Effects of dietary forage sources on rumen microbial protein synthesis and milk performance in early lactating dairy cows

Complementary transcriptomic and proteomic analyses reveal regulatory mechanisms of milk protein production in dairy cows consuming different forages

Forage plays a critical role in the milk production of dairy cows; however, the mechanisms regulating bovine milk synthesis in dairy cows fed high forage rations with different basal forage types are not well-understood. In the study, rice straw (RS, low-quality) and alfalfa hay (AH, high-quality) diets were fed to lactating cows to explore how forage quality affected the molecular mechanisms regulating milk production using RNA-seq transcriptomic method with iTRAQ proteomic technique. A total of 554 transcripts (423 increased and 131 decreased) and 517 proteins (231 up-regulated and 286 down-regulated) were differentially expressed in the mammary glands of the two groups. The correlation analysis demonstrated seven proteins (six up-regulated and one down-regulated) had consistent mRNA expression. Functional analysis of the differentially expressed transcripts/proteins suggested that enhanced capacity for energy and fatty acid metabolism, increased protein degradation, reduced protein synthesis, decreased amino acid metabolism and depressed cell growth were related to RS consumption. The results indicated cows consuming RS diets may have had depressed milk protein synthesis because these animals had decreased capacity for protein synthesis, enhanced proteolysis, inefficient energy generation and reduced cell growth. Additional work evaluating RS- and AH-based rations may help better isolate molecular adaptations to low nutrient availability during lactation.

Biomarker and pathway analyses of urine metabolomics in dairy cows when corn stover replaces alfalfa hay

BACKGROUND

Alfalfa hay and corn stover are different type of forages which can significantly impact a cow's lactation performance, but the underlying metabolic mechanism has been poorly studied. We used biomarker and pathway analyses to characterize related biomarkers and pathways based on urine metabolomics data from different forage treatments. Urine was collected from 16 multiparous Holstein dairy cows fed alfalfa hay (AH, high-quality forage, n = 8) and corn stover (CS, low-quality forage, n = 8) respectively. Gas chromatography-time of flight/mass spectrometry (GC-TOF/MS) was performed to identify metabolites in urine and the metaboanalyst online platform was used to do biomarker and pathway analysis.

RESULTS

Hippuric acid (HUA) and N-methyl-glutamic (NML-Glu) indicated the most significant difference between the two diets, when statistically validated by biomarker analysis. HUA was also validated by standard compound quantitative method and showed significant higher concentration in CS group than AH group (2.8282 vs. 0.0005 mg/mL; P < 0.01). The significant negative correlation between milk yield and HUA (R(2) = 0.459; P < 0.01) and significant positive correlation between milk yield and NML-Glu (R(2) = 0.652; P < 0.01) were characterized. The pathway analysis revealed that these different metabolites were involved in 17 pathways including 7 influential pathways (pathway impact value > 0): Tyr metabolism, starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism, galactose metabolism, Phe, Tyr and Try biosynthesis, purine metabolism, and glycerolipid metabolism. Based on the metabolome view map, the Phe, Tyr and Try biosynthesis pathway exhibited the highest impact value (0.50), and the Holm-Bonferroni multiple testing-based analysis revealed the most significant difference in the Tyr metabolism pathway (Holm P = 0.048).

CONCLUSIONS

The identified HUA and NML-Glu may serve as potential biomarkers for discriminating CS and AH diets and could be used as candidates for milk yield related mechanistic investigations. Integrated network pathways associated with related metabolites provide a helpful perspective for discovering the effectiveness of forage quality in lactation performance and provides novel insights into developing strategies for better utilization of CS and other low-quality forage in China.

Milk fatty acids profiles and milk production from dairy cows fed different forage quality diets

Thirty lactating Holstein cows were used to investigate the effects of different forages quality on milk fatty acids (FA) profiles and production. The cows were assigned to 3 dietary treatments (n = 10 per treatment) in a randomized block design with 3 repeated measures. They were fed the experimental diets for 90 d with 3 days of collection of samples for analysis at about 27 d intervals (samples were collected on days 28, 29, 30, 58, 59, 60, 88, 89 and 90). The treatments were (DM basis): 1) mixed forages diet (MF) consisting of 3.7% Chinese wild rye, 26.7% corn silage and 23.4% alfalfa hay; 2) corn stalk diet 1 (CS1) where corn stalk was used to formulate a similar chemical nutrient level to MF; 3) corn stalk diet 2 (CS2) which used corn stalk to formulate a similar forage level to MF for the diet. Dry matter intake and BW were similar between treatments, but daily milk yield, milk fat and protein yield decreased (P < 0.05) in CS1 and CS2 compared with MF, with CS2 being the lowest (P < 0.05). In total FA of milk, the compositions of C18:1c9, C18:3 and unsaturated FA increased (P < 0.05) in CS1 and CS2 compared with MF, and C18:0 and trans-C18:1 were trended to increase (P < 0.10), but C4:0-C16:0 were decreased (P < 0.05). Compared with cows fed CS2, cows receiving CS1 increased the compositions of C4:0 to C12:0 and C18:2 (P < 0.05). The results suggests feeding corn stalk could produce a greater proportion of unsaturated fatty acid (UFA) in milk fat without resulting in milk fat depression (MFD) in mid lactation cows, but simply increasing the ratio of concentrate in low forages diets is not an effective way to increase milk fat synthesis and milk production.

Milk production and composition responds to dietary neutral detergent fiber and starch ratio in dairy cows

This study was designed to investigate whether dietary neutral detergent fiber (NDF) : starch ratio could be considered as a nutritional indicator to evaluate carbohydrate composition and manipulate milk production and composition synthesis. Eight primiparous dairy cows were assigned to four total mixed rations with NDF : starch ratios of 0.86, 1.18, 1.63 and 2.34 from T1 to T4 in a replicated 4 × 4 Latin square design. Dry matter intake and milk production were decreased from T1 to T4. Digestibility of dry matter, organic matter, NDF and crude protein were linearly decreased from T1 to T4. As NDF : starch ratio increased, milk protein content and production, and milk lactose content and production were linearly reduced. However, milk fat content was linearly increased from T1 to T4. Quadratic effect was observed on milk fat production with the highest level in T3. Averaged rumen pH was linearly increased from T1 to T4, and subacute rumen acidosis occurred in T1. Ruminal propionate and butyrate concentration were linearly decreased, and microbial crude protein and metabolizable protein decreased from T1 to T4. It is concluded that NDF : starch ratio can be considered as a potential indicator to evaluate dietary carbohydrate composition and manipulate milk production and composition synthesis.

Effects of replacing wild rye, corn silage, or corn grain with CaO-treated corn stover and dried distillers grains with solubles in lactating cow diets on performance, digestibility, and profitability

The objective of this study was to measure the effects of partially replacing wild rye (Leymus chinensis; WR), corn silage (CS), or corn grain (CG) in dairy cow diets with CaO-treated corn stover (T-CS) and corn dried distillers grains with soluble (DDGS) on performance, digestibility, blood metabolites, and income over feed cost. Thirty tonnes of air-dried corn stover was collected, ground, and mixed with 5% CaO. Sixty-four Holstein dairy cows were blocked based on days in milk, milk yield, and parity and were randomly assigned to 1 of 4 treatments. The treatments were (1) a diet containing 50% concentrate, 15% WR, 25% CS, and 10% alfalfa hay (CON); (2) 15% WR, 5% CG, and 6% soybean meal were replaced by 15% T-CS and 12% DDGS (RWR); (3) 12.5% CS, 6% CG, and 5% soybean meal were replaced by 12.5% T-CS and 12%DDGS (RCS); (4) 13% CG and 6% soybean meal were replaced by 7% T-CS and 13% DDGS (RCG). Compared with CON treatment, cows fed RCS and RCG diets had similar dry matter intake (CON: 18.2 ± 0.31 kg, RCS: 18.6 ± 0.31 kg, and RCG: 18.4 ± 0.40 kg). The RWR treatment tended to have lower dry matter intake than other treatments. The inclusion of T-CS and DDGS in treatment diets as a substitute for WR, CS, or CG had no effects on lactose percentage (CON: 4.96 ± 0.02%, RWR: 4.97 ± 0.02%, RCS: 4.96 ± 0.02%, and RCG: 4.94 ± 0.02%), 4% fat-corrected milk yield (CON: 22.7 ± 0.60 kg, RWR: 22.1 ± 0.60 kg, RCS: 22.7 ± 0.60 kg, and RCG: 22.7 ± 0.60 kg), milk fat yield (CON: 0.90 ± 0.03 kg, RWR: 0.86 ± 0.03 kg, RCS: 0.87 ± 0.03 kg, and RCG: 0.89 ± 0.03 kg), and milk protein yield (CON: 0.74 ± 0.02 kg, RWR: 0.72 ± 0.02 kg, RCS: 0.73 ± 0.02 kg, and RCG: 0.71 ± 0.02 kg). Cows fed the RWR diet had higher apparent dry matter digestibility (73.7 ± 1.30 vs. 70.2 ± 1.15, 69.9 ± 1.15, and 69.9 ± 1.15% for RWR vs. CON, RCS, and RCG, respectively) and lower serum urea N (3.55 ± 0.11 vs. 4.03 ± 0.11, 3.95 ± 0.11, and 3.99 ± 0.11 mmol/L for RWR vs. CON, RCS, and RCG, respectively) than cows fed other diets. No significant differences were noted in apparent neutral detergent fiber digestibility among the treatments. Compared with CON treatment, the RWR, RCS, and RCG treatments generated an additional $0.77, $0.70, and $0.81 income over feed cost per cow per day, respectively. In conclusion, feeding diets containing a portion of T-CS and DDGS can improve profitability of the treatment groups without negatively affecting the lactation performance of mid- to late-lactation cows.

New Primers Targeting Full-Length Ciliate 18S rRNA Genes and Evaluation of Dietary Effect on Rumen Ciliate Diversity in Dairy Cows

Analysis of the full-length 18S rRNA gene sequences of rumen ciliates is more reliable for taxonomical classification and diversity assessment than the analysis of partial hypervariable regions only. The objective of this study was to develop new oligonucleotide primers targeting the full-length 18S rRNA genes of rumen ciliates, and to evaluate the effect of different sources of dietary fiber (corn stover or a mixture of alfalfa hay and corn silage) and protein (mixed rapeseed, cottonseed, and/or soybean meals) on rumen ciliate diversity in dairy cows. Primers were designed based on a total of 137 previously reported ciliate 18S rRNA gene sequences. The 3'-terminal sequences of the newly designed primers, P.1747r_2, P.324f, and P.1651r, demonstrated >99% base coverage. Primer pair D (P.324f and P.1747r_2) was selected for the cloning and sequencing of ciliate 18S rRNA genes because it produced a 1423-bp amplicon, and did not amply the sequences of other eukaryotic species, such as yeast. The optimal species-level cutoff value for distinguishing between the operational taxonomic units of different ciliate species was 0.015. The phylogenetic analysis of full-length ciliate 18S rRNA gene sequences showed that distinct ciliate profiles were induced by the different sources of dietary fiber and protein. Dasytricha and Entodinium were the predominant genera in the ruminal fluid of dairy cattle, and Dasytricha was significantly more abundant in cows fed with corn stover than in cows fed with alfalfa hay and corn silage.

Effect of dietary energy source and level on nutrient digestibility, rumen microbial protein synthesis, and milk performance in lactating dairy cows

This study was conducted to examine the effects of dietary energy source and level on intake, digestion, rumen microbial protein synthesis, and milk production in lactating dairy cows, using corn stover as a forage source. Eight multiparous Holstein cows, 4 of which were fitted with rumen cannulas, were evaluated in a replicated 4 × 4 Latin square design, with each period lasting 21 d. The cows were randomly assigned into 4 treatment groups: low-energy (LE) ground corn (GC), LE steam-flaked corn (SFC), high-energy (HE) GC, and HE SFC. Changes to ruminal energy degradation rates were induced by feeding the cows diets of either finely ground corn or SFC as components of diets with the same total energy level. Milk yield, milk protein content and yield, and milk lactose yield all increased in response to higher levels of dietary energy, whereas contents of milk fat and lactose were unaffected. Cows fed HE diets had a higher crude microbial protein yield and total-tract apparent digestibility than those receiving LE diets. Milk yield, milk protein yield, and microbial protein yield were also higher when SFC replaced GC as the main energy source for lactating cows fed LE diets. These results suggest that an increased dietary energy level and ruminal degradation rate are beneficial to milk protein production, which we suggest is due to increased yields of microbial proteins, when cows are fed corn stover as a dietary forage source.

Effects of different model diets on milk composition and expression of genes related to fatty acid synthesis in the mammary gland of lactating dairy goats

This study examined the effects of different roughage diets on milk composition and the expression of key genes associated with fatty acid (FA) synthesis in the mammary gland of lactating dairy goats. Eight multiparous lactating goats (body weight=43.6±2.5kg, 90±12 d in milk) fitted with external pudic artery and subcutaneous abdominal vein catheters were assigned to 2 treatments in a crossover design. The goats were fed different roughage diets with a similar concentrate-to-roughage ratio. The diets were (1) a high-quality roughage treatment (HQR) containing 28.5% Chinese wildrye hay, 19% corn silage, 9.5% alfalfa, and 43% concentrate or (2) a low-quality roughage treatment (LQR) containing 28% Chinese wildrye hay, 28% corn stover, and 44% concentrate, on a dry matter basis. Each feeding period lasted 21 d. The first 18 d served as an adaptation period, and the last 3 d served as a sample collection period. Dry matter intake, milk yield, and milk composition were measured. Milk and blood samples were collected for FA analysis. Mammary gland biopsies were performed after milking on the last day of each period and the tissues were analyzed for the mRNA expression of acetyl-coenzyme A carboxylase-α (ACACA), FA synthase (FASN), stearoyl CoA desaturase (SCD), and lipoprotein lipase (LPL). Dry matter intake and milk yield were not affected by the treatments. Milk fat (3.16 vs. 2.96%) and protein (2.99 vs. 2.89%) contents were higher in HQR goats than in LQR goats, and milk fat yield tended to be higher in HQR goats (16.7 vs. 15.1g/d). Milk FA composition was not different between treatments, except for C18:3n-3 (0.27 vs. 0.15g/100g). Compared with LQR goats, HQR goats had a higher vein concentration of total FA (0.62 vs. 0.44mg/mL). In HQR goats, the mammary balance of total FA increased (9.17 vs. 5.51g/d), whereas the clearance rate of total FA decreased (103.03 vs. 138.25 L/d). No differences were found in mammary blood flow, artery concentration, and mammary uptake of FA between treatments. Compared with LQR, the expression of FASN and ACACA tended to be increased by 20 and 18%, and the expression of LPL and SCD were increased by 39 and 50% in HQR, respectively. The results demonstrated that diets with HQR can increase milk fat content and yield as well as the expression of LPL and SCD in the mammary gland of dairy goats.

Pectin induces an in vitro rumen microbial population shift attributed to the pectinolytic Treponema group

Pectin is a non-fiber carbohydrate (NFC) that exists in forages, but it is not clear how pectin exerts its effect on populations of either known microbial species or uncultured ruminal bacteria. PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR analysis were used in the present study to investigate the effects of pectin on microbial communities in an in vitro rumen fermentation system. The fermentations were conducted using forage (corn stover or alfalfa), an NFC source (pectin or corn starch), or their combination as the substrates. Addition of pectin increased acetate (P < 0.05), whereas inclusion of starch increased butyrate production (P < 0.05). The pectate lyase activity was higher with alfalfa than with corn straw, or with pectin than with corn starch (P < 0.05), while the amylase activity was higher in corn starch-included treatments than the others (P < 0.05). The cluster analysis of the bacterial 16S rRNA gene showed that the DGGE banding patterns differed significantly between the treatments and led to the identification of three groups that were highly associated with the NFC sources. The specific bands associated with pectin-rich treatments were identified to be dominated by members of the Treponema genus. The growth of the Treponema genus was remarkably supported by the inclusion of pectin, highlighting their specific ability to degrade pectin. The results from the present study expand our knowledge of the microbial populations associated with pectin digestion, which may not only facilitate future research on utilization of pectin in feeds, but also improve our understanding of pectin digestion with respect to the rumen micro-ecosystem.

Effects of forage sources on rumen fermentation characteristics, performance, and microbial protein synthesis in midlactation cows

Eight multiparous Holstein cows (632±12 kg BW; 135±16 DIM) were used in a replicated 4×4 Latin square design to evaluate the effects of forage sources on rumen fermentation characteristics, performance, and microbial protein (MCP) synthesis. The forage portion of the diets contained alfalfa hay (AH), oat hay (OH), Leymus chinensis (LC), or rice straw (RS) as the primary source of fiber. Diets were isonitrogenous and isocaloric, and cows were fed four corn silages based total mixed rations with equivalent nonfiber carbohydrate (NFC) and forage neutral detergent fiber (NDF). Dry matter intake was not affected by the source of dietary forages, ranging from 18.83 to 19.20 kg/d, consequently, milk yield was similar among diets. Because of the numerical differences in milk fat and milk protein concentrations, 4% FCM and ECM yields were unchanged (p>0.05). Mean rumen pH, NH₃-N content, and concentrations of volatile fatty acids in the rumen fluid were not affected by the treatments (p>0.05). Dietary treatments did not affect the total tract apparent digestibility of dry matter, organic matter, and crude protein (p>0.05); however, digestibility of NDF and acid detergent fiber in RS diet was higher compared with AH, OH, and LC diets (p<0.05). Total purine derivative excretion was higher in cows fed AH, OH, and LC diets compared with those fed RS diet (p<0.05), consequently, estimated MCP synthesis was 124.35 g/d higher in cows fed AH diet compared with those fed RS diet (p<0.05). The results indicated that cows fed AH, OH, LC, and RS diets with an equivalent forage NDF and NFC have no unfavourable effect on the ruminal fermentation and productive parameters.

Variations in protein and fat contents and their fractions in milk from two species fed different forages

This study aimed at determining the variations in milk constituents which could be varied by feed and animal species. To achieve this goal, two groups of homoparity Baladi cows and Egyptian buffaloes (n = 20 per species) were used. Each group was divided into two subgroups (n = 10): subgroup I received legume forage (Egyptian clover) and subgroup II received grass forage (sorghum forage). All experimental animals were fed the diet consisting of concentrate, forage and rice straw as 50, 25 and 25% of dry matter intake respectively. Milk samples were taken for analysis. The trial lasted until the 3rd month of parturition. The main results indicated that lactating cattle fed legume forage significantly (p ≤ 0.01) had more content of casein nitrogen (513 mg/100 ml milk), lower content of glutamic acid (23.56 g/100 g milk protein) and more content of cis-9, trans-11 18:2 conjugated linoleic acid (CLA) (0.77 g/100 g milk fat) compared with 433, 26.67 and 0.53, respectively, for cattle fed grass forage. With regard to the species effect, results showed that buffalo milk appeared to contain significantly higher (p ≤ 0.01) contents of casein nitrogen, phenylalanine, glutamic and arachidonic acid compared with cow's milk. However, the latter was significantly (p ≤ 0.01) more in the cis-9, trans-11CLA (0.59 g/100 g milk fat) than that in buffalo milk (0.47 g/100 g milk fat). The results revealed that not only forage type played a critical role in determining the variations of milk nitrogen distribution, milk amino acids and fatty acids but also animal species had a significant effect on these parameters.

Effect of dietary forage sources on rumen microbiota, rumen fermentation and biogenic amines in dairy cows

BACKGROUND

Fifteen lactating Holstein dairy cows were assigned to three diets in a 3 × 3 Latin square design to evaluate the effects of dietary forage sources on rumen microbiota, rumen fermentation and biogenic amines. Diets were isonitrogenous and isocaloric, with a forage/concentrate ratio of 45:55 (dry matter basis) but different main forage sources, namely cornstalk (CS), Leymus chinensis (LC) or alfalfa hay (AH).

RESULTS

Pyrosequencing of the V3-V6 hypervariable coding region of 16S rRNA revealed that the rumen microbiota was significantly affected by forage sources. AH feeding increased the proportion of genera Prevotella and Selenomonas compared with the CS diet, while CS feeding increased the proportion of genera Anaerotruncus, Papillibacter, Thermoactimoyces, Bacillus and Streptomyces compared with the LC or AH diet. AH and LC feeding both increased the propionate concentration compared with the CS diet. AH feeding decreased the concentrations of tyramine, putrescine and histamine compared with the LC diet.

CONCLUSION

These results indicate that a high proportion of alfalfa hay in the ration is beneficial for milk yield and a healthy and balanced rumen microbiota in lactating cattle. This can be attributed to the higher degradation of rumen organic matter and the more balanced carbohydrates and proteins for optimal rumen microbial growth.

High-throughput Methods Redefine the Rumen Microbiome and Its Relationship with Nutrition and Metabolism

Diversity in the forestomach microbiome is one of the key features of ruminant animals. The diverse microbial community adapts to a wide array of dietary feedstuffs and management strategies. Understanding rumen microbiome composition, adaptation, and function has global implications ranging from climatology to applied animal production. Classical knowledge of rumen microbiology was based on anaerobic, culture-dependent methods. Next-generation sequencing and other molecular techniques have uncovered novel features of the rumen microbiome. For instance, pyrosequencing of the 16S ribosomal RNA gene has revealed the taxonomic identity of bacteria and archaea to the genus level, and when complemented with barcoding adds multiple samples to a single run. Whole genome shotgun sequencing generates true metagenomic sequences to predict the functional capability of a microbiome, and can also be used to construct genomes of isolated organisms. Integration of high-throughput data describing the rumen microbiome with classic fermentation and animal performance parameters has produced meaningful advances and opened additional areas for study. In this review, we highlight recent studies of the rumen microbiome in the context of cattle production focusing on nutrition, rumen development, animal efficiency, and microbial function.

Monitoring the rumen pectinolytic bacteria Treponema saccharophilum using real-time PCR

Treponema saccharophilum is a pectinolytic bacterium isolated from the bovine rumen. The abundance of this bacterium has not been well determined, reflecting the lack of a reliable and accurate detection method. To develop a rapid method for monitoring T. saccharophilum, we performed pyrosequencing of genomic DNA isolated from rumen microbiota to explore the 16S rRNA gene sequences of T. saccharophilum candidates. Species-specific primers were designed based on fifteen sequences of partial 16S rRNA genes generated through pyrosequencing with 97% or higher similarity with T. saccharophilum DSM2985 along with sequence from type strain. The relative abundance of T. saccharophilum was quantified in both in vitro and in vivo rumen systems with varied pectin-containing forages using real-time PCR. There was a clear association of T. saccharophilum with alfalfa hay, which contains more pectin than Chinese wild rye hay or corn stover. The relative abundance of T. saccharophilum was as high as 0.58% in vivo, comparable with the population density of other common rumen bacteria. It is recognized that T. saccharophilum plays an important role in pectin digestion in the rumen.

Milk production performance of Friesian-Holstein cows fed diets containing Medicago sativa, Centrosema pubescens, or groundnut haulms (Arachis hypogaea)

To investigate the effect of feeding dairy cows diets containing lucerne hay, centrosema hay, and groundnut haulms (crop residue) on dry matter intake (DMI), milk yield, and milk composition, nine multiparous Friesian-Holstein cows in their mid-lactation stage were used in a 3 × 3 crossover design replicated three times. Dairy cows fed lucerne hay had significantly (p < 0.001) higher DMI than dairy cows fed centrosema hay. DMI for cows fed groundnut haulms and lucerne hay was not significantly different. Daily milk yield for dairy cows fed diet containing lucerne hay was significantly (p < 0.01) higher than that for dairy cows fed diets containing groundnut haulms or centrosema hay. Milk composition and body condition scores of the cows were not significantly affected by either lucerne hay, groundnut haulms, or centrosema hay. Overall, the results in this study indicated that feeding dairy cows diets containing lucerne hay increased milk yield.