Associations between individual food intake characteristics and indicators of gut physiology of group-housed weanling pigs differing in genotype

A total of 198, 27-day-old weanling gilts (7.7 kg) were used to study the associations between food intake characteristics measured in individual pigs but which were group-housed, and indicators of gut physiology at 5 days after weaning. All piglets were offered ad libitum access to food and water and were housed in pens (11 piglets per pen) equipped with feeding stations in order to determine the time between weaning and the start of the first food intake (latency time; h), and the increase in daily food intake (daily increase; g/kg(0.75) per day) for each individual. Forty piglets were selected that either had an early (less than or equal to 2 h) or a late (greater than or equal to 23 h) start of food intake and subsequently either had a relatively fast (greater than or equal to 18 g/kg(0.75) per day) or slow (less than or equal to 2 g/kg(0.75) per day) increase in daily food intake so that there were four different groups. Five days after weaning, the 40 piglets were killed in order to determine histological (villous height, crypt depth, number of goblet cells) and functional (maltase and sucrase activities) measures in the proximal small intestine (SI), and microbial measures (ammonia and volatile fatty acid (VFA) concentrations) and dry-matter (DM) content in the distal SI, caecum and colon. Thirteen unweaned piglets were killed to serve as the reference group. Villous height/crypt depth ratio (P < 0.05), number (P < 0.01) of goblet cells on the villi and crypts, and sucrase activity (P < 0.001) in the proximal SI of the unweaned piglets were higher than in the weaned piglets. The proportion of branched-chain VFA (bcVFA; P < 0.01), ammonia-nitrogen (P < 0.001) and DM concentrations (P < 0.01) in the contents of the caecum as well as proportions of bcVFA in the contents of the colon of the unweaned piglets were higher than in the weaned piglets. Apart from a tendency towards an interaction (P < 0.1) between latency time and daily increase with regard to villous height/crypt depth ratio and number of goblet cells on the villi of the proximal SI, histology and function of the proximal SI and digesta characteristics of the distal SI, caecum and colon were not affected by latency time. Piglets with a fast increase in food intake tended to have longer villi on the proximal SI (P < 0.1), and had less acid-mucin containing goblet cells (P < 0.05) on these villi than had the piglets with a slow increase. The piglets with a fast increase had a higher DM content in the colon and tended to have a higher total VFA-concentration in the caecum than did their counterparts with a slow increase. The genotype of the piglets affected maltase (P < 0.01) and sucrase (P < 0.05) activities in the proximal SI and tended to affect the villous height/crypt depth ratio (P < 0.06). Genotype also affected total VFA concentrations (P < 0.05) and tended to affect the ammonia nitrogen (P < 0.1) in the colon and caecum, respectively. This study indicates that within the range of practical food intake levels recorded, the physiology and function of the gut is not markedly affected by the time between weaning and the onset of feeding or by the subsequent increase in daily food intake.