Identification of nonpregnant dairy cows early after insemination, and coupling a nonpregnancy diagnosis with a strategy to rapidly rebreed nonpregnant cows, can improve the pregnancy rate in a dairy herd. This can be accomplished twofold by reducing the interval between A.I. services, thereby raising A.I. service rate.
Methods for early pregnancy diagnosis in cattle can be classified as either direct or indirect. Direct methods involve detection of the tissues and/or associated fluids of the conceptus either manually (through rectal palpation) or via electronic means such as ultrasound.
Direct methods for pregnancy diagnosis have been around longer and are the most popular methods for determining pregnancy status. By contrast, indirect methods for early pregnancy diagnosis use measures of hormones or pregnancy-specific substances in maternal body fluids as indicators of pregnancy. Indirect pregnancy tests recently have been developed based on progesterone in milk; however, the latest indirect pregnancy tests are based on detection of pregnancy-associated glycoprotein (PAG) levels in blood or milk.
In the October 26, 2015 Hoard’s Dairyman article Timing is Everything in Pregnancy, UW-Extension Dairy Reproductive Specialist Paul Fricke shares what they have learned regarding factors associated with PAG levels in the blood and milk of dairy cows during early pregnancy and how to determine the best way to incorporate PAG testing into a reproductive program on a dairy farm.