Effect of Abomasally Infused Nitrogen Sources on Nitrogen Retention of Growing Lambs

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Abstract
A study involving a series of abomasal infusions was conducted to evaluate the amino acid nutritional status of lambs fed a purified diet with urea as the sole nitrogen source. When the diet was fed ad libitum the abomasal administration of casein resulted in an increase in feed consumption and an increase in nitrogen retention. When feed intake was controlled, abomasal infusion of casein increased nitrogen retention. Abomasal infusion of acid-hydrolyzed casein or a mixture of essential L-amino acids also increased nitrogen retention, but to a lesser extent than when casein was infused. When a mixture of arginine, histidine, lysine, phenylalanine and methionine was infused nitrogen retention increased, but the response was less than that observed from infusion of all 10 essential amino acids. Infusion of methionine or phenylalanine did not result in a statistically significant nitrogen retention response. In contrast, infusion of either lysine or glutamic acid increased nitrogen retention by the same magnitude as that of the mixture of the five amino acids.