The digestive function of low birth weight (LBW) pigs post-weaning has been poorly studied. Therefore, newborns from eleven hyperprolific sows were weighed, weaned at 27·2 d and fed a starter diet until sampling. Sampling was done between 18 and 28 d post-weaning. An LBW piglet (n 19) was defined as a piglet having a birth weight less than 1 kg and less than the lower quartile of litter birth weights. Normal birth weight (NBW) piglets (n 13) were having a birth weight close to the mean litter birth weight. For each piglet, eighty-eight variables were determined. Data were analysed with linear models with type of piglet and litter as predictors. A principal component analysis was performed to determine the most important discriminating variables. In the LBW pig, the development of the digestive tract post-weaning was delayed: lower small-intestinal weight:length ratio due to a thinner tela submucosa and tunica muscularis and a higher secretory capacity, both in the distal jejunum. These observations might be a consequence of lower circulating insulin-like growth factor-1 (IGF-1) concentrations (126 (se 10·0) v. 158 (se 12·0) ng/ml for LBW and NBW, respectively) and a lower density of IGF-1 receptors in the proximal small intestine. Additionally, the plasma antioxidant capacity was lower for the LBW pig. Taken together, in the LBW piglet, the normal gut maturation post-weaning was retarded and this did not seem to be related to the weaning transition as such.

Within the genus Cryptosporidium 2 lineages have evolved, one adapted to the acid environment of the stomach and abomasum, the other comprising parasites that multiply in the small intestine. We tested whether the release of sporozoites from oocysts, a process known as excystation, is triggered by conditions which mimic the site of infection. Specifically, we exposed oocysts from gastric and intestinal Cryptosporidium species to acid conditions or to a neutral solution of taurocholic acid, at 37°C. We found that oocysts from the gastric species C. muris and C. andersoni excysted in both conditions, whereas the intestinal species C. parvum and C. hominis did not respond to acid. When the effect of temperature alone was tested on C. muris and C. parvum, only oocysts from the former species excysted in significant numbers. Oocysts from intestinal species did not respond to temperature alone, nor to acidity. These observations are consistent with the need of gastric species to rapidly excyst and release the sporozoites upon ingestion, and indicate that Cryptosporidium oocysts have evolved to maximize delivery of sporozoites to the region of the gastro-intestinal tract where the parasite multiplies.