Response of feed supplementation of virginiamycin on feed utilization and organ growth of broilers

Commercial broiler chicks divided into four groups (18 chicks each) received virginiamycin @ 0 (control), 5, 10 and 20 mg (treatment) per kg feed from first week through 7 week of age. Final body weight recorded was significantly (P<0.05) higher in all the treatment groups (1465, 1455 and 1490 g respectively) compared to the control birds (1351 g). Feed conversion ratio was also superior (P<0.05) in experimental groups (2.35, 2.36 and 2.25 respectively) compared to the controls (2.47). Weights of liver, gizzard, spleen and length of intestines and femur were significantly (P<0.05) higher in third experimental group. PCV, Hb and total plasma protein concentrations were significantly lower in all three experimental groups compared to controls indicating a favourable nutrient partitioning influence. Virginiamycin supplementation also resulted in improved carcass quality of the birds under study. Among various dose rates used, 20 mg/kg of feed supplementation produced best growth promoting effect.