Alterations in piglet small intestinal structure at weaning.

The small intestinal mucosa of 112 piglets aged between 21 and 32 days was examined to identify the effects on its structure of weaning and of consumption of creep food. In unweaned control pigs a gradual increase in crypt depth occurred with age, while villus height altered little. In contrast, weaned pigs showed a highly significant increase in crypt depth and an increase in the complexity of villus morphology with a dramatic reduction in villus height. Crypts elongated most in the distal small intestine, while the loss of villus height was greatest proximally. No inflammatory reaction was seen and the alterations were not influenced by consumption of creep food before weaning. This failed to support the hypothesis that hypersensitivity to dietary antigens is involved in the aetiology of such intestinal changes. The reduction in small intestinal absorptive area and the appearance of a less mature enterocyte population help to explain the increased susceptibility of the pig to diarrhoea and growth checks in the post-weaning period.