The effects of low dietary levels of DDT on breeding performance in hybrid mice

A combination of breeding experiments was used to study the effects of various levels of dietary DDT on the reproductive efficiency in mammals. The results of feeding B6D2F₁ hybrid mice 5, 10, or 20 ppm of DDT in the first breeding experiment showed an increase in litter size and number weaned over controls. Ten ppm of DDT caused increases over controls in the number born and alive on day 1 (P<0.05). DDT caused decreases in the weight of pups at 5 ppm on days 15 and 30 (P<0.05 and 0.01, respectively), at 10 ppm on day 15 (P<0.005), and at 20 ppm on day 30 (P<0.05). A second breeding experiment using 30, 60, or 120 ppm of DDT showed a general detrimental effect on reproduction. Thirty ppm DDT-fed animals produced fewer pups than controls (P<0.01) at days 1, 15, and 30, and the pups weighed less than controls at 30 days of age (P<0.05). DDT at 120 ppm resulted in fewer mice at birth and at 30 days of age (P<0.01) than control diet. The third, fourth, and fifth breeding experiments involved diets with 0, 5, 10, and 20 ppm of DDT and with the addition of a 40-ppm level in the third and fourth studies. The data showed larger litter sizes on days 1, 15, and 30 for DDT-fed animals. This investigation indicates that 5, 10, 20, or 40 ppm of DDT in the diet often results in larger litter sizes and more pups weaned than controls. Animals fed levels of 30, 60, or 120 ppm of DDT generally produced fewer offspring than did control animals. DDT-fed mice often weighed less before weaning than control pups. Although variable responses were found, it appears from these studies that environmental levels of DDT are not detrimental to the reproductive efficiency of mice and may under certain circumstances be beneficial.