Effect of dihydrostreptomycin or oxytetracycline on reproductive capacity of bulls.

Young beef bulls (n = 27) were used in a trial to study the effect of dihydrostreptomycin sulfate (DHS) or oxytetracycline (OTC) hydrochloride on spermatogenesis, epididymal sperm maturation, and freezability of sperm. Nine of the bulls were given a 22 mg/kg dose of DHS twice, 12 hours between doses. Nine other bulls were treated with OTC--1 dose of 26.4 mg/kg of body weight, and then 6 more doses each of 17.6 mg/kg, ca 12 hours between doses. The remaining 9 bulls were nontreated controls. The treatment regimens with the 2 antibiotics were without effect on spermatogenesis. These treatments also were without effect on seminal pH, ejaculate volume, percentage of motile spermatozoa, rate of spermatozoal motility, or concentration of spermatozoa in ejaculates harvested on day 3 or 7 of the study (day 0 = 1st day of treatment). There was a treatment-by-day effect on spermatozoal concentration; the number of sperm per milliliter was markedly increased on day 3 for OTC-treated bulls. The increased spermatozoal concentration in the OTC-treated group was associated with an influence of the antibiotic on ejaculation. All bulls given this antibiotic ejaculated without palpable penile engorgement or erection on day 3. On day 7 the rate of spermatozoal motility was increased in the 2 treatment groups compared with the rate in the control bulls. Also on day 7, the percentage of motile spermatozoa was greater in the OTC-treated bulls than in the control or DHS-treated bulls.(ABSTRACT TRUNCATED AT 250 WORDS)