Growth and development of broiler breeders. 1. Effect of early plane of nutrition and growth rate.

In two experiments, male and female broiler breeders were reared on two different planes of growth as a result of early nutritional treatment. The starter treatment(s) consisted of a 19.5% crude protein, (CP), 2970 kcal diet from 0 to 14 days and 15.5% CP, 2750 kcal ration from 2 to 10 weeks. The birds in the grower treatment were fed the latter diet from 0 to 10 weeks. Both treatments were ad libitum fed from 0 to 3 weeks and then restricted to meet the breeder's recommended body weight targets. In Experiment 1, the starter treatment resulted in significantly heavier body weights at 3 weeks of age but not at later ages. The initiation of feed restriction was necessarily more severe for those chicks fed the starter diet. This restriction resulted in a significantly smaller liver at 10 weeks of age in breeder cockerels and dwarf breeder females. Vaccination titers [Newcastle, Infectious Bursal Disease (IBD),] and response to sheep red blood cells (SRBC) brachial vein injection were not affected by treatment. In a second experiment, there were no differences in bursa, spleen, or thymus weights between starter and grower treatments at 10 weeks of age, and the liver weights were again significantly larger in the grower treatment. One treatment of dwarf and normal pullets was overly restricted from 3 to 10 weeks (Grower-R), and lighter body weights were obtained at all ages. Only the spleen in the normal breeders was significantly smaller at 10 weeks of age in this treatment.(ABSTRACT TRUNCATED AT 250 WORDS)