Species: Cattle, sheep
Specimens: Serum or liver (serum preferred)
Optimum number of animals to test for mob/herd/flock deficiency: 6-10 (serum) and 4 (liver).
General information about the test:
There are no significant mobilisable stores of zinc in the body. High levels of calcium, soil, copper and sulphur in the diet can reduce zinc availability to the animal. Do not test sick animals or cows within two weeks of calving as initial values can double within 24 hours.
Reference interval (serum):
- Adequate 9-20 umol/L
- Potentially toxic >27 umol/L
- Facial eczema control* 18-34 umol/L
Reference interval (liver):
- Adequate 460-1,150 umol/kg
- Toxic 1,760-10,200 umol/kg
*Please note that serum zinc levels for facial eczema prevention are general guidelines as clinical and subclinical sporidesmin toxicity can still occur with serum zinc values within this range depending on level of toxin challenge, other trace element intake e.g. Copper and other host or environment factors. Also note that zinc toxicosis can potentially occur with serum zinc levels at the upper end of this range.
References:
Smith BL. Controlling facial eczema in sheep using zinc salts. Proceedings 17th annual seminar. Society of Sheep and Beef Cattle Veterinarians NZVA pp 227-233. 1987.
Dawson C, Laven RA. Failure of zinc supplementation to prevent severe facial eczema in cattle fed excess copper, New Zealand Veterinary Journal, 55:353-355, 2007.