ASSESSMENT OF APPARENT ILEAL DIGESTIBILITY OF AMINO-ACIDS AND NITROGEN IN COTTONSEED AND SOYBEAN MEALS FED TO PIGS DETERMINED USING ILEAL DISSECTION UNDER HALOTHANE ANESTHESIA OR FOLLOWING CARBON-DIOXIDE STUNNING

Two experiments were conducted to determine apparent ileal digestibili ty of amino acids (AIDAA) and nitrogen (AIDN) in cottonseed meal (CSM) and soyabean meal (SBM) fed to growing pigs. In the first experiment, twenty-four male pigs (37.3 (SE 2.7) kg) were individually penned and randomized to either CSM or SBM diets. The diets contained 40 % of th e protein meal (either CSM or SBM) in a wheat starch-sucrose (1:1, w/w ) base containing vitamins and minerals, and Cr2O3 as an indigestible marker. Rigs were acclimated to the experimental diets over a 3 d peri od and on day 4 through today 14 were offered 1800 gld of the diet. Di ets were offered in three meals/d from day 4 to day 11 and in eight me als/d from day 12 to day 13. After the eighth hourly-meal on day 14, t welve pigs were anaesthetized with halothane while the remaining twelv e pigs were CO2-stunned and processed using commercial slaughter proce dures. Ileal digesta were collected from a 1500 mm portion of the term inal ileum of each pig and subsequently analysed for amino acids, N, o rganic matter and Cr. Results indicated that AIDAA of CSM and SBM were lower when digesta were collected following CO2-stunning than when di gesta were obtained under halothane anaesthesia. Consistently, AIDN in CSM (0.51 v. 0.56) and SBM (0.55 v. 0.71) were lower (P<0.05) in CO2- stunned pigs than in halothane-anaesthetized pigs. Furthermore, when d igesta collection was conducted under halothane anaesthesia, AIDN of C SM was lower (P < 0.001) than that of SBM. In the second experiment, s ix male pigs (45 (SE 2.6) kg) were fitted with T-piece cannulas implan ted in the terminal ileum, housed individually in metabolism cages, an d randomly allocated to either CSM or SBM diets in a single reversal a rrangement. Ileal digesta were collected for AIDAA and AIDN determinat ion. Although statistical comparisons could not be made between the tw o experiments, the AIDAA and AIDN data obtained via cannulated pigs we re similar to those values obtained using the halothane-anaesthesia me thod. Overall, the CO2-stunning method is not recommended for studies of amino acid or nitrogen ileal digestibilities, but may be useful for the study of other dietary constituents.