Effects of rumen-protected PUFA supplementation to late-gestating beef cows on performance and physiological responses of the offspring

Abstract Text: Our objective was to evaluate the effects of PUFA supplementation to beef cows during late gestation on performance and physiological responses of the offspring. On d 0 of the experiment, 96 multiparous, non-lactating, pregnant Angus × Hereford cows at the end of their 2^nd trimester of gestation were stratified by BW and BCS, and divided into 24 groups of 4 cows/group. Groups were randomly assigned to receive (as-fed basis) 452 g of soybean meal per cow daily in addition to 1) 200 g/cow daily of rumen-protected PUFA mix based on eicosapentaenoic, docosahexaenoic, and linoleic acids (PF) or 2) 200 g/cow daily of rumen-protected fatty acid mix based on palmitic and oleic acids (CON). Groups were maintained in 2 pastures (12 groups/pasture) with ad libitum access to water and alfalfa hay. However, groups were segregated 3 times/week and offered treatments (Mondays, Wednesdays, and Fridays) from d 0 until calving. Within 12 h after calving, calf BW was recorded. Calves were weaned on d 280, and preconditioned for 45 d. Blood samples were collected from all calves on d 280, 282, 285, 288, and 293 to evaluate plasma haptoglobin concentration. Supplementing beef cows with PF did not (P ≥ 0.24) impact cow BW change or pre-calving BW, as well as cow BCS change and pre-calving BCS. No treatment effects were detected (P ≥ 0.14) for calf birth BW, calving rate, percentage of male calves born, and kg of calf born per cow assigned to the experiment. At weaning, no treatment differences were detected (P ≥ 0.24) for weaning rate, calf weaning BW (205-d adjusted or not), and kg of calf weaned per cow assigned to the experiment. Calves from CON cows were older at weaning (P = 0.03) than PF cohorts. No treatment effects were detected (P ≥ 0.22) for calf preconditioning ADG, BW, and percentage of calves treated for BRD symptoms. Nevertheless, a treatment × day interaction was detected (P= 0.03) for plasma haptoglobin concentration, which was greater for calves from CON vs. PF cows on d 282. In summary, PF supplementation to late gestating beef cows did not impact overall cow and offspring productive parameters, but reduced offspring acute-phase protein reaction elicited by weaning.

Keywords: beef cows, offspring, PUFA, supplementation