科研之友
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摘要
The responses of broilers to increments of dietary P concentration in P retention and P prececal digestibility were studied in 2 experiments using Ross 308 broilers in their fourth week of age. The low-P basal diet was mainly based on corn, potato protein, and corn starch. Titanium dioxide was used as the indigestible marker. Monobasic calcium phosphate was added in 6 (experiment 1) or 5 (experiment 2) graded levels up to a maximum of 8.1 g of P/kg of the diet. Five (experiment 1) and 6 (experiment 2) replicated pens of 10 birds were used. Excreta were collected from trays underneath the pens. Birds were asphyxiated by carbon dioxide exposure and the ileum (from Meckel%26apos;s diverticulum to 2-cm anterior to the ileo-ceca-colonic junction) was dissected. Digesta was collected from the entire section (experiment 1) or from 3 subsections of equal lengths (experiment 2). Excretion of P increased linearly with increasing dietary P concentration up to a level of about 5.2 g of P/kg of the diet and increased nonlinearly with further increase in dietary P. In contrast, P flow in the ileum increased linearly over the entire range of P intake. Up to the level of 5.2 g of P/kg of the diet, P excretion was slightly lower than P flow in the ileum, but responses in P excretion and P flow in the ileum were similar, suggesting that P excretion with urine is very low and unaffected by P intake when the birds are supplied with P below their requirement. Between the 3 subsections of the ileum, calculated digestibility was significantly different for the basal diet and the diet with the 3 lowest levels of P supplementation. We concluded that the response in P prececal digestibility to increments in dietary P concentration is linear over a wider range of dietary P than the response in P retention. When digesta is collected from the ileum for determination of P prececal digestibility, the first third of the ileum should not be considered.
- 出版日期2012-4-1
