Breeding and Genetics

Differences among eight commercial broiler strains in factors indicating susceptibility to ascites were investigated. Chicks from eight crosses were obtained from two hatcheries (one was obtained from both hatcheries to give a total of nine) and raised to 6 wk of age on commercially prepared rations containing 3,300 kcal/kg energy with 24% protein to 3 wk of age and 20% protein from 3 to 6 wk. Each cross was represented by four pens of 90 broilers each. At 21 and 42 d, groups of 20 birds per pen were weighed and feed consumption was measured in order to calculate the feed conversion ratio. At 21 and 42 d, a blood sample was taken from two birds per pen to determine the hematocrit value. These birds were killed and dissected to determine heart, liver, lung, and spleen weights. Lung volume was determined by water displacement. Significant differences were observed between crosses for all of the measures with the exception of feed conversion ratio and mortality. These differences were most prominent for hematocrit value, which is an initial adaptation to anoxia, suggesting that broiler lines could be chosen that resist anoxic environmental conditions. (