Long days in winter or the presence of adult sexually active rams did not influence the timing of puberty of autumn-born Rasa Aragonesa ram-lambs

The effect of being housed with adult female flock-mates on the age at puberty of autumn-born ewe-lambs

Twenty-five ewe-lambs born in November were used to measure the effect of the presence of cyclic or non-cyclic adult ewes on the age at first fertile estrus. Lambs were weaned at 45 days of age and kept in a single flock until 3 Mar (4 months old), when they were assigned to one of the following three groups: Group CE (n = 8), housed with six cyclic adult ewes; Group NCE (n = 8), housed with three non-cyclic ovariectomized adult ewes, and Group ISO (n = 9), housed isolated from adult ewes. On 2nd May (6 months old), two rams were introduced into each group, until 31st Oct (12 months old), when rams were removed. Adult ewes in group CE were separated from rams and ewe-lambs by a metal fence, allowing visual, olfactory, and nose-to-nose contact between animals. Average earliest fertile estrus was significantly (P < 0.01) earlier in NCE ewe-lambs (8th Aug) than it was in ISO (9th Sep) and CE (17th Sep) ewe-lambs, they lambed about 35 d earlier (1st Jan) than did the other two groups (2nd Feb and 10th Feb, respectively) (P < 0.01), and at an earlier age (14 mo, 15.2 mo, and 15.3 mo, respectively; P < 0.01). In conclusion, the presence of non-ovulatory adult ewes advanced puberty in autumn-born ewe-lambs of a Mediterranean genotype. The factor(s) that delayed age at puberty in isolated females and those housed with estrous adult ewes remains to be elucidated.

The continuous presence of ewes in estrus in spring influences testicular volume, testicular echogenicity and testosterone concentration, but not LH pulsatility in rams

The continuous presence of active male small ruminants prevents seasonal anestrus in females, but evidence of the same mechanism operating from the females to the males is scarce. This study assessed the effects of the continuous presence of ewes in estrus in spring on ram sexual activity, testicular size and echogenicity, and LH and testosterone concentrations. On 1 March, 20 rams were assigned to two groups (n = 10 each): isolated (ISO) from other sheep, or stimulated (STI) by 12 ewes, which were separated from the rams by an openwork metal barrier, allowing contact between sexes. Each week, four ewes were induced into estrus by intravaginal sponges. Live weight, scrotal circumference, testicular width (TW) and length (TL) were recorded at the beginning and at the end of the experiment, and testicular volume (TV) was calculated; at the same time, testicular ultrasonography and color Doppler scanning were performed. Blood samples (March to May) were collected once per week for testosterone determinations, and at the end of the experiment, blood samples were collected for 6 h at 20-min intervals for LH analysis. Rams were exposed to four estrous ewes in a serving-capacity test. Scrotal circumference, TW and TL were higher in the STI than in the ISO rams (P < 0.05) in May, and TV was higher (P < 0.05) in the STI (391 ± 17 cm3) than in the ISO rams (354 ± 24 cm3). In ISO rams, the number of white pixels was higher (P < 0.01) in May (348 ± 74) than in March (94 ± 21) and differed significantly (P < 0.01) from that of the STI rams in May (160 ± 33). In ISO rams, the number of grey pixels was higher (P < 0.05) in May (107 ± 3) than it was in March (99 ± 1). Stimulated and ISO rams did not differ significantly in mean LH plasma concentrations (0.8 ± 0.5 v. 0.9 ± 0.4 ng/ml), LH pulses (2.1 ± 0.5 v. 2.2 ± 0.2) and amplitude (2.0 ± 0.4 v. 3.2 ± 0.7 ng/ml, respectively). Stimulated rams had significantly higher testosterone concentrations than ISO rams from April to the end of the experiment. Stimulated rams performed more (P < 0.05) mountings with intromission (3.0 ± 0.4) than did ISO rams (1.5 ± 0.5). In conclusion, after 3 months in the continuous presence of ewes in estrus in spring, rams had higher TV and some testicular echogenic parameters were modified than isolated rams. Although exposed rams also had higher levels of testosterone after 2 months in the presence of estrous ewes, their LH pulsatility at the end of the study was not modified.