Amino acids(AAs) are nutrients primarily responsible for protein synthesis. They play a crucial role in almost all tissues and participate in various metabolic pathways, even in small quantities (NASEM, 2021).
Supplementation of dairy cow diets with essential amino acids aims to meet needs and improve the amino acid balance when protein sources in the diet are insufficient. Effects on milk production, milk protein synthesis (BRAKE et al., 2013), cow weight gain, and immune response have been observed with supplementation (ABREU et al., 2023).
Among the essential amino acids that need to be supplemented in ruminants, lysine and methionine are the most restrictive and thus provide greater productive benefits with supplementation (SCHWAB; BRODERICK, 2017).
In this context, this article aims to summarize the main aspects of amino acid supplementation in the nutrition of dairy cattle.
PROTEINS
These are the main nitrogenous compounds present in the feeds offered in ruminant diets, varying in concentration levels and ruminal degradation. According to the National Research Council (NRC, 2001), proteins are macromolecules that differ in size, types, structure, and functions. They are composed of building units, amino acids, which are linked by peptide bonds and can be defined in Nitrogen X 6.25, amounting to 16g of nitrogen in 100g of true protein.
Protein can be divided into two fractions:
a) rumen-degradable protein (RDP) and
b) rumen-undegradable protein (RUP)
The degradation of CP occurs through the action of enzymes (proteases, peptidases, and deaminases) secreted by ruminal bacteria, which degrade the RDP fraction of CP into amino acids, peptides, and ammonia for their own consumption, such as microbial protein synthesis and cell multiplication (NRC 1996; NRC, 2001).
RUMEN DEGRADABLE PROTEIN (RDP)
It is the fraction of CP utilized by the consumption of microorganisms in the rumen. In this degradation process, RDP undergoes the action of various enzymes secreted by ruminal microorganisms, including proteases, peptidases, and deaminases, which use amino acids, peptides, and ammonia to carry out the process of cell multiplication to synthesize MicP (MABJEESH et al., 1997; MARINO, 2015).
RUMEN UNDEGRADABLE PROTEIN (RUP)
Also known as “bypass” protein, is the fraction of protein that “escapes” ruminal degradation, either due to low degradability of the feed or because it has undergone some form of treatment (MCDONALD et al., 2012)...
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