EVALUATION OF THE DURATION OF SPERM FERTILIZING ABILITY IN 5 LINES OFCOMMERCIAL BROILER BREEDER AND DELAWARE CROSS MALES

The ability to characterize the reproductive potential of male fowl ca n be affected by a number of factors, including age, type, inseminatio n scheme, and number of sperm inseminated. Fertility is a complex inte raction of traits involving two individuals of differing genetic compo sition: in modern broiler breeders, selected predominantly for growth and carcass characteristics, fertility problems may be exacerbated. Ln order to evaluate the male components of fertility, an experiment inv estigating the effects of male line on both average fertility and the duration of fertility was completed. Male chicks from five commercial broiler breeder male lines or sired by subfertile Delaware cross roost ers were reared to adulthood. Between 30 and 60 wk of age, semen was c ollected from five males per line, extended and used to inseminate eac h of 10 to 12 hens from four broiler breeder female lines or Single Co mb White Leghorn hens with 80 x 10(6) live sperm. Following a single i nsemination eggs were collected for 21 d and fertility determined by v isual inspection following 4 d incubation. The percentages of Live spe rm and overall fertility data for the replicate trials were analyzed, following transformation, with a linear model and daily fertility data were analyzed by iterative least squares regression. Whereas there we re large differences in fertility among individual males (durations fr om 3.4 to 14.5 d) within a line, there were no significant male line o r replicate effects on overall fertility or the duration of fertility. However, there was a significant (P < 0.05) line-dependent reduction in the percentage of live sperm in broiler breeder males, with the sub fertile Delaware cross males being intermediate. There were no signifi cant female line or replicate effects on the duration of fertility; ho wever, there were significant female line effects on overall fertility at both 7 and 21 d. These data suggest that although individual males varied widely, there were no male line effects on the duration of fer tility in the lines of broiler breeders evaluated when analyzed by ite rative least squares. Furthermore, these data suggest that although fe males may have significant affects on overall fertility, the duration of fertility appears to be a predominantly male characteristic. Theref ore, iterative least squares regression may be a useful tool for ident ifying males with superior sperm fertilizing ability.