Behavioural and morphological effects of 5 alpha-dihydrotestosterone and oestradiol-17 beta in the prepubertally castrated boar.

Three groups of 5 prepubertally castrated boars received twice weekly subcutaneous injections from 16 to 28 weeks of age of 5 alpha-dihydrotestosterone propionate (1 mg/kg), oestradiol-17 beta dipropionate (0.1 mg/kg), or a combination of the two steroids. The pigs were tested each week for sexual behaviour with an oestrogen-treated ovariectomized gilt. 5 alpha-Dihydrotestosterone did not induce copulatory behaviour whereas oestradiol initiated mounting, although this behaviour was not maintained. However, the combined hormonal treatment induced the full pattern of copulation, including ejaculation, in 4/5 pigs. Oestrogen-treated animals also showed champing and salivation. None of the pigs treated with 5 alpha-dihydrotestosterone showed lordosis when exposed to a mature boar. Increases in the size of the penis, the ischio- and bulbocavernosus muscles, seminal vesicles and bulbourethral glands were produced by 5 alpha-dihydrotestosterone, and, with the exception of the penis, this hypertrophy was further enhanced by additional treatment with oestradiol. Increases in the weight of the prostate and muscular urethra were due mainly to the effects of oestrogen; this steroid caused extensive development of fibromuscular tissue and also increased mammary teat length. In the submaxillary salivary glands, synergism between 5 alpha-dihydrotestosterone and oestradiol resulted in hypertrophy of the serous cells.