EFFECTS OF AGE AT PHOTOPERIOD CHANGE AND DIETARY PROTEIN ON PERFORMANCES OF FOUR DWARF MATERNAL MEAT PARENT GENOTYPES AND THEIR BROILER CHICKEN PROGENY

Abstract

A factorial experiment was conducted with 3030 chickens of four maternal dwarf genotypes mated with normal males to estimate the effects of age at a photoperiod change from 8 to 12 h (daily) at 140 or 154 days, and two levels of dietary protein (15 or 17%) on general performance, incidence of Fatty Liver Syndrome and monetary returns. Three of the four maternal genotypes performed similarly for most traits measured but one genotype exhibited better feed efficency of egg production, produced more eggs and, although the eggs were smaller resulted in the highest monetary returns. Delaying the increase in photoperiod change retarded sexual maturity and reduced egg weight at 203 days and egg specific gravity at 406 days. The 17% protein diet improved egg production (including hatching eggs), feed efficiency of egg production, egg weights; and female body weights at 154 and 446 days of age were also heavier. Dietary protein levels had no effect on mortality (P > 0.05). Mean monetary returns from the sale of table eggs, hatching eggs and salvage meat in excess of the costs of day-old breeder stock and feed, averaged $1.07 more per bird fed the 17% diet. The progeny test revealed significant differences among genotypes for male mortality, male and female body weights, and feed conversion; however, monetary returns over feed and chick cost were similar. The time of change in photoperiod and dietary treatments had no significant effect on the overall performance of broiler progeny but there was a genotype × parental diet interaction for 43 day female body weights. Key words: Dwarfs, meat breeders, hens, broilers, photoperiods, diets