Repeated systemic β-NGF administration improves ejaculate characteristics in rams.

β-Nerve growth factor (β-NGF) influences reproductive function in several mammalian species, but the effects of repeated systemic administration on ram ejaculate traits are unknown. We evaluated the effects of four intramuscular administrations of 1 mg β-NGF purified from llama seminal plasma, given at 5-day intervals during the transition from the non-breeding to the breeding season, in adult Corriedale rams. Rams were assigned to a β-NGF-treated group or an untreated control group (n = 9/group). Semen was collected repeatedly from before treatment until Day 58, and evaluated scrotal circumference, serum testosterone, ejaculate traits, sperm motility, morphology, membrane functionality, and sperm kinematics were evaluated. β-NGF enhanced the temporal profiles of ejaculate volume and total sperm per ejaculate. Treated rams had a greater total number of sperm per ejaculate on 18, 30, and 37 days after beginning the treatment, and a greater ejaculate volume on day 37. Treatments did not affect the percentages of motile, morphologically normal, and HOST-positive sperm. Circulating testosterone concentrations and scrotal circumference were also unaffected. Thus, repeated systemic β-NGF administration transiently increased total sperm per ejaculate at specific post-treatment times without detectable changes in the evaluated indicators of sperm quality. The mechanisms underlying this response and its consequences for semen preservation and fertility remain to be determined.