EFFECT OF TIMING OF ARTIFICIAL INSEMINATION ON THE FERTILITY AND SEX RATIO IN NELORE HEIFERS

Authors

  • Artur Emilio Freitas e Silva UFRGS
  • Miguel Joaquim Dias UFG
  • Darci Silva de Oliveira Dias UFG
  • João Batista Duarte UFG
  • José Ricardo Almeida de Andrade UCG

DOI:

https://doi.org/10.5216/cab.v9i4.1668

Keywords:

diagnóstico de gestação, gado de corte, manejo, sexagem, ultra-sonografia.

Abstract

The aim of this study was to evaluate the effect of timing of artificial insemination on the fertility and calf sex ratio in Nelore heifers (n = 200) submitted a protocol of timed artificial insemination (TAI).  The heifers, distributed into five groups (GC, GT6, GT12, GT18 and GT24), presented a mean of 2.5 years old and 342 Kg of body weight. The inseminations were performed in the moments 0 (GC), 6 (GT6), 12 (GT12), 18 (GT18) and 24 (GT24) hours after the injection of GnRH. The conception rates were 87.5% (GC), 82.5% (GT6), 77.5% (GT12), 85.0% (GT18) and 77.5% (GT24). There was no statistical difference (p>0.05) in the conception rates between the five treatments. The percentage of calved males was 38.2% (GC), 48.5% (GT6), 45.2% (GT12), 55.9% (GT18) and 58.6% (GT24). The male/female ratio was 0.62 (GC), 0.94 (GT6), 0.82 (GT12), 1.27 (GT18) and 1.42 (GT24). Statistical difference was found (p<0.05) in the male/female ratio between the five treatments. The timing of artificial insemination has influence on the sex ratio, showing an increase in the proportion of calved males when the insemination is progressively delayed. Within of the measured interval of time (0-24h after GnRH), the fertility of Nelore heifers is not influenced by the moment of the artificial insemination.

KEY WORDS: Beef cattle, management, pregnancy test, ultrasound, sexing.

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Author Biographies

Artur Emilio Freitas e Silva, UFRGS

Doutorando em Ciências Veterinárias na área de Reprodução Animal pela Universidade Federal do Rio Grande do Sul - UFRGS, Av. Bento Gonçalves, 9090, CEP 91540-000, Porto Alegre, RS. Bolsista CAPES. E-mail: tursilva@terra.com.br.

Miguel Joaquim Dias, UFG

Prof. Dr. Departamento de Produção Animal da Universidade Federal de Goiás – UFG.

Darci Silva de Oliveira Dias, UFG

Prof. Dr. Departamento de Produção Animal da Universidade Federal de Goiás – UFG.

João Batista Duarte, UFG

Prof. Dr. Departamento de Melhoramento Genético – Escola de Agronomia, Universidade Federal de Goiás - UFG

José Ricardo Almeida de Andrade, UCG

Prof. Dr. Departamento de Zootecnia da Universidade Católica de Goiás - UCG

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Published

2008-12-21

How to Cite

SILVA, A. E. F. e; DIAS, M. J.; DIAS, D. S. de O.; DUARTE, J. B.; ANDRADE, J. R. A. de. EFFECT OF TIMING OF ARTIFICIAL INSEMINATION ON THE FERTILITY AND SEX RATIO IN NELORE HEIFERS. Brazilian Animal Science/ Ciência Animal Brasileira, Goiânia, v. 9, n. 4, p. 997–1003, 2008. DOI: 10.5216/cab.v9i4.1668. Disponível em: https://revistas.ufg.br/vet/article/view/1668. Acesso em: 23 nov. 2024.

Issue

Vol. 9 No. 4 (2008)

Section

Animal Production

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