title: The influence of daylength, body weight, and age on the reproductive ability of broiler breeder cockerels.
abstract: June-hatched broiler breeder cockerels of two strains were evaluated for reproductive performance in mating pens from 22 to 48 weeks of age. Two light programs with maximum daily daylengths of 15.5 or 16.5 hr were studied. An increase in the light day to 16.5 hr did not significantly affect the male reproductive traits except in number of completed matings and percent packed sperm volume (PSV). The males on 16.5 hr of light had significantly fewer completed matings than did the males on 15.5 hr. Strain 1 males on 16.5 hr produced significantly more spermatozoa at 35 and 40 weeks of age than males on 15.5 hr of light. Male body weights of both strains were significantly lower at 30 weeks of age on the longer daylength. Body weights of cockerels in all treatment groups increased with aging. The range in male body weight markedly influenced the percentage of producing cockerels with aging. During the late egg cycle, the number of producing males increased as body weight increased. The overall mean age of peak in the percentage of males in semen production was 44 weeks of age, which was 7 weeks later than peak egg production. Hatchability was significantly lower for male Strain 2, which had a higher percent PSV and a higher number of attempted matings than did Strain 1. Body weight was significantly correlated with male vent feather-wear at all ages and with the percentage of producing males at 48 weeks of age. The percentage of producing males was correlated with vent feather-wear, evert score, semen volume, and PSV. These results emphasize the importance of body weight selection for optimum breeding flock performance.
mesh_terms: D000375:Aging; D000818:Animals; D001835:Body Weight; D002645:Chickens / Q000502:physiology*; D008029:Lighting; D008297:Male; D012098:Reproduction; D012661:Semen / Q000166:cytology; D012726:Sexual Behavior, Animal; D013997:Time Factors