Effects of omega-3 polyunsaturated fatty acid supplementation to first-calf beef heifers during late gestation on offspring physiology and performance.

Forty-four pregnant Angus first-calf heifers (initial body weight [BW] = 490 ± 8 kg, body condition score [BCS] = 5.4 ± 0.06) were selected and assigned to the experiment at the end of their second trimester of gestation. From d 0 until calving, first-calf heifers were gathered and individually fed three times a week with dry distillers' grain (DDG; 3.5 kg/heifer per feeding; as-fed basis) + treatments. Treatments were: 1) 234 g/heifer per feeding of Ca salts of PUFA based on eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (OMG, Strata; Virtus Nutrition LLC, Corcoran, CA; n = 22), or 2) 234 g/heifer per feeding of Ca salts of saturated and monosaturated fatty acids based on palmitic and oleic acids (CON; EnerGII, Virtus Nutrition; n = 22). From d -11 (d of gestation 192 ± 5.1) to calving, heifers were allocated to rangeland pasture. First-calf heifer BW and BCS were recorded (d -10 and -9), and blood was collected on d -10, and upon calving. Calves were weaned on d 260, and preconditioned from d 260 to 302, and feedlot received from d 303 to 350. No differences were detected (P ≥ 0.33) for heifer BW or BCS changes at calving. A tendency for greater concentration of colostrum IgG (P = 0.08) was observed in heifers supplemented with OMG vs. CON cohorts. There were no differences (P ≥ 0.31) among treatments at calving for calving rate, birth BW, heart girth, and % of male calves born. Calves from OMG heifers had greater (P = 0.04) plasma IgG concentration compared to CON calves. No differences were observed (P ≥ 0.11) for weaning rate and age, birth to weaning ADG, weaning weight, liver enzymes, and serum antibodies against respiratory viruses. During the preconditioning, OMG calves had greater (P ≤ 0.05) final BW and ADG compared with calves born to CON heifers. These differences in performance remained (P ≤ 0.05) throughout the receiving phase. A treatment × day interaction was detected (P = 0.05) for plasma cortisol concentration, which was greater (P < 0.01) for calves born to OMG first-calf heifers on d 260 and 263 and lower (P < 0.01) on d 306 compared to CON cohorts. Supplementing omega-3 fatty acids to late-gestating first-calf beef heifers enhances IgG concentrations in both heifers and their offspring. While offspring growth from birth to weaning remained unaffected, OMG calves demonstrated increased weight during the preconditioning and receiving phases, suggesting potential long-term growth benefits.