Gut morphology of young pigs fed diets differing in standardized ileal digestible threonine and wheat gluten used as a source of non-essential amino acids

The aim of the study was to determine whether non-essential amino acids (NEAA) in form of wheat gluten (WG) have a threonine (Thr)-sparing effect on gut structure in young pigs. A two-factorial experiment was conducted on 12 groups of 6 pigs. Pigs of 12.5 kg initial body weight (BW) were fed for about 20 days diets differing in the Thr level (5.1, 5.7, 6.3 and 6.9 g standardized ilea) digestible Thr.kg(-1)) and WG level (20.4, 40.4 and 60.4 g of WG protein . kg(-1) of respective WG20, WG40 and WG60 diets). After slaughter at about 22.4 kg of BW, samples of duodenum, middle jejunum, ileum and proximal colon were taken for histological analysis. Morphology of all segments was not affected neither by Thr level nor by Thr and WG levels interaction, whereas effect of WG level differed among segments. In the duodenum, villi length and tunica mucosa thickness were decreased by WG60. In the duodenum and proximal colon, crypt depth was greater in WG20 than WG60 and/or WG40 groups, whereas in the ileum was greater in WG60 than WG20 group, and in the middle jejunum it was not affected. Villi length : crypt depth ratio was affected by WG only in the ileum, being greater in WG20 group. Myenteron was thicker in the ileum and proximal colon in WG60 than WG20 and WG40 group, respectively. The results do not evidence a sparing effect of NEAA provided by WG on Thr utilization for maintaining the proper gut structure in young pigs.