Influence of Genotype and Diet on General Performance and Incidence of Leg Abnormalities of Commercial Broilers Reared to Roaster Weight

Two experiments were conducted to study the influence of genotype and diet on general performance and incidence of leg abnormalities of commercial broiler chickens reared to roaster weight. In Experiment 1 a total of 1960 male day-old chicks of seven different commercial genotypes were housed separately in 14 pens (25.64 m2) with 140 birds per pen and fed one dietary regimen. In experiment 2, 3000 male day-old chicks of two commercial genotypes were randomly assigned to 20 pens (13.54 m2) with 150 birds per pen, and two replicate pens were fed one of the five different dietary regimens designed to promote rapid, intermediate, or slow growth. Differences (P less than .05) were observed among the genotypes tested (Experiment 1) in the incidence of mortality, leg abnormalities, live weight, and feed conversion but not for mean monetary returns per bird housed. In Experiment 2, significant differences (P less than .01) were observed among the dietary regimens tested for live weight, feed conversion, and monetary returns per bird housed. As the protein content of starters, growers, and finishers decreased, body weight decreased but monetary returned improved. Feeding the birds beyond 63 days resulted in substantial reduction in monetary returns. A dietary regimen which included starter, grower, developer, and finisher with 18, 24, 22, and 14% protein, respectively, resulted in significantly better feed conversion and a significantly lower incidence of leg abnormalities. Genotype X diet interactions were considered of no practical importance.