Influence of size and asymmetry of sexual characters in the rooster and hen on the number of eggs laid

The quality of secondary sexual characteristics is thought to signal the desirability of an individual. That the attractiveness and/or quality of an individual, male or female, can have an effect on reproduction is also well known. In the present experiment we studied how asymmetry and size of secondary sexual characteristics in hens and roosters (Gallus gallus domesticus) affected the egg laying of hens. The strain used was a relaxed selection line of Brown Leghorn with a relatively low egg production (approx. 0.6–0.8 eggs/day). Each hen spent 24 h/week with the rooster, there were 4 females/rooster, in total 32 roosters and 127 hens. We found a significant effect of wattle asymmetry of roosters on the number of eggs laid by hens mated with them, hens mated with symmetrical males laying more eggs in total (rs = 0.50, P = 0.003, Spearman Rank Corr.), hens mated with roosters with larger wattles laid fewer fertilised eggs (rs = −0.40, P = 0.02, Spearman Rank). No effect was found for asymmetry of the wattles of the hens on total egg production (rs = 0.10, P = 0.36, Spearman Rank) or on fertilised eggs (rs = 0.020, P = 0.85, Spearman Rank). These results indicate that the original factors that affected reproduction in the wild ancestor of the domestic hen, e.g., male quality, might still be important in affecting the egg production of domestic poultry