greater apparent total tract NDF and ADF digestibility and lesser (P < 0.05) blood glucose concentration than control and fishmeal calves. These data indicate that maternal methionine supply during the periconception period plays an important role in programming future performance of the offspring.

Relative availability of metabolizable methionine from 2 ruminally protected sources of methionine fed to lactating dairy cattle

Our objective was to evaluate the lactational responses of dairy cows to methionine provided from 2 ruminally protected sources of methionine activity. Twenty-one Holstein dairy cows [11 primiparous (634 kg of body weight, 140 d in milk) and 10 second-parity (670 kg of body weight, 142 d in milk)] were assigned to a treatment sequence in 4 replicated 5 × 5 Latin squares plus 1 cow, with 14-d periods. Treatments were as follows: control; 7.5 or 15 g/d of a ruminally protected product of 2-hydoxy-4-methylthio-butyric acid (NTP-1401; Novus International Inc., St. Charles, MO); or 7.5 or 15 g/d of a ruminally protected dl-methionine product (Smartamine M; Adisseo, Alpharetta, GA). The diet was predicted to meet metabolizable protein and energy requirements. Diets contained 16.1% crude protein, and the control diet was predicted to be deficient in metabolizable methionine (1.85% of metabolizable protein) but sufficient in lysine (6.8% of metabolizable protein). Feed intake and milk yield were measured on d 11 to 14. Blood was collected on d 14. Dry matter intake, milk yield, energy-corrected milk, milk fat yield and percentage, and efficiencies of milk and energy-corrected milk yield were not affected by treatment. Milk protein percentage and milk protein yield increased linearly with supplementation, without differences between methionine sources or interactions between source and level. Linear regressions of milk protein percentage and milk protein yield against supplement amount within source led to slope ratios (NTP-1401:Smartamine M) of 95% for protein percentage and 84% for protein yield, with no differences between sources for increasing milk protein. Plasma methionine concentrations were increased linearly by methionine supplementation; the increase was greater for Smartamine M than for NTP-1401. Plasma d-methionine was increased only by Smartamine M. Plasma 2-hydoxy-4-methylthio-butyric acid was increased only by NTP-1401. Our data demonstrated that supplementation with these methionine sources can improve milk protein percentage and yield, and the 2 methionine sources did not differ in their effect on lactation performance or milk composition.

Effects of supplementing limiting amino acids on milk production in dairy cows consuming a corn grain and soybean meal-based diet

Limiting amino acids (AAs) for milk production in dairy cows fed on a concentrate diet of corn grain and soybean meal was evaluated in this study. Four lactating and multiparous Holstein cows (in third or fourth parities, with an average body weight of 633 ± 49.2 kg), 8 to 9 weeks into their lactation period, were used in a 4 × 4 Latin square design. The experiment comprised four dietary treatments: (1) no intravenous infusion (control); (2) control plus intravenous infusion of an AA mixture of 6 g/d methionine, 19.1 g/d lysine, 13.8 g/d isoleucine, and 15.4 g/d valine (4AA); (3) control plus intravenous infusion of the AA mixture without methionine (no-Met); and (4) control plus intravenous infusion of the AA mixture without lysine (no-Lys). All animals were fed on a controlled diet (1 kg/d alfalfa hay, 10 kg/d silage, 14 kg/d concentrate mixture, ad libitum timothy hay). The AA composition of the diet and blood were determined using an automatic AA analyzer. Milk composition (protein, fat, lactose, urea nitrogen, and somatic cell counts) was determined using a MilkoScan. The results showed that feed intake for milk production did not differ from that of intravenous infusion using a limiting AA mixture. The 4AA treatment numerically had the highest milk yield (32.4 kg/d), although there was no difference when compared with the control (31.2 kg/d), no-Met (31.3 kg/d), and no-Lys (31.7 kg/d) treatments. The concentration of AAs in blood plasma of cows in all treatments, mainly isoleucine and valine, increased significantly compared with that of control. The no-Met treatment increased (p < 0.05) the concentration of lysine in the blood relative to the control and no-Lys treatments, whereas the no-Lys treatment increased (p < 0.05) the concentration of methionine relative to the control and no-Met treatments. In conclusion, milk production increased when feeding 10 g/d methionine to the cows, together with their concentrate diet of corn grain and soybean meal.

Estimating degradation of individual essential amino acids in fish meal and blood meal by rumen microbes in a dual-flow continuous-culture system

Current feeding systems are based on the assumption that the AA profile of rumen undegraded protein is similar to that of the original feed. The objective of this experiment was to determine rumen bacterial degradation of individual essential AA in fish meal (FM) and blood meal (BM). Eight dual-flow continuous-culture fermentors were used in a completely randomized block design with a factorial arrangement of treatments and 3 replicated periods. Fermentors were supplied with 95 g of dry matter/d of isonitrogenous diets. Treatments contained a nonprotein N source (urea and tryptone) that was substituted with increasing proportions of FM or BM (0, 33, 67, or 100%). Diets consisted of 22.0% crude protein, 35.2% neutral detergent fiber, 34.6% nonfiber carbohydrates, 2.0% ether extract, and 9.2% ash. We hypothesized that the increase in the flow of individual AA would be attributed to the increase in the supply of the AA from each protein supplement. True organic matter degradation was decreased by increasing levels of FM or BM, but did not affect degradation of neutral detergent fiber and acid detergent fiber, total volatile fatty acids (VFA) concentration, or the molar proportion of propionate. There was a substrate by level of inclusion interaction in acetate molar proportion and branched-chain VFA. Butyrate concentration decreased linearly with increasing levels of FM and BM in treatment. Changes in branched-chain VFA reflected differences in content of branched-chain AA between supplements and the level of inclusion, although the quadratic effect suggests that other factors were involved. Ammonia-N concentration showed a substrate by level of inclusion interaction. Total dietary N and AA flows increased with increasing levels of FM or BM in treatment. The efficiency of bacterial crude protein synthesis was not affected by treatment, but the flow of bacterial N decreased in FM diets as the level of FM increased. Flows of AA increased linearly with increasing levels of the respective AA from supplements. Arginine, Ile, Met and Phe were more degradable, while His was more resistant to bacterial degradation. Results suggest that the resistance to rumen bacterial degradation of individual AA varies within FM and BM protein and may affect the estimates of dietary supply of individual AA to the small intestine.

Changes in Metabolites from Bovine Milk with β-Casein Variants Revealed by Metabolomics

Simple Summary

Changes in milk protein content have been associated with β-casein variants. However, the specific changes in the metabolites of β-casein variant milk remain unclear. Thus, a metabolomics approach was employed to determine the abundance of different metabolites in milk samples with β-casein variant A1/A1, A2/A2, and their heterozygote. The metabolites with the highest abundance were methionine, proline, and α-lactose in variant A2/A2 milk, choline, glycine, citric acid, and cyclic adenosine monophosphate (cAMP) in variant A1/A1 milk, and uric acid and cytosine in heterozygote milk. These results may facilitate further explorations of the differences in the biosynthesis of milk components in the mammary gland and help to elucidate the potential influence of β-casein variants on the physiological function of milk.

Abstract

β-casein is a primary protein in milk, and its variants have been associated with changes in the protein content of bovine milk. However, there has been little research focused on the effects of β-casein variants on milk metabolites. In the present study, dairy cows producing milk with β-casein variant A1/A1 (A1), A2/A2 (A2), and their heterozygote A1/A2 (A12) were screened by a high-resolution melting method. Individual milk samples were then collected from each of the cows, and the milk metabolites were separated and analyzed using nuclear magnetic resonance spectroscopy- and liquid-chromatography mass spectrometry-based metabolomics techniques. Differences in metabolites among the variant groups were evaluated by multivariate statistical analysis. The relative abundances of methionine, proline, and α-lactose were the highest in β-casein variant A2 milk, whereas choline, glycine, citric acid, and cyclic adenosine monophosphate (cAMP) showed the highest abundances in variant A1 milk. Metabolic pathways analysis indicated that the differential metabolites between variants A1 and A2 were involved in pantothenate and coenzyme A biosynthesis, butanoate metabolism, and valine, leucine, and isoleucine biosynthesis. Our results reveal the differences in milk metabolites among the β-casein variants A1, A2, and the heterozygote. These findings, thus, provide novel insights into the effects of β-casein variants on milk metabolites, facilitating further research into the mechanism of the biosynthesis of milk components in the mammary gland and the potential physiological function of milk associated with β-casein variants.

Review: Control of feed intake by hepatic oxidation in ruminant animals: integration of homeostasis and homeorhesis

Feed intake is controlled through a combination of long- and short-term mechanisms. Homeorhetic mechanisms allow adaptation to changes in physiological states in the long term, whereas homeostatic mechanisms are important to maintain physiological equilibrium in the short term. Feed intake is a function of meal size and meal frequency that are controlled by short-term mechanisms over the timeframe of minutes that are modulated by homeorhetic signals to adapt to changes in the physiological state. Control of feed intake by hepatic oxidation likely integrates these mechanisms. Signals from the liver are transmitted to brain feeding centers via vagal afferents and are affected by the hepatic oxidation of fuels. Because fuels oxidized in the liver are derived from both the diet and tissues, the liver is able to integrate long- and short-term controls. Whereas multiple signals are integrated in brain feeding centers to ultimately determine feeding behavior, the liver is likely a primary sensor of energy status.

Methionine-balanced diets improve cattle performance in fattening young bulls fed high-forage diets through changes in nitrogen metabolism

Ruminants fed high-forage diets usually have a low feed efficiency, and their performances might be limited by methionine (Met) supply. However, the INRA feeding system for growing cattle does not give recommendation for this amino acid (AA). This study aimed to assess the effects of Met-balanced diets on animal performance and N metabolism in young bulls fed high-forage diets formulated at or above protein requirements. Four diets resulting from a factorial arrangement of two protein levels (Normal (13·5 % crude protein) v. High (16·2 % crude protein)) crossed with two Met concentrations (unbalanced (2·0 % of metabolisable protein) v. balanced (2·6 % of metabolisable protein)) were tested on thirty-four fattening Charolais bulls for 7 months before slaughter. Animal growth rate was greater in Met-balanced diets (+8 %; P = 0·02) with a trend for a greater impact in High v. Normal protein diets (P = 0·10). This trend was observed in lower plasma concentrations of branched-chain AA only when Met supplementation was applied to the Normal protein diet (P ≤ 0·06) suggesting another co-limiting AA at Normal protein level. Feed conversion efficiency and N use efficiency were unaffected by Met supplementation (P > 0·05). However, some plasma indicators suggested a better use of AA when High protein diets were balanced v. unbalanced in Met. The proportion of total adipose tissue in carcass increased (+5 percent units; P = 0·03), whereas that of muscle decreased on average 0·8 percent units (P = 0·05) in Met-balanced diets. Our results justify the integration of AA into dietary recommendations for growing cattle.

Dietary supplementation of rumen-protected methionine decreases the nitrous oxide emissions of urine of beef cattle through decreasing urinary excretions of nitrogen and urea

BACKGROUND

Two consecutive trials were carried out to study the effects of dietary supplementation of rumen-protected methionine (RPM) on nutrient digestibility, nitrogen (N) metabolism (Trial 1), and consequently the nitrous oxide (N₂ O) emissions from urine in beef cattle (Trial 2). Eight 24-month-old castrated Simmental bulls with liveweights of 494 ± 28 kg, and four levels of dietary supplementation of RPM at 0, 10, 20, and 30 g head^-1 d^-1 , were allocated in a replicated 4 × 4 Latin square for Trial 1 and the N₂ O emissions from the urine samples collected in Trial 1 were measured using a static incubation technique in Trial 2.

RESULTS

Supplementation of RPM at 0, 10, 20, and 30 g head^-1 d^-1 to a basal ration deficient in methionine (Met) did not affect the apparent digestibility of dry matter, organic matter, neutral detergent fiber, or acid detergent fiber (P > 0.05), but decreased the urinary excretions of total N (P < 0.05) and urea (P < 0.001), increased the ratio of N retention / digested N (P < 0.05) in beef cattle, and decreased the estimated cattle urine N₂ O-N emissions by 19.5%, 23.4%, and 32.6%, respectively (P < 0.001).

CONCLUSION

Supplementation of RPM to Met-deficient rations was effective in improving the utilization rate of dietary N and decreasing the N₂ O emissions from urine in beef cattle. © 2019 Society of Chemical Industry.

Effects of a novel heat-treated protein and carbohydrate supplement on feed consumption, milk production, and cheese yield in early-lactation dairy cows

Protein is an expensive component of the dairy cow diet, and overfeeding protein can have adverse economic and environmental impacts. Our objective was to maintain milk production and components while decreasing dietary crude protein (CP) through use of a heat-treated, rumen-resistant sugar amino acid complex (SAAC) as the Schiff base, as an addition to low-protein diets. Dietary treatments included a negative control [NC, 146 g of CP/kg of dry matter (DM)], a positive control (PC, 163 g of CP/kg of DM), and the NC supplemented with SAAC in lieu of some barley grain (SAAD, 151 g of CP/kg of DM). Diets were fed to 30 multiparous Holstein-Friesian dairy cows for the first 50 d postpartum. Dry matter intake (DMI) was determined daily. Milk yield and content of fat, protein, lactose, and casein were recorded weekly from wk 2 to 7 of lactation. The fixed effects of treatment, week, treatment × week, month of calving, and BCS at calving, and a random effect of cow, were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). The SAAD treatment had greater energy-corrected milk yield than did NC. The PC treatment had greater DMI than did NC, and SAAD tended to have greater DMI than did NC. We found significant treatment effects for fat percentage and yield. The NC and SAAD treatments had higher fat percentages than did PC, and SAAD had a higher fat yield than did the NC and PC treatments. Treatment effects were found for casein yield and percentage. We discovered a treatment effect for protein percentage and yield. The PC treatment had higher protein percentage than did NC and SAAD. The PC treatment had a higher protein yield than did NC, and analysis revealed no difference in protein yield between PC and SAAD. The SAAD treatment had higher total milk solids than did the NC treatment. Lactose yield tended to be higher in PC than in NC, and no differences were found between PC and NC and SAAD treatments. The PC treatment had a higher casein percentage than did NC and SAAD; however, the SAAD and PC treatments had higher casein yields than did NC. The PC treatment had a higher casein:fat ratio than did the NC and SAAD treatments. The NC and SAAD treatments had higher Cheddar cheese yields than did PC. We found no treatment × week interactions for any parameter. Supplementing low-protein dairy cow diets with a heat-treated, rumen-resistant SAAC caused beneficial effects by improving milk components and increasing cheese yield to levels similar to those found when feeding expensive and environmentally damaging high-protein diets.

Feeding diets varying in forage proportion and particle length to lactating dairy cows: II. Effects on duodenal flows and intestinal digestibility of amino acids

A study was conducted to evaluate the effects of forage-to-concentrate (F:C) ratio and forage particle length (FPL) on intake, duodenal flow, and digestibility of individual AA in the intestine of lactating dairy cows. The experiment was designed as a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments using 4 lactating dairy cows (parity 2) with ruminal and duodenal cannulas. Low (35:65) and high (60:40) F:C ratios (dry matter basis) were combined with 2 FPL of alfalfa silage (short vs. long; 7.9 vs. 19.1 mm). Few interactions between F:C and FPL for duodenal flow and intestinal digestibility of AA occurred, but interactions were detected for intakes of several AA. Intake of essential AA and nonessential AA decreased with increasing F:C, and the intake of several individual AA increased or decreased with increasing FPL. Increasing F:C decreased duodenal flows of essential AA, nonessential AA, and microbial AA due to consistent decreased flows of most individual AA (except Glu). Degradability of most individual AA in the rumen was not affected by F:C ratio or FPL except that the degradability of His was greater with high than low F:C diets, and the degradability of Ser was greater with long versus short FPL diets. However, the degradability of individual AA within diet varied considerably. Overall, F:C ratio and FPL did not affect intestinal digestibility of AA and rumen undegradable protein AA, whereas the digestibility of individual AA in the intestine varied considerably regardless of dietary treatment. These results indicate that increasing F:C ratio decreased AA supply due to decreased flow of AA to the duodenum but altering FPL did not affect AA supply. The results also revealed the necessity to consider both the flows and digestibility of individual AA when optimizing ration formulation to meet AA requirements of dairy cows.

Methionine increases yolk production to offset the negative effect of caloric restriction on reproduction without affecting longevity in C. elegans

Caloric restriction (CR) or Dietary restriction (DR) is known to improve health and in many cases increases lifespan. However, its negative effect on reproduction has not been fully studied. Practicing CR/DR without adequate knowledge on its side effect may risk complications such as infertility, birth defect, or malnutrition. In this study, by using several CR strategies in C. elegans, we examine key functions of reproduction including embryonic development and larvae growth. We find that CR significantly decreases the survival of embryos and slows the growth of the offspring. We further determine that defect in oocyte but not sperm is responsible for the compromised reproduction under CR. Interestingly, adding methionine to the medium reverses the reproduction defects, but does not affect the long lifespan resulted from CR. The beneficial effect of methionine on reproduction requires the yolk protein vitellogenin. CR down-regulates vitellogenin expression, which can be reversed by supplementing methionine in the food. Lacking the yolk protein transport due to rme-2 mutation blocks methionine’s beneficial effects. Our study has revealed a novel, methionine-mediated genetic pathway linking nutrient sensing to reproduction and suggested methionine as a potential food supplement to mitigate the side effect of CR.

Effects of supplementing rumen-protected lysine and methionine during prepartum and postpartum periods on performance of dairy cows

An experiment was conducted to examine effects of prepartum, postpartum, or continuous prepartum and postpartum supply of rumen-protected lysine (RPLys) and rumen-protected methionine (RPMet) on performance and blood metabolites of transition cows. The experiment consisted of a prepartum (3 wk), postpartum (3 wk), and carryover (10 wk) period. Eighty-eight prepartum cows (36 primiparous and 52 multiparous cows) were blocked by parity and expected calving date and assigned to 1 of 4 treatments arranged factorially. Treatments were a prepartum diet (12% crude protein on a dry matter basis) without (Pre-) or with supplemental RPLys (10 g of digestible Lys/cow per day) and RPMet (4 g of digestible Met/cow per day; Pre+) followed by postpartum diets (16% crude protein on a dry matter basis) without (Post-) or with supplemental RPLys (26 g of digestible Lys/cow per day) and RPMet (11 g of digestible Met/cow per day; Post+). Prepartum, only 2 treatments were applied, but postpartum cows received treatments of Pre-Post-, Pre-Post+, Pre+Post-, or Pre+Post+. During the prepartum period, treatment did not affect dry matter intake and body weight. During the postpartum period, milk protein content was greater (3.23 vs. 3.11%) for Post+ compared with Post- independent of prepartum treatment. However, dry matter intake, body weight, milk yield, and yields of milk components were not affected by Post+ versus Post-. No effects of prepartum treatment or interactions between pre- and postpartum treatments were observed on postpartum performance of cows. No effects of pre- and postpartum supplementation of RPLys and RPMet on performance during the carryover period were found except prepartum supplementation of RPLys and RPMet decreased somatic cell count (4.60 vs. 4.83; log₁₀ transformed) compared with Pre- in the postpartum period and this effect continued during the carryover period [i.e., 4.42 and 4.55 (log₁₀ transformed) for Pre+ and Pre-, respectively]. Prepartum supplementation of RPLys and RPMet increased or tended to increase plasma concentration of Lys, Met, and branched-chain AA compared with Pre- in prepartum cows. Cows on Post+ tended to have greater plasma Lys concentration compared with Post-, but plasma Met concentration was not affected. Health events of postpartum cows were not affected by treatments. In conclusion, we did not observe positive effects of supplementing with RPLys and RPMet on performance of prepartum and postpartum cows. However, prepartum supply of RPLys and RPMet may have potential to improve udder health and immune status of fresh cows.

Beneficial effects of rumen-protected methionine on nitrogen-use efficiency, histological parameters, productivity and reproductive performance of ruminants

Providing essential amounts of balanced nutrients is one of the most vital aspects of livestock production. Among nutrients, protein has an essential role in many physiological functions of animals. Amino acids in needs for both high and medium yielding ruminant animals are not fully covered by microbial degraded feed sources in the rumen of animals, and they must be met by protecting the proteins from being broken down in the rumen; hence, the dietary supplementation of rumen-protected proteins (RPP), including mainly rumen-protected methionine (RPM), became imperative. Many researchers are interested in studying the role of (RPM) in ruminant animals concerning its effect on milk yield, growth performance, digestibility, dry matter intake and nitrogen utilization efficiency. Unfortunately, results obtained from several investigations regarding RPM indicated great fluctuation between its useful and useless effects in ruminant nutrition particularly during early and late lactation period; therefore, this review article may be helpful for ruminant farm owners when they decide to supplement RPM in animal's diet. Conclusively, supplementation of RPM often has a balanced positive influence, without any reported negative impact on milk yield, growth performance and blood parameters especially in early lactating ruminant animals and when used with the low crude protein diet.

Supplementing rumen-protected methionine to lactating multiparous dairy cows did not improve reproductive performance

There is evidence that supplementing methionine has positive effects on uterine environment, oocyte quality and embryo development in cattle. Thus, the objective of this study was to evaluate reproductive traits of cows supplemented with rumen‐protected methionine (RPM) during early to mid‐lactation in comparison with an untreated control group (CON). An additional focus was on the effect of puerperal diseases on reproductive performance parameters in RPM‐supplemented group MET and in CON. A total of 1,709 multiparous Holstein‐Friesian cows were enrolled in this field trial conducted on a commercial dairy farm in Slovakia. Cows were allocated at approximately 12 days post‐partum (dpp) to either CON or MET, the latter supplemented with 25.0 g–27.2 g RPM per cow per day incorporated into the total mixed ration (TMR) until leaving the study pen at approximately 140 dpp. The amount of RPM was calculated based on individual feed ingredients analysis and adjusted during the study period when TMR changed. Cows were monitored during the post‐partum period by vaginal examination (day 5 pp), measuring of beta‐hydroxybutyrate in blood (3, 5, and 8 dpp) and by vaginal examination, uterine cytology and measuring of back fat thickness by ultrasound (all at 31 ± 3 dpp).

Compared with CON, cows supplemented with RPM did not show better reproduction performance parameters (first service submission rate, days to first service, conception risk, days open 140). Results from binary logistic regression model for the risk of conception showed that metritis had a significant effect, but the supplementation of methionine had not. Results of Cox regression analysis for the odds of conception within 140 dpp revealed only metritis and clinical endometritis as significant factors. In conclusion, supplementation of RPM had no beneficial effect on reproductive performance in this study farm compared with an untreated control group.