In the two previous pieces, we saw the importance and benefits of artificial insemination in improving our livestock. Now in this last part, we are going to see how you can know the right time to inseminate, how to make effective heat detection, and other basic practical information for breeders.
First of all, a farmer must observe the animals and detect heat at least three times in a day (morning, afternoon and evening) at times other than feeding and milking. He must take at least 20 minutes for each time to observe cows. Some of the signs of heat are:
- Pre-heat signs: restlessness, separates from herd, ear movements, attempts to mount others, clear mucus, reduced milk production, bellowing
- Standing heat: stands still when mounted; other signs include clear and copious mucus, vulva enlarged, rests head on back of other cows, tail head roughened (the last sign could also be seen post-heat)
- Post-heat (2-3 days after start of heat): moves away when mounted, tired and lying while others graze, clear or bloody mucus on tail or legs.
Ideally, if a cow is first seen in heat in the morning, she should be inseminated in the afternoon of the same day and if she is first seen in heat in the afternoon or evening, she should be inseminated the next morning.
How to make effective heat detection?
The reproduction management is one of the critical aspects of the herd production. Delayed reproductions lead to different consequences:
- As the reproductions are delayed, the dry periods are extended and the lifetime milk productions are reduced.
- The number of calves per year decreases and the genetic value of the herd is slow, which gives few opportunities to cull old cows.
- The costs for treatments of reproduction disorders, breeding and veterinary fees are increased.
The good reproduction management begins by an effective heat detection, which allows choosing the right moment for insemination.
What is “heat”?
Heat is a period in which the female accepts mating with the male. That period occurs normally in non-pregnant, pubescent heifers and non-pregnant cows. The period of receptivity may last from 6 to 30 hours. The heat period occurs generally every 21 days and may vary from 18 to 24 days. Some general or specific signs help to recognize a female in heat, but it calls for acute observation. The best indicator that a cow is in heat is when she stands and allows herself to be mated by other cows or a bull. Different signs are chronologically observed on the female in heat:
- The signs of heat at the beginning: the cow rushes forward as if attacking, shows various signs of nervousness, pushes against the sides of other animals, sniffs vulva or urine of other animals (that is sometimes followed by inversion of nostrils), vulva becomes pink and swollen, clear mucus begins to appear on the vulva.
- The real signs of heat: the cow bellows like a bull, attempts to rest her chin on the back of other animals and this may lead to the attempt of mounting, but specifically stands immobile and accepts to be mounted (by a bull or a cow), the clear mucus is still visible.
- The late signs of heat: the clear mucus is still visible; the cow refuses to be mounted.
In order to detect more than 90% of the heats in a herd, the cows must be carefully observed in the early hours of the morning, the late hours of the evening and at four to five hour – intervals during the day. Research shows that 70% of mounting activity happens between 7:00 at night and 7:00 in the morning.
What are factors influencing the heat expression?
Heats can be more or less easily detected depending on a number of factors:
– The type of housing: in the stanchion barn, it is difficult to detect a cow in heat because there are no herdmates with her, while in the free stall offers the best opportunity to detect heat, as in a herd more than one cow can be in heat at the same time and increase mounting activity.
– Other environmental factors tend to inhibit the expression of heat: high temperature and humidity, wind, rain, snow, confined space and conditions that may cause falling, slipping and hoof pain.
– The health factors like poor nutrition, severe infection of the reproductive tract and other different factors can disturb the heat expression.
What is the right moment for natural service or insemination?
To lead to fecundation, spermatozoa must be “at the right place at the right time”. The egg is released from the ovary about 10 to 14 hours after the end of heat and survives unfertilized 6 to 12 hours. The spermatozoa can live up to 24 hours in the reproductive tract of a cow.
For the artificial insemination, in order to maximize the chances of fecundation, there is a “morning-evening” rule: cows observed in heat the morning are inseminated the evening and those seen in heat the afternoon are inseminated the next morning.
For the natural service, the cow and the bull may be allowed to mate starting a few hours after the cow accepts mounting until the cow refuses to be mounted.
What can cause low conception rate?
Most of cows in a herd (more than 90%) may require less than three services to conceive. The reasons of low conception rates may be:
- Problems of heat detection: false identification that leads to error in records, servicing a cow that is not in heat or not servicing a cow that is in heat and improper timing of heat and/or service.
- Problems related to bull: low fertility.
- Problems related to artificial insemination: improper techniques.
- Cow factors: hormonal disorders, infections of the reproductive tract, early embryo death, obstructed oviducts, problems of nutrition.
The reproduction has a major role in the economic and genetic improvement of the livestock. It goes through good heat detection and best time of service. Let’s choose best bulls, best techniques and make our livestock best!!
Special thanks goes to Eng. Syridion DUSABIMANA, M.Sc, Rwanda Agriculture Board (RAB), +2507885207 E-Mail: firstname.lastname@example.org
Dr.Jean Claude BYISHIMO, DVM, Rwanda Agriculture Board (RAB), E-Mail: email@example.com
for their support in preparation of this article in a series.