Effect of Semen Collection Frequency and Scrotal Circumference on Semen Quality Parameters in Brahman x Local Crossbred Bulls

摘要

Five Brahman crossbred bulls were ejaculated twice weekly (2x) and 5 bulls four times weekly (4x) for 16 weeks to determine the effect of ejaculation frequency on semen characteristics and sperm output. Each of 10 bulls was ejaculated 4 times weekly for 4 weeks to determine sperm output and the relationship between scrotal circumference and semen parameters. For 4x bulls as compared to 2x bulls, ejaculation volume was smaller (P<0.01) but sperm concentration per ejaculate and total progressive motile sperm (TPMS) output per week were greater (P<0.01). Weekly semen output was greater (P<0.01) in 4x bulls (11.4 mL) compared to 2x bulls (7.99 mL). Average weekly TPMS output for 4x bulls was 1.61 times higher compared to 2x bulls. Occurrence of total abnormalities, proximal droplets and tail abnormalities was higher (P<0.05) in 4x bulls as compared with 2x bulls. When 2x bulls were placed at 4x for 4 weeks, they produced numerically higher TPMS (14.2x109) per week than that (12.8x109) of continued 4x bulls. Scrotal circumference was highly correlated (P<0.01) with semen volume and TPMS per ejaculate while the correlations between scrotal circumference and sperm motility and scrotal circumference and sperm concentration were found at medium and weak levels, respectively. Therefore, it seems appropriate to recommend the collection of semen from Brahman crossbred breeding bulls at the rate of 4 ejaculates per week and recording of scrotal circumference as a criterion to select young bulls as sires