| The main objective was to study the effect of elevated temperatures, gossypol, Vitamin E, and breed differences on spermatogenesis and spermatogenic apoptosis. First, induction and assessment of apoptosis were studied. Experiment (exp.) 1 (Angus, n = 11), included; (1) control, (2) E. coli endotoxin, and (3) scrotal insulation (SI). Spermatogenesis (daily sperm production, DSP and DSP/g, DSPG) and apoptosis were assessed at 10 d. Experiment 2, (Angus, An; Senepol, Se; Romosinuano, Ro; n = 18) included; (1) control and (2) SI. Assessment was done at 2 d and 4 d. In exp. 1 and 2 treatment had no effect on spermatogenesis and apoptosis.;Second, effects of gossypol and vitamin E on spermatogenesis and apoptosis were tested. Young Holstein bulls (n = 24) were supplemented with either; (1) CONT (soybean meal, corn, and vitamin E, (2) GOSS (cotton seed meal, CSM, corn, and vitamin E), and (3) G+VITE (CSM, corn, and vitamin E). Spermatogenesis was less (P ≤ 0.05) in GOSS than CONT or G+VITE. Gossypol had no effect on apoptosis, although there was an inverse relationship between spermatogenesis and apoptosis (P < 0.05).;Third, young B. taurus, B. indicus, and crossbred bulls were evaluated during the summer in Florida. In exp. 1 (n = 36), An, Ro, Brahman (Br), and Nelore x Brahman bulls were used. Breed had no effect on spermatogenesis, extragonadal sperm reserves (ESR) (caput), and ESR (cauda). However, ESR (corpus) in Br was higher than in An and Ro (P ≤ 0.05). In exp. 2, crossbred bulls (n = 112; Senepol x Angus, SA; Tuli x Angus, TA; Brahman x Angus, BA) were used, and DSP (perhaps DSPG) was less in BA than in SA and TA (P < 0.05). In exp. 3, mature Brahman (n = 2) and miniature Brahman (n = 5) bulls were used, and DSP was less in miniature than in Brahman bulls (P < 0.05). In exp. 2 and 3 breed did not affect apoptosis.;This study failed to observed increases in spermatogenic apoptosis as a result of E. coli endotoxin, SI, gossypol, summer temperatures, and breed. In general, low levels of apoptosis were detected and reasons for this may include inappropriate sampling times and test sensitivity. |
