Infertility is bad news to any farmer. It means more costs in disease treatment, low milk production and slow stock build due to culling of affected animals.
A cow is infertile when it is unable to deliver a viable egg, conceive after successful mating, or carry 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 fertilise the egg is categorised as infertile.
There are several causes of infertility in cattle, some of them complex involving a number of factors while others simple and straight forward in terms of diagnosis and management. In cows, these factors hinder production of viable ovum (female egg), its fertilisation, implantation in the uterus, development to maturity of feotus 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 timely diagnosis of infertility while properly designed breeding and culling programme can help reduce incidences of infertility in a herd.
Repeat breeder is a common term applied to a cow served for more than three times without conceiving. Repeat breeding, lack of heat or frequent heat are primary signs of infertility.
Developmental abnormalities
There are many developmental abnormalities that interfere with anatomical structure or 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 fertilisation, 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 shaft resulting in production of poor quality semen or inability to deliver semen into 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 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.
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 developmental of female reproductive system. The female cow will therefore not show feminine characteristics and will remain infertile all her life.
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 characterised 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 genetic predisposition and has 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 delayed serving of cows or prolonged inter-calving periods. Some feeds like lucern 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.
Tomorrow, we shall look at the second part of why your dairy cow is failing to produce and what you can do to help it.
