Potential for Producing Viable Embryos in Post Pubertal Heifers. Comparison during the Dry and Wet Seasons in the Tropics Using a Protocol Based on FSH or eCG

Abstract

The use of pubertal heifers to produce embryos before their natural breeding period which is normally at 3 years is a possibility that needs to be researched thus the objective of this assay was to superovulate pubertal Bos indicus heifers to obtain embryos in the dry and wet season, two phases were fodder availability is quite distinct.Twenty Brahman heifers 18 to 24 months and weighing 300 to 330 kg were synchronized with a progesterone releasing device (CIDR, Pfizer, Mexico) for 9 days and concomitantly applying a superovulatory regimen, using a total of 280 mg of FSH (Folltropin-V Bioniche Mexico) in eight applications with decreasing dosages 12 h apart, starting with two dosages of 50 mg followed by another two of 40, two of 30, and ending with two of 20 mg.One day before the device was withdrawn; an injection of 25 mg of prostaglandin F2α (Dinoprost Pfizer, México) was administered. For treatment with eCG an injection of 2000 I.U. of Equine Chorionic Gonadotropin eCG (Folligon, Intervet México) was administrated at day 6 after CIDR insertion. There were differences in the total follicular response between the dry season average n = 84 and the wet, average n = 51 (p < 0.05) but not between treatments. The number of good quality embryos recovered in either season was not more than 4. Response in relation to number of corpus luteum (CL) present and number of embryos was affected by season (p < 0.05) regardless of the treatment utilized.The production of embryos in post pubertal heifers is not feasible based in our results. Heat stress, nutritional inconsistencies, season when treatment applied and age might be some of the main driving factors for this poor response.

Prospects for increasing the utilization of cattle embryo transfer by small‐scale milk and meat producers in tropical regions

“…An alternative for these producers is to use young replacement heifers as recipients with the shortcoming that they can be unpredictable in their responses to any sort of hormonal manipulation (Paez et al., 2015; for review see Maquívar & Galina, 2010). In addition, they can be more prone than multiparous females to losing pregnancies between 30 and 60 days of gestation (14.5% (39/269) vs. 9.2% (27/294), respectively, p =.05) (Baruselli et al., 2010).…”