The effect of ACTH and progesterone on semen characteristics, blood hormones and testicular histology in the bull

Two experiments were designed to hormonally induce spermatozoal abnormalities in the ejaculate specifically, those abnormalities associated with the cytoplasmic droplet syndrome. The endocrine response during and following hormone administration was monitored to determine if there was an association between the appearance of spermatozoal abnormalities and plasma hormone changes. During Experiment 1, one 7-yr-old and two yearling Holstein bulls were injected with 200 IU ACTH every 8 hr for 6 days. In Experiment 2, two groups of three yearling Holstein bulls each were injected daily with crystalline progesterone in propylene glycol (.84 mg/kg body wt) for 21 days. Semen characteristics (sperm abnormalities, percent motility, sperm concentration and ejaculate volume) were measured for each of four ejaculates collected weekly from each bull. Semen was collected 9 wk prior to hormone treatment, during and for 8 and 9 wk after the treatment period in Experiments 1 and 2, respectively. During Experiment 1, percent intact acrosomes were measured weekly. Tonometer measurements of testicular consistency were made weekly for each bull during Experiment 2. Blood samples were obtained prior to, during and after hormone treatment in both experiments. The hormonal response in total corticoids, testosterone and androstenedione was monitored in Experiment 1. During Experiment 2 corticoids, testosterone, LH and progesterone concentrations were monitored. Corticoid concentrations were determined by competitive protein binding; androstenedione, progesterone, LH and testosterone were determined by radioimmunoassay.

In Experiment 1, mean (±SE) corticoid concentrations for all three bulls were elevated from 11.9±2.7 to 73.5±4.1 ng/ml during ACTH administration. Testosterone was suppressed in the yearling bulls from 5.5±.9 to 0.5±.5 ng/ml beginning 8 hr following the initial ACTH injection until 24 hr following the last injection. The mature bull maintained normal testosterone concentrations for the first four injection days, and then concentrations were suppressed for the last 2 days of injection. Although not significant, androstenedione concentrations for all bulls were elevated during treatment. Semen quality and sperm output were unaffected by ACTH treatment.

In Experiment 2 progesterone administration increased plasma progesterone concentrations during and after treatment in both groups of bulls. There was a significant group by treatment interaction for progesterone. Endogenous (pre-treatment) progesterone levels were higher in Group 2 than in Group 1 (2.5±.4 vs 0.5±1.0 ng/ml). However, the magnitude of the progesterone response to treatment was higher in Group 1 than Group 2 (7.3±.9 vs 5.6±.3 ng/ml). In addition, testosterone and LH concentrations were significantly lowered during treatment. There was no change in corticoids.

Although only two bulls in Group 1 and none of the bulls in Group 2 responded with increased abnormals, there was a significant increase in abnormals associated with progesterone treatment. Proximal, translocating and distal cytoplasmic droplets and detached sperm heads were the predominant abnormalities induced by progesterone treatment. Percent motility and ejaculate volume were significantly decreased for the three week period following progesterone treatment in both groups. Changes in sperm concentration and weekly sperm output were noted. No change in testicular tonicity was observed.

There was no evidence of premature spermiation or change in frequency of the stages of the cycle of the seminiferous epithelium in testicular tissue from treated bulls. However, variation in acrosomal development and nuclear condensation was observed among syncytia of spermatids within the same cross section of a seminiferous tubule. This was not associated with progesterone treatment.