Dietary protein reduction on microbial protein, amino acid digestibility, and body retention in beef cattle: 2. Amino acid intestinal absorption and their efficiency for whole-body deposition

Abstract

The objective of this study was to determine the apparent and true intestinal digestibility of total and individual AA, and to estimate the efficiency of whole-body AA retention from individual and total absorbed AA. Four Nellore animals (241.3 kg initial BW) and four crossbred Angus × Nellore (263.4 kg initial BW) cannulated in rumen and ileum were randomly allocated in two 4 × 4 Latin squares. The experiment lasted four 17 d periods, with 10 d for adaptation to diets and another 7 d for data collection. The diets consisted of increasing CP levels: 100, 120, or 140 g/kg of DM offered ad libitum, and restricted intake diet with 120 g CP/kg DM (experiment 1). In experiment 2, forty-four bulls (22 Nellore and 22 crossbred F1 Angus × Nellore) with 8 months and initial shrunk BW 215.0 ± 15.0 kg (Nellore = 208.0 ± 12.78 kg; Angus × Nellore = 221.9 ± 14.16 kg) were used. Eight of those animals were slaughtered at the beginning of the experiment. The remaining 36 bulls were allocated in a completely randomized design with six replicates, in a 2 (genetic groups) × 3 (CP contents) factorial scheme. The amount of essential AA (EAA) and nonessential AA (NEAA) reaching the small intestine increased linearly (P < 0.05) in response to CP content. The apparent digestibility of EAA was not affected (P > 0.05) by CP content, with exception for histidine (P = 0.07, linear effect), leucine (P = 0.01, linear effect), and methionine (P = 0.05, linear effect). Differences existed among AA when compared the apparent digestibility of NEAA. The apparent digestibility of alanine (P = 0.05), aspartic acid (P = 0.07), glutamic acid (P = 0.02), glycine (P = 0.05), proline (P = 0.02), and serine (P = 0.04) responded quadratically to CP content increase. However, the apparent digestibility of cystine and tyrosine was not affected (P > 0.05) by increasing dietary CP. The true intestinal digestibilities of total, essential, nonessential AA, lysine, and methionine were 75.0%, 77.0%, 74.0%, 77.0%, and 86%, respectively. The true intestinal digestibility of total microbial AA was 80%. The efficiency of utilization of total AA for whole-body protein deposition was 40%. The efficiency of utilization of lysine and methionine was 37% and 58%, respectively. It was concluded that the AA flow to the omasum increases in response to dietary CP content. In addition, there are differences among AA in the efficiency that they are used by beef cattle.

Dynamic alterations in rumen bacterial community and metabolome characteristics in response to feed nutrient levels of cashmere goats

“…The main metabolites were amino acids, peptides and analogues in this study, which was consistent with the previous reports [43,60]. Amino acids in the rumen are the key precursors for protein and polypeptides synthesis and are mainly obtained from the dietary proteins and microproteins [61].…”

Dynamic Alterations in Yak Rumen Bacteria Community and Metabolome Characteristics in Response to Feed Type

“…We found that the feed type significantly altered the concentration of most metabolites associated with protein digestion and absorption as well as biosynthesis of amino acids. In the rumen, amino acids, which are key precursors for the synthesis of proteins and polypeptides, regulate some metabolic pathways and are mainly derived from the degradation of dietary proteins and microproteins by the ruminal microbiota (Mariz et al, 2018). In the concentrate group, we observed increased levels of L-phenylalanine and L-tyrosine, both of which have specific characteristics that make them useful as markers of protein metabolism.…”

“…In most rumen microorganisms, a significant amount of L-methionine is synthesized from glucose, inorganic sulfur and homocysteine. In addition, L-methionine also plays important roles in rumen bacteria cell protein synthesis and regulation of the mucosal response to antigens (Or-Rashid et al, 2001; Sakkas et al, 2012; Firkins et al, 2015; Mariz et al, 2018). In the present study, we also observed increased levels of L-DOPA, which is a non-protein amino acid with strong allelopathic activity and a precursor of dopamine and sulpiride as well as a D2-type DA receptor blocker.…”

Alterations in Rumen Bacterial Community and Metabolome Characteristics of Cashmere Goats in Response to Dietary Nutrient Density

“…The main metabolites were amino acids, peptides, and analogues in this study, which was consistent with the previous reports [ 38 , 53 ]. Amino acids in the rumen are the key precursors for protein and polypeptides synthesis and are mainly obtained from the dietary proteins and microproteins [ 54 ].…”