The effect of copper on the response of lambs to selenium supplementation when grazing a selenium deficient pasture.

Two trials were undertaken with lambs grazing selenium deficient pasture to determine if copper would enhance liveweight and fleece-weight responses to selenium supplementation. In the first trial, lambs given selenium or selenium plus copper gained significantly more weight and had higher fleece-weights after 260 days than did control lambs or lambs given copper alone. Copper given alone or together with selenium had no significant effect on liveweight or fleece-weight when compared with control lambs and lambs that were given selenium alone respectively. This finding was confirmed in a second trial when growth and fleece-weights of selenium and selenium plus copper treated lambs were compared and no significant differences found. In both trials copper significantly raised liver copper levels. In selenium supplemented but not in selenium deficient sheep, copper significantly increased blood selenium levels.

Failure of copper or vitamin D supplements to affect the dental condition of young sheep on two Wairarapa farms.

Regular injections of copper or vitamin D had no overall effect on growth rate, fleece weight, or the amount of wear of the central incisor teeth of sheep on two Wairarapa farms over 26 months. The greatest amount of tooth wear occurred during the period when soil ingestion (measured by acid-insoluble residue, titanium or aluminium in the faeces) was also greatest. Various indicators of copper, calcium or nutritional status were measured in the blood of control sheep and those receiving vitamin D or copper. At no sampling time was there a significant difference for any of these between groups on either farm. Pasture samples were analysed regularly for calcium, cobalt, copper, magnesium, manganese, molybdenum, phosphorus, sulphur, zinc and percentage ash. At most times values were, on the basis of existing criteria, considered normal. Although the pasture calcium/phosphorus ratio fell below one on several occasions this did not result in a change in plasma calcium or phosphorus levels. On the basis of criteria established for pen-fed sheep, dietary available copper levels on both farms were considered low for much of the time. However, liver and blood copper values were adequate at alI times.

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.

Copper metabolism in growing sheep given kale (Brassica oleracea) and ryegrass (Lolium perenne)-clover (Trifolium repens) fresh forage diets.

Kale (Brassica oleracea) and ryegrass (Lolium perenne)-clover (Trifolium repens) pasture grown under similar soil conditions were grazed in the vegetative state by growing lambs of 23.6 kg initial live weight for 24 weeks. Forty-eight lambs grazed each forage. The kale and pasture contained respectively 4 and 14 mg copper/kg dry matter (DM), 7.2 and 3.1 g total sulphur/kg DM and 0.4 and 1.1 mg molybdenum/kg DM. Subcutaneous injections of Cu (12 mg) were given to half the animals grazing each forage during weeks 1, 6, 12 and 18. All ninety-six animals were slaughtered at the end of the experiment and an additional group of twelve animals was slaughtered when the experiment commenced. Liver Cu was determined on all slaughtered animals and heart muscle cytochrome oxidase (EC 1.9.3.1) activity on those slaughtered at week 24. Blood samples removed at 6-week intervals were assayed for activity of superoxide dismutase (EC 1.15.1.1; SOD) and serum Cu concentration determined. Wool growth, live-weight gain and cytochrome oxidase activity of biopsied hind-limb muscle were also measured at 6-week intervals. Control animals grazing pasture showed an accumulation of total liver Cu during the experiment. Animals grazing this diet and given Cu injections showed an additional accumulation of liver Cu equivalent to the supplementary Cu administered, but Cu supplementation did not affect the activity of any of the Cu-containing enzymes measured and did not affect live-weight gain or wool growth. Control animals grazing kale showed a depletion of total liver Cu and reductions in serum Cu concentrations during weeks 18 and 24.(ABSTRACT TRUNCATED AT 250 WORDS)