Controlling estrus in dairy cows - A comparative field study

Two prostaglandins, Estrumate and Dinolytic, and two progestagens, PRID and Norgestomet were compared for their effectiveness in controlling estrus in dairy cows. A total of 636 animals on 62 different farms in southern Lower Saxony/FRG were used in this study. After treatment with one of the four drugs a double fixed time insemination was always performed at 24-hour intervals. Later, an additional untreated animal was assigned to each group of four. The conception rate in the 734 cows which were inseminated and evaluated under standardized experimental conditions were ES, 51.0%; DY, 46.0%; PRID, 44.5%; NOR, 34.7% and untreated animals, 46.9%. When only those cows which had already calved were considered, the rates were 48.0%, 44.6%, 46.9%, 31.9% and 59.1% respectively. The time of treatment post-partum proved to be significant for the non-return rate 90 (P < 0.01) and the conception rate (P < 0.05). Treatment influenced the estrus cycle in all of the cows. Abnormal cycle length following treatment was observed in 50.7%, 52.0%, 41.6% and 52.8% of the cows in each group as compared to 12.1% in the untreated animals. After the third insemination at least 90% of the cows in each group had conceived. The effect of the various farms proved to be significant with regard to the insemination index (P < 0.01), NRR 90 (P < 0.05) and the conception rate (P < 0.05). All four drugs established their suitability for use under field conditions. Still, modifications in the treatment methods and the insemination regimen could lead to higher fertilization rates.