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Estrus synchronization protocols for planned breeding and GnRH-agonist after timed insemination for pregnancy rate enhancement in dairy cattle Mohamed, Hirad


The aim of was to develop management protocols to improve reproductive efficiency in dairy cattle. The objective of Experiment 1 was to compare two methods of estrus synchronization. Eighty-nine dairy animals (67 cows and 22 heifers) were randomly assigned to either the Ovsynch or the Prostaglandin F[sub 2α] (PGF[sub 2α]) treatment group. Animals in the Ovsynch group received gonadotropin-releasing hormone (GnRH) followed by PG[sub 2α] on day 7 and second GnRH on day 9. Animals in the PGF[sub 2α] group were given two injections of PGF[sub 2α] 14 days apart. Both synchronization methods were followed by timed artificial inseminations. Milk progesterone (P₄) concentrations during the cycle were used to asses corpus Luteum (CL) function. Pregnancy was diagnosed 35 days after insemination. Estrus synchrony, based on Kamar heat mount detector and milk P₄ concentrations < lng/ml on the day of breeding, was not significantly different between the two groups. Mean milk P₄ during the synchronized cycle was also not significantly different between the two groups. Pregnancy rates were higher (P

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