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

Methionine and Leucine Promote mTOR Gene Transcription and Milk Synthesis in Mammary Epithelial Cells through the eEF1Bα-UBR5-ARID1A Signaling

Amino acids are essential for the activation of the mechanistic target of rapamycin (mTOR), but the corresponding molecular mechanism is not yet fully understood. We previously found that Met stimulated eukaryotic elongation factor α (eEF1Bα) nuclear localization in bovine mammary epithelial cells (MECs). Herein, we explored the role and molecular mechanism of eEF1Bα in methionine (Met)- and leucine (Leu)-stimulated mTOR gene transcription and milk synthesis in MECs. eEF1Bα knockdown decreased milk protein and fat synthesis, cell proliferation, and mTOR mRNA expression and phosphorylation, whereas eEF1Bα overexpression had the opposite effects. QE-MS analysis detected that eEF1Bα was phosphorylated at Ser106 in the nucleus and Met and Leu stimulated p-eEF1Bα nuclear localization. eEF1Bα knockdown abrogated the stimulation of Met and Leu by mTOR mRNA expression and phosphorylation, and this regulatory role was dependent on its phosphorylation. Akt knockdown blocked the stimulation of Met and Leu by eEF1Bα and p-eEF1Bα expression. ChIP-PCR detected that p-eEF1Bα bound only to the -548 to -793 nt site in the mTOR promoter, and ChIP-qPCR further detected that Met and Leu stimulated this binding. eEF1Bα mediated Met and Leu' stimulation on mTOR mRNA expression and phosphorylation through inducing AT-rich interaction domain 1A (ARID1A) ubiquitination degradation, and this process depended on eEF1Bα phosphorylation. p-eEF1Bα interacted with ARID1A and ubiquitin protein ligase E3 module N-recognition 5 (UBR5), and UBR5 knockdown rescued the decrease of the ARID1A protein level by eEF1Bα overexpression. Both eEF1Bα and p-eEF1Bα were highly expressed in mouse mammary gland tissues during the lactating period. In summary, we reveal that Met and Leu stimulate mTOR transcriptional activation and milk protein and fat synthesis in MECs through eEF1Bα-UBR5-ARID1A signaling.

Evaluation of different ratios of neutral detergent-soluble carbohydrate fractions on performance, ingestive behavior, and nitrogen balance in dairy goats

Cell components soluble in neutral detergent are a diverse group, both compositionally and nutritionally. The present study aimed to evaluate production responses, behavior (eating, ruminating, and idling), and nitrogen balance of dairy goats fed different ratios of neutral detergent-soluble carbohydrate fractions. Five multiparous Alpine does with mean ± SD initial body mass of 49.5 ± 7.9 kg and 60 days of lactation were randomly assigned in a 5 × 5 Latin square design. The treatments were the ratios of starch (starch associated with soluble sugar [StSS]) to neutral detergent-soluble fiber (NDSF) (StSS:NDSF): 0.89, 1.05, 1.24, 1.73, and 2.92. No effect was observed (P > 0.05) of StSS:NDSF on the intakes of neutral detergent fiber (NDF) and NDSC. However, DM intake showed a quadratic behavior (P = 0.049). The ingestive behavior was affected by StSS:NDSF linearly increased (P = 0.002) the feeding efficiency. The increase in StSS:NDSF caused a linear increase in fecal (P = 0.011), urinary (P < 0.001), and milk nitrogen excretion (P = 0.024). The increase in StSS:NDSF affected (P = 0.048) milk yield and net energy lactation (P = 0.036). In conclusion, dairy goats experience reduced dry matter intake and milk yield when subjected to high-NDSC diets, specifically those above 1.24 StSS:NDSF ratio. Elevated NDSC levels in the diets lead to decreased feeding time, whereas rumination remains unaffected. Nitrogen losses in goats increase linearly with high-NDSC diets, and a significant impact on nitrogen balance.

Genetics, environmental stress, and amino acid supplementation affect lactational performance via mTOR signaling pathway in bovine mammary epithelial cells

Mammary glands are known for their ability to convert nutrients present in the blood into milk contents. In cows, milk synthesis and the proliferation of cow mammary epithelial cells (CMECs) are regulated by various factors, including nutrients such as amino acids and glucose, hormones, and environmental stress. Amino acids, in particular, play a crucial role in regulating cell proliferation and casein synthesis in mammalian epithelial cells, apart from being building blocks for protein synthesis. Studies have shown that environmental factors, particularly heat stress, can negatively impact milk production performance in dairy cattle. The mammalian target of rapamycin complex 1 (mTORC1) pathway is considered the primary signaling pathway involved in regulating cell proliferation and milk protein and fat synthesis in cow mammary epithelial cells in response to amino acids and heat stress. Given the significant role played by the mTORC signaling pathway in milk synthesis and cell proliferation, this article briefly discusses the main regulatory genes, the impact of amino acids and heat stress on milk production performance, and the regulation of mTORC signaling pathway in cow mammary epithelial cells.

The Role of Protein Intake on the Total Milk Protein in Lead-Exposed Lactating Mothers

Protein is an essential macronutrient for the growth and development of infants. Protein levels in lactating mothers are dynamic and influenced by various factors, particularly the environment and maternal characteristics. Therefore, this study aimed to evaluate the complex correlation between maternal blood lead levels (BLLs), maternal diet, and total milk protein. The Kruskal-Wallis test was used to compare total milk protein in the three groups of lead exposure, while Spearman's correlation was used to assess the correlation between maternal diet, BLLs, and total milk protein. The multivariate analysis used multiple linear regression. The results showed that the median of maternal BLLs and total milk protein were 3.3 µg/dL and 1.07 g/dL, respectively. Maternal protein intake and current BMI had a positive correlation with total milk protein, while BLLs had a negative correlation. BLLs ≥ 5 μg/dL had the most significant impact on reducing the total milk protein (p = 0.032). However, increasing maternal protein intake can effectively maintain total milk protein levels in mothers with BLLs under 5 μg/dL (p < 0.001). It is crucial to measure BLLs in lactating mothers residing in areas exposed to lead because high maternal protein intake can only maintain total milk protein levels when the BLLs are <5 μg/dL.

The Impact of Biotechnologically Produced Lactobionic Acid in the Diet of Lactating Dairy Cows on Their Performance and Quality Traits of Milk

Dairy processing is one of the most polluting sectors of the food industry as it causes water pollution. Given considerable whey quantities obtained via traditional cheese and curd production methods, manufacturers worldwide are encountering challenges for its rational use. However, with the advancement in biotechnology, the sustainability of whey management can be fostered by applying microbial cultures for the bioconversion of whey components such as lactose to functional molecules. The present work was undertaken to demonstrate the potential utilization of whey for producing a fraction rich in lactobionic acid (Lba), which was further used in the dietary treatment of lactating dairy cows. The analysis utilizing high-performance liquid chromatography with refractive index (HPLC-RID) detection confirmed the abundance of Lba in biotechnologically processed whey, corresponding to 11.3 g L-1. The basic diet of two dairy cow groups involving nine animals, Holstein Black and White or Red breeds in each, was supplemented either with 1.0 kg sugar beet molasses (Group A) or 5.0 kg of the liquid fraction containing 56.5 g Lba (Group B). Overall, the use of Lba in the diet of dairy cows during the lactation period equal to molasses affected cows' performances and quality traits, especially fat composition. The observed values of urea content revealed that animals of Group B and, to a lesser extent, Group A received a sufficient amount of proteins, as the amount of urea in the milk decreased by 21.7% and 35.1%, respectively. After six months of the feeding trial, a significantly higher concentration of essential amino acids (AAs), i.e., isoleucine and valine, was observed in Group B. The percentage increase corresponded to 5.8% and 3.3%, respectively. A similar trend of increase was found for branched-chain AAs, indicating an increase of 2.4% compared with the initial value. Overall, the content of fatty acids (FAs) in milk samples was affected by feeding. Without reference to the decrease in individual FAs, the higher values of monounsaturated FAs (MUFAs) were achieved via the supplementation of lactating cows' diets with molasses. In contrast, the dietary inclusion of Lba in the diet promoted an increase in saturated FA (SFA) and polyunsaturated FA (PUFA) content in the milk after six months of the feeding trial.

Identification of Immune-Active Peptides in Casein Hydrolysates and Its Transport Mechanism on a Caco-2 Monolayer

In this study, we investigated the transport mechanism of immune-active peptide fragments isolated from casein gastrointestinal hydrolysates via a Caco-2 monolayer. The casein gastrointestinal hydrolysates could stimulate B-lymphocyte proliferation and reduce the TNF-α level. Then, we identified the bioactive peptide fragments derived from casein gastrointestinal hydrolysis using LC-MS/MS. Our results demonstrated that the transport mechanism of five immune-active peptides at the cell level was bypass transport. In addition, the majority of peptide RYPLGYL was transported through the monolayer cell membrane as an intact form for playing immune-active functions. The KHPIK and FFSDK were mainly degraded into small fragments, except for a small amount passing through Caco-2 cells in an entire form. Overall, these results suggested that casein or its immune-active peptides might play a role in regulation of the intestinal immune system.

Effect of a biosynthetic bacterial 6-phytase on the digestibility of phosphorus and phytate in midlactating dairy cows

The effect of a biosynthetic bacterial 6-phytase (PhyG) on the digestibility and excretion of crude protein (CP), phosphorus (P), and phytate-P (PP) in midlactating dairy cows was investigated. Thirty Holstein-Friesians were assigned to three treatments with 10 cows per treatment in a randomized block design. Cows were fed forage (grass and corn silage) provided ad libitum, and a concentrate (without added inorganic phosphate) administered separately in amounts individualized per cow according to milk production, supplemented with phytase according to treatment. The formulated forage-to-concentrate-ratio was ~65%:35%. Dietary treatments comprised the control diet (CON) and CON supplemented with 2,000 (PhyG2,000) or 5,000 (PhyG5,000) phytase units (FTU)/kg DM in the total diet. The experiment comprised an 18-d preperiod for the collection of data to facilitate the allocation of cows to the treatments, followed by a 19-d experimental period comprising a 14-d diet adaptation period and 5 d of twice daily feces collection. Fecal samples were analyzed for the determination of apparent total tract digestibility (ATTD) of chemical constituents in the diet. The ATTD of PP was 92.6% in CON suggesting a high but incomplete degradation of phytate by ruminal microbial phytases. Cows fed PhyG2,000 exhibited increased ATTD of CP and PP [68.4% (2.7% points above CON) and 95.1% (2.5% points above CON), respectively] whilst PhyG5,000 further increased ATTD PP and also increased ATTD P [54.1% (7.8% points above CON)]; ATTD of Ca tended to be increased in PhyG5,000 vs. CON. Linear dose-response relationships were observed for ATTD of DM, CP, P, Ca, and PP. In addition, fecal excretion of P, and PP linearly reduced and that of Ca and CP tended to linearly reduce with increasing PhyG dose level. No difference was observed for DM intake and milk composition was unaffected except for milk protein which tended to be higher in cows fed PhyG5,000 than CON. In summary, the addition of exogenous phytase at 2,000 FTU/kg or higher to diets of lactating dairy cows improved P, PP, Ca, and CP digestibility and reduced fecal excretion of P, PP, and CP in a dose-dependent manner.

Effects of L-arginine and arginine-arginine dipeptide on amino acids uptake and αS1-casein synthesis in bovine mammary epithelial cells

Arginine (Arg), as an important functional amino acids (AA), is essential for milk protein synthesis in lactating ruminants. Arg shares transporters with cationic and neutral AA in mammary epithelial cells. Therefore, competitive inhibition might exist among these AA in uptake by mammary epithelial cells. In this study, cultured bovine mammary epithelial cells (BMEC) were used as the model to investigate whether the availability of L-Arg (0.7, 1.4, 2.8, 5.6, and 11.2 mM) affects the uptake of other AA and if this related to αS1-casein synthesis, and whether Arginine-Arginine (Arg-Arg) substituting part of free L-Arg can alleviate competitive inhibition among Arg and other AA, so as to promote αS1-casein synthesis. Our results showed that 2.8 mM L-Arg generated the greatest positive effects on αS1-casein synthesis and the activation of mammalian target of rapamycin (mTOR) signaling pathway (P < 0.01). With L-Arg supply increasing from 0.7 to 11.2 mM, the net-uptake of other AA (except Glu and Ala) decreased linearly and quadratically (Plinear < 0.01; Pquadratic < 0.01). Compared with 2.8 mM, the net-uptake of essential amino acids (EAA) and total amino acids (TAA) were lower at 11.2 mM L-Arg group, while greater at 1.4 mM L-Arg group (P < 0.01). Arg-Arg dipeptide replacing 10% free L-Arg increased αS1-casein synthesis (P < 0.05), net-uptake of EAA and TAA, as well as phosphorylation level of mTOR and p70 ribosomal protein S6 kinase (P70S6K) and mRNA expression of oligopeptide transporter 2 (PepT2; P < 0.01). These observations suggested that the increased αS1-casein synthesis by 10% Arg-Arg dipeptide might be related to the increase of AA availability and the activation of mTOR signaling pathway in BMEC.

Effect of Methionine Analogues on Growth Performance, Serum Biochemical Parameters, Serum Free Amino Acids and Rumen Fermentation of Yaks

This experiment was conducted to investigate the effects of methionine analogues 2-hydroxy-4-methylthio butanoic acid isopropyl ester (HBMi) on growth performance, nutrient apparent digestibility, serum metabolite, serum free amino acids, and rumen fermentation parameters of yaks. Twenty-four male Maiwa yaks (252.79 ± 15.95 kg) were randomly allocated to four dietary treatments: basic diet (CON), or three HBMi (MetaSmart (MS); Adisseo Inc., Antony, France) supplementation treatments: MS1 (5 g), MS2 (10 g), and MS3 (15 g). The results showed that the increase in the supplemented MS levels linearly increased the average daily gain (p < 0.05), while the serum alkaline phosphatase activity and malondialdehyde content were increased when yaks were fed with 15 g/d MS (p < 0.05). The diet supplemented with MS linearly increased the percentages of glutamic acid and proline, and linearly or quadratically decreased the percentages of isoleucine, phenylalanine, and valine (p < 0.05). Furthermore, supplementation of 10 g/d and 15 g/d MS increased ruminal microbial crude protein (p < 0.05). The ratio of acetate to propionate in the MS2 group was lower than those in CON and MS1 groups (p < 0.05). In summary, a diet supplemented with 10 g/d MS could be an effective way to improve the growth performance of fattening yaks without negative effects.

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.