Variability in the composition of commercial pig diets with particular reference to minerals

Abstract

Samples of 28 pig diets fed to grower pigs in 24 commercial piggeries in Victoria were analysed for proximate constituents, fibre components, energy, Ca, P, K, Mg, Na, Cu, Zn, Fe, Cd, Pb and As. Vitaminmineral premixes, salts used in the premixes, and some other additives were analysed for Cd and Pb. There was a wide variability in the composition of all components in the diets except gross energy. 'Home mix' diets tended to have lower contents of ash and fibre, compared with diets supplied by feed manufacturers. Comparisons with recommended nutrient requirements showed that 8 diets were apparently deficient in crude protein (less than 16%) and only 7 diets contained sufficient crude protein to meet the requirements of pigs up to 50 kg liveweight (20% or more). However, amino acid contents were not determined. One diet was deficient in Na, six diets were deficient in Ca, and eight diets had Ca : P ratios less than 1:1. Seven diets contained Cu at levels recommended for growth promotion (125-250 mg kg-1) ; 20 diets contained added Cu but at levels insufficient for growth promotion. All diets contained excessive amounts of Zn and Fe (up to 317 and 701 mg kg-1 respectively) ; the mean concentration of Zn was three times the recommended requirement and the mean concentration of Fe was six times the recommended requirement. Concentrations of Cd occurred up to 0.61 mg kg-1 and of Pb up to 5.53 mg kg-1. One diet contained 32.41 mg As kg-1 but the next highest concentration was 1.07 mg kg-1. Vitamin-mineral premixes contained up to 81 mg Cd kg-1 and up to 1292 mg Pb kg-1. Copper sulphate contained 376 mg Cd kg-1; copper oxide contained 2550 mg Pb kg-1; zinc oxide contained 114 mg Pb kg-1.