A cow exhibiting signs of heat is considered of utmost importance to a farmer.
This could be the beginning of a new life that will, upon successful conception, be brought forth in nine months. The average estrus cycle of a cow is approximately 21 days, though sometimes may vary between 18 to 24 days.
Most farmers have indicated that some of the typical signs associated with a cow in heat include increased nervousness/restlessness, mounting, head mounting, chin resting, standing to be mounted and a swollen vulva, amongst others.
Farmers must be vigilant and know what to watch out for in relation to how cows will behave in estrus, know which cows to watch by keeping good reproduction records, know how to make good use of heat detection kits such as marking crayons (often applied on the rump of the animal and will be wiped off or smeared if the animal is mounted); pressure-sensitive pads often glued to the rump of the animal emitting some red liquid when pressure is applied and heat-mount detectors amongst others. It is also recommended that farmers adjust their management regime to improve estrus detection. This can be realised by taking advantage of the “hot spots and times”.
Observation of behaviour in the “hot spots” is critical, as is the establishment of the “hot time” to detect cows in estrus often in the mornings or evenings before milking is key.
However, there have been numerous cases where the farmer seeks the services of an artificial inseminator and the services yield naught. This could either be due to poor heat detection or that the animal is not in heat. The latter is not a strange phenomenon as often farmers have indicated that some cows within the herd do not exhibit estrus behaviour.
This phenomenon is commonly referred to as anestrus, a condition defined as the lack or absence of the expression of estrus. This should not be confused with silent estrus, where no clear signs or estrus can be detected in an animal despite the ovarian changes taking place.
In dairy cattle, anestrus has been known to be associated with various factors. These factors affect the demonstration of estrus and knowledge of them is highly informative to dairy farmers and herein are possible solutions to these problems upon diagnosis.
These are issues that are associated with the surroundings and possibly management. Cows that have not been turned out, a situation whereby the cows are kept for long periods within the housing environment as opposed to being left to graze periodically in open fields, have a tendency to not display estrus.
It has been observed that movement from enclosed areas to open fields stimulates estrus. In addition, the type of housing affects the display of estrus behaviour.
The predisposing factor is slippery floor surfaces. It has been documented that on average, animals that have access to a grooved or non-cemented surface exhibit a longer duration of heat as opposed to those that have access to slippery floors.
It has also been observed that mounting occurs more frequently when cows are on a grooved or non-cemented surface.
It is thus recommended that floors should be either grooved to provide firm ground on which to stand. Good footing is very critical.
Heat stress is also a contributing factor. Some cows exhibit estrus behaviour better in cooler temperatures.
Another minor but relatively important issue is the number of animals in the herd. Sometimes, overcrowding may result to poor estrus detection but also small animal herds have been reported to affect the exhibition of estrus behaviour due to the reduced interactions between the animals.
The occurrence of some diseases such as ovarian cysts and leptospirosis has also been associated with anestrus. It is reported that approximately 70 percent of cows with ovarian cysts are anestrus.
It is thus recommended that cows diagnosed with this condition be treated immediately by a veterinarian. Cows that have sole lesions or poor structural conformation or any form of lameness have delayed estrus.
This is a common cause of anestrus and can be treated through following a prescribed hormonal programme such as progesterone supplementation. This treatment can also be used to reduce the incidence of ovarian cysts.
Poor nutrition has also been known to contribute significantly to non-cycling. There has been an observed lack of exhibition of estrus behaviour in cows that have lost weight after calving as opposed to their mates in the herd who have minimal weight loss.
In addition, nutritional deficiencies such as low dietary phosphorous and vitamin A have been reported to cause anestrus. Anaemia due to iron deficiency or high levels of intestinal parasites could also cause cows to be anestrus.
Farmers are advised to put in place the necessary corrective measures such as introducing supplements and following a well-balanced feed program.
Often after calving, cows experience postpartum anestrus. This period is a natural occurrence and cannot be avoided. It could be termed as a form of biological shut down by the dam for protection of both itself and its offspring. This can also be treated through hormonal and management strategies.
Indeed, as farmers grapple with inability to detect estrus, some of the above mentioned issues should be looked into and resolved before a farmer concludes that the animal is unproductive and thus opt to cull it.
Dr. Muchunguh is a livestock expert