Efficient heat detection in dairy and beef cattle farms

06 May 2019

One of the most frustrating tasks for dairy cattle producers is to detect the cow in heat and are considered the critical component of the reproductive management worldwide. The efficient and accurate detection of estrus and the timing of resulting artificial insemination (AI) are significant challenges for the improvement of reproductive and economic performances of either smaller- and larger-scale dairy farms.

Failure to detect estrus is a major factor contributing to low fertility. The bovine estrus cycle averages 20 days in heifers and 21 days in multiparous cows, but the fluctuations in the cycle length is ranging between 18 and 25 days. As a result of this progress approximately half of the heats are undetected on dairy farms. According to recent research based on milk progesterone concentrations up to 15 percent of the cattle presented for insemination are not in heat. Failure to detect cows that are in heat and breeding cows not in heat result in economic loss for the producer because of because of extended days open and calving interval, and increased number of AI services (ovulation synchronization/induction programs, hormone treatments, additional semen expense) needed before pregnancy all means extra expenses for the farm. Efficient heat detection and timely insemination also are important to beef producers who use AI. Failure to detect estrus early in the breeding season or improper timing of AI due to heat detection problems results in extended calving intervals and additional semen expense.

Based on earlier and recent research, the transport of viable spermatozoa to the oviducts requires a minimum of 6 h to obtain a population capable of fertilization, and sperm numbers progressively increase over 8 to 18 h. The functional vital life of the bovine spermatozoa in the reproductive tract has been estimated at 24 to 30 h.

The estrous cycle can be divided into four periods: proestrus, estrus, metestrus, and diestrus. Proestrus is the period when progesterone declines with regression of the corpus luteum, estrogen increases, and secondary signs of estrus begin to occur. Estrus is characterized by standing behavior (true heat). Metestrus begins immediately after estrus when ovulation and early development of the corpus luteum occur, a period that lasts three to five days. Finally, diestrus is the time when the corpus luteum is functional, the longest phase of the estrous cycle.

A cow standing to be mounted is the most accurate sign of estrus. Standing heat is the most sexually intensive period of the estrous cycle. During this period, cows stand to be mounted by other cows or move forward slightly with the weight of the mounting cow. Cows that move away quickly when a mount is attempted by her herdmate are not in true estrus. The expression of heat is due to the elevated level of estrogen in the blood when progesterone is very low. The average duration of standing heat is 15 to 18 hours, but heat duration may vary from 8 to 30 hours among cows. An estrous cow usually stands to be mounted 20 to 55 times during her estrous period. Each mount lasts 3-7 seconds.

The secondary signs of estrus vary in duration and intensity. These signs may occur before, during, or after standing heat and are not necessarily related to time of ovulation. Farmers should use these signs as clues or check individuals more closely for standing behavior. The so called ‘mounting behavior’ is exhibited by the cow when she is in heat or approaching heat. Mounting activity is performed much less frequently by cows in midcycle. Although mounting cannot be used as a true primary sign of heat, cows exhibiting such behavior should be watched closely for standing behavior.

Various technological aids are available to detect heat helping farmers to perform the AI at the optimal time. Electronic pedometers or activity tags use changes in behavior to detect estrus in dairy cows and heifers. Restlessness behavior and overall physical activity increase significantly during estrus. The Moonsyst Smart Rumen Bolus System is designed to identify restlessness and elevated physical activity, when cows are standing heat, moreover, our innovation can detect behavioral changes (secondary signs) even during proestrus (mounting behavior) to help the farmer to prepare AI early in time.