Abstract:The aim of this study was to evaluate the use of melengestrol acetate (MGA) as a strategy to improve the production efficiency in ewes of rural areas in México. Twenty ewes of breeds (Dorper and Dorper with Pelibuey) non-pregnant and with ovarica activity were used. The treatment consisted of the administration of 0.22 mg MGA/ewe/d for 17 d. The MGA efficiency was measured once the treatment finalized, and the producer was responsible for the registration of the estrus presentation and prolificacy rate. 95% of the sheep presented estrus in a period of 14 d after stopping treatment. The prolificacy percentage was of 1.2 lambs born by ewe during a period of six months (including treatment and period of gestation). In conclusion, the use of MGA represents an alternative to improve the efficiency of sheep production in rural areas in México, since it can increase the number of lambs by 30% in a period of 12 months.
The aim of this study was to evaluate the effect of a Prolonged Melengestrol Acetate (MGA) treatment in prepubertal goats on the induction of ovarian activity, induction and synchronization of estrus and pregnancy rate. 10 pre-pubertal Saanen goats, 9 months of age, body condition of 2.1±0.32 (scale 1-5), a live weight of 30.44±1.93kg and size of 62.1±2.69cm were used. The treatment consisted on the administration of 0.22mg/goat/day of MGA orally, during 46 days. During the treatment, the ovaries were evaluated by rectal ultrasonography using a 7MHz transducer on days 15, 30 and 45 to observe the presence or absence of follicles. Once the treatment was completed, the sire was placed in the pen with the goats and estruses were detected during 10 days post-treatment. The pregnancy diagnosis was performed 45 days after breeding via transabdominal ultrasound using a 3.5 and 5MHz transducer. Since the first evaluation of ovarian activity, the 10 goats showed follicle development; in the right ovary an average of 9.66˂4mm and 9.33≥4mm was observed and in the left ovary 11.33˂4mm and 9.66≥4mm, without the presence of corpus luteum. 100% of the goats presented estrus and the pregnancy rate was 90%; concluding that the use of MGA at a dose of 0.22mg/goat/day in pre-pubertal goats during prolonged treatment induces follicular development, estrus synchronization and a high percentage of fertility by natural mating is obtained.
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