animal health Cancerous eyes are the leading cause of carcass condemnations at slaughter and so it pays to deal with this condition early
Cancerous eyes are a regular occurrence in most western Canadian beef herds, but early detection and treatment will alleviate the pain and suffering — and provide financial benefits for the producer.
Cattle with white pigment around the eyes are more susceptible to this condition, as well as pink eye. Ultraviolet light, flies and other irritants such as dust may accelerate the development of lesions.
There is thought to be a genetic susceptibility, but this is not proven — although I’ve never seen cancer eye in Charolais. Most producers should try and select for dark pigment around both eyes. Herefords are even being developed with this in mind.
Cancer eye (squamous cell carcinoma) usually starts with a plaque, which can progress to a papilloma (wart-like growth) and eventually to invasive tissue-destroying mass.
With early detection, surgery can be successful. However, about half of precancerous plaques regress spontaneously, so if you observe these on a cow, simply note her number and keep an eye on her. These plaques may even remain for several years before advancing.
About 80 per cent of entire carcass condemnations are the result of cancer eyes, although that number is decreasing as more cows are treated for this condition.
About one to two per cent of U.S. cows will develop cancer eye, with a much higher incidence in white-pigmented cattle. So this is definitely an economic disease. If left until the orbit gets eaten away and the cow or bull is losing weight, infection can set in and tremendous constant pain is the result. In some cases the SPCA will be called in and charges can be laid.
It used to be that if spread (metastasis to the local lymph nodes in the head and neck) was evident at slaughter, condemnation was the result. Metastasis only occurs in approximately 10 per cent of the cases, and is considered a locally invasive tumour. Now regulations are more stringent and if some of the boney orbit is eaten out, or infection is present, then condemnation will almost always result. So early intervention by your veterinarian is critical.
Several procedures can be done and this varies depending on severity and the veterinarian’s expertise. A high percentage of cancers start on the third eyelid (nictitating membrane). This can be frozen and surgically removed without losing the eye. Sometimes a duct is damaged and the tears will run out the eye but this is only a blemish and at least the eye and sight is salvaged.
When pregnancy testing in the fall I see this as an ideal opportunity to closely watch for eye and other problems. Cryosurgery (freezing with liquid nitrogen), heat therapy or an advanced surgery called a tarsoraphy may be performed if tumours are not too advanced and on the eyelids. When performing these procedures always have your veterinarian closely check the other eye as precursors to cancer are sometimes picked up.
In more advanced cases, especially if the cancer is on the eyeball itself, surgical removal of the eye and lids is the only option. Your veterinarian will usually need to consider several points in each case. At our clinic in late pregnancy (seven-month-plus bred) we may wait until just after parturition and painkillers may be used in the meantime. Likewise in early pregnancy, we may wait a month till the viability of the fetus is stronger and less likely to be aborted. When deciding on surgery, you need to consider if you want to keep the cow long term and the economic viability of the fetus. If the prognosis is good, the cow can be kept for several more years. If guarded, she can be kept till weaning or if the surgery site starts to weep a bit it may be an indication of reoccurrence and she should be shipped immediately. Some cancer eyes, especially in large bulls, are simply removed to make sure they pass slaughter. As soon as they are healed and the hair is starting to grow back and antibiotics and anti-inflammatory have had their withdrawals looked after, they can be shipped.
I always suggest quiet cows will remain that way even with one eye whereas wild cows just get worse and should be culled. Cows are always a danger working on the blind side and bulls ideally should have binocular vision to breed but I have seen bulls with one eye in small pasture situations breed quite well. Fly control should be adequate, especially in the summer months. A fly tag or pour-on fly control is a wise idea until the surgery heals.
Early recognition is the key — often a few weeks can make a big difference in the success rate. If you think it is time to have it attended to, then don’t delay. But you need to ensure the condition isn’t pink eye. Small tumours can cause irritation to the eye, which greatly mimics pink eye. Check closely in the early stages cancer eye is not painful and no eye spasms occur.
The cost of these procedures varies considerably, but are always substantially less than the cost of the cow or bull. In order to avoid condemnations, or to extend the life of a productive cow or bull, get those affected eyes attended to. If in doubt, at least have it checked, as bad tearing eyes are something all veterinarians can help you with.