Six experiments were conducted with male broiler chicks kept in battery brooders to investigate the effects of feeding diets high in copper on the integrity of the gizzard lining. Conventional and corn starch-soy basal diets were used. Slight improvements in body weight gain and/or feed efficiency were observed when the diets were supplemented with 250 p.p.m. copper as as CuSO4-5HSO, but higher levels (500 to 1000 p.p.m.) depressed growth and decreased feed efficiency. Little or no gizzard erosion was seen in birds fed the practical ration without added copper. Gizzard erosion was observed with 250 p.p.m. copper and the severity of the condition increased with higher levels. With the same level of copper supplementation, severity of gizzard erosion was greater when chicks were fed the corn starch-soy diet than when fed the practical diet. Adding 0.5 p.p.m. selenium to the practical diet containing 1000 p.p.m. copper slightly improved the appearance of the gizzard lining, although the subjective scoring index was significantly (P less than 0.05) lower in only one of two experiments. The addition of zinc, vitamin E, and vitamin B12 did not prevent the gizzard damage caused by high copper levels. Severity of gizzard erosion was significantly reduced by adding 0.35% cholic acid to the semipurified diet with 500 p.p.m. copper, but not to the practical diet with 100 p.p.m. copper. There was no correlation between acidity of the gizzard contents and severity of the erosion.

Three experiments were conducted to study the effect of varying levels of dietary copper on fatty acid composition of adipose and liver tissue of male broiler chicks. Chicks were fed the experimental diets to 4 weeks at which time leg adipose and liver samples were obtained for fatty acid determination. Adding 500 or more p.p.m. copper to either a practical or corn starch-soy basal diet caused significant changes in fatty acid composition but the differences were variable perhaps due to a depression of growth caused by these levels of copper. Fatty acid composition of the tissue was not greatly affected by adding 250 p.p.m. of copper to the practical diet which contained 1.5% poultry fat. When a corn starch-soy diet was fed with 0, 2, or 8% added corn oil, the ratio of 16:0 + 18:0 to 16:1 to 18:1 was not lowered in leg adipose lipids by copper supplementation (250 p.p.m.) with any level of added corn oil. With liver lipids copper appeared to reduced the ratios in birds fed the diets with 0 or 2% added corn, but the differences were not statistically significant. The results indicate that using copper levels in practical diets that do not depress growth rate will not have much effect on fatty acid composition of carcass lipids and probably not on physical characteristics of the fat.