Temporada corta de reprodución controlada com ovejas Santa Inês criadas em clima tropical húmedo

Abstract

The objective of this work was to evaluate the adoption of management techniques that could allow for a shorter controlled breeding season. In three consecutive mating seasons (MS1: September/2021, n=45; MS2: June/2022, n=42 and MS3: March/2023, n=43), lactating Santa Ines ewes, multiparous, aged between two and four years, mean live weight of 62.20 ± 4.60 kg and mean body condition score of 3.4 ± 0.4 (scale 1-5), two vasectomized males and two breeding rams with prior andrological evaluation, one Santa Ines and one Dorper. A pre-mating period was implemented with biostimulation using vasectomized males for 21 days. After this period, on day 0 (D0), an IM injection of 120.5µg of cloprostenol, a prostaglandin F2alpha analogue (PGF2α), was performed and estrus was observed until D3; ewes with identified estrus were mated by the breeding rams, as per controlled breeding. Ewes that did not show estrus were submitted to a second IM injection of PGF2α seven days after the first dose (D7), then repeating the management of estrus observation and controlled mating. Ewes were allowed three attempts at conception. Pregnancy diagnosis was performed by ultrasonography (D30). During biostimulation, 100% of the ewes showed estrus in the three mating seasons. There was no significant difference in performance between seasons (P>0.05). From the total of ewes in season (n= 130), 90.0% (n=117) became pregnant, 71.5% (n=93) in the first, 13.9% (n=18) in the second and 4.6% (n= 6) in the third mating. Prior biostimulation was efficient in inducing estrus to lactating Santa Ines ewes and the use of PGF2α was sufficient to synchronize estrus and generate a shorter controlled breeding season with up to three matings, presenting an efficient method to concentrate births and standardize allotments of lambs in a production system under humid tropical climate.