Intraruminal Urea Infusion and Abomasal Amino Acid Passage

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Abstract
Urea was continuously infused intraruminally into growing wether lambs meal-fed a high-energy diet. Nitrogen balance was slightly improved over the basal 1.4% nitrogen (N) corn grain based diet when urea was infused to provide 1.9% N on a dry matter basis. Further addition of 17 or 30 g urea to provide 2.2 or 3.0% N diets depressed N retention. Postruminal dry matter disappearance and total digestibility increased slightly with a low level of added urea, but entry rates of total and essential amino acids into the abomasum were not markedly changed with urea infusions. Although considerable rearrangement of dietary amino acids was evident, the quantity of amino acids traversing the abomasum correlated well with previous reports and estimates. Abomasal entry rate of most amino acids was influenced by post-prandial time interval, peaking 4 to 7 hr. post-feeding. Comparison of abomasal supply with amino acid requirements of sheep estimated by equating with swine needs or by factorialization of amino acid uses for various functions indicated that amino acids containing sulfur were least adequate relative to need among the amino acids. Lysine, valine, threonine and isoleucine, in this order, may become the next limiting amino acids for lambs with rapid growth rates. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.

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