Ruminant Articles on Breeding and Genetics

Mastitis in your herd may be costing you more money than you think, suggests a study linking mastitis and poor reproductive performance in dairy cows.

Keeping environmental mastitis in check during summer and fall can boost your herd's reproductive performance.

Abortion in dairy cattle is commonly defined as a loss of the fetus between the age of 42 days and approximately 260 days. Pregnancies lost before 42 days are usually referred to as early embryonic deaths, whereas a calf that is born dead between 260 days and full term is defined a stillbirth. A low rate of abortions is usually observed on farms and 3 to 5 abortions per 100 pregnancies per year is often considered "normal." However, the loss of any pregnancy can represent a significant loss of (potential) income to the producer and appropriate action should therefore be taken to prevent abortions and to investigate the cause of abortions that may occur. Each abortion is estimated to cost the producer $500 to $900 - depending on such factors as the current value of replacement stock, feed and milk prices, and the stage of gestation when the abortion occurs.

Many dairy producers practice some crossbreeding, and the numbers increase every year. Motivating factors include a desire to improve fertility, survival, milk components, and calving ease. Some producers want cows smaller than mature Holsteins. Several large, long-term dairy crossbreeding experiments have been conducted in the United States in the past. Cows involved in previous projects were not the result of intensive selection programs for type and production that produced today’s purebred populations.

The main objective of a reproductive program in a dairy herd should be to maximize pregnancy rate (PR) to first service. Pregnancy rate is the product of the heat detection and conception rates of the herd (PR = HDR x CR). Pregnancy rate represents the proportion of cows that become pregnant each estrous cycle, and determines the number of days cows are open after the voluntary waiting period. As the PR increases from a higher HDR, greater CR or both, days open decreases (Figure 1). Ferguson and Galligan 13, have shown that PR to first insemination explained 79% of the variation in the calving interval. These authors concluded that maximizing the HDR and CR for first insemination is the most important factor influencing the calving interval. Therefore, dairy herds should allocate significant resources to maximize PR to first service.