The laboratory rat as a model animal for determining ileal amino acid digestibility in meat and bone meal for the growing pig

Abstract

The use of the laboratory rat as a model animal to allow the determination of apparent ileal amino acid digestibility in the growing pig using the slaughter method, was evaluated. Sixteen male rats and 16 male pigs were fed diets containing as the sole protein source one of two meat and bone meals which were expected to differ in quality. Chromic oxide was included in the diets as an indigestible marker. Ileal contents from the terminal 20 cm of ileum were collected after slaughter of the rats and pigs, 4 and 9 h from the start of feeding, respectively. The latter sampling times were shown to be optimal for each species. Interspecies comparisons made under defined conditions indicated close agreement between rats and pigs for the apparent ileal digestibility of nitrogen (N) and most of the amino acids for each of the two meat and bone meals. Mean apparent ileal N digestibility coefficients for the rat and pig respectively were 0.64 and 0.66, and 0.73 and 0.73 for the two meat and bone meal based diets. A significant ( P <0.05) interspecies difference in apparent digestibility was found only for glutamic acid, where the pig had a lower apparent ileal digestibility. There were no significant differences in amino acid digestibility when correction was made for the endogenous ileal amino acid component. It was concluded that the growing rat is a satisfactory model for the growing pig, for determining ileal amino acid digestibility in meat and bone meal. The measurement of digestibility at the terminal ileum indicated differences in amino acid digestibility between the two meat and bone meals. However, the faecal approach which generated significantly higher digestibility coefficients than the ileal method, did not allow these differences to be detected.