Bittar, J.H., Pinedo, P.J., Risco, C.A., Santos, J.E.P., Thatcher, W.W., Hencken, K.E., Croyle, S., Gobikrushanth, M., Barbosa, C.C., Vieira-Neto, A., and Galvão, K.N. (2014) Inducing ovulation early postpartum influences uterine health and fertility in dairy cows. Journal of Dairy Science, 97 (6). pp. 3558-3569.

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Abstract

The objective of the current study was to evaluate the effect of GnRH early postpartum on induction of ovulation, uterine health, and fertility in dairy cows. Holstein cows without a corpus luteum (CL) at 17±3 DIM were assigned randomly to receive i.m. GnRH (n=245) at 17±3 and 20±3 DIM or remain as controls (n=245). Ovaries were scanned by ultrasonography twice weekly totaling 4 examinations. Ovulation was characterized by the appearance of a CL ≥20mm at any ultrasound or CL <20mm in 2 consecutive examinations. Clinical and cytological endometritis were diagnosed at 35 DIM. Compared with control, GnRH increased ovulation up to 3.5d after the last treatment (78.7 vs. 45.0%) and did not affect the prevalence of clinical endometritis (23.9 vs. 18.6%) or cytological endometritis (30.9 vs. 32.8%). Prevalence of clinical endometritis increased in cows that had calving problems (32.6 vs. 15.9%) and metritis (40.6 vs. 15.8%). Metritis increased prevalence of cytological endometritis (50.7 vs. 23.5%). Treatment with GnRH did not affect pregnancy per artificial insemination at 32 (37.6 vs. 38.6%) or 74d after artificial insemination (35.0 vs. 31.5%), but reduced pregnancy loss (6.8 vs. 18.1%). No overall effect of GnRH treatment on hazard of pregnancy was observed; however, an interaction between GnRH treatment and ovulation showed that GnRH-treated cows that ovulated had increased hazard of pregnancy by 300 DIM compared with GnRH-treated and control cows that did not ovulate (hazard ratio=2.0 and 1.3, respectively), but similar to control cows that ovulated (hazard ratio=1.1). Gonadotropin-releasing hormone early postpartum induced ovulation without affecting uterine health, but failed to improve pregnancy per artificial insemination or time to pregnancy, although it reduced pregnancy loss.

Item ID:	84113
Item Type:	Article (Research - C1)
ISSN:	1525-3198
Related URLs:	http://www.scopus.com/inward/record.url?...
Copyright Information:	© American Dairy Science Association, 2014.
Date Deposited:	05 Dec 2024 01:48
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