Instituto Universitario de Investigación en Ciencias Ambientales de Aragón, Universidad de Zaragoza, Facultad de Veterinaria, Miguel Servet, 177, 50013 Zaragoza, Spain.
Facultad de Estudios Superiores de Cuautitlán (FES-C), Universidad Nacional Autónoma de México (UNAM), Estado de México, Mexico.
Instituto Universitario de Investigación en Ciencias Ambientales de Aragón, Universidad de Zaragoza, Facultad de Veterinaria, Miguel Servet, 177, 50013 Zaragoza, Spain.
Instituto Universitario de Investigación en Ciencias Ambientales de Aragón, Universidad de Zaragoza, Facultad de Veterinaria, Miguel Servet, 177, 50013 Zaragoza, Spain.
Department of Veterinary Medicine, University of Sassari, Via Vienna 2, Sassari, Italy.
Department of Veterinary Medicine, University of Sassari, Via Vienna 2, Sassari, Italy.
Instituto Agroalimentario de Aragón (IA2), Universidad de Zaragoza, Facultad de Veterinaria, Miguel Servet, 177, 50013 Zaragoza, Spain.
This study aimed to investigate whether a specific genotype of the MTNR1A gene influences social dominance and reproductive performance in rams. Thirty-one rams were genotyped for Rsal and Mnll polymorphism of the gene: CC (n=19), CT (n=5), and TT (n=7), and GG (n=20), GA (n=6), or AA (n=5), respectively. Maintenance (standing still, lying down, drinking, feeding, walking, or stereotyping) and social behavior (agonistic and antagonistic interactions among rams) were recorded by direct observations involving instantaneous scan sampling and continuous behavior sampling. For each animal, his Index of Success (IS) and Displacement (ID) were calculated. One week after the social-behavioral observations, rams were tested in individual serving-capacity tests involving three ewes that were synchronized into estrus in a 15-m2 pen for 20 min. The genotypes did not differ in the number of aggressions they performed (CC: 88.95±12.85; CT: 106.20±21.00; TT: 70.43±8.50; GG: 76.05±8.72; GA: 119.00±16.16; AA: 95.80±36.39) or received (CC:75.79±5.82; CT:92.40±8.68; TT: 86.14±15.05; GG: 79.25±6.58; GA: 86.83±11.51; AA: 79.80±12.74), and their active and passive behaviors were similar. The genotypes did not differ significantly in IS or ID, and the proportion of rams in each success category was similar among groups. For the Rsal and Mnll polymorphism, TT and GG rams were responsible for 54% and 56% of recorded sexual events (P < 0.05), respectively. Results of this study confirm that the best sexual performance of rams was among those that carried certain genotypes of the MTNR1A gene. Still, it was not correlated with differences in social dominance.
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