STOCK THIAMINE DEFICIENCY
Why are my cows going blind? Dietary changes, weaning and other stressors on cattle can cause vitamin B1 deficiency, which in turn can cause blindness. Dr Rory Dean describes the signs to watch for and what to do when you see them.
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n 1884, Polish scientist Casmir Funk discovered four chemical substances were required in humans’ diets for essential functions. He found these substances seemed to contain an amine chemical group and he termed them “vital amines”, which would eventually be shortened to “vitamins”. One of the original four vitamins he discovered was thiamine, or vitamin B1. All ruminants have an essential requirement for thiamine, which helps support, among other things, a healthy neurological system. In healthy ruminants fed sufficient roughage, plentiful thiamine is normally produced by thiamine-producing bacteria in the rumen. Thiamine deficiency in cattle occurs 68
under several circumstances that are not production of thiaminase, an enzyme that fully understood. breaks down thiamine. Certainly, when cattle are fed diets Vitamin B1 is essential for energy supply containing insufficient roughage, to the brain in ruminants. Deficiency thiamine deficiency causes a type of degeneration is common, and this in the brain called Conditions your vet may consider for similar cases: is often a problem in polioencephalomalacia, • Lead poisoning feedlots around the which causes a variety of • Salt poisoning world. Changes in diet, symptoms. Affected animals • Thiamine deficiency weaning, physiological may appear restless, blind, stress, and sulphur show seizure activity, or toxicity following fertiliser application wander aimlessly. Often death ensues are commonly associated with thiamine within 24 hours. deficiency. The current and most likely theory for the progression of vitamin B1/ CASE EXAMPLE: thiamine deficiency in these cases is that During an August weekend, a contract the stressor causes a shift in the population milker sought veterinary advice for a cow of bacteria in the ruminal “soup”. This that had appeared to be aggressive and had change in rumen bacteria leads to shown seizure activity the night before. Dairy Exporter | www.nzfarmlife.co.nz | October 2020
