Short-term energy restriction during late gestation of beef cows decreases postweaning calf humoral immune response to vaccination.

Our objectives were to evaluate the pre- and postweaning growth and measurements of innate and humoral immune response of beef calves born to cows fed 70 or 100% of NEm requirements during the last 40 d of gestation. On d 0 (approximately 40 d before calving), 30 multiparous Angus cows pregnant to embryo transfer (BW = 631 ± 15 kg; age = 5.2 ± 0.98 yr; BCS = 6.3 ± 0.12) were randomly allocated into 1 of 10 drylot pens (3 cows/pen). Treatments were randomly assigned to pens (5 pens/treatment) and consisted of cows limit-fed (d 0 to calving) isonitrogenous, total-mixed diets formulated to provide 100 (CTRL) or 70% (REST) of daily NEm requirements of a 630-kg beef cow at 8 mo of gestation. Immediately after calving, all cow-calf pairs were combined into a single management group and rotationally grazed on tall fescue pastures (6 pastures; 22 ha/pasture) until weaning (d 266). All calves were assigned to a 40-d preconditioning period in a drylot from d 266 to 306 and vaccinated against infectious bovine rhinotracheitis, bovine viral diarrhea virus (BVDV), , and spp. on d 273 and 287. Blood samples from jugular vein were collected from cows on d 0, 17, and 35 and from calves within 12 h of birth and on d 266, 273, 274, 276, 279, and 287. By design, REST cows consumed less ( ≤ 0.002) total DMI, TDN, and NEm but had similar CP intake ( = 0.67), which tended ( = 0.06) to increase BW loss from d 0 to calving, than CTRL cows (-1.09 vs. -0.70 ± 0.14 kg/d, respectively). However, gestational NEm intake did not affect ( ≥ 0.30) plasma concentrations of cortisol, insulin, and glucose during gestation and BCS at calving as well as postcalving pregnancy rate, BW, and BCS change of cows. Calf serum IgG concentrations and plasma concentrations of haptoglobin and cortisol at birth as well as calf pre- and postweaning BW and ADG did not differ ( ≥ 0.15) between calves born to REST and CTRL cows. However, calf postweaning overall plasma concentrations of cortisol; plasma haptoglobin concentrations on d 274, 276, and 279; and serum BVDV-1a titers on d 306 were less for REST calves than for CTRL calves ( ≤ 0.05). Hence, a NEm restriction to 70% of daily requirements during the last 40 d of gestation had minimal effects on cow precalving growth and did not affect postcalving cow growth and reproductive performance. However, it decreased postweaning vaccination-induced humoral immunity, inflammatory, and physiological stress responses of calves.