Use of FSH: LH as an alternative to stimulate follicular growth in sheep estrus synchronization / Utilização de FSH: LH como alternativa para estimular o crescimento folicular na sincronização do estro ovino

ABSTRACT

Background: Estrus synchronization is extensively applied in reproductive management of sheep world-wide. The use ofequine chorionic gonadotropin (eCG) in estrus synchronization protocols in sheep is well established. However, development of anti-eCG antibodies after repeated synchronizations results in poor synchronization and, eventually, in reducedfertility and lambing rates, especially when fixed time AI is applied. Works using FSH in estrus synchronization have beenscarce to date. So, the objective of the current study was to evaluate the effect of different follicular growth promoters(FSHLH and eCG) on estrus synchronization and ovulation in sheep.Materials, Methods & Results: Forty four ewes were submitted to estrus synchronization with medroxyprogesterone acetate (MAP) intravaginal devices for 12 days and a single i.m. treatment of either eCG (Group 300eCG, 300 UI, n = 11) orFSHLH (Group 20FSHLH, 20 UI, n = 11; Group 40FSHLH, 40 UI, n = 11; Group G20/20FSHLH, 40 UI divided intotwo doses injected 12 h before removal device time and at the exact removal time, n = 11) at the time of device removal.At the sponge removal, ewes were exposed to a teaser and estrus was monitored at 4-h intervals until all females showedthe clinical estrus. After 12 hours of estrus onset, ultrassonografic exams were performed to record ovarian response.Besides, blood samples were collected for progesterone (P4) measurements. Statistical analyses were performed usingANOVA and means were compared by Duncan test. Kurskal-Wallis test was used for corpus luteum and progesteronecomparison, considering a 5% significance level. There was no difference (P > 0.05) on the time of estrus (46.3 ± 11.8;52.4 ± 10.7; 53.0 ± 7.2; 51.8 ± 7.1) or ovulation (80.4 ± 17.3; 86.9 ± 11.0; 95.3 ± 6.1; 85.0 ± 5.7) among the 300eCG,20FSHLH, 40FSHLH, 20/20FSHLH groups, respectively. It was noticed, however, that there has been a variation in the...