Vitamin A and E deficiency in a cattle feedlot. (Short Communication)

Abstract

10B VITAMIN A AND E DEFICIENCY IN A CATTLE FEEDLOT B.A. VANSELOW* and R.J. HUNTER** A combined deficiency of vitamin A and E was diagnosed in finisher cattle in a 12,000 head feedlot producing beef for the Japanese market. It was estimated that approximately 2,000 cattle were affected at any one time (i,eu cattle between 220 and 300 days in the feedlot).The diet was based on grain and corn silage and although each animal had been injected with l,000,000IU vitamin A and 1OOIU vitamin E at the time of entry, there was no additional supplementation. The clinical condition became obvious in the summer months. Animals were noticed to be suffering from clear ocular and nasal dicharges, swollen hind J-WS I varying degrees of lameness and into-ordination, exophthalmus, 'glazed' bluish appearance to the eyes, poor adaption to dull light with pupils more dilated than normal and occasional cases of complete blindness. In advanced cases the swelling or oedema in the hind legs progressed to include oedema of all four legs, and extended to the shoulder and under the jaw. A number of affected animals were also seen to have cornea1 ulcerations,possibly as a result of injuries incurred through poor vision. Affected animals also showed a poor tolerance of hot weather. Their body temperatures were above normal in the middle of the day (ambient temperature 23.8T) when compared with unaffected cattle. This was associated with increased respiration,drooling of saliva and occasionally panting. When observed in the cool evening these same animals showed no evidence of heat stress. Deaths of clinically affected animals occurred during hot weather and during prolonged transportation. Pathological findings consistent with vitamin A deficiency included sq;uamous metaplasia of the parotid salivary duct and papilloedema of the q3tic nerve, Grossly and histopathologically oedema occurred in subcutaneous tissue, within muscle bundles and within nerve bundles. zlicrsangiopathy was identified in association with and probably as a cause of the oedema. It has yet to be ascertained as to whether the n&zroangiopathy was due to low vitamin A or E, or both. Fro-m severely affected animals both serum and liver levels of vitamin A and E were below normal. Serum levels of both vitamins were measured in relation to 'days on feed? Both levels dropped with time, with vitamin A dropping to it's critically low level at approximately 180 days and vitamin E not dropping to it's accepted low level. From liver samples collected at *slaughter, vitamins A and E were deficient. Following the commencement of oral supplementation at a rate of 40,8@OHU vitamin A, 11.2IU vitamin E per head per day, the clinical condition disappeared and serum vitamin A levels rose above the critical level. Vitamin A and E requirements are high for rapidly growing animals and be particularly high when the preference is for marbled meat with a high fat content.The requirement for vitamin A is greater in hot weather and it is conceivable from our observations that either vitamin A or E or both are required for effective thermoregulation. may * Regional Veterinary Laboratory, NSW Agriculture, PMB (UNE) Armidale,NSW, 2351. ** Glen Innes Veterinary Clinic, 233 Ferguson St., Glen Innes, NSW, 2370