This is one of the most common questions and complains I get from many farmers I have attended to their animals. Infertility issues are a real threat in the dairy sector after mastitis and lameness. It is the major cause of culling of even pedigree cows and heifers, with whom farmers have great hope in terms of production. Every farmer is happy to see a calf from a cow every other year (calving interval), a cow unable to achieve this is a great liability to the farmer. In this article I will highlight the most common infertility issues especially in relation to estrus cycle/heat in cattle.
Heat is a term used to refer to the estrus cycle. In cattle, the interval from one heat to the next is 18-21days. Its when they are on heat when they are inseminated or mated, its therefore an important period and occurrence in dairy sector. A cow should give calf every 365 days (calving interval) in every profitable dairy enterprise. After calving a cow should return on heat and be mated at most after 90 days. Heifers should be bred at the age of 14-18 months. Any delays beyond this stipulated time should sound an alarm to the farmer. A vet is required to do a reproductive check-up on the affected cows and heifers. Do not wait, as time is really important in the farm, get the most out of that heifer/cow before it ages and production start declining.
Scientifically a heifer/cow that is non-cycling i.e. not seen on heat and is passed puberty age and not pregnant is said to Anestrus. It occurs due to myriads of reasons which I’m going to pin down here. They include: –
Animals that are pregnant are acyclic, this is because of the hormone progesterone that shuts down the release of the gonadotrophic hormones (FSH & LH) uterine environment favorable for the growing fetus. A cow therefore that has never been seen on heat should first be checked to ascertain its physiological status i.e. if pregnant or not
2. Cystic ovarian disease:
In my little years of experience this is by far the most common cause of anestrus and infertitlity in cattle. It usually occurs due to failure of ovulation. There are two types of cysts that can be found on the ovaries: –
i) Follicular cyst- this is usually thinned walled and can rupture during palpation. This kind of cyst continuously releases the hormone estradiol: and the cow fattens and appear like a bull(virilism), comes on heat irregularly (nymphomania) they may be inseminated but they return on heat again and will be referred to repeat breeders, the tail head is raised (sterility rump) due to relaxed sacro-iliac ligament.
ii) Luteal cyst- with this type of cyst the cow will just be inactive and acyclic as though they are pregnant. This because the cyst continually produces progesterone, a hormone normally found on pregnant animals. The cyst during palpation is hard and firm.
The function of the ovary and the expression of the signs of heat are energy demanding. Animals with poor body condition have their energy shunt and diverted for vital body functions i.e. for maintenance, secondary activities like reproduction and growth are adversely affected and slowed. On the other hand, animals that are overfed have poor reproduction. This is because of fat deposition in the ovary that hinders normal ovarian function and ovulation.
4. Ovarian hypofunction and atrophy:
This usually occur secondary to reduced function of the anterior pituitary gland, which is responsible in the release of the very crucial gonadotrophin releasing hormone. A hormone in charge of the activity of the ovary. The common finding is usually a very small and smooth ovary with no follicle(s) nor corpus luteum. Ovarian hypofunction and atrophy are a common finding in animals that are fed poor quality and quantity food i.e. animals with poor body condition(malnutrition).
5. Silent heat:
This is an aberrant group that I shouldn’t have included in anestrus or infertile category. I should talk about this, as many heifers and cows have been referred to being infertile when they’re cycling normally, they only do not show the behavioral signs of heat. Cows /heifers with silent heat have been associated with deficiency syndromes especially phosphorus deficiency. They require a teaser bull (vasectomized bulls) to help detect heat and then inseminated.
All these reproductive problems are temporary and can easily be treated when proper examination and diagnosis is made on time. The diagnosis is made using either ultrasonography and per-rectal palpation. Call the vet as early as possible; heifers should be routinely examined at the age of between 12-18 months and cows at 2-3 months post calving to detect any reproductive problems and solve the early.
Dr. E.K. Ngetich (VetMed, UoN)