Correlations of protein deposited in growing female pigs to ileal and faecal digestible crude protein and amino acids

Abstract The objective of the investigation was to study the value for protein synthesis of crude protein/amino acids disappearing in different intestinal segments by correlating deposited protein to the amounts disappearing in the small intestine, the caecum—colon and in the whole digestive tract, to learn whether practical diet formulation could be improved by replacing faecal digestible crude protein/amino acids with ileal digestible crude protein/amino acids. The study included 24 diets varying widely in chemical composition. The ileal and faecal digestibility of crude protein/amino acids was determined in five experiments per diet with growing cannulated female pigs and the protein deposition was determined in five N-balance experiments per diet with normal growing, uncannulated, bladdercatheterized female pigs under standardized conditions. The digestibility of crude protein/amino acids in the caecum—colon decreased with increasing levels of crude fibre and potato starch, whereas the digestibility of energy increased. Increasing dietary levels of crude protein increased the proportion of lysine and methionine disappearing in the caecum—colon. Ileal digestible crude protein/amino acids had considerably higher correlations to deposited protein than crude protein/amino acids disappearing in caecum—colon, and slightly higher correlations to deposited protein than crude protein/amino acids disappearing in the whole digestive tract.