EFFECT OF WINTER AND SUMMER ON THE REPRODUCTIVE BEHAVIOR OF THE CROSSBRED BULLS

Objective. To evaluate summer and winter effect on the seminal quality of crossbred bulls in the Sinu valley river. Materials and methods. Eight bulls of genetic composition 75% Bos indicus and 25% of Bos taurus, were included, four of them were 20.5 and 27 months (group smaller than 30 months), and the remained four with an age among 32 to 37.5 months (group bigger than 30 months). Corporal weight increase, score of condition corporal, scrotal circumference (CE) as well as their sperm viability were assessed every 28 days. Results. Weather variations during the rainy season and the dry season showed a maximun temperature of 33.2 Vs 35.1°C and a minimum temperature of 24.1 Vs, 23.9°C, a relative humidity of 81.8 Vs, 75.4%, precipitation rain of 516.4 Vs, 24.1 mm and sunshine measures of 6.3 Vs, 5.6. Differences were found in terms of weight increase (p<0.01) and body of condition score (p<0.01). In the group of the bulls under 30 months of age, some differences were found for fast MPI (p<0.02). In the group of bulls over 30 moths of age, there were only statistical differences for secondary abnormalities, AS (p<0.02). There were no statistical differences for scrotal circumference, the ejaculated volume, motility and normal spermatozoids during the dry season and rainy season (p>0.05). The correlations between the weather variables with sperm variables in the two age group are low (r<0.2). Conclusions. The season affects the sperm morphology (MPRI, MPIL, and AE), specially in young bulls. Nonetheless, the main effect is intermingled between the season (dry season) and the deficient forage offered to the animals.