1407
RAMS TREATED WITH TESTOSTERONE INDUCE SEXUAL ACTIVITY IN ANOVULATORY DORPER ADULT SHEEP
The aim of this study was to determine whether rams treated with testosterone induce estrus in multiparous anovulatory ewes in northern Mexico (26 ° N). On April 15, Dorper multiparous ewes (n=60) were randomly distributed to two experimental groups; all females received daily 30 mg i.m. of progesterone from day -8 and day -4 prior to contact with males. On April 20, while one group (GMT, n = 31) was exposed to three males treated with testosterone (25 mg i.m., every 3 days x 2 weeks before mating), the other group (GMC, n = 29) was exposed to three non-testosterone treated males. Estrous response was evaluated in two periods. The first period from day 0 to 14 while the second period from 15 to 25 days after male introduction (twice daily, during 1 hour). On day 10 and 25 of the experimental period, ovulation rate was assessed throughout ultrasonographic scanning. Estrus activity was compared using chi2 (SYSTAT program 12). During the first 14 days after male introduction, 87% of the GMT-ewes (27/31) ovulated but only 9.6 % (3/31) showed estrus activity, whereas 68% of the GMC-females (20/29) ovulated and 3.4 % (1/29) showed estrous activity. After 15 days post-male introduction, 83% of the GMT-females(26/31) ovulated, with 80% of the ewes showing signs of estrus (25 /31). Regarding the GMC-females, 51 % (15/ 29) ovulated, and 68% (13 /29) showed signs of estrus activity. Results of this study confirm that males treated with testosterone are more effective to induce ovulation and estrus activity during the second phase of the experimental period (15-25 days after male introduction) in Dorper adult ewes, regarding the untreated-males.
Table 1. Sexual response in sheep exposed to male control group (GC) or treated with testosterone (GT).
|
Response 0-14 days after introduction of males |
Response 15-25 days after introduction of males |
||
|
Ovulation |
Estrous |
Ovulation |
Estrous |
GT |
87% (27/31)a |
9.6% (3/31)a |
83%(26/31)a |
80%(25/31)a |
GC |
68%(20/29)a |
3.4%(1/29)a |
51%(15/29)b |
68%(13/29)b |
Different letters in columns indicate different statistical differences P> 0.05
Keywords: testosterone, sheep, anestrus, estrus activity