Heat detection aids
Heat detection is paramount to the successful establishment of pregnancy in dairy cows. How heats are detected is less important than determining (accurately) by whatever means, that a cow is on heat and should be served. There are many things connected with fertility that a farmer/herd manager has little control over, but this does not apply to heat detection, which is totally under the control of the farmer/herd manager. However, with ever increasing herd size and competing pressures on time, there is usually less time spent observing cows for signs of heat. Also, with modern dairy cows, expression of heat is often less pronounced than what it used to be, so it is harder to determine if and when a cow is on heat and ready for service.
Heat detection aids
There are a number of heat detection aids that can be used to help the farmer/herd manager establish if a cow is actually on heat. These include tail paint, KaMars or similar, vasectomised bull and activity monitors. All have varying degrees of success in diagnosing a cow in heat and in reality all are proxies for what is happening inside the cow. The gold standard for establishing if a cow is on heat is the level of progesterone in milk or blood at the time of heat determination, which should be at its lowest during the heat phase of the cow’s 3-week fertility cycle. However, this method is not often used to check if heat is actually occurring, unless a system such as the Herd Navigator system from DeLaval is installed. On-farm test kits for progesterone in milk are commercially available and are a useful backup to existing information to determining a cow on heat.
There has been an increase in the use of activity monitors as a proxy for heat detection and some farmers rely totally on this method to detect heats and timing of AI. It should be remembered that these systems are an aid to heat detection and are not always, 100% accurate. They will not detect anoestrous cows and can throw up false positives and false negatives. Most systems can have the sensitivity adjusted to get a better balance between false positives and false negatives. Systems should adjust themselves via their algorithms for changes in herd activity, as well as individual cow activity, e.g. a herd walking 100m to a field today and 1.0km to a field tomorrow could show a lot of cows on heat, if the system is not properly adjusting itself. In general, neck collar monitors are not significantly different from leg mounted monitors in their ability to detect heats.
A number of studies have evaluated various types of heat detection aids, compared them to visual observations and against milk progesterone levels. In general, activity monitors are on a par with visual observations, but this depends on the amount of time dedicated to heat detection by staff. A UK study found that 26% of heats, (as measured by low progesterone levels), were not detected by any of several different methods: activity monitors, visual observation and KaMars.
Activity monitors are the ‘spy in the sky’ 24/7, but should not be relied on solely as a method of heat detection. It is hard to beat a ‘pair of eyes’, particularly during times when general activity of cows is lowest during the daily cycle. Use as many methods of detection as you may, but endeavour to establish when cows are on heat by whatever means. As a reasonable target, in any 3 week period, of cows eligible for insemination, at least 75%+ of heats should be detected on heat and submitted for insemination.
Voluntary waiting period and submission rate
The voluntary waiting period is defined as the number of days between calving and being available for service. It is normally around 6 weeks, but may be longer in high producing herds. This time period gives the cow a chance to recover from calving, including involution of the uterus, recovery from metritis if present and/or endometritis, (whites) and also to resume ovarian activity again. First heats may be silent/short and irregular, but help to ‘clean’ the uterus and prepare it for conception. The more heats a cow has before being served the better the chance of conception, but this will be a compromise between number of heats pre-service and possible reduced conception with early service in order to shorten the calving index. Late calved cows may be served on first signs of heat in order to tighten the calving pattern, otherwise they may not be pregnant at the end of the breeding season, and be culled in seasonal calving herds.
Submission rate is the number of cows available for service, (at, or past the voluntary waiting period), that get served, (normally in a 3 week window), divided by the total number of cows that could be served in that window, multiplied by 100, to get a percentage. A reasonable target is 75%. The CAFRE herd submission rate is ~ 85%. Submission rate is generally only applied to 1st service cows, as it is very hard to compute availability and submission rate for later services, as this depends on whether cows got pregnant to 1st service or not.
Heat detection at CAFRE
CAFRE have used a number of different heat detection systems over the years, including vasectomised bulls, tail paint, manual observations and the use of different activity monitor systems. Activity monitors are part of the Fullwood parlour identification system and do work, but can only download at milking time, which is a drawback, as information may be out of date by the time it is received and/or viewed after milking when the cow is gone. A number of other systems have constant monitoring and uploading of activity to the ‘cloud’ which is available to view 24/7. Some systems also have a text service to indicate a cow on heat, which allows drafting at next milking, if the cow is due to be served.