329
Dairy cattle pregnancy rates and progesterone concentrations in Kuwait following single and double injection PGF2a estrus synchronization protocols
The objective of this study was to compare in vivo progesterone (P4) function and pregnancy rates (PR) in cows following single and double PGF2α injections estrus synchronization protocols. Ninety-five lactating Holstein dairy cows were randomly divided into the single PGF2α injection group (n = 42) and double PGF2α injections group (n = 53) estrus synchronization protocols. The single PGF2α injection protocol consisted of a PGF2αinjection (Lutalyse®) regardless of the stage of the estrous cycle; the double PGF2α injections estrus synchronization protocol consisted of two injections of Lutalyse® 12 d apart regardless of the stage of the estrous cycle. Artificial insemination (AI; Day 0) was conducted 72 h after Lutalyse® (2nd injection in the double Lutalyse® treatment protocol). Milk P4 concentrations were determined for days of Lutalyse® injections (-3), 0, 7, 14, 21, 28 and 35 post AI. Pregnancy was diagnosed by ultrasonography on day 35 post AI. The pregnancy rates (PR; based on ultrasound) for the single Lutalyse® and double Lutalyse® treatment protocols, respectively were 28 ± 13.0% and 33 ± 11.0% (P > 0.05). Progesterone profiles from the time of AI until pregnancy diagnosis were similar (P > 0.05) between the PGF2α estrus synchronization methods. In conclusion, PR and corpus luteum function were not enhanced by the addition of a second PGF2α injection and therefore, a single PGF2α injection was recommended to the farmers for synchronization of their cows.
Keywords: PGF2α, corpus luteum, pregnancy