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RESEARCH ARTICLE

Effect of hCG administration during corpus luteum establishment on subsequent corpus luteum development and circulating progesterone concentrations in beef heifers

V. Maillo A , P. Duffy B , L. O’Hara B , C. de Frutos A , A. K. Kelly B , P. Lonergan B and D. Rizos A C
+ Author Affiliations
- Author Affiliations

A Departamento de Reproduccion Animal, Instituto Nacional de Investigacion y Tecnologıa Agraria y Alimentaria (INIA), Carretera de la Coruna, KM 5.9, 28040 Madrid, Spain.

B School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.

C Corresponding author. Email: drizos@inia.es

Reproduction, Fertility and Development 26(3) 367-374 https://doi.org/10.1071/RD12353
Submitted: 1 November 2012  Accepted: 6 February 2013   Published: 5 March 2013

Abstract

This study examined the effect of a single administration of human chorionic gonadotrophin (hCG) on Day 1 to 4 after oestrus on corpus luteum (CL) development and circulating progesterone (P4). Oestrus-synchronized heifers (n = 43) were administered a single intramuscular injection of saline on Day 1 (control) or 3000 IU hCG on Day 1, 2, 3 or 4 after oestrus. Administration of hCG on Day 1 had no effect on CL area, on Day 2 increased CL area from Day 6 to 12 (P < 0.05), on Day 3 increased CL area from Day 9 to 11, while on Day 4 increased CL size on Days 9 and 10 (P < 0.05). Administration of hCG on Day 4 induced the formation of an accessory CL in 89% of heifers, resulting in a significant increase in total luteal tissue area on the ovaries compared with all other groups. Consistent with the effects on the CL, hCG on Day 1 did not affect P4 concentrations, on Day 2 significantly increased P4 compared with the control from Day 6 to 11 (P < 0.05), on Day 3 resulted in a non-significant increase in P4 while hCG on Day 4 increased P4 from Day 8 to 13 compared with the control (P < 0.05). In conclusion, administration of hCG as early as Day 2 after oestrus results in increased P4 in circulation from Day 6, which should have beneficial downstream effects in terms of uterine receptivity and conceptus elongation.

Additional keywords: cattle, conceptus elongation, fertility, pregnancy.


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