Response of Early- and Late-Developing Broilers to Nutritionally Adequate and Restrictive Feeding Regimens During the Summer

Male broilers, characterized as either early- or late-developing based on their growth characteristics, were compared under summer conditions in their response to an adequate feeding regimen designed to optimize growth and a restrictive one intended to minimize late mortality. Accordingly, the early-developing strain grew faster initially, whereas the late-developing strain had the advantage prior to marketing. Ultimately, both strains had similar body weights at 49 d of age. Both broiler sources also responded similarly to each of the feeding regimens. Under summer conditions, adequate nutrition enabled reasonable growth rate throughout production, but restriction of effective protein relative to energy severely limited performance without an advantage to mortality. Differences in chilled carcass weights after processing paralleled differences in live body weight. Fillet yields and their physical dimensions were similar between strain-crosses, but they were both reduced as a consequence of using the restrictive regimen.