Good Heat Detection for Organising Insemination
The identification of behavioural signs preceding ovulation
"Heat detection" is the common name for the identification of behavioural signs preceding ovulation in the cow (release of an ovocyte at a more or less regular interval in the region of 21 days but which may fluctuate depending on the animal, its breed, its parity and its physiological condition) with a view to performing insemination. Heat detection is a key stage in breeding in herds where animal artificial insemination (AI) is practised.It is based on two elements which interact: the expression of oestrus by cows and the monitoring of the cows by the farmer. Good heat detection requires good knowledge of the following behavioural signs:
- Acceptance of mounting (immobilisation of the animal when it is mounted by another): the most specific sign of oestrus, but rare and fleeting. If a cow expresses this behaviour it is considered to be in heat and must be inseminated.
- The secondary sexual signs (sniffing and licking the genital area, Flehmen response, placing the head on the rump) and mounting by other cows: signs that are less specific but expressed much more frequently than the acceptance of mounting. If a cow expresses a minimum of 3 of these behaviours over an observation period, it is considered to be in heat and must be inseminated.
- The time spent standing up is a good indicator of oestrus subject to being able to calculate it. To be used in combination with other signs to strengthen the decision-making.
- Social behaviour: signs frequently expressed outside periods of heat. To be used carefully and only in addition to more specific signs of heat.
- Cervical mucus: not very specific sign of oestrus and therefore not reliable. To be used very carefully and only in addition to more specific signs of heat.
Failures of heat expression are more and more frequent in dairy herds with, in particular, a duration of heat expression which has moved from 18-20 hours in the 1980s to only 4-8 hours now between the first and last acceptance of mounting. In addition, irregular cyclicity linked to cycle anomalies and more discrete heat expression (only 6 ovulations out of 10 are accompanied by mount acceptance in the Holstein breed) do not favour heat detection. In suckler herds the problems linked to heat expression are fewer than those in dairy herds. In fact, heat is generally expressed more distinctly and cycle anomalies are rarer. Conversely, post-partum restarting of cycles linked to the presence of the calf is later: only 68% of Charolais cows are cycled at 50 days post-partum as opposed to 79% of Prim'Holstein cows and 92% of Normande cows.
Even if heat detection is an essential activity for the use of AI, it is nonetheless affected by the increase in the sizes of cattle herds and the competition with other farms, thus limiting the time available per animal and per labour unit. The consequences of poor heat monitoring by the farmer may result in significant zootechnical impacts on fertility with AIs performed on heats outside the oestrus period, and/or on fertility with lengthening of the breeding period due to heats that have not been seen. In North America, in order to be free of heat detection, large herds have adopted management of reproduction with heats induced by the use of routine hormone treatments, whereas in France the use of cycle control treatments only concerns a very few inseminated dairy cows,mainly to bring forward and group calving periods together. With the same aim of making it easier to identify females to be inseminated automated heat detection has undergone notable technological advances with an ever wider range of tools available to farmers, such as activity detectorswhich use sensors placed on the animal to monitor females continuously. In the event of physical over-activity linked to the expression of heat behaviours, the device then emits an alert to the farmer who decides whether or not to breed from the animal. These automated tools to assist heat detection enable farmers, who do not or cannot take the time for monitoring, to show good detection rates. In order to optimise detection performance it is now recommended that the farmer's visual monitoring and the use of these monitoring tools be combined. The alerts from the tools must be confirmed by decision-making rules taking into account the history and activity level of each animal.