Dietary lead: Effects on hepatic fatty acid composition in chicks

Arbor Acre broiler chicks were fed diets containing 0, 500, 750, 1000, 2000, or 4000 ppm lead (as Pb acetate · 3 H₂O) from day-old through 21 days of age. There were 8 groups of 10 male chicks per lead level. Eight chicks from each dietary lead level were killed at 21 days, and hepatic fatty acid composition was determined for each chick by gas-liquid chromatography. Increasing dietary lead levels decreased the concentrations of 16:1 and 18:1 fatty acids (first No. = No. carbons; second No. = No. double bonds) and increased the concentrations of 18:0 and 20:4. The concentration of 18:2 fatty acids did not differ significantly from control values for any level of lead. However, the ratio $\text{18:2}\text{20:4}$ declined from a control value of 3.3 to approximately 2 for all lead treatments. The ratio of saturated/monoenoic fatty acids increased with dietary lead levels above 1000 ppm. In a second experiment 10 male broiler chicks per treatment were fed either a control diet or the control diet plus 2000 ppm lead, 60 ppm cadmium, 500 ppm mercury, or 10 ppm selenium (as Pb acetate · 3 H₂O, CdSO₄, HgCl₂, or Na₂SeO₃, respectively) for 21 days. Six chicks from each group were killed at 21 days, and hepatic fatty acid composition was determined for each chick. In comparison to control, the ratio $\text{18:2}\text{20:4}$ was lowered by lead but unaffected by cadmium, mercury, and selenium. The data suggest that lead may increase tissue peroxidation (as noted by other workers) via a relative increase of 20:4 fatty acid and that a decrease of hepatic ratio $\text{18:2}\text{20:4}$ may be a specific sign of lead toxicity.