Infertility is bad news to any farmer. It means more costs in disease treatment, low milk production, and slow stock build due to the culling of affected animals. A cow is infertile when it is unable to deliver a viable egg, conceive after a successful mating, or carry a pregnancy to term and deliver a healthy calf. Similarly, a breeding bull that cannot produce viable spermatozoa and deliver them into the female reproductive tract to fertilize the egg is categorized as infertile.
Causes of infertility in cattle
Some of them are complex involving several factors while others are straightforward in terms of diagnosis and management.
In cows, these factors hinder the production of the viable ovum (female egg), its fertilization, implantation in the uterus, development to maturity of fetus, and eventual delivery at term.
Causes of infertility can be developmental disorders, nutritional, environmental, management, and infectious diseases.
Other causes of infertility are heavy internal and external parasite infestations, high ambient temperatures, and low body weight.
Good breeding records keeping can assist in the timely diagnosis of infertility while properly designed breeding and culling programs can help reduce incidences of infertility in a herd.
Repeat breeder is a common term applied to a cow served more than three times without conceiving. Repeat breeding, lack of heat, or frequent heat are primary signs of infertility.
1. Developmental abnormalities:
Many developmental abnormalities interfere with anatomical structure or the reproduction hormone production process directly causing infertility. These abnormalities in cows can occur in the ovaries, oviduct, uterus, cervix, vagina, or vulva. These conditions can result in disturbances in the pattern of hormone production, hinder fertilization, implantation, or mating. The disturbance in hormonal patterns can further cause other conditions like cystic ovaries which cause infertility.
In bulls, developmental disorders are common in testicles or penile shafts resulting in the production of poor quality semen or inability to deliver semen into the female reproductive tract.
Cryptorchidism or undescended testicles is a common disorder in bulls where the testicles fail to descend into the scrotum but remain in the body trunk. When this happens it interferes with the production of spermatozoa which is optimal at a slightly lower temperature a reason why testicles hang outside the body. When this condition affects both testicles it results in infertility.
2. Freemartinism:
When a cow conceives twins of different sexes, the cow will develop male characteristics and its reproductive organs will not develop fully. This results from intrauterine cross hormonal interference which affects the proper development of the female reproductive system. The female cow will therefore not show feminine characteristics and will remain infertile all her life.
3. Cystic ovaries:
This is a relatively common cause of infertility in cows and can only be diagnosed by a vet through rectal palpation of the ovaries of suspected animals. Cystic ovaries are caused by a hormonal disturbance that is characterized by a prolonged, frequent, irregular, or lack of signs of heat in a cow. In some instances, the cow will show “homosexual” tendencies called virilism where it will mount other animals but will not stand being mounted by a bull as happens with a cow on heat.
This condition has a genetic predisposition and has a high correlation with high milk production and has been commonly observed in 5th to 6th lactations. The condition is also common following retained placenta that causes inflammation of the uterine wall. The condition has also been associated with the delayed serving of cows or prolonged inter-calving periods. Some feeds like lucerne and clovers also cause this condition when fed to animals because they are rich in phytoestrogens. With proper diagnosis by a vet, the condition is easily treatable using prostaglandins.
4. Infectious diseases:
There are several bacterial, protozoan, and viral diseases that affect the reproductive system and therefore result in infertility. These diseases include brucellosis, trichomoniasis, leptospirosis, bovine viral diarrhea, campylobacteriosis/vibriosis among others we shall discuss in detail only two which are of great importance not only to animals but can also be transmitted to human beings.
Brucellosis:
This is a bacterial disease that affects man, domestic and wild animals (commonly known as undulating fever or bang disease in humans and animals respectively). Brucellosis is still prevalent in the tropics. It is a costly disease as it leads to infertility and culling. In cattle, it causes inflammation of the uterus and cervix and causes repeat breeding. The disease is commonly referred to as a professional hazard for farmers and veterinarians.
Brucellosis is spread from the vaginal discharge of an infected cow or an aborted fetus. Breeding bulls can get or spread the disease during mating. In man, it is spread through oral ingestion of bacteria in milk of infected cow; the bacteria can also be transmitted through skin, wounds, mucus membranes of the eye, nose, and teat opening in animals.
In a pregnant cow, brucellosis causes abortion which characteristically occurs between the 5th and 8th months. People who handle aborted fetuses without proper protection or drink milk from infected cows can get infected.
Sometimes the dead fetus can be retained in the womb and will be mummified or macerated. In cases where calves are born from infected mothers, they will be weak and prone to diarrhea and will in most instances die at infancy.
The aborting cows are sources of infection to other animals and men as they shade the infection into pastures, buildings, and drinking water.
The disease is diagnosed in cows using simple milk tests but has no treatment. The disease can only be prevented through vaccination, the use of artificial insemination instead of bulls, and screening of new animals to minimize the introduction of the disease into farms.
Eradication can be achieved through a rigorous test and slaughter strategy/policy of infected cows. Countries that have eradicated the disease like Denmark, the UK, Netherlands, and Romania have employed this strategy. In humans, the disease is treatable but cases of misdiagnosis for malaria and typhoid are common.
Leptospirosis:
Leptospirosis is a bacterial zoonotic disease that in animals is characterized by fever, red urine, mastitis, and abortion.
It is transmitted through contact with infected urine and affects the digestive and reproductive tracts. The common mode of transmission from cow to cow is through urine splashes. Although transmission at mating has also been documented.
Abortions occur in the last three months; the disease also causes retained after birth. Farmers get infected through urine splashes from infected cows. For example during milking or by breathing in the aerosol of urine droplets.
Clinical signs in man include flu symptoms, muscle pain, headaches in some cases liver and kidney complications may follow. To control and prevent the disease vaccination can be done and observation of hygiene. The disease respondents well to streptomycin when diagnosed early.