In a 2-year study, Univ. of Wyoming researchers nutritionally managed 3-yr.-old crossbred cows to achieve a body condition score (BCS) of either 4 or 6 at parturition to evaluate the effects of prepartum energy balance and postpartum fat supplementation on cow and calf performance. At 3 days postpartum, cows within each BCS group were allotted to be fed hay plus a low-fat control supplement or hay plus high-fat safflower seed supplements containing either oleic or linoleic fatty acids. Diets were formulated to be equivalent in energy and protein. Safflower seed diets were formulated to provide 5% of dry matter intake as fat, and were fed until day 60 of lactation.

• Ultrasonic rib fat thickness and ribeye area were significantly lower for BCS 4 cows throughout the study.
• BCS 4 cows maintained their condition over the course of the study, whereas BCS 6 cows lost some condition.
• BCS score had no effect on milk yield or composition, except for protein percentage, which was lower for BCS 4 cows.
• BCS had no significant effect on first-service conception rate, but overall pregnancy rate was greater in BCS 6 cows (88.9 vs. 63.9%).
• BCS did not influence calf birth wt. or calf avg. daily gain.
• Dietary fat supplementation did not affect cow wt. change, BCS change, rib fat thickness, milk yield, milk composition, cow reproduction, or calf performance.