Protein kinase C (PKC) has been proposed to play an important role in the aetiology of colon cancer. Therefore, we investigated whether the amount and type of saturated fat could affect colonic PKC activity by modifying either mucosal phospholipid fatty acid composition or faecal diacylglycerol production. Male Wistar rats (n 13 per group) were fed on diets containing butter or coconut oil at energy levels of 10 % and 43 % for 4 weeks. The control group received a low-fat diet providing 10 % of energy from sunflowerseed oil. PKC activity was higher in the distal than the proximal colon but the quantity or type of fat did not alter PKC activity in either region of the colon. Saturated fats caused moderate changes in the fatty acid composition of caecal phospholipids, which were more obvious in the phosphatidylethanolamine than in the phosphatidylcholine fraction. A significant correlation was found between fatty acid composition of phosphatidylcholine and membrane PKC activity. In particular, there was a positive correlation between the proportion of saturated 14:0 and 18:0 and increased PKC activity while unsaturated 18:2n-6, 20:4n-6 and 16:1n-7 were inversely correlated with PKC activity. No relationship was found between phosphatidylethanolamine fatty acids and PKC activity. Concentration of faecal diacylglycerol was not affected by the diet. Overall the data suggest that diets high in saturated fat may not alter colonic PKC activity to a significant extent.

Two experiments were performed with post-valve T-cannulated growing pigs, using five animals in each experiment in a change-over design to evaluate the effect of inclusion of four different dried forage meals on ileal crude protein (CP) and amino acid (AA) digestibilities. The control diets (C1 and C2) were barley-based and the experimental diets were formulated by replacing the barley with 100 or 200 g/kg of either lucerne (Medicago sativa) or white clover (Trifolium repens) meal in Expt 1 and red clover (Trifolium pratense) or perennial ryegrass (Lolium perenne) meal in Expt 2. A decrease (P < 0·05) in the apparent ileal digestibility of CP and most of the essential and nonessential AA was found with the inclusion of lucerne, white clover and perennial ryegrass meal in the barley-based diets. When red clover meal was included, only the apparent ileal digestibilities of CP, leucine, phenylalanine, tyrosine and glutamic acid were found to decrease (P < 0·05). The estimated apparent ileal digestibilities of most essential AA in the forage meals were lower than in the barley-based diets. The ileal flow of glucosamine and ornithine was found to increase (P < 0·05) with increasing proportion of fibre in the diet, suggesting an increase in endogenous N secretions and small-intestinal microbial activity. With the minor changes found for ileal essential AA digestibilities with forage meal inclusion in the diet the present data confirm the potential of forage meals as a source of protein in pig diets.

To investigate the relationships between maternal, umbilical cord and piglet fatty acid status, multiparous sows (six per diet) were fed on diets containing supplements (30 g/kg) of either soyabean oil or tuna oil for the last 21 d of pregnancy. The proportions of most fatty acids differed between diets: in particular, the tuna-oil-containing diet supplied more 22:6n-3 and less 18:2n-6 fatty acids than the soyabean-oil-containing diet. Maternal plasma fatty acid concentrations (mg/l) were greater than those in umbilical plasma and 20:4n-6 and 22:6n-3 fatty acids were present in higher proportions (g/100 g fatty acids) in umbilical than maternal plasma. Feeding tuna oil increased the proportionate amounts (g/100 g fatty acids) of total n-3 fatty acids (particularly 22:6n-3) in umbilical cord, plasma and piglet tissues compared with feeding soyabean oil: in contrast, the proportion of 20:4n-6 was decreased by feeding tuna oil. Changes in piglet fatty acid proportions as a result of oil feeding were not influenced by piglet weight. While proportions of the long-chain n-3 and n-6 polyunsaturated fatty acids in piglet liver, spleen and reproductive tract (ovaries plus uterus of the female, testes of the male) correlated well with those of umbilical plasma, those in brain and retina were poorly correlated. Therefore umbilical plasma cannot be used to predict the fatty acid status of piglet brain.

Some data suggest that the colonic microflora may adapt to produce more butyrate if given time and the proper substrate. To test this hypothesis, we investigated the effect of prolonged feeding of resistant potato starch on butyrate production. Rats were fed on either a low-fibre diet (basal) or the same diet supplemented with 90 g resistant potato starch/kg (PoS) for 0·5, 2 and 6 months. Short-chain fatty acid (SCFA) concentrations were determined in caecal and colonic contents at the end of each ingestion period. Total SCFA concentration increased over time throughout the caecocolonic tract with PoS, but was not modified with the basal diet. While propionate concentration was unchanged, butyrate concentration was highly increased by PoS at each time period in both the caecum and colon. Moreover, the butyrogenic effect of PoS increased over time, and the amount of butyrate was increased 6-fold in the caecum and proximal colon and 3-fold in the distal colon after 6 months compared with 0·5 months. Accordingly, the ratio butyrate: - total SCFA increased over time throughout the caecocolonic tract (12·6 (SE 2·8) v. 28 (SE 1·8) % in the caecum, 10·5 (SE 1·4) v. 26·8 (SE 0·9) % in the proximal colon, and 7·3 (SE 2·4) v. 23·9 (SE 2·7) % in the distal colon at 0·5 v. 6 months respectively), while the proportion of acetate decreased. Neither the proportion nor the concentration of butyrate was modified over time with the basal diet. Butyrate production was thus promoted by long-term ingestion of PoS, from the caecum towards the distal colon, which suggests that a slow adaptive process occurs within the digestive tract in response to a chronic load of indigestible carbohydrates.

Incubation trials were carried out with the rumen simulation technique (RUSITEC) to study the effects of four forms of N on the growth of ruminal micro-organisms and the fermentation variables when an all-fibre basal diet was incubated. The basal diet consisted of 10 g neutral-detergent fibre (NDF) from grass hay plus 2 g NDF from sugarbeet pulp. N forms were isolated soyabean protein, soyabean peptides, amino acids blended to profile soyabean protein and NH3 as NH4Cl. Half of the daily N supply was infused as NH4Cl and the other half was infused as each of the four treatments described. Non-NH3 N (NAN) forms increased NDF (P = 0·006), acid-detergent fibre (P = 0·003) and cellulose (P = 0·015) disappearance after 48 h incubation, CO2 (P < 0·001), CH4 (P = 0·002) and total volatile fatty acids production (P < 0·001), as well as the molar percentages of isobutyrate, isovalerate and valerate, which reflected the fermentation of amino acid C skeletons. NAN treatments also increased microbial N flow (P < 0·001) compared with NH3, with peptides and protein supporting more (P = 0·036) than amino acids. The proportion of microbial N derived from NH3 decreased successively (P < 0·05) with NH3 > amino acids > peptides > protein treatments, indicating preferential uptake of peptides without passage through the NH3 pool. Microbial efficiency (g microbial N/kg organic matter apparent disappearance) was greater (P = 0·002) for the NAN forms than for the NH3 treatment, with peptides and protein treatments supporting higher (P = 0·009) values than amino acid treatment. These results indicate that N forms other than NH3 are required for optimal fibre digestion and microbial growth.