Arsenic in tissues of sheep and milk of dairy cows fed arsanilic acid and 3-nitro-4-hydroxyphenylarsonic acid.

Arsenic from two sources--arsanilic acid and 3-nitro-4-hydroxyphenylarsonic acid (3-nitro)--was fed to mature wethers and lactating dairy cows, and the uptake and depletion of arsenic in tissues and milk were determined. In experiments with sheep, arsenic concentration in liver, kidney and blood increased as the level of arsenic from arsanilic acid and 3-nitro was increased in feed. Muscle arsenic was relatively unaffected by the level of arsenic in feed from either source. No statistically significant differences in arsenic levels were observed between liver and kidney tissue, over all levels fed, or for either source of arsenic. When comparisons were made within each tissue, arsenic levels were found to be significantly lower in sheep fed 3-nitro. This difference between 3-nitro and arsanilic acid within tissues was not observed in muscle or blood. The depletion rates for arsenic were the same for all tissues, and the time required for tissue to return to pretreatment arsenic levels was dependent on the initial tissue concentration. Within 6 days of removal of arsenic from the sheep diets, 85% of the arsenic in the liver of sheep fed arsanilic acid and 81% of the arsenic in the liver of sheep fed 3-nitro was depleted. Arsenic levels in the kidneys of sheep fed arsanilic acid and 3-nitro were depleted by 87 and 83%, respectively. In the experiments with lactating dairy cows, significantly higher levels of arsenic in milk were observed for cows fed either 3.2 or 4.8 mg of arsenic per kilogram of body weight from arsanilic acid or 3-nitro. In the experiment in which 3-nitro was fed at a level of 4.8 mg/kg of body weight for 28 days, arsenic levels plateaued after 14 days of feeding and remained constant for the next 14 days. Milk arsenic from 3-nitro returned to pre-experiment levels within 5 days after arsenic was removed from the feed. In the experiment conducted with arsanilic acid, arsenic feeding was stopped after 5 days and milk arsenic levels returned to pre-experiment levels within 7 days. Because of the short duration of this study, no plateauing effect was observed.