Technical Abstract: Results of feeding supplemental fat obtained from various oil-seed plants have been determined in heifers and cows. Fat supplementation of the dam during the last 55 days of gestation resulted in improved cold tolerance in their newborn calves that were exposed to a constant temperature of 32 deg F for 140 minutes after birth. Results to date indicate that fat supplementation also results in a positive effect on rebreeding of the dam and increased weaning weights of the calf with pregnancy rates being increased up to 13% and weaning weights increased up to 30 pounds. Results in lactating first-calf heifers have been more consistent and of greater magnitude than in mature cows. The mechanisms of action have not been determined.