Kamani Dinesh Reddy and Chakravarthi.R,
Final Year, BVSc and AH, Madras Veterinary College, TANUVAS.
One calf per year is the goal set by Dairying people of India, but practically getting one calf out of a cow in the herd requires lot of expertise. Ruling out the genetic make-up, highly potent sire and dam, proper farming conditions and yearlong supply of feeds and fodder, let us discuss some of the aspects of Reproductive failure in farming conditions.
Reproductive failure is extremely costly for producers. However, the exact cause of loss is often very hard to determine as the problem is usually not identified until many months after the breeding season. Reproductive losses can occur as a result of a number of factors that limit the percentage of females that are cycling at the start of the breeding season or factors that interfere with conception or cause loss of the foetus.
The most commonly recognized causes for reproductive failure are poor cow nutrition; venereal diseases, such as Trichomoniasis and Vibriosis; other infectious diseases, such as BVDV, IBR, and Leptospirosis; bull infertility, disease and injury. Reproductive failure is the most common reason associated with culling cows from the breeding herd. In addition to cows failing to become pregnant or aborting, other cows may take longer to become pregnant and calve late. Calves from these cows will have significantly lower weight gain on pasture. There is also greater chance a late calving cow won’t become pregnant the next year.The expense of an open cow i.e cow that haven’t conceived and calved in a cycle, to a producer is not only the lost value of a calf, but also the cost of maintaining the cow for a year without a calf being produced.
Nutrition is the most important factor for cow fertility. Cows with a diet that is deficient in energy and that have low body condition score and/or lose condition after calving are much less likely to be pregnant in the fall than cows in better condition.
Body condition score
Adequate winter nutrition is necessary to maintain an optimal cow body condition score (3.0 or 3.5 out of 5) in order to:
- minimize time to rebreeding and enhance pregnancy rates
- decrease the risk of abortion and calf death at or near birth
- encourage calving ease (very thin cows at highest risk of difficult calving)
- sustain adequate milk production
To ensure good reproductive success adequate body condition is required before calving and before breeding. However, it is also critical the cow does not lose a substantial amount of condition after calving or after the start of the breeding season. The loss of even a single condition score category can have a measurable impact particularly for cows that have a BCS of less than 3 out of 5.
Copper deficiency
Copper is a critical mineral when it comes to reproduction. Copper deficiencies can result in
- increased number of open cows
- poor growth
- changes in hair colour
Mineral supplementation is one way that producers can help to combat copper deficiencies. While most producers will provide free choice trace mineral supplements, not all cows consume enough to maintain adequate levels. This suggests a need for further field research to identify cost-effect trace mineral supplementation programs to improve fertility of beef cows.Maintaining a year-round mineral program is recommended to ensure that mineral requirements are met and don’t negatively impact pregnancy rates. Trace mineral supplementation should be undertaken carefully following product recommendations. Region specific mineral mixtures are adviced and formulated after studying the mineral wealth of the soil.
Trichonomoniasis and Vibriosis:
- Causes
- Trich is caused by a protozoan parasite called Tritrichomonas foetus (T. foetus).
- Vibrio is caused by bacteria called Campylobacter fetus subsp. venerealis.
Both trich and vibrio are transmitted through physical contact when a bull breeds a cow. Once a cow is infected they act as a source of infection for other non-infected bulls within the herd which then spread the disease(s) to other cows.If a bull tests positive for either disease they will most likely remain infected for life.
- Symptoms
Neither disease causes noticeable swelling or other clinical signs in the bull. The semen of affected bulls will also appear normal on a breeding soundness examination. Decreased conception rate may give a clue about these infections.
- Consequences
Herds infected with trich or vibrio will typically have:
Low or very low pregnancy rates due to early embryonic death
High numbers of open cows at calving in herds that do not pregnancy test
Early abortions
Extended breeding season, with cows that conceive much later than expected (i.e. cows can lose their first pregnancy and rebreed later in the breeding season)
Newly infected cows may still conceive, but their resulting pregnancy is commonly absorbed between 40 and 70 days after breeding. Cows that have aborted will typically start to cycle again, but experience temporary infertility for 1 to 5 months as they clear the infection.
Bovine viral diarrhea virus (BVD) and Infectious Bovine Rhinotracheitis virus (IBR):
BVD infection can lead to poor conception rates and both BVD and IBR can cause abortions in cattle. These are the important viral causes of Bovine abortion causing early abortions. IBR virus causes Infectious pustular vulvovaginitis in cows and Infectious Balanoposthitis in bulls.
Leptospirosis
Infection with leptospirosis can lead to poor conception rates and abortions in cattle. The main clinical symptom absorbed is early abortion, blood in milk. It is highly zoonotic in nature.
Neosporosis
Neospora caninum is a protozoal parasite of canids such as coyotes and dogs that can be passed to a number of species including cattle. It is a very common cause of abortions in dairy cattle. The infection can be transmitted from the cow to her unborn calf. Not all exposed cows will abort. There is no effective vaccine or treatment for Neosporosis. Careful dead stock management might help to minimize contact with coyotes in some areas.
Bull Fertility, Disease, and Injury
Breeding Soundness Evaluations
Depending on the survey, approximately 50 to 60% of cow-calf producers, who work with veterinarians, have reported having their bulls’ semen tested before the breeding season. Veterinarians will check scrotal circumference, the reproductive tract for any signs of abnormalities, and the semen for motility and defects. . A breeding soundness evaluation also provides assurance that there have been no changes in semen quality from one year to the next due to disease, trauma or frostbite in bulls that might otherwise appear normal.
Reducing the risk of poor fertility
Bulls should be monitored for excessive weight loss and illness. Heat detection, breeding attempts, and semen quality can be reduced in bulls that are under-conditioned or sick. Lameness due to footrot can be an important cause of poor pregnancy rates on pasture as bulls are less likely to seek out cows in heat.
Preventing Calving Difficulties
Cows that have problems at calving are less likely to rebreed during the next calving season. Selection of bulls with low birth weight to minimize calving difficulties has the added benefit of minimizing later impacts on fertility. Cows where fetal manipulation due to a malpresentation or a Caesarean section was performed are less likely to be pregnant the following year. Thin or excessively overconditioned cows are also more likely to have problems at calving.
Toxins
Exposure to various types of toxins can also impact reproductive performance. Ergot has a number of effects on cattle including an increased risk of abortions. Fusarium mycotoxins have also been identified more frequently in grains in recent years. The wide variety of mycotoxins produced by Fusarium have also leads to abortion
To sum up we have discussed about the common causes of Bovine reproductive failure in detail in this essay. Having a calf is the only way to double up the farmer’s income.
