Reasons she won’t conceive through AI
Dear Dr Othieno,
I am a dairy farmer near Machakos town, I recently acquired a cow from Murang’a to add to my stock. The seller had indicated that it was in its early pregnancy stages, however, that wasn’t true as it started showing signs of heat and when I called in a vet, he said it wasn’t pregnant. It is now the third time it has been served through Artificial Insemination but doesn’t seem to conceive. What could be the problem?
First, A.I has many advantages over the natural or bull mating. It is affordable, it can be used to quickly improve genetics for high productivity and it protects the herd from getting infected with diseases of the reproductive tract that are sexually transmitted. Examples of sexually transmitted diseases include brucellosis, bovine viral diarrhea, vibrosis and trichomonosis.
However, there are conditions that must be observed for it to be successful.
There are several reproductive diseases that can be spread through natural mating or even through AI when handled inappropriately resulting in contamination of semen. Vibriosis, for example, will result in up to 75 per cent reduction in conception rates and subsequently long calving intervals. Trichomonosis will cause early embryonic deaths and return to heat in initially pregnant cows. Trichomonosis has few observable outward clinical signs and can stay in herds for long periods of time without the farmer noticing. Infected bulls spread the disease during mating. Farmers should get a full medical history of animals they are purchasing to avoid buying already infected cows. The involvement of a vet during purchase can be of great help. At the time of purchasing a dairy cow, the seller should be viewed as a marketer more than a farmer because his or her interested at the point is to sell. Actually repeated serving is among reasons for culling.
Successful AI is dependent on careful observation of heat signs by the farmer who calls the inseminator to do the insemination at an optimum time. The female egg released by the cow and the male sperm all have a limited lifespan during which the ovum should be fertilised by the sperm. After this limited time, they die. Their perpetuation is dependent on fertilisation and implantation in the uterus. To increase the chances of fertilisation the cow should be inseminated between eight and 12 hours after the start of signs of heat. The rule of the thumb is that if she starts showing heat signs in the morning then insemination should be done in the evening and if she starts showing the signs in the evening, then insemination should be done early in the morning.
When a farmer misses these timings, then he is likely to call in the insemination at the wrong time which will negatively affect the rate of conception. The signs of a cow on heat include bellowing, reduced appetite, slight reduction in milk production, mounting other animals and secretion of clear mucus discharge from the vulva.
Semen is fragile and should remain frozen up to the point of delivery where it is activated by thawing (passed through warm water). Similarly, if the semen isn’t deposited at the right place by the inseminator, this can result in failure.
(Dr Othieno was the winner of the Vet of the Year Award in 2017 and works with the Kenya Tsetse and Trypanosomiasis Eradication Council -KENTTEC, firstname.lastname@example.org).