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

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 3000IU 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. © 2014 CSIRO.

Bibliographic Details

Main Authors:	Maillo, V., Duffy, P., O'Hara, L., De Frutos Benítez, Celia, Kelly, A. K., Lonergan, P., Rizos Dimitrios, Dimitrios
Format:	artículo biblioteca
Language:	English
Published:	CSIRO Publishing 2014
Subjects:	Cattle, Conceptus elongation, Fertility, Pregnancy,
Online Access:	http://hdl.handle.net/20.500.12792/2571 http://hdl.handle.net/10261/290402
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