Endocrine events during the periestrous period and the subsequent estrous cycle in ewes after estrus synchronization.

The aim of the present study was to investigate the endocrinology of the periestrus period and that of the subsequent estrous cycle in ewes synchronized during the breeding season. Animals were treated for 14 days with either MAP intravaginal sponges or subcutaneous progesterone implants, followed by administration of 500 IU PMSG at the time of withdrawal. The time to estrus occurrence following progestagen withdrawal differed significantly between groups (45.3+/-2.7h for the MAP and 21.5+/-1.2h for the implant group, P<0.001). Estradiol levels around estrus did not differ between groups, but a significant difference was detected for the interval from peak estradiol to estrus, with a shorter interval for the implant group (26.7+/-0.7 and 2.7+/-0.9h, P<0.001). Progesterone implants shortened the interval from removal to LH surge, compared to the MAP group (31.2+/-4.4 and 56.5+/-3.6h, respectively, P<0.05). An earlier response was also observed for the interval from estradiol peak to LH peak in the implant group (12.1+/-3.3 and 37+/-2h, respectively, P<0.005), but no difference was observed for the interval from estrus to LH surge. Progesterone levels, particularly during the Days 6 to 10 of the subsequent estrous cycle were significantly higher (P<0.05) in the implant group. It is concluded that the kind of progesterone treatment may affect the time of estrus and the LH peak as well as the progesterone levels of the subsequent cycle.

Sexual activity and body and testis growth in prepubertal ram lambs of Friesland, Chios, Karagouniki and Serres dairy sheep in Greece.

Sexual activity, body size and testis growth in the prepubertal period (120-210days of age) were studied in five male lambs of each of four dairy sheep breeds. Sexual responses developed earlier in Friesland than in Chios and Karagouniki and latest in Serres ram lambs. Friesland lambs expressed interest in females at 127days of age and 34kg live weight 18-36days younger and 3.4-6.3kg lighter than the three Greek breeds. Puberty (first mounting with ejaculation occurred) of ram lambs appeared to be more closely associated with body weight than with chronological age. Age at puberty averaged 179days in Friesland, 8, 10 and 30days younger (P<0.05) than in Karagouniki, Chios and Serres, respectively. On the other hand, weight at puberty averaged 50kg for Friesland and Chios compared to about 44kg for the two other breeds (P<0.05). In the four breeds studied there was a 41-52days interval between the time when lambs first expressed interest in females and the time puberty occurred, the longest was that of Friesland lambs. There was a significant breed difference in scrotal circumference. At puberty the scrotal circumference was 33.9cm in Friesland lambs, 4-6cm greater than in the three Greek breeds. Friesland ram lambs had a greater scrotal circumference throughout the entire period studied.