Early Postnatal Zinc Deficiency and Aggression in the Rat

The effects of a transitory zinc deficiency on subsequent aggression were assessed. Eleven Sprague Dawley dams were assigned to three dietary conditions.on days 1—21 postpartum. They were fed either a low zinc diet (less than 1 ppm) or an equal amount of the same diet but with zinc supplementation via their water supply, or unrestricted amounts of the zinc supplemented regimen. Within the first two days postpartum, litter sizes were equalized. All dams were returned to zinc adequate diets on day 22, and the pups were weaned on day 24. Food intake data for pups and dams were recorded as well as weights of dams and pups. After approximately 130 days of ad libitum access to a zinc sufficient diet, the pups were tested for levels of shock-elicited aggression. The animals were tested in pairs with each pair receiving 100 2 inA shocks. Human judges counted aggressive attacks between pairs, and their judgments were statistically compared for reliability. The judges viewed videotapes of the testing sessions. Pups whose dams were made zinc deficient on days 1-21 postpartum exhibited more aggressive attacks than pups of dams pair- fed or given ad libitum, access to the zinc supplemented diet