The digestibility of amino acids in the small intestine of the sheep

Abstract

Present address: Drayton Experimental Husbandry Farm, Alcester Rd, Stratford upon Avon, Wanvickshire. 1. The digestibilities of microbial and food proteins in the small intestine were studied in three sheep fitted with reentrant cannulas in the proximal duodenum and terminal ileum.2. The quantities of microbial and food proteins at the small intestine were varied by infusion of a microbial isolate or by dietary manipulation and the balance of amino acids along the small intestine was determined. 3. A mean value of 0.69 for the apparent digestibility and 0.86 for the true digestibility of total amino acids was obtained. 4.From the composition of digesta at the duodenum the daily flows of microbial and food proteins were estimated. Their true digestibilities in the small intestine were calculated by regression and found to be: microbial protein 0.87 and food protein 0.82. The mean endogenous loss of amino acids secreted into the small intestine was estimated to be 13.3 g/d.Although there has been widespread interest in the synthesis of microbial protein in the stomachs of ruminants there have been few reports on the subsequent utilization of this protein source. In particular, there are few values for the true digestibility of microbial protein in the small intestine, one of the chief factors that determine its nutritional value to the host animal.Most investigators have used the digestibility of microbial cysteine as a measure of microbial protein digestibility, 3sS-labelled rumen bacteria being infused post-ruminally and the recovery of [3bS]cysteine in ileal digesta or in faeces measured. Bird (1972) was the first to use 36S for this purpose, estimating total organic non-reducible S which consisted chiefly of methionine and cysteine. Bird (1972) estimated digestibility between the abomasum and the faeces and reported the digestibility in sheep to be 0-74. Bird's (1972) experiment was of long duration which would have given s5S a chance to recycle and the results were

Studies on N-metabolism in different gastrointestinal sections of sheep using the digesta exchange technique. 2. Passage of endogenous nitrogen

“…In the ileum this fraction was only 19 to 22%) of the NAN, demonstrating the high digestibility of microbial N, on average 77%). This value is in agreement with numerous data from literature (Tas et al,1981;Storm et al, 1983;Hvelplund, 1985).…”

Supply of the dairy cow with amino acids from dietary protein

“…Estimates of true digestibility in the small intestine for amino acid nitrogen in bacterial protein have been obtained by Tas et al (1981), Storm et al (1983) and by infusing bacterial protein into the abomasum. The values obtained varied between 0.85 and 0.87.…”

“…Applying regression techniques, Tas et al (1981) reported a value of 0.82 for the true digestibility of undegraded amino acids passing to the duodenum of sheep fed a diet of grass and concentrates. measu shee red the increments in protein and amino acids passing the terminal ileum when different proteins, which had previously been exposed to some degradation in the rumen, were infused into the abomasum of sheep.…”

True Digestibility of Protein in the Small Intestine and the Hind Gut of Cows Measured with the Mobile Bag Technique using15N-Labelled Roughage

“…While amino acid absorption in the caecum-colon is generally of minor importance (Ulyatt et al, 1975), protein degradation can be substantial if degradable protein is available in this section of the gut (Ulyatt et al, 1975;Varvikko & Vanhatalo, 1990). Recent in vivo studies have focused on digestion in the small intestine between the proximal duodenum and the terminal ileum (Tas et al, 1981;Storm et al, 1983;Hvelplund, 1985;Hvelplund, 1987). The mobile bag technique with the insertion of bags in the duodenum and faecal recovery is an alternative to in vivo methods for estimating postgastric digestion (Hvelplund, 1985;Voight et al, 1985;Varvikko & Vanhatalo, 1990;Todorov & Girginov, 1991;Hvelplund et al, 1992).…”