Live and Processing Performance Responses of Broilers Fed Low and Extra-Low Nutrient Density Withdrawal Diets Supplemented with Virginiamycin

Abstract

SUMMARY Two experiments were conducted to demonstrate the nutrient-sparing effects and cost-effectiveness of virginiamycin (VM) when fed to broiler chickens in extended withdrawal diets. In experiment 1, broiler chickens (Ross × Cobb) were fed the same starter and grower diets. On d 30, the chickens were switched to the withdrawal diets, and these were fed until 49 d when the experiment ended. Treatments were as follows: 1) standard broiler withdrawal diet (17.1% CP), 2) a broiler withdrawal diet with low nutrient density (16% CP), and 3) the same broiler withdrawal diet as treatment 2 but supplemented with 15 ppm VM. In experiment 2, broiler chickens (Ross × Cobb) were fed the same starter and grower diets to d 35 when they were switched to the withdrawal diets, and these were fed until the experiment ended (d 49). Birds on treatment 1 received a standard broiler withdrawal diet similar to the one used in experiment 1, birds on treatment 2 received a broiler withdrawal diet with extra-low nutrient density (15% CP), and birds on treatment 3 received the same broiler withdrawal diet as in treatment 2 but supplemented with 15 ppm VM. In both experiments, the chickens fed the withdrawal diet containing VM had the heaviest BW, and the unadjusted feed conversions were comparable for the standard withdrawal diet (without reduced nutrient density) and the reduced nutrient density diets with VM. In both experiments, the chickens fed the withdrawal diets with VM had the lowest mortality. An analysis of the breast meat yield results showed that in both experiments, the birds fed the extended withdrawal diets with VM produced more total pounds of breast meat than the other 2 treatments.