ORIGINAL ARTICLE: The effect of dietary methionine levels on endogenous nitrogen and endogenous amino acids flows in growing goats

Abstract

The effect of dietary methionine (Met) levels on endogenous N and amino acids (AA) flows at different part of the digestive tract of growing goats was determined using a (15)N isotope dilution technique. Three goats (25 ± 2.5 kg) were fitted with the ruminal, duodenal and ileal cannulae and allocated to three dietary treatments in a 3 × 3 Latin square design. The dietary treatments consisted of a total mixed ration containing three levels of Met (0.15%, 0.25% and 0.35%) respectively. It was found that at 0.15% Met level, the lowest flow in endogenous N and total AA at the duodenum and ileum occurred. The endogenous N secretion contributed to 26% and 23% of the duodenal and ileal total N flows, respectively, and the proportions were not affected by the dietary Met levels. The duodenal and ileal flows of endogenous total AA were 11.1, 11.8, 11.3 g/d and 2.9, 3.9, 4.1 g/d respectively. The average real digestibility of N was 65%, 87% and 95% in the forestomach, intestine and whole digestive tract respectively.

Effect of dietary dry matter intake on endogenous nitrogen flows in growing lambs

“…In this experiment, the enrichments in TCA‐soluble plasma and urine were the highest, followed by faeces, ileal and duodenal digesta, while the isolated rumen bacteria was the least, the values were higher for the more distal samples taken within the GIT, and this result was in agreement with that of goats (Zhou et al., ) and pigs (De Lange et al., ), but contrary to observations reported in dairy cow (Ouellet et al., ; Lapierre et al., ). These discrepancies might be due in part to an additional excreting route for 15 N through milk for lactating animal than non‐lactating animals.…”

“…These research works have contributed towards a limited understanding of dietary effects on EN or AA losses. By far, the stable isotope dilution method has been accepted by most researchers to determine the EN losses in animals owing to its unique characteristics of distinction between feed‐derived and EN (Ouellet et al., , ; Lapierre et al., ; Zhou et al., ).…”