Rumen-protected Form Research Articles

Milk Production, Nutrient Utilization, and Endocrine Responses to Increased Postruminal Lysine and Methionine Supply in Dairy Cows

The effect of increased postruminal supply of lysine and methionine was investigated in a production trial involving 64 dairy cows in early lactation. Within each of two basal rations, based on either corn silage or grass silage, rations were either naturally deficient in lysine or fortified with 24g of lysine in a rumen-protected form and naturally deficient in methionine or fortified with 12g of methionine in a rumen-protected form. The data were analyzed separately for the four lysine and the four methionine treatment groups. Milk production, body weight gain, and plasma concentrations of insulin-like growth factor-I, bovine somatotropin, insulin, glucose, nonesterified fatty acids, and urea were monitored over a 12-wk period. Supplementation with protected methionine led to increases in milk fat and protein contents of 2.4 and 1.8 g/kg of milk, respectively. Supplementation with protected lysine or methionine numerically increased protein yield comparable to values reported in the literature, but the treatment effects were not statistically significant. Efficiency of utilization of absorbed amino acids for milk protein synthesis and efficiency of utilization of metabolizable energy for milk production were not significantly altered in response to increased postruminal lysine and methionine flow, but a numerically increased efficiency of utilization of total amino acids was observed. No significant effect of lysine or methionine supplementation was observed on endocrine parameters nor on plasma metabolite concentrations. However, across treatment groups, high milk yield was correlated with low plasma insulin-like growth factor-I concentrations (r = −0.44) and partially with low plasma nonesterified fatty acids concentration and insulin levels (r = −0.26), while body weight gain was negatively correlated (r = −0.33) with elevated plasma bovine somatotropin concentrations.

Effects of Alimet on Nutrient Digestibility, Bacterial Protein Synthesis, and Ruminal Disappearance During Continuous Culture

A dual effluent continuous culture system was used to investigate the effects of inclusion of Alimet (Novus International, Inc., St. Louis, MO) feed supplement [an 88% aqueous solution of dl, 2-hydroxy-4-(methylthio) butanoic acid (HMB)] in the diet on nutrient digestibility, bacterial protein synthesis and ruminal disappearance of HMB. Four fermenters were fed three times daily a basal diet that consisted of 50% grain mixture and 50% forage for 9 d. In experiment 1, four concentrations of HMB (0, 0.20, 0.77, and 1.43% DM basis) were added to the diet and fed to the fermenters twice daily. In experiment 2, two concentrations of dietary HMB (0 and 0.88% DM basis) were fed twice daily and evaluated with two solids retention times (16.7 vs. 25.0h) and two liquid dilution rates (0.15 vs. 0.125h–1). Increasing the amount of HMB in the diet did not affect nutrient digestibility, volatile fatty acid concentrations, or ruminal escape of HMB. Bacterial protein synthesis was improved with the addition of HMB during high and low retention times. The extent of HMB escaping ruminal degradation ranged from 21.6 to 43.2% and was highest at the lower retention time. It can be concluded that a fraction of HMB survives rumen microbial degradation and, therefore, provides a rumen-protected form of methionine at the same time that it improves bacterial protein synthesis.

Amino acid metabolism in ruminants

All animals require amino acids (AA) which are the building blocks of proteins required for optimal growth, reproduction, lactation, and maintenance. In ruminants, proteins and AA are first subject to microbial degradation in the rumen making it difficult to predict the quality and quantity of AA that are absorbed by the animal. In ruminants, absorbed AA comes from microbial protein synthesis in the rumen and from dietary amino acid sources that are undergraded in the rumen. Production of microbial protein alone is insufficient to supply adequate amounts of amino acids for optimal production. In cattle, methionine and lysine are generally the first limiting AA for production. Improving the quality of absorbable AA can be accomplished through several means. For example, feeds can be chosen whose proteins are relatively resistant to rumen degradation. However, this does not ensure overcoming the limiting AA. A better method would be to predict which AA were limiting and then to supply these AA in a rumen protected form. The future of understanding requirements of AA for ruminants will rely on the ability of models to accurately predict the need for supplemental AA.

The effect of protected methionine and lysine on milk production and composition on grass-silage based diets

Methionine and lysine have been shown to be the two amino acids most limiting for milk protein synthesis in lactating dairy cows. Many studies have shown positive effects of adding protected forms of methionine to cows on maize silage-based diets supplemented with soyabean meal. The aim of this study was to evaluate the effect on milk production and composition of adding protected methionine and lysine to cows fed a grass silage diet.24 Autumn-calved cows (2nd lactation or greater) were blocked into groups of 4 based on calving date and milk yield in the immediate pre-experimental week. Cows within each group were subjected to each of the following 4 treatments in a latin square design: (1) 7 kg of by-product concentrate per day (C), (2) C plus 4.8 g digestible methionine per day (3) C plus 4.8 g digestible methionine and 6.2 g digestible lysine per day (4) 7 kg of barley-soya concentrate + 7.7 g digestible methionine per day. Each period lasted 4 weeks and data from weeks 3 and 4 were used to compare treatment effects. The amino acids were supplied in a rumen protected form (SmartamineTM, RPAN Technology) and all figures relate to estimated intestinally digestible amino acids based on the French system of calculating digestible lysine and methionine. The cows received primary growth unwilted grass silage ad libitum (Oven Dry Matter 189 g/kg, in-vitro DMD 714 g/kg DM, Crude protein 160 g/kg DM, pH 3.9).

The effect of protected methionine and lysine on milk production and composition on grass-silage based diets

Methionine and lysine have been shown to be the two amino acids most limiting for milk protein synthesis in lactating dairy cows. Many studies have shown positive effects of adding protected forms of methionine to cows on maize silage-based diets supplemented with soyabean meal. The aim of this study was to evaluate the effect on milk production and composition of adding protected methionine and lysine to cows fed a grass silage diet.24 Autumn-calved cows (2nd lactation or greater) were blocked into groups of 4 based on calving date and milk yield in the immediate pre-experimental week. Cows within each group were subjected to each of the following 4 treatments in a latin square design: (1) 7 kg of by-product concentrate per day (C), (2) C plus 4.8 g digestible methionine per day (3) C plus 4.8 g digestible methionine and 6.2 g digestible lysine per day (4) 7 kg of barley-soya concentrate + 7.7 g digestible methionine per day. Each period lasted 4 weeks and data from weeks 3 and 4 were used to compare treatment effects. The amino acids were supplied in a rumen protected form (SmartamineTM, RPAN Technology) and all figures relate to estimated intestinally digestible amino acids based on the French system of calculating digestible lysine and methionine. The cows received primary growth unwilted grass silage ad libitum (Oven Dry Matter 189 g/kg, in-vitro DMD 714 g/kg DM, Crude protein 160 g/kg DM, pH 3.9).