Effect of Fat Retention on the Rachitogenic Effect of Rye Fed to Broiler Chicks

Two experiments were conducted to determine the influence of fat retention on bone mineralization and amino acid retention for broiler chicks fed rye diets containing marginal levels of vitamin D3. In Experiment 1, rye diets containing tallow were supplemented with high vitamin D3, bile salt (sodium taurocholate), or a detergent (sodium lauryl sulphate). Fat retention and tibia ash were improved (P less than .05) with bile salt addition, and tibia ash alone (P less than .05) was improved when high vitamin D3 or the detergent was added to the diet. In Experiment 2, rye diets contained tricaprylin (TC), tristearin (TS), or triolein (TO) as a fat source. Both fat retention (TS less than TO less than TC) and tibia ash (TS less than TC less than TO) showed a significant (P less than .05) treatment effect. The results of both experiments support the hypothesis that the rachitogenic effect of feeding rye may be related to inadequate fat digestion. There was no significant treatment effect on amino acid retention in either experiment. A third experiment indicated a similar bile acid pool size for chicks fed rye as opposed to wheat; however, bile acid concentration of jejunal fluid was lower (P less than .05) for chicks fed rye. A possible microbial involvement in the disturbance of bile acid metabolism was indicated by the capacity of Streptococcus organisms derived from chick small bowel to degrade sodium taurocholate.