Variation in puberty phenomena in inbred boars.

H ISTOLOGICAL studies of testes from developing boars have given information on the initiation of spermatogenesis but do not provide information on the age at which young boars develop the ability and desire to mate. Phillips and Andrews (1936) examined the testes of eight Chester White and Berkshire boars castrated at ages varying from 10 to 147 days of age. Little testicular development was noted before 84 days and sperm were found at 147 days. Phillips and Zeller (1943) studied the testes of 44 large type and 35 small type Poland China boars castrated at ages varying from 5 to 40 weeks. No sperm were found in the tubules of boars of either type before 20 weeks and in some individuals of both types no sperm were found at 20 or at 22.5 weeks. However sperm were found in some tubules in all animals of both types at 25 weeks or later. Boars of both types developed sperm at about the same average age but the small type was more variable in the time at which a major portion of tubules began producing sperm. There was some indication that the mature size of the tubules was greater in the large type and that the testes weight was greater in the large type at all ages above 25 weeks. More recently Andrews and Warwick (1949) studied the testes of more than 200 boars (outbreds, inbreds, crossbreds and linecrosses) castrated at ages varying from 70 to 140 days. In one strain sperm were found rather consistently at i10 days while in another strain sperm were not present in all individuals until 140 days; boars of other strains were intermediate between these two. In a similar study of 3 inbred lines and the crosses between them, Hauser, Squires, Dickerson and Mayer (1949) found that the crosses exceeded inbreds by 30 percent in body and testis weight and by 21 percent in epididymis weight and stage of spermatogenesis at an average age of 150 days. From the above studies it appears fairly certain that sperm are present in the testes of most boars at about 5 months of age and there is an indication of breed and strain differences in rate of testicular