Can body condition and other external characteristics predict semen production and quality in layer roosters?

Male fertility is one of the main factors determining the reproductive efficiency of a breeding flock, and aging is a process that impacts the production of fertile eggs in both broiler and layer lines. With the aim of developing selection criteria for males, phenotypic aspects are routinely used in the rearing and production phases allowing, for example, broiler males to reach puberty at the appropriate age without delays in production, premature decline, or low fertility persistence. However, layer lines were not selected for the same traits over the decades, and consequently, the roosters are lighter, more agile, and do not exhibit problems related to body conformation, pododermatitis, or abdominal fat accumulation as their broiler congeners. Therefore, we question whether the phenotypic aspects routinely assessed in layer lines are as useful in predicting semen production and quality as in broiler lines. Thus, 50 Bovans White roosters from a commercial parent-stock house were periodically monitored from 26 to 86 weeks of age for their body characteristics and semen parameters. Aging had a significant effect on the number of progressive spermatozoa, but individuals of different weight or fleshing categories showed no differences in this variable. Males with below-standard weights exhibited higher percentages of inactive cloacas and unsuccessful semen collection than those with standard or above-standard weights. We also observed that roosters with lower fleshing scores had higher percentages of inactive cloacas but no difference in semen collection success rates. Although the success rate for semen collection was higher in roosters with active cloacas, no differences in the number of progressive spermatozoa was found between individuals with active and inactive cloacas. Taken together, these data expand our understanding of the applicability of selecting layer roosters based on weight and fleshing. Further research regarding the correlation between these indicators and steroidogenic activity, sexual behavior and, above all, fertility in layer lines is needed. This information can greatly contribute to the processes of genetic improvement and reproductive management of layer lines.