Impact of diet composition on ileal digestibility and small intestinal morphology in early-weaned pigs fitted with a T-cannula

Piglets, separated from their dam at 12 days of age and fed a milk substitute hourly, were used as a model for suckling. Animals were fitted with a terminal ileal T-cannula and a jugular vein catheter At 28 days of age, half of the pigs had a dietary change to a cereal-based weaner diet fed as slurry, and the others remained on milk substitute. Animals were labelled by oral administration of N-15-labelled yeast for 10 days (days 15 to 25). Blood samples were taken twice a day to monitor N-15 enrichment of the blood plasma. Diets included polyethylenglycol (PEG 4000) to allow calculation of apparent ileal digestibility of nitrogen and individual amino acids. Ileal bacterial nitrogen was calculated from D-alanine content of the digesta. Furthermore, small intestinal (SI) villus height and crypt depth were measured. Feed intake was increased by the dietary change. The total nitrogen flow was 3.2 +/- 0.4g/day and 5.9 +/- 0.4 for the milk and weaner diet, respectively. Endogenous nitrogen flow at the terminal ileum was similar for both groups (milk diet 2.4 +/- 0.4 v. weaner diet 2.2 +/- 0.3 g/day), whereas the bacterial nitrogen content (0.08 +/- 0.01 g/day milk diet v. 0.15 +/- 0.01 g/day weaner diet, P < 0.01) and exogenous nitrogen flow (0.94 +/- 0.16g/day milk diet v. 3.29 +/- 0.12g/day weaner diet, P < 0.001) increased significantly in the weaner-diet group. The ileal apparent digestibility coefficient of protein was 0.81 +/- 0.06 and 0.68 +/- 0.01 for the milk replacer and the weaner diet, respectively Morphology measurements made along the SI at 25%, 50% and 75% were similar between piglets fed milk replacer and those fed a cereal-based weaner diet. The only statistical effect (P < 0.01) of dietary change was an increase in crypt depth in the weaner-diet group. In conclusion, pigs, following a dietary change analogous to weaning, lack the capacity to fully digest a standard weaner diet. This may result in an increased nutrient content entering the large intestine and an altered microbiota. In the absence of a period of anorexia, often associated with traditional weaning, we saw no evidence of villous atrophy, but report here a significant crypt hyperplasia, especially at the 75% level, as a result of dietary change.