This review explores sexual aggression in broiler breeder males, aiming to synthesize existing scientific evidence regarding its causes, behavioral manifestations, and consequences, while addressing the genetic, neuroendocrine, and environmental mechanisms involved. Through an extensive analysis of scientific literature, the paper highlights that intensive genetic selection aimed at enhancing growth and productivity has resulted in unintended behavioral dysfunctions. These include the reduction or absence of courtship behavior, the occurrence of forced copulations, and a notable increase in injury rates among hens. Reproductive challenges observed in meat-type breeder flocks, in contrast to those in layer lines, appear to stem from selection practices that have overlooked traits related to mating behavior. Environmental and managerial conditions, including photoperiod manipulation, stocking density, nutritional imbalances, and the use of mixed-sex rearing systems, are also identified as contributing factors to the expression of sexual aggression. Furthermore, recent genetic findings indicate a potential link between inherited neurobehavioral factors and aggressive behavior, with the SORCS2 gene emerging as a relevant candidate. Based on these insights, the review emphasizes the importance of considering behavioral parameters in breeding programs in order to reconcile productivity objectives with animal welfare standards. Future research may benefit from a more integrative approach that combines behavioral, physiological, and genomic data to better understand and address the multifactorial nature of sexual aggression in poultry systems.

In broiler breeder flocks, mating may cause traumatic skin lesions in hens, yet their biological significance remains insufficiently understood. This study aimed to investigate associations between mating-related lesions and physical and physiological status in broiler breeder hens, focusing on lesion severity and anatomical location. At 40 weeks, 39 hens were examined, including 29 with mating-related lesions and 10 lesion-free controls. Birds underwent clinical examination, body weight and plumage assessment, serum corticosterone measurement, and ultrasonographic evaluation of ovarian activity. Affected hens had lower body weight than controls, and 58.6% showed ovarian inactivity. Within affected hens, body weight was positively associated with plumage score and ovarian activity. Gross lesion severity was not consistently associated with body weight, plumage condition, or ovarian activity, whereas lesion location provided additional information on these indicators. Hens with cephalic lesions had lower body weight, poorer plumage condition, and lower ovarian activity than hens with trunk lesions, despite less severe lesions macroscopically. Serum corticosterone concentrations did not differ between groups or vary with lesion severity or location. These findings suggest that mating-related lesions may reflect more than superficial injury and that lesion location, particularly cephalic involvement, may provide useful information on the biological status of affected hens.