116 Differences between 5- and 6-day progestogen-based oestrus induction protocol in Saanen and Toggenburg goats

Abstract

Hormonal oestrus induction treatment is an important tool for the success of reproductive biotechniques in anoestrus goats. In the nonbreeding season, oestrus induction can be performed by the use of several protocols, including those varying in their duration. This study aimed to compare short-term (for either 5 or 6 days) progestogen-based oestrus synchronization protocols in dairy [Toggenburg (n=12) and Saanen (n=12)] goats during the nonbreeding season. This study was performed in Minas Gerais State, Brazil (21°35′S and 43°15′W), with 12 nulliparous (12–14 months old) and 12 pluriparous (2–4 years old in final third of lactation) goats, all with body condition scores (BCS) of 3.0 to 3.5. They were equally assigned to both treatments according to their order of parturition, BCS, and breed. On a random day (Day 0), 24 goats received an intravaginal device of 60mg of medroxyprogesterone acetate (Progespon®, Zoetis) which remained for 5 (G5; n=12) or 6 (G6; n=12) days. On Day 5, goats from both groups received 30µg of cloprostenol intramuscularly (IM) (Prolise®, ARSA S.R.L.) and 200IU of equine chorionic gonadotrophin (eCG) IM (Novormon®, Schering Plough Animal Health). Both groups received cloprostenol and eCG on the same day (regardless of device removal) to ensure they were administered at the same follicular wave. Both device insertion and removal were performed in the morning. Ultrasound evaluations were performed every 12h from device removal to ovulation detection. Ovulations were considered as the average interval between the last observation of follicles and the first exam in which it was no longer seen. The normal distribution of variables was determined by Shapiro-Wilk test and homocedasticity by Levene’s test. All variables were not normally distributed and thus analysed by Mann–Whitney U test, with P<0.05 considered significantly different. Values are presented in median±interquartile range. There was no difference between G5 and G6, respectively, in the interval to oestrus (48.0±0.0 vs. 48.0±12.0h), interval from oestrus onset to ovulation (18.0±9.0 vs. 18.0±12.0h), interval from device removal to ovulation (66.0±18.0 vs. 66.0±24.0h), number of ovulated follicles (2.0±2.0 vs. 2.5±2.0), or mean diameter of ovulated follicles (6.6±1.6 vs. 6.6±1.4mm). All ovulations were detected in the morning. In conclusion, our data demonstrate that short-term hormonal treatment for 5 or 6 days is similarly efficient to induce synchronous oestrus in Saanen and Toggenburg goats. This research was supported by EMBRAPA (Project 20.19.01.004.00.03.001) and CNPq (314952/2018-7).