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One day before the device was withdrawn; an injection of 25 mg of prostaglandin F2a (Dinoprost Pfizer, México) was administered.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.

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