169 Influence of breed, season, and ejaculate number on the sperm quality of breeding bulls in Inia, Peru

Semen quality can be affected by a wide range of genetic and environmental factors, including bull breed, collection interval, collection frequency, and season (Snoj et al. 2013). The objective of this study was to evaluate the effect of breed, collection season (warm and cold season), and number of consecutive ejaculates on the quality of bull sperm. The ejaculates (n = 887) were collected using an artificial vagina from bulls of three breeds (Braunvieh [BU] n = 2; Simmental [SM] n = 4; Gyr [GI] n = 3), aged between 4 and 5 years, from the Central Genetic Nucleus (EEA Donoso, National Institute of Agrarian Innovation). The samples, three successive ejaculates per collection/bull, were analysed in two seasons of the year. In each ejaculate obtained, the concentration was measured using a photometer; the sperm concentration was displayed in million sperm/mL. Immediately, the volume was measured using a micropipette and the semen was extended (1:1 or 1:2 or 1:3) according to the sperm concentration. In the laboratory, three drops of 5-µL semen from each ejaculate were placed on a slide pre-heated to 37°C and the motility was evaluated using a light microscope at ×100 magnification. Data were analysed in R studio using ANOVA and Tukey’s test. The results showed a significant difference (P = 0.0001) between the breeds in sperm concentration (×10⁶/mL) BU = 1178.2, SM = 1087.8, GI = 961.1, and volume (mL) GI = 6 0.4, SM = 4.6, BU = 3.8. The sperm concentration was significantly lower (P = 0.0001) in the second and third ejaculates than in the first ejaculate (1 = 1175.1, 2 = 1032.4, 3 = 815.3 [× 10⁶/mL]) and volume (1 = 5.02, 2 = 4.5, 3 = 4.2 [mL]). In contrast, sperm motility was significantly (P = 0.001) reduced in the first ejaculate (2 = 67%, 3 = 64%, 1 = 63%). Finally, we were able to observe that sperm motility was not influenced by breed but showed a difference (P = 0.0001) between the seasons of the year, being higher in the warm season (67%) than in the cold season (63%). In conclusion, the BU breed showed a higher sperm concentration and the GI breed a higher ejaculate volume compared with the other breeds. Furthermore, the second and third consecutive ejaculates showed reduced sperm concentration and ejaculate volume although sperm motility was not affected. Finally, in the hot season, motility was higher in all breeds.

This study is supported by PromegNacional of the National Institute of Agrarian Innovation.