EFFECT OF SHORT PHOTOPERIODIC CYCLES ON MALE GENITAL-TRACT AND TESTICULAR PARAMETERS IN MALE GOATS (CAPRA-HIRCUS)

This study was performed in adult male goats in which seasonal variati ons were abolished by rapid alternations of long days and short days. These treatments have been shown previously to prevent seasonal change s in the hypothalamo-pituitary axis and to maintain testis weight and sperm production at a high level. The experimental groups were exposed for 3 years to an alternation of either a 1 month short (16 h dark; 8 h light) and 1 month long (16 L; 8 D) photoperiod (2 month cycle; n = 5) or of a 2 month short and 2 month long photoperiod (4 month cycle; n = 4). The control groups were maintained in natural photoperiodic c onditions (45 degrees N) and goats were slaughtered in the non-breedin g season (end of April RS; n = 5) at the same period as light-treated bucks, or in the breeding season (end of September BS; n = 6). The tot al weight of the testes, the length and mean diameter of the seminifer ous tubules of light-treated goats were similar to those in the breedi ng season, and higher than those in the non-breeding season. The total number of A(0) spermatogonia was increased by light treatments as com pared to control goats in the breeding and non-breeding season. The da ily production of A(1) spermatogonia, leptonene primary spermatocytes and round spermatids in light-treated goats was maintained at the peak breeding season level. The intra-testicular concentration of testoste rone, total volumes of intertubular tissue and of Leydig cells, and th e number of Leydig cells per testis did not differ between groups. Alt hough the mean cross-sectional area of Leydig cells in light-treated g oats was similar to this area in non-breeding season goats, it was sig nificantly lower than that of breeding season goats. In conclusion, th e rapid alternation of short and long days allowed an increase in all the germ cells from the A(0) spermatogonia onwards, which was responsi ble for the maintenance of high spermatogenetic activity of light-trea ted goats.