The rapid increase in cattle rearing has led to much focus on cows and their overall well-being. This includes every aspect of the animal including the colour of their eyes. The answer to the question regarding the eye colour of cows is often dark. However, in extremely rare cases, cows can have blue eyes. Due to the usual dark eyed colour of cattle, those born with blue eyes are usually placed under scrutiny as this can be a symptom of health related issues. As such, it becomes highly necessary for farmers to be able to distinguish between livestock with natural blue eyes and those suffering from illness.
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Blue Eyes Associated with Recessive Genes
As already noted, cows can have blue eyes though in rare cases. This is attributed to recessive genes inherited from the parents. The condition of blue eyes in cows is known as Oculocutaneous Hypopigmentation, abbreviated as OH. It is said that OH is due to a recessive mutation on a single cattle chromosome. Cattle that are homozygous for the mutated gene will exhibit this condition. Therefore, it is not always the case that blue eyed cows are suffering from illness. According to research conducted by some of the world’s renowned institutions, this birth defect dates back to the late 1970s. Note that it is termed a ‘defect’ since cows naturally do not have blue eyes. Cows with OH have eyes with irises that are pale blue around the pupil and a tan periphery. Their coats often have a slightly bleached colour. An important point to note is that this condition is not lethal and has no effects on productivity. It is sometimes referred to as simply cosmetic. Nonetheless, some calves with blue eyes can be sensitive to light.
Oculocutaneous Hypopigmentation is often caused by a carrier breed known as the Angus or Angus-cross cow. This basically includes the heifer, bull and the steer. These usually carry the recessive OH mutation in their DNA resulting in the birth of calves with blue eyes. Cows can have blue eyes inherited from parents that may appear perfectly normal with nothing indicating that they carry these recessive genes. In simple terms, if a normal cow gives birth to a blue eyed calf, it simply means that it is a carrier of the OH mutation and so is the sire of the calf. An important point to be aware of is therefore that although cows can have blue eyes due to recessive genes, there is a very slim chance that the calf will have blue cows.
How to Determine if Cows Can Have Blue Eyes
A DNA test is available to determine whether reared cows can have blue eyes. As such, blue eyes in cattle can be effectively managed. The test requires varied samples depending on the lab. Among the basic sample items needed are the hair root, blood spot, whole blood, tissue samples from ears and semen samples. If farmers seek to eliminate the risk of blue eyes in cows, it is advisable to breed non-carriers together. An alternative is to breed carrier cows to non-carrier bulls and keep the calves as market animals instead of breeding stock. Farmers should keep in mind that blue eyed cows are not inferior to other livestock and can be just as productive.
Blue Eyes Associated with Disease or Infection
Cows can have blue eyes as a result of disease or infection. In fact, blue eyes in calves is often associated with bovine infection or as popularly known, silage eye. Additionally, cows can have blue eyes if they are suffering from Infectious Bovine Keratoconjunctivitis, though temporarily. Other diseases associated with blue eyes in calves includes the bluetongue infection. As clearly indicted, blue eyes can pose a serious problem in the health of livestock. Infections and diseases associated with blue eyes can have detrimental effects on eye-sight. It is therefore advisable to consult a veterinary medical professional if a cow with naturally dark eyes begins to develop a cloudy blue colour. Failure to do so does not only affect eyesight and health but productivity and profitability, hence the overall success of the agricultural venture. That being said, farmers should keep in mind that cows can have blue eyes without necessarily suffering from disease or infection.
What Colour Eyes Do Cows Have?
Cows can have blue eyes, however, they almost always have brown coloured eyes. Studies reveal that the eyeballs of humans and those of cows have a similar structure in overall, with slight variations in size among other factors. Similar to humans, cows have eyes with the sclera, cornea, retina and choroid. Nevertheless, their eye ball size averages a little over 15mm with a diameter of approximately 30mm. Cows have oval shaped eyes with an iris that is often brown. As a matter of fact, brown is considered as the normal eye colour in cows. Although it has been established that cows can have blue eyes, it is very rare; in almost all cases their eyes are brown.
Do Cows Have Bad Eyesight?
Similar to humans, cows can have blue eyes. However, their eye sight is said to be inferior to that of people. Cows take more time to process things and tend to be easily distracted by motion on the side of their eyes. This is because they have a panoramic vision with an excess of 300 degrees. They only have a blind spot directly in the back of their heads. While they have practically unlimited vision, cows have bad eyesight. They generally have poor depth perception of nearby objects and are said to have limited vertical vision. Due to this limitation, they lack the ability to focus timeously. According to research, cows can distinguish all colours on a grey background, but have a difficulty identifying some colours such as blue. Basically cows can distinguish colours with long wave length such as red, orange and yellow. Colours with a shorter wave length are difficult to identify. These include green, blue, purple and grey. To add on, cows are known to be sensitive to sharp contrast. This makes them more alert to shadows, for instance, they may see the shadow of a building as a big hole in the ground. As such, they tend to shy away from places with poor lighting. They however have a light reflecting surface known as tapetum lucidum which makes them see better in the dark.