Estimation of standardized mineral availabilities in feedstuffs for broilers

Two experiments were conducted to estimate standardized mineral (Ca, P, Cu, Fe, Mn, and Zn) availabilities (SMA) in commonly used feedstuffs and verify the additivity of SMA for diet formulation of broilers. In Exp. 1, after 3 d of acclimation, a total of 96 22-d-old Arbor Acres male broilers were fasted for 24 h. Then the broilers were fed a mineral-free, corn, soybean meal (SBM), or corn-soybean meal (C-SBM) diet for 4 h and the excreta samples were collected for 48 h after feed withdrawal (totally 52 h). The results showed that the endogenous losses of Ca, P, Cu, Fe, Mn, and Zn for chickens fed the mineral-free diet were 13.7, 113, 0.064, 0.593, 0.094, and 0.132 mg/52 h per bird, respectively. The standardized availability values of Ca, P, Cu, Fe, Mn, and Zn were 20.8%, 39.6%, 37.8%, 47.4%, 10.7%, and 45.2% in corn as well as 54.3%, 51.1%, 39.7%, 27.6%, 26.1%, and 51.0% in SBM, respectively. The determined values of SMA in C-SBM diet were close (P > 0.09) to the predicted summations of SMA from corn and SBM (Ca, 48.6% vs. 48.1%; P, 44.9% vs. 46.0%; Cu, 41.7% vs. 39.1%; Fe, 35.3% vs. 33.2%; Mn, 22.7% vs. 22.2%; Zn, 46.2% vs. 48.4%). In Exp. 2, a total of 144 22-d-old Arbor Acres male broilers were used to estimate the SMA values in 6 feedstuffs by using the above procedure. The results showed that the standardized availability values in wheat, wheat bran, corn distillers dried grains with solubles, cottonseed meal, rapeseed meal, and corn gluten meal diets were 24.7% to 55.8% for Ca, 35.6% to 46.6% for P, 24.5% to 45.7% for Cu, 21.6% to 43.5% for Fe, 9.3% to 34.5% for Mn, and 22.9% to 52.9% for Zn, respectively. The results from the present study indicated that the mineral-free diet could be used for estimating the endogenous losses of the above minerals and SMA values of feedstuffs for broilers, and the estimates of SMA in feedstuffs for the C-SBM diet formulation were additive.