Over the course of the past few decades, the proportion of cows that go into standing heat has fallen from 80 to 50 percent, and the duration of standing heat has dropped from 15 to 5 hours. This presents a challenge when determining the right time for insemination in relation to ovulation. In terms of biology, it is natural that some cows should be inseminated again, which is why it is important to detect when the next estrus occurs. There can be several reasons why cows should be inseminated again:
- Because insemination failed and the cow is not pregnant
- Loss of embryos after insemination
- Presence of follicular or luteal cysts.
Classifying the problem
It is important to differentiate between the percentage of inseminations that are not successful and the percentage that are successful but result in early embryo loss. Calculate the gap between the first and second insemination performed in the period. These gaps are shown in a graph, which enables you to see, for example, the percentage in the 18-24 day range. If this is a high percentage, this suggests that insemination has failed, and that the cows will come into heat again during the next cycle. If there are several insemination gaps that e.g. range from 25-45 days, this indicates that insemination was successful but that a high proportion resulted in early embryo loss. When the insemination gaps are even greater, this can be due to follicular or luteal cysts that cause irregular heat – BUT, this can also be because you have missed some estrus periods.
Causes
If fertilisation is to be successful, insemination must be performed at the correct time in the cow's estrus cycle. There is namely a good correlation between the time the cow begins to show behavioural heat signs and the time of ovulation. There are three types of heat signs:
1 No particular definite signs of heat
2 Reasonable signs of heat, that show the cow is starting to go into heat
3 Very sure signs of heat.
Investigations show that the greatest chance of pregnancy is achieved when insemination is performed 4-12 hours after the cow goes into standing heat. As not all animals show signs of standing heat, it can be a good idea at such times to inseminate cows in group 2 after 10-20 hours. This will increase the chances of success if several signs of heat are observed in group 2 cows before insemination. Heat signs in group 1 cows should not give rise to insemination, unless signs from groups 2 and 3 have also been observed.
Points for action plan
Basic training in heat observation for individuals who work with this is vital. Provide opportunities to inform each other (three-week calendar, whiteboard etc.). In practice, we recommend combining visual heat observation and activity monitoring.
Focus on
- What and how many heat signs determine if an animal should be inseminated
- How heat information is recorded
- Combine heat observation with activity monitoring
