Missouri By Dale G. Watson
University Extension Center
The calving season is soon followed by the breeding season for 2001.
We are seeing an increase in the number of questions related to the use of artificial insemination and estrus synchronization. Heat detection is an essential step in the use of artificial insemination, which promotes genetic selection that is a major part of any breeding program. Standing heat, or the time in the estrus cycle that the cow is receptive to fertilization, is essential for a successful program utilizing artificial insemination or a combination of estrus synchronization and artificial insemination.
The individual doing the heat detection is a very important element of the entire breeding season. This individual should be familiar with the daily management routine, knows the feeding schedule and, most importantly, one with whom the cow herd is familiar. Knowing each individual animal and being able to recognize each one for identification purposes at a glance is a major contribution to a successful conception.
One method is to remove the individuals observed in standing heat, with a minimum of effort from the rest of the herd. Let the herd move on their own into a feeding trap and separate out the individuals that exhibit standing heat. Moving a suspect in front of another individual using a minimal amount of assistance and observing if she hesitates, stops or turns her head to observe what is behind her is an indication of approaching estrus. Excessive and intense handling by individuals unfamiliar to the cow herd promotes lower conception, which adds to the cost of improving the overall herd genetics.
There are numerous signs to be recognized when cows are leading up to the period of time recognized as standing heat. Every individual that observes heat has a personal thought on this process. Visually recognizing the standing heat is essential, when artificial insemination or a combination of estrus synchronization and artificial insemination is being adopted.
The secondary heat signs often are summed up as any physical actions that are not normal throughout the yearly activity of the beef female. A very important initial concept is to know your cow herd. Each individual animal has a definite personality and reacts to environmental changes in a different way.
Generally, the secondary signs of heat become evident and lead up to the period of hours known as standing heat. Normally, this is approximately 18 hours. However, there are exceptions to this, I have seen individuals that exhibit standing heat for as little as two hours and others as long as 36 hours. Beef females that vary in the length of standing heat put added pressure on individuals doing heat detection. This is where knowing the cow herd pays big dividends. Becoming efficient and recognizing that something different is taking place within the herd is important. Some indications are an increase in nervousness, walking the fence and congregating with other cows that are near the same stage of the reproductive cycle.
Other signs include bawling, spooking easily, butting heads with other cows and standing, while herd mates are lying down. Frequently individuals approaching heat will try to mount other herd mates or lay their head over the rump of other cows. If you have nursing calves with the herd, the male calves tend to congregate with individuals approaching heat oftentimes two days ahead of standing heat, and they will continue to follow a cow up to two days after standing heat has occurred. It is important not to be fooled with these observations.
Over the years, crutches have been used extensively to assist with detecting heat. Some of these are detector animals, such as altered bulls, aggressive cows or yearling steers, that indicate an interest in cycling females, or just utilizing certain females that exhibit more interest than others. When these methods are used, I have achieved the best results by removing all females that exhibit standing heat prior to turning the so-called marker individuals with the cow herd. This method reduces the number for the marker individual to check and speeds up heat detection greatly. Other methods used include paint markers, similar to those used by the sheep producers or KaMar heat detectors glued to the tail head of individuals that change from white to red when pressure is applied. The Heat Watch method probably is the most current detection device and involves the use of a computer. This method requires the fastening of transponders on the tail head of the potential cycling females. When other animals mount the individual that is in standing heat, a computer records the date, animal's number, time and number of mountings.
Often indication of the onset of estrus is mud on the rump and sides of the cycling female, roughed or matted hair on the tail head and mucus discharge. The roughed hair and mucus discharge often occurs in the later portions of the heat cycle, which is too late for conception to occur.
Knowing the cow herd, completing observation soon after daylight and just prior to dusk and devoting extra time and effort will pay big dividends when using artificial insemination. Using percentage calculation over a five-day period will provide you with an indication of the reproduction capability of your herd. Simply take the total number in the herd and divide this by 17 (days in a normal cycle). Imagine you have 60 head you are observing. If post-calving days are a minimum of 60 to 80 days, nutrition and herd health are satisfactory, there should be 17 head observed in standing heat over a given five-day period.