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.