[MUSIC] Hello, now that you know a bit about the estrus cycle of the cow, let's focus on challenges of detecting estrus or heat, and inseminating cows at the appropriate time to maximize the chances of establishing a pregnancy. Heat detection is important in the US, because the majority of cows are bred by artificial insemination. Remember from our discussion of the life cycle of the cow, after she calves, we give the cow roughly two months to adjust to the demands of lactation and to heal her uterus in preparation for the next pregnancy. We want cows to calve roughly every 12 to 13 months for profitable dairy production. In order to accomplish this, dairy farmers must be good at detecting estrus. However, there is a wide variation in the ability of dairy workers to accurately detect heats, and in many cases, they will detect less than 50% of heats in their herds. Even worse, in some cases, cows are called in heat that are not in heat. When this happens you not only lose time, but money is wasted on insemination that will not result in a pregnancy. This can be a real problem for getting cows pregnant in a timely fashion. Now, if the farm uses bulls to breed the cows, heat detection is done by the bull, which is housed with the cows. Bulls are generally considered to be much better at detecting heat in cows than humans are, which should be no surprise to anyone. So you might be asking, well, if heat detection is so difficult for humans and bulls are so good at it, why not just use bulls to breed all the cows? Well, there are a number of reasons why bull breeding is not desirable. First and probably most important, is that a farm's ability to improve the genetics of their cow herd will be reduced if they use bulls for breeding. Adoption of artificial insemination has allowed the dairy industry to rapidly improve the genetic value of dairy cows. This is because every farmer can now purchase a straw of semen from the best bull. For example, in the US, we are producing two-thirds more milk today than we did 60 years ago, and we're doing it with about one-third of the cows. This is because of the increased genetic value for milk production that resulted from widespread adoption of artificial insemination. Now, this increased milk production has greatly reduced the environmental impact of dairying. This rate of genetic progress would not have been possible with bull breeding. Another reason is the cost of purchasing and maintaining a bull, which can amount to several thousands of dollars per year. Bulls can also carry and spread venereal disease, and will occasionally become infertile. Finally, bulls are unpredictable, and every year we hear stories of people being injured or killed by bulls. For these reasons, most dairies use artificial insemination, and accurate heat detection is a key component to a successful AI program. Like every challenge, to overcome it we must break the challenge down into its essential elements. First, we need to inseminate cows after they come into estrus, but before they ovulate. Research has shown that cows will ovulate about 30 hours from the point they enter estrus. The problem is that we rarely know exactly when a cow comes into heat. Current recommendations for heat detection stipulate that dairy personnel should watch cows three times a day for 30 minutes, especially during times when cows are moving to and from the milking parlor. Now, this recommendation is rarely adopted, because farmers are busy and often multitask heat-checking with other duties on the farm. Furthermore, cows in modern dairies are often housed in barns with concrete floors that can be slippery. This will discourage cows from mounting other cows or allowing other cows to mount them. In hotter climates, it is essential that cows are cooled with fans or water sprinklers, because hot cows will not exhibit signs of estrus, especially during the day. Cows that have feet or leg injuries, or that are losing weight due to the demands of lactation, will also not show signs of estrus. If you remember, I mentioned previously that cows come into heat during all hours of the day and night. So how often are cows being watching during the night? If a mature cow comes into heat at 9PM, she might be out of heat by 6AM the next morning. Thus her entire cycle will be missed, and her breeding will be delayed. Finally, it is important to remember that signs of heat covered in the last lecture, including increased activity, vocalization, chin resting, mounting other cows and evidence of mucus discharge are all called secondary signs of estrus. And they can be seen before, during, and after a cow is in heat. The defining sign that a cow is in heat is that she will stand for several seconds when being mounted by another cow or a bull. Ideally, this is what is used to make a decision to inseminate a cow. >> Let's focus in on the period of heat itself and the signs of heat that may occur prior to or during heat. The primary and most reliable sign is that the cow stands to be mounted by another animal. A cow that is not in heat will quickly walk away, if an attempt is made to mount her, or she may turn and butt the cow attempting to mount her. A cow standing to be mounted is the only accurate sign of of estrus. Other signs, called secondary signs, which are less reliable, but are good clues that heat may be near, include mounting other cows. These cows may or may not be in heat. Mounting other cows may be a sign that they are approaching heat. These cows should be observed closely for other behavior, like a clear mucous discharge from the vulva and swelling and reddening of the vulva. Persistent trailing and attempting to mount other cattle and less time resting, bawling, and general excitement and nervousness. Tail head hair that has rubbed off or fluffed off, and dirty flanks, sniffing the genitalia of other cows, head raising and lip curling, and chin resting and rubbing the backs of other cows. >> Once the cow is detected in standing estrus, it is important to inseminate that cow such that the sperm have time to travel to the oviduct prior to the arrival of the ovulated egg. Remember, fertilization takes place in the oviduct. As a general rule, we say that sperm have a life span of about 24 hours in the female reproductive tract. And that the egg has a life span of about 12 hours after it is ovulated. Remember, we know that a cow will ovulate roughly 30 hours after she enters estrus. Yet we almost never know the precise time when the cow first entered estrus. So the best recommendation is that cows detected in estrus should be inseminated as soon as possible, within the next couple of hours. If the farmer knows precisely when the cow entered estrus or stood to be mounted, then we use what's called the AM/PM rule. The AM/PM rule states that if a cow is first detected in estrus in the morning, then breed her that afternoon. And if she's first detected in heat in the afternoon, then breed her first thing the next morning. Once again, the AM/PM rule works well when the farm feels confident they know when the cow first entered estrus. If the cow is seen in heat first thing in the morning, it is possible that that cow came into heat the night before. In this case, our first recommendation should be followed, and the cow should be bred as soon as possible. To summarize, accurate estrus detection is a key component of artificial insemination breeding. The goal is to have viable sperm in the oviduct when the egg arrives shortly after ovulation. To accomplish this, we need to breed cows towards the end of estrus, a period of time that can be as short as six to nine hours in mature, lactating dairy cows. However, we often don't know precisely when the cow first came into heat. Therefore, we recommend that cows detected in estrus should be bred as soon as possible, unless it is known when the cow first came into heat. Then we recommend that cows detected in heat in the morning are bred in the afternoon, and those detected in the late afternoon are bred the following morning. This is called the AM/PM rule. Of course, all of this relies on accurate estrus detection. Secondary signs of estrus including increased activity, vocalization, chin resting, and mounting other cows are good signs that the cow is close to estrus. However, a definitive diagnosis of estrus is that the cow will stand for several seconds when mounted by another cow or a bull. To detect estrus accurately, farms should conduct dedicated heat detection at least three times per day for 30 minutes each time. Personnel tasked with estrus detection should have this as their primary duty during this time, and the cows should be in a comfortable, cool environment with good footing. In the next lecture, we wrap up our module on reproduction with a discussion of factors affecting conception rate and how to detect pregnancy. [MUSIC]