Abstract

FERRAZ, H.T. et al. LH pre-ovulatory peak in synchronized Nellore breed (Bos taurus indicus) females. Arch. zootec. [online]. 2009, vol.58, n.224, pp.757-760. ISSN 1885-4494.

The aim of this work was to evaluate the frequency of pulses and the amplitude of the pre-ovulatory peak of the luteinizing hormone (LH) in Nellore heifers and cows submitted to a hormonal protocol. In six females owning to each category the following protocol was used: placement of the norgestomet implant (NOR) and application of 2.0 mg of estradiol benzoate (EB) on day zero, with retreat after eight days, followed by the application of 0.5 mg of sodic cloprostenol. After 24 hours (day nine) 1.0 mg of EB was used. The blood sampling was initiated 27.00 hours after the application of the second dose of EB, and repeated every 15 minutes for a six hours period. Seric levels of LH were detected by radioimmunoassay method. In one heifer and in four cows the pre-ovulatory peak of LH was observed. In the heifer the peak was verified in the first sampling, 27.00 hours after the ovulation induction. In the cows this occurred on 28.20±0.55 hours after application of EB. The maximum amplitude verified was 4.58±0.67 ng/ml. In the animals in which LH peak was not observed, the average concentrations were 0.90±0.03 ng/ml for the heifers and 0.86±0.03 ng/ml for the cows. It suggests that in the heifers the pre-ovulatory peak of LH, probably, have occurred more precociously than in the cows. However, more studies about the LH peak moment in bovine females with synchronized ovulation are needed.

Keywords : Estradiol benzoate; Bovine; TAI; Progestins; Reproduction.

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