The use of progesterone intravaginal devices is superior to use of the ram effect at hastening the reproductive performance in transitional Targhee ewes

Catalina Cabrera; Gabriele U Maier; Matthew Cuneo; Bret R McNabb

doi:10.1016/j.theriogenology.2019.01.015

The use of progesterone intravaginal devices is superior to use of the ram effect at hastening the reproductive performance in transitional Targhee ewes

Theriogenology. 2019 Apr 1:128:17-22. doi: 10.1016/j.theriogenology.2019.01.015. Epub 2019 Jan 15.

Authors

Catalina Cabrera¹, Gabriele U Maier², Matthew Cuneo², Bret R McNabb²

Affiliations

¹ Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA. Electronic address: lcabrerarocha@ufl.edu.
² Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA.

PMID: 30716689
DOI: 10.1016/j.theriogenology.2019.01.015

Abstract

To compare the use of controlled intravaginal drug release (CIDR, EAZI-BREED™ CIDR^® Sheep, USA, Zoetis) with the ram effect, a combination of CIDR and ram effect and the addition of P.G.600^® to each of these scenarios on their contribution to inducing the onset of cyclicity and their ability to improve reproductive efficiency in a commercial sheep flock, a randomized clinical trial was conducted. Multiparous ewes (n = 283) were randomly assigned to one of six treatments prior to intact male introduction on day 0: only CIDR devices (day -5 to day 0) (n = 40), exposure to two vasectomized rams (d-14 to d0) (n = 55), CIDR (d-5 to d0) and an intramuscular injection of P.G.600^® (d0) (n = 40), exposure to two vasectomized rams (d-14 to d0) and treated with CIDR devices (day -5 to day 0) (n = 40). exposure to vasectomized rams (d-14 to d0), CIDR (d-5 to d0) and an intramuscular injection ofP.G.600^®, (d0) (n = 38), and a control group, without exposure to vasectomized rams, CIDRs or P.G.600^® (n = 70). Ewes were exposed to intact males on day 0. Days to lambing from the earliest expected lambing date at 150 days post introduction of rams was compared between groups with survival analysis. The mean survival time was significantly shorter in all groups that used CIDR compared to the control group (P < 0.003, adjusted for multiple comparisons). The addition of a teaser ram or a P.G.600^® injection did not change survival time. In a Cox proportional hazard model for time to lambing, the use of CIDR had a hazard ratio of 1.62 (95% CI: 1.07, 2.45, P = 0.23), while other variables (teaser ram, P.G.600^®) were not significant. In a Poisson regression for the number of lambs born to each ewe, P.G.600^® was not a significant variable, even when adjusted for age of ewe (P = 0.74). The combination of the ram effect and CIDRs did not have an additive effect. The use of CIDR shortened time to cyclicity in study ewes and may provide an attractive option to advance lambing season. Further studies on the economics of this method are warranted.

Keywords: CIDR; Ram effect; Seasonality; Sheep; Transition.

Publication types

Comparative Study

MeSH terms

Administration, Intravaginal
Animals
Breeding / methods
Estrous Cycle
Photoperiod
Poisson Distribution
Progesterone / administration & dosage
Progesterone / therapeutic use*
Proportional Hazards Models
Regression Analysis
Seasons
Sheep / physiology*

Substances

Progesterone