Postpartum non payment is the main reason for economic losses in the dairy and beef industries, leading to an increase in calving intervals. Reducing financial returns and extending postpartum intervals by reducing the number and treatment costs can lead to a decrease in the number of pregnancies. Due to malnutrition and insufficient estrus detection, long-term postpartum amenorrhea is common, resulting in a low pregnancy rate. About 40% of postpartum cows do not detect estrus after completing one or more ovarian cycles. Poor estrus detection and prolonged calving interval are the main problems in the dairy industry. Missing one estrus can cause a 21 day delay in calving interval, resulting in economic losses. To achieve the ideal one-year calving interval, a voluntary waiting period of 60 days is required, followed by conception within 85 to 90 days after calving.

The calving interval of cows is influenced by the recovery of postpartum ovarian activity. Ovarian inactivity is the most important reason for delaying the recovery of ovarian periodicity. Cattle can easily detect ovarian periodicity, pregnancy, and uterine condition through ultrasound examination.

Checking cows with B-ultrasound machine

After excreting feces, use a cow ultrasound machine to perform rectal ultrasound examination on the cow's ovaries. The probe is coated with a coupling agent and covered with a lubricated plastic sleeve. Cows were divided into two groups (silent estrus and true estrus). Cows with corpus luteum (CL) and normal uterus are considered to be in silent estrus. When examined 10 days apart, cows without CL and follicles, smooth and relatively small ovaries, and normal uterus are considered to have true amenorrhea.