Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 18 COPPER, MANGANESE AND ZINC CONCENTRATIONS IN SOUTH AUSTRALIAN BARLEY AND WHEAT GRAIN T.S. KOH* Copper (Cu) manganese (Mn) and zinc (Zn) concentrations were determined in samples of wheat and barley grain collected in 1981-82 from 98 South Australian silos. The majority of the samples had Cu, Mn and Zn concentrations which were below the dietary requirements recommended for ration-fed poultry and livestock. With the exception of Zn, higher Cu and Mn values were recorded in the Central region while the lower values were in the Lower Eyre and the South East regions. A significant (P~0.01) year to year variation was observed in Mn and Zn concentrations of barley. Such variation indicates the need to monitor trace element concentrations in grain-based rations for livestock. INTRODUCTION A number of studies have assessed the suitability of Australian wheat rations for supplementary feeding of sheep, for finishing steers and lambs (Briggs et al. 1956; Morris et al. 1969; Saville et al. 1973) but little information is available regarding the adequacy of trace elements in South Australian grain for livestock consumption. Where grain forms part of the ration, information on trace elements in the grain will be of value when formulating feed to meet the trace element requirements of the animal. This paper reports the findings of a survey involving the assay of Cu, Mn and Zn in wheat and barley grain collected from South Australian silos. XATERIALSANDHETBODS Sample collection, preparation and statistical analysis of data are as described by Babidge (1990). Copper, Mn and Zn were assayed by atomic absorption spectrophotometry (Judson et al. 1982). Standard Reference Material Wheat Flour (NBS SRM 1567, United States National Bureau of Standards) and Reference Material Rye Flour (V-8, International Atomic Energy Agency) were included with each batch of assays to ascertain analytical accuracy. Results were expressed on an air-dry basis in umol/kg. RESULTS AND DISCUSSION To examine the effect of sample inhomogeneity, 3-4 replicate samples of barley (1981) each from 10 silos were assayed for the trace elements. The average variability within each silo was 25% for Cu, 9% for Mn and 8% for Zn. The reason for the higher variation of Cu compared with Mn and Zn was unclear but its influence was allowed for when interpreting the results. The frequency distributions of the trace element concentrations in wheat and barley were non-normal and hence median concentrations were reported. Copper, Mn and Zn results of grain samples were grouped into five regions (Fig. l), and the summary of these results is shown in Table 1. The results for wheat grain in this study were comparable with literature reports for Cu (Davies et al., -84); Mn (Miller et al. 1979; Schultz and French, 1976) and Zn (Davies et al. 1984). * Central Veterinary Laboratories, Department of Agriculture, IMPS Building, Frome Road, Adelaide, S.A. 5000. 276 Proc. Aust. Soc. Anim. Prod. Vol. 18 Fig. 1 Regions where Cu, Mn and Zn results of grain samples were combined. Table 1 Median concentrations (umol/kg, air-dry basis)* and ranges of Cu, Mn and Zn in South Australian wheat and barley grain**. The median values for Cu in wheat, barley 81 and barley 82 obtained from all sources were 62, 75 and 72 umol/kg respectively. The median Cu concentration for the wheat samples was significantly lower than those for the barley samples (P<LOOl). The median value for Mn in wheat was 600 umol/kg and-was significantly (P<O.OOl) higher than that for barley 81 (260 umol/kg) and barley 82 (280 umol/kg). For En, the median concentration for wheat was 300 umol/kg and was significantly lower than that for barley 81 (320 umol/kg) but similar to that for barley 82 (275 umol/kg). These data indicate that in comparison to 277 Proc Aust. Soc. Anim. Prod. Vol. 18 barley, wheat is a poorer source of dietary Cu but a better source of dietary &Sn for livestock. Barley 81 had a higher median Zn concentration and a lower overall median Xn concentration than barley 82 (P<O.Ol). No significant difference was observed for the median Cu concentrations in barley between the two years (P>O.OS). The reason for the observed difference for Mn and Zn was unknown but could be due to rainfall. A significant (P<O,OOl) regional variation was observed for the three trace elements in wheat and barley (Table 1). With the exception of Zn, higher Cu and Mn values were generally recorded in the Central regions while lower values were recorded in the lower Eyre and the South East regions. There was a significant correlation between Cu and Mn (r* = 0.4, P<O.OOl) and between Zn and Mn (r* = 0.2, P~O.001) in wheat and barley samples. These data imply that samples with low Cu or Zn concentrations were likely to have low Mn concentrations. No significant correlation was observed between Cu and Zn for either wheat or barley samples. The recommended dietary requirements of Cu, Mn and Zn for mature animals of several species are given in Table 2. It was evident that for wheat and barley grown in South Australia, over 90% of the samples had Cu concentrations in wheat and Zn concentrations in wheat and barley which did notmeet the dietary requirements of pigs, sheep and cattle (Table 3). Wheat appears to be a good sourde of Mn as only l-14% of the wheat Mn results were below the dietary requirement for all classes of livestock, In contrast, barley was found to be a poor dietary source of Mn with 75-100% of the samples containing inadequate Mn for all classes of livestock. Table 2 Dietary requirements* (umol/kg DM)** for copper, manganese and zinc for mature animal species. These findings indicate that where grain forms part of a ration for poultry or livestock, trace element concentrations of the ration should be monitored to ensure adequate supply of dietary trace elements. Reliance on published values is of doubtful value. As bioavailability of trace elements in a ration is dependent on various factors, ration-fed livestock should also be monitored for their trace element status. 278 Proc, Aust. Soc, Anim- Prod, Vol. 18 Table 3 Percentage* of silos with trace-element concentrations in grain the dietary requirements for animal species, below I am grateful to the Australian Barley Board and the Austraiian Wheat Board for the supply of the survey samples and to Mr. C.F. Frith for skilled technical assistance. BABIDGE, P.J. (1990). Aust. Soc. Anim. Prod. 18:452. BRIGGS, P-K,, FRANKLIN, MC. and McCLYMONT, G-L. (1956). Aust. Vet. J. 32: 299. DAVIES, K-R., PETERS, L-J., CAIN, R-F., LETOURNEAU, Da and MCGINNIS, J. (1984). Cereal Foods World 29: 246. GRACE, N-D. Ed. (1983). In 'The Mineral Requirements of Grazing Ruminants' (New Zealand Society of Animal Production), JUDSON, G-J., BROWN, T-H., GRAY, D., DEWEY, D-W., EDWARDS, 'J-B. and McFarlane, J.D. (1982). Aust. J. Agric. Res. 33: 1073. MILLER, E-R., STOWE, H-D., KU, P-K. and HILL, G.M. (1979). In 'National Feed Ingredients Association Literature Review on copper and zinc in poultry, swine and ruminant nutrition' p-1 (National Feed Ingredients Association: Iowa, U.S.A.) MORRIS, J-G., PEPPER, P.M. and GARTNER, R.J.W. (1969). Aust. J. Exp. Agric. Anim. Hush. 9: 57. NATIONAL RESEARCH COUNCIL (1973, 1975, 1976, 1977). In 'Nutrient Requirements of Domestic Animals' (National Academy of Sciences, Washington: U.S.A.). SAVILLE, D-G., DAVIS, C-H., WILLATS, H-G. and McINNES, P. (1973). Aust. J. Exp. Agric. Anim. Hush. 13: 22. SCHULTZ, J-E. and FRENCH, R.J. (1976). Aust. J. Exp. 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