The effect of nocturnal sampling on semen quality and the efficiency of collection in bovine species.

This study evaluated night and day semen collection regimes in Holstein and Brahman bulls (four bulls of each breed) that were collected weekly, each during a morning and a night collection. Ejaculates (n=64) were obtained via artificial vagina over 4 weeks. The first collection of each week alternated between night and day. Two collection teams were employed. Bull behavior parameters included reaction time to first mount, time to ejaculation, a refractory period test, and a thrust intensity test. The numbers of interruptions were counted as a managerial parameter. Pre-freeze semen parameters included total volume, initial motility and concentration. Post-freeze semen parameters measured were: 0- and 3-h post-thaw motility; percent intact acrosomes; and percent sperm abnormalities. Data were analyzed by least squares methods. The bull within breed effect differed (P<0.05) for behavior parameters. The bull within breed effect for total motile sperm harvested was not significant. The bull within breed response was mixed for post-freeze semen viability parameters. Bull within breed was not significant for sperm abnormalities. The night versus day treatment was significant for the managerial parameter (P=0.002). Although a different collection schedule for Bos indicus cattle was not warranted, the efficiency of the collection process was affected by extraneous environmental conditions.