Mineral and vitamin supplementation of diets for growing pigs. 4. Effects of copper, zinc and iron supplements in a wheat/animal protein diet on performance, liver mineral stores and backfat quality

Abstract

The effects of supplementing a wheat/animal protein diet with copper (nil, 125 or 250 ppm), zinc (nil or 150 ppm) and iron (nil or 150 ppm) were studied in a 2 x 2 x 2 x 3 factorial experiment with 48 pigs. The diet was restrictively and individually fed to barrows and gilts between 18 and 73 kg liveweight. Daily rate of gain, feed conversion ratio and carcase score were not affected by the supplementary minerals. Supplementary copper increased the storage of manganese, zinc and copper in the liver. Although liver copper levels were greater in both sexes at 250 than at 125 ppm copper, barrows stored more copper than gilts at the higher level. Adding 150 ppm zinc at the same time as 250 ppm copper reduced liver copper storage in the barrows to the level of that in gilts given the same amount of copper. The iodine number, i.e, softness, of backfat in barrows was increased to that of gilts by 250 ppm copper; gilts were unaffected. Zinc supplementation also increased backfat softness in barrows but not in gilts. Despite this, 150 ppm zinc partially reduced the effect of 250 ppm copper on backfat in barrows.