Meta-analysis to predict the effects of metabolizable amino acids on dairy cattle performance

Abstract

Meta-analytic methods were used to determine statistical relationships between metabolizable AA supplies and milk protein yield, milk protein percentage, and milk yield in lactating dairy cows. Sixty-three research publications (258 treatment means) were identified through a search of published literature using 3 search engines and met the criteria for inclusion in this meta-analysis. The Cornell Net Carbohydrate and Protein System (CNCPS) version 6.5 was used to determine dietary nutrient parameters including metabolizable AA. Two approaches were used to analyze the data. First, mixed models were fitted to determine whether explanatory variables predicted responses. Each mixed model contained a global intercept, a random intercept for each experiment, and data were weighted by the inverse of the SEM squared. The second analysis approach used classical effect size meta-analytical evaluation of responses to treatment weighted by the inverse of the treatment variance and with a random effect of treatment nested within experiment. Regardless of the analytical approach, CNCPS-predicted metabolizable Met (g/d) was associated with milk protein percentage and yield. Milk yield was positively associated with CNCPS-predicted metabolizable His, Leu, Trp, Thr, and nonessential AA (g/d). Milk true protein yield was also associated with CNCPS-predicted metabolizable Leu (g/d). Predicted metabolizable Lysine (g/d) did not increase responses in production outcomes. However, mean metabolizable Lys supply was less than typically recommended and the change with treatment was minimal (157 vs. 162 g; 6.36 vs. 6.38% metabolizable protein). Experiments based solely on Lys or Met interventions were excluded from the study database. It is possible that the inclusion of these experiments may have provided additional insight into the effect of these AA on responses. This meta-analysis supports other research indicating a positive effect of Met and His as co-limiting AA in dairy cows and suggests Leu, Trp, and Thr be given greater consideration in future research.

Enhanced supply of methionine or arginine alters mechanistic target of rapamycin signaling proteins, messenger RNA, and microRNA abundance in heat-stressed bovine mammary epithelial cells in vitro

“…Supplementation of Met significantly improves milk protein percentage and yield in dairy cows (Zhou et al, 2017;Batistel et al, 2018;Lean et al, 2018). Furthermore, enhancing the supply of Met to cultured bovine mammary cells consistently upregulates mRNA abundance of CSN1S1, CSN1S2,CSN2,CSN3,LALBA,JAK2,STAT5, and MTOR, which reflects an increase in protein synthesis (Nan et al, 2014;Dong et al, 2018).…”

Phosphorylation of AKT serine/threonine kinase and abundance of milk protein synthesis gene networks in mammary tissue in response to supply of methionine in periparturient Holstein cows

“…These nutrients provide energy and the building blocks for the protein synthetic machinery, and AA themselves can serve as signaling molecules to regulate this process (Dong et al, 2018). The importance of proper dietary balancing of EAA, and Met in particular, for milk protein synthesis in dairy cows was recently underscored by a large meta-analysis of published data (Lean et al, 2018). However, despite substantial work on the regulation of milk protein synthesis, knowledge of the intracellular signaling networks and their connections is in its infancy (Cant et al, 2018).…”

Review: Epigenetics, developmental programming and nutrition in herbivores

“…In the recent literature, research has focused on adjusting nutritional recommendations for herbivores to adapt to global warming, reduce the C footprint of dairy cattle (Wilkinson and Garnsworthy, 2016) and enhance cow health, fertility and welfare (Sordillo, 2016;McGuffey, 2017;Lean et al, 2018).…”

“…Indeed, supplementation with carbohydrates in pregnant mares has been associated with increased osteoarticular pathology and impaired glucose homeostasis in offspring (Peugnet et al, 2016). In ruminants, diets high in dietary fibre reduce the proportion of methionine and lysine in the duodenum, important amino acids (AA) that have been considered the most limiting AA in North American diets for lactating cows (Lean et al, 2018).…”