Copper, molybdenum and sulphur contents of oats and barley in relation to chronic copper poisoning in housed sheep

Abstract

SUMMARYThe copper, molybdenum, and total sulphur contents were estimated in 124 samples of oats and 67 samples of barley obtained from various parts of Northern Ireland. Copper contents were in the low-normal range, the average of all oat samples being 3–9 ppm and of barley samples 4–9 ppm, and the range 1–5 to 8–4 ppm covering all samples analysed. The corresponding averages for molybdenum were 0–25 ppm and 0–30 ppm, about 10% of the samples in each case containing less than 0–02 ppm. Sulphur contents (expressed as sulphate) ranged from 0–23 to 0–46 %. The low molybdenum contents are considered to be of significance in the copper metabolism of housed sheep.

Recent studies of the copper-molybdenum antagonism

“…It would, therefore, appear that the Cu-Mo antagonism affects sheep and probably cattle over a far wider range of pasture conditions than has hitherto been believed (Allcroft & Lewis, 1957;Hartmans, 1970). These results also lend support to the thesis of Todd (1972) that the relatively low concentrations of Mo and S in cereals contribute to the high risk of Cu toxicity in sheep given concentrated foodstuffs; serious consideration should be given to the routine use of small Mo supplements in such foodstuffs. T h e most useful formula for predicting the effects of dietary Mo and S on the availability of Cu in herbage and concentrates may be the product log (Mo concentration) x log (S concentration).…”

Effects of organic and inorganic sulphur on the availability of dietary copper to sheep

“…More extensive investigations may reveal a widespread influence of herbage S on the Cu status of the grazing animal. Furthermore, the increase in Cu status which commonly occurs when ruminants are housed during winter or reared intensively may be partly explained by the relatively low concentrations of S in cereals (Todd, 1972) and the relatively low yields of sulphide from conserved forages (Bosman, 1965(Bosman, , 1966Hartmans & Bosman, 1970).…”

“…Sulphur compounds are broken down extensively by rumen microflora to yield sulphide (Anderson, 1956;Bosman, 1965Bosman, , 1966 and it has been suggested that the subsequent formation of insoluble copper sulphide in the rumen lowers the availability of dietary Cu (Dick, 1954;Van Koetsveld, 1955;Spais, 1959). If this hypothesis is valid, one would expect the availability of Cu to decrease as S intake increases and organic S and inorganic sulphate to have similar effects, since both are readily degraded to yield sulphide (Bosman, 1965; Hume & Bird, 1970).…”

Involvement of molybdenum in feather growth

“…Titus and Fritz commented that " any practical diet will contain more than this quantity of molybdenum and therefore there is no need to add molybdenum to practical poultry diets ". Although individual batches of cereals may contain less than 20 /xg Mo/kg (Todd, 1972;Payne, 1976), mixed diets in Australia, especially those containing leguminous seeds such as soyabean, are unlikely to contain less than 200 /xg/kg (Nell, personal communication). However, it has been suggested that much of the molybdenum in soyabean protein is unavailable to the chick (Leach et al, 1962).…”