A proposed new approach and protocol to defining mineral deficiencies using reference curves. Cobalt deficiency in young sheep is used as a model.
The most conclusive way of determining whether animals are deficient in a trace element is to measure production responses to supplementation in a field trial. However the opportunity, expertise and resources necessary to run such trials are not always readily available and there is often a considerable delay in reaching a diagnosis. Provided the degree of a production response can be closely related to a tissue level of the element or its metabolite then analysis of tissue samples can replace the need for field trials. The paper uses data from a series of cobalt liveweight response trials with lambs to outline a proposed methodology for constructing response curves which, for any specified level of Vitamin B12 in serum, can be used to determine (a) the expected liveweight response to supplementation, and (b) the probability of getting a response at least as great as some given level eg. that considered sufficient to just cover the costs of rectifying the deficiency. A protocol for future production response trials is described. It is planned that all appropriate production response trial data will be used to derive ;response; and ;probability of response; curves for use in diagnosing cobalt, selenium and copper deficiencies in sheep and cattle. It is suggested that the methodology could be applied in many biological systems involving deficiencies.
Clark
R G
RG
Ruakura Animal Health Laboratory, Private Bag, Hamilton, New Zealand.
Wright
D F
DF
Millar
K R
KR