Protein Feeding and Balancing for Amino Acids in Lactating Dairy Cattle.
Patton, R.A., Hristov, A.N., and Lapierre, H. (2014). "Protein Feeding and Balancing for Amino Acids in Lactating Dairy Cattle.", Veterinary Clinics of North America: Food Animal Practice, 30(3), pp. 599-621. doi : 10.1016/j.cvfa.2014.07.005 Access to full text
Key points: • Amino acid (AA) nutrition of the dairy cow is complicated because of feeding 2 systems at the same time: one microbial and one mammalian. • The cow must detoxify ammonia to urea; excess urea is secreted in urine. • Several nutrition models can predict duodenal flow of protein and essential AA (EAA) with reasonable accuracy as well as the digestible flow of individual EAA leading to a prediction of metabolizable protein (MP). • Metabolism of absorbed AA still has not been well characterized. • All EAA can become limiting depending on the diet, but lysine, methionine, histidine, and leucine have been the most studied. • Requirements for MP and AA for the lactating dairy cow have also not been well defined. • Balancing for MP and AA should allow feeding of lower protein rations resulting in greater milk nitrogen efficiency and less environmental impact. • AA balance for dairy cattle is still an evolving science.
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