The experiments were carried out to clarify the effects of PGF_2α on the contractility of boar testis, epididymis and vas deferens in vitro. The prepared specimens were placed in a Magnus tube containing Tyrode solution (33°C). Contractile responses were recorded isotonically on a Kimograph, with addition of PGF_2α into Tyrode solution in varying levels (10^-7, 10^-6, and 2x10^-5g/ml). The contractile responses to PGF_2α were not clear in the parenchyma and mediastinum of the testis, whereas both the epididymis and vas deferens showed a slight response to 10^-7g/ml of PGF_2α and notable contraction to PGF_2α in concentrations over 10^-6g/ml. The magnitude of the contractility of the tail of epididymis and that of vas deferens were greater than those of the head and the body of epididymis (p<0.05). Tonic contraction was most often observed among other types of the contraction. Rhythmical contraction was observed partly in the tail of epididymis and phasic contraction was noted mainly in vas deferens.

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The effects of sex on differences in carcass traits and physico-chemical properties of muscle and adipose tissues were investigated using four castrated males and four females of crossbred Berkshire sow×wild boar (Sus scrofa leucomytax), all wich were littermate. These animals were slaughtered at a live weight of approx. 90kg and were subjected to the experiment. The following results were obtained.
1) There were no appreciable differences in dressing percentage, and in the balance of anterior, central and posterior parts of body between the castrated males and the females. As to the ratios of composition of bone, fat and muscles in the posterior part, the ratios of bone and fat were significantly higher in the castrated males than in the females, while that of muscles was significantly higher in the females than in the castrated males.
2) Back fat tended to be thicker in the castrated males than in the females. The loineye area was significantly larger between the 5th and the 6th and between the 10th and the 11th thoracic vertebrae of the females than in the castrated males.
3) There were no significant differences between the castrated males and the females in terms of the chemical composition of muscles and the color shade of M. longissimus dorsi.
4) No appreciable difference was observed between the castrated males and the females in the composition of fatty acids in muscles. There was no significant difference between the castrated males and the females in the composition of fatty acids of back fat, whereas the content of oleic acid in kidney leaf fat of castrated males was significantly higher than that of the females, although the content of linoleic acid in it was significantly higher in the females than in the castrated males.
From the above-mentione results, it was conceived that the differences in physico-chemical properties between the castrated males and the females were comparatively small as compared with carcass traits.

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Two hundred and forty six litters from imported purebred guts including Landrace (L), Large White (W), Duroc (D), Hampshire (H) and locally introduced Tauyen (T) natives were used to investigate reproductive performance. The ages at first farrowing were found youngest for L and followed by D, W, T, H in the order. The durations of gestation were longest for T (116.9 days) while D, W, H and L were in the range of 114-115 days. L had the shortest farrowing interval (between the first and second parity) while W and D took approximately 10 days longer and H 15 days longer. The best conception rate was found in T (82.76%), follwed by L, D, H, W in the order. Farrowing rates of W, D, T, L were high while that of H was low. Litter size was large at bornin T, L and W. At three and eight weeks, litter-size of L and W were large while that of T was similar to L, but H and D were smaller at these ages. Survival rates in L, W, D, T were similar but in H poor. L had the heaviest litter weight at born, 3 weeks and 8 weeks, followed by W but T had the lightest litters except at 3 weeks. The average pig weights of L were the heaviest and that of T the lightest. There were similar average pig weights at 3 weeks for all breeds but at 8 weeks T were the smallest of them.

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