No abstract

An experiment was conducted to estimate the true ileal digestibility of P in wheat, sorghum, soybean meal, and corn distiller's dried grains with solubles (DDGS) in broiler chickens. Four semipurified diets were formulated from each ingredient (wheat and sorghum: 236.5, 473, 709.5, and 946 g/kg; soybean meal and corn DDGS: 135, 270, 405, and 540 g/kg) to contain graded concentrations of nonphytate P. The experiment was conducted as a randomized complete block design with 4 weight blocks of 16 cages each (5 birds per cage). A total of 320 21-d-old broilers (Ross 308) were assigned to the 16 test diets with 4 replicates per diet. Apparent ileal digestibility coefficients of P were determined by the indicator method and the linear regression method was used to determine the true P digestibility coefficients. The results showed that the apparent ileal P digestibility coefficients of wheat-based diets were not influenced (P>0.05) by increasing dietary P concentrations, whereas those of diets based on sorghum, soybean meal, and corn DDGS differed (P<0.05) at different P concentrations. Apparent ileal P digestibility in broilers fed diets with soybean meal and corn DDGS linearly (P<0.001) increased with increasing P concentrations. True ileal P digestibility coefficients of wheat, sorghum, soybean meal, and corn DDGS were determined to be 0.464, 0.331, 0.798, and 0.727, respectively. Ileal endogenous P losses in birds fed diets with wheat, soybean meal, and corn DDGS were estimated to be 0.080, 0.609, and 0.418 g/kg DMI, respectively. In birds fed sorghum-based diets, endogenous P losses were estimated to be negative (-0.087 g/kg DMI). True digestible P contents of wheat, sorghum, soybean meal, and corn DDGS were determined to be 1.49, 0.78, 5.16, and 5.94 g/kg, respectively. The corresponding nonphytate P contents in wheat, sorghum, soybean meal, and corn DDGS were 1.11, 0.55, 2.15, and 4.36 g/kg, respectively. These differences between digestible P and nonphytate P contents may be suggestive, at least in part, of overestimation of P digestibility under the calcium-deficient conditions used in the regression method.

The study reported herein was conducted to determine and compare the nonphytate P, digestible P, and retainable P contents of corn and canola meal for broiler chickens. Four semipurified diets were formulated from each of ingredient to contain graded concentrations of nonphytate P. The experiment was conducted as a randomized complete block design with 4 weight blocks of 8 cages each (6 birds per cage). A total of 192 broilers (Ross 308), 21 d old, were assigned to the 8 test diets. Ileal digestibility and total tract retention coefficients of P were determined by the indicator and total collection methods, respectively, and linear regression method was used to determine the true P digestibility and true P retention coefficients. The apparent ileal digestibility of P in corn was influenced (quadratic, P < 0.05) by increasing dietary nonphytate P concentrations, whereas P retention was unaffected (P > 0.05). The apparent ileal P digestibility in broilers fed diets based on canola meal was similar (P > 0.05) at different P concentrations. Phosphorus retention in broilers fed diets based on canola meal (linear, P < 0.01) decreased with increasing P concentrations. True ileal P digestibility and true P retention coefficients of corn were determined to be 0.676 and 0.632, respectively. The corresponding values for canola meal were 0.469 and 0.486, respectively. In both ingredients, the determined true ileal digestibility and total tract retention coefficients were not different (P > 0.05). Total P, nonphytate P, true digestible P, and true retainable P contents of corn were determined to be 2.5, 0.8, 1.7, and 1.6 g/kg (as received), respectively. The corresponding values for canola meal were 9.7, 2.8, 4.6, and 4.7 g/kg (as received), respectively. The present data demonstrated that the regression method can be successfully used to measure true P digestibility of low and high P feed ingredients and that both true ileal digestibility and retention coefficients are suitable to assess P availability in broilers.

An experiment was conducted to estimate true ileal phosphorus (P:) digestibility of 3 meat and bone meal samples (MBM-1, MBM-2: , and MBM-3:) for broiler chickens. Four semipurified diets were formulated from each sample to contain graded concentrations of P. The experiment was conducted as a completely randomized design with 6 replicates (6 birds per replicate) per dietary treatment. A total of 432 Ross 308 broilers were assigned at 21 d of age to the 12 test diets. The apparent ileal digestibility coefficient of P was determined by the indicator method, and the linear regression method was used to determine the true P digestibility coefficient. The apparent ileal digestibility coefficient of P in birds fed diets containing MBM-1 and MBM-2 was unaffected by increasing dietary concentrations of P (P > 0.05). The apparent ileal digestibility coefficient of P in birds fed the MBM-3 diets decreased with increasing P concentrations (linear, P < 0.001; quadratic, P < 0. 01). In birds fed the MBM-1 and MBM-2 diets, ileal endogenous P losses were estimated to be 0.049 and 0.142 g/kg DM intake (DMI:), respectively. In birds fed the MBM-3 diets, endogenous P loss was estimated to be negative (-0.370 g/kg DMI). True ileal P digestibility of MBM-1, MBM-2, and MBM-3 was determined to be 0.693, 0.608, and 0.420, respectively. True ileal P digestibility coefficients determined for MBM-1 and MBM-2 were similar (P < 0.05), but were higher (P < 0.05) than that for MBM-3. Total P and true digestible P contents of MBM-1, MBM-2, and MBM-3 were determined to be 37.5 and 26.0; 60.2 and 36.6; and 59.8 and 25.1 g/kg, respectively, on an as-fed basis.

The effects of dietary calcium (Ca) concentration on the digestion of Ca, phosphorus (P), nitrogen (N), fat and starch along the intestinal tract of broilers were assessed. Three-week old broilers were fed maize-soy diets containing 6, 9 or 12 g/kg of Ca (Ca: total P ratios of 1:1, 1.4:1 and 2:1, respectively) for six days and digesta were collected from the duodenum, jejunum, upper ileum and lower ileum. Apparent digestibility coefficients of P, Ca, N, fat and starch in different intestinal segments were calculated based on indigestible marker ratios in the diet and digesta. Apparent digestibility coefficients of P and Ca were determined to be negative in the duodenum. Apparent P digestibility was reduced (P＜0.05) by increasing dietary Ca concentrations, but there was a Ca x intestinal site interaction (P＜0.05). Jejunum was the major site of P absorption in birds fed the low Ca and normal Ca diets, but both the jejunum and upper ileum were involved in birds fed high Ca diets. Dietary Ca concentration had no effect (P ＞0.05) on apparent Ca digestibility. Calcium was absorbed predominantly in the jejunum. Digestibility of N and fat was reduced (P＜0.05) by increasing dietary Ca concentrations. A significant (P＜0.05) dietary Ca x intestinal site interaction was observed for N. In birds fed low Ca and normal Ca diets, N was primarily digested by the end of jejunum, but in birds fed high Ca diet both jejunum and upper ileum were involved. At all dietary Ca concentrations, fat was digested mainly in the jejunum and upper ileum, but digestion continued in the lower ileum. Apparent starch digestibility and AME were unaffected (P＞0.05) by dietary Ca concentrations. Most of the starch digestion was completed by the end of the jejunum. The present data suggest that the site of digestion of P and N shifts depending on dietary Ca concentrations. Increasing dietary Ca concentrations negatively influenced the digestion of P, N and fat, but had no effect on those of Ca and starch.