The Effect of Dietary Lasalocid or Monensin in the Presence of Roxarsone and Graded Methionine Levels on Broiler Performance and Processing Characteristics

Abstract

Two, eight-week broiler experiments were conducted in floor pens to study the feeding of either lasalocid (75, 100 or 125 p.p.m.) or monensin (99 or 121 p.p.m.) at three levels of methionine (0, 0.1 or 0.2 percent supplemental) in the presence of roxarsone (50 p.p.m.). Nine day-old chicks of each sex were randomly placed into each pen, with four replicate pens assigned to each of 18 dietary treatments. Group body weights were taken at 28 and 56 days of age for each sex and feed conversion values calculated. At 8 weeks of age, completeness of body feathering over the thigh area of all male birds was visually determined along with percent ready-to-cook yield and abdominal fat scores on selected treatment groups. In a combined analysis of the factorial experiments no significant coccidiostat × methionine interaction was found. Supplementation with 0.10 percent methionine produced a significantly heavier body weight than the unsupplemented diet. Increasing the methionine level by 0.20 percent resulted in a further numerical weight improvement, but did not affect feather scoring. Feed conversion also improved with methionine level; however, ready-to-cook yield and abdominal fat scores were not significantly affected. Feeding of lasalocid levels higher than 75 p.p.m. numerically depressed body weights. Ninety-nine p.p.m. monensin caused a significant weight reduction as compared to the basal diet and all of the lasalocid treatments. Increasing monensin to 121 p.p.m. resulted in a further significant reduction in body weights. No significant differences due to coccidiostat feeding were noted in feed efficiency, body feathering scores, ready-to-cook yield and abdominal fat scores.