Three experiments employing 40, 39 and 15 Large White × (Landrace × Large White) gilts respectively were carried out to investigate possible primer pheromone activity (i.e. regulating endocrine systems) for those 16-androstene steroids with known signalling pheromone activity (i.e. immediate behavioural effects) in the pig. Experiment 1 consisted of groups of prepubertal gilts exposed to one of the following odour sources (a) 5α-androstenone (5α-androst-16-en-3-one), (b) 3α-androstenol (5α-androst-16-en-3α-ol), (c) a mixture of both steroids, and (d) a diethyl ether extract of boar submaxillary salivary gland. Age at the onset of puberty in these gilts was compared with that in an unstimulated control group. Experiment 2 was similar to Experiment 1 except that the steroids were used at a higher concentration (100 fold), and a fifth group of gilts was exposed to an intact boar. In the third experiment, age at the onset of puberty was noted following exposure of groups of gilts to one of the following (a) a castrated boar which had received long term injections of testosterone, (b) urine from an intact boar, (c) an intact boar.
The results confirmed that the intact boar accelerates puberty in gilts. Although there was no conclusive evidence indicating that isolated boar odours had an effect on the onset of puberty, it is noteworthy that of those gilts exposed to 3α-androstenol, more reached puberty earlier than control gilts. However there is the possibility that transportation may have enhanced the earlier puberty found in some of the gilts taken to a source of 3α-androstenol. Prolonged treatment of a castrated boar with testosterone did not maintain its ability to accelerate puberty in gilts.