I.Six 45 kg pigs with re-entrant ileal cannulas were used in two 3 x 3 Latin-square design experiments to study the site of absorption of protein and amino acids. Semi-purified diets containing soya-bean meal (SBM), rapeseed meal (RSM) or no protein source (protein-free) were offered at the rate of I kg dry matter/d.2. Flow-rates of ileal contents for 24 h collection periods, corrected for recovery of marker, were 3135, 3127 and 1243 ml (SE 390) for SBM, RSM and protein-free diets respectively.3. Amounts of dry matter digested in the small intestine were 730,669 and 809 g/d for SBM, RSM and protein-free diets respectively, all values being significantly different ( P < 0.001).4. Nitrogen intakes were 32'6,29'9 and 5.9g/d, and amounts digested in the small intestine were 25'7, 20.2 and 1.6 g/d for SBM, RSM and protein-free diets respectively, all values being significantly different (P < 0.001). Amounts digested in the large intestine were 2.6, 3.7 and 0.7 g/d. . Total amino acid intakes and amounts collected at the ileum and in the faeces were (g/d):SBM, 177,24 and 18; RSM, 149,~s and z z ; protein-free 3,9 and IZ. Digestibility in the small intestine was higher for SBM than RSM for seventeen of the eighteen amino acids estimated. Greater quantities of arginine, methionine, cystine and tyrosine were voided in the faeces than passed through the ileal cannulas for pigs receiving the SBM and RSM diets. For those receiving the protein-free diet this was true for each amino acid except proline.6. Significant differences were found between all diets in the concentration of some amino acids in ileal and faecal amino-N, and endogenous protein secretions did not mask the differences between diets.7. Differences in digestibility between SBM and RSM were greater at the ileum than in the faeces. Amino acid fermentation in the large intestine obscured or reduced differences between SBM and RSM.

I . Protein digestion in the gastro-intestinal tract of cattle receiving diets with either low or high content of maize was investigated. Digesta obtained from the duodenum and ileum were separated into three fractions; soluble, microbial and particulate, and the amino acid composition of the three fractions and that of the total digesta were determined. The proportion of particulate material digested in the intestine was less from the high-maize than from the lowmaize diet, but more of the particulate fraction entered the duodenum from the high-maize than from the low-maize diet, so the absolute amount of particulate fraction which was digested was greater for the high-maize diet.2. More protein was digested in the rumen from the low-maize diet (high-roughage) than from the other diet. Total digestion of protein from the low-maize diet was also higher.3. Although more protein from the high-maize than from the low-maize diet reached the duodenum, the protein from the low-maize diet was more digestible in the intestine, so the total amount of dietary protein digested in the intestine was the same for both rations.

No abstract