Effects of recombinant bovine somatotropin during the periparturient period on innate and adaptive immune responses, systemic inflammation, and metabolism of dairy cows

The aim of this experiment was to determine effects of treating peripartum dairy cows with body condition score ≥3.75 with recombinant bovine somatotropin (rbST) on immune, inflammatory, and metabolic responses. Holstein cows (253 ± 1 d of gestation) were assigned randomly to 1 of 3 treatments: untreated control (n = 53), rbST87.5 (n = 56; 87.5 mg of rbST), and rbST125 (n = 57; 125 mg of rbST). Cows in the rbST87.5 and rbST125 treatments received rbST weekly from −21 to 28 d relative to calving. Growth hormone, insulin-like growth factor 1, haptoglobin, tumor necrosis factor α, nonesterified fatty acids, β-hydroxybutyrate, glucose, and cortisol concentrations were determined weekly from −21 to 21 d relative to calving. Blood sampled weekly from −14 to 21 d relative to calving was used for hemogram and polymorphonuclear leukocyte (PMNL) expression of adhesion molecules, phagocytosis, and oxidative burst. Cows were vaccinated with ovalbumin at −21, −7, and 7 d relative to calving, and blood was collected weekly from −21 to 21 d relative to calving to determine IgG anti-ovalbumin concentrations. A subsample of cows had liver biopsied −21, −7, and 7 d relative to calving to determine total lipids, triglycerides, and glycogen content. Growth hormone concentrations prepartum (control = 11.0 ± 1.2, rbST87.5 = 14.1 ± 1.2, rbST125 = 15.1 ± 1.3 ng/mL) and postpartum (control = 14.4 ± 1.1, rbST87.5 = 17.8 ± 1.2, rbST125 = 21.8 ± 1.1 ng/mL) were highest for rbST125 cows. Cows treated with rbST had higher insulin-like growth factor 1 concentrations than control cows (control = 110.5 ± 4.5, rbST87.5 = 126.2 ± 4.5, rbST125 = 127.2 ± 4.5 ng/mL) only prepartum. Intensity of L-selectin expression was higher for rbST125 than for control and rbST87.5 cows [control = 3,590 ± 270, rbST87.5 = 3,279 ± 271, rbST125 = 4,371 ± 279 geometric mean fluorescence intensity (GMFI)] in the prepartum period. The PMNL intensities of phagocytosis (control = 3,131 ± 130, rbST87.5 = 3,391 ± 133, rbST125 = 3,673 ± 137 GMFI) and oxidative burst (control = 9,588 ± 746, rbST87.5 = 11,238 ± 761, rbST125 = 12,724 ± 781 GMFI) were higher for rbST125 cows than for control cows during the prepartum period. Concentrations of serum IgG anti-ovalbumin tended to be higher for rbST125 cows than for control cows (control = 0.75 ± 0.11, rbST87.5 = 0.94 ± 0.10, rbST125 = 1.11 ± 0.11 optical density) in the prepartum period. Haptoglobin concentration was significantly reduced 7 d postpartum for rbST125 treatment compared with control and rbST87.5 treatments (control = 2.74 ± 0.28, rbST87.5 = 2.81 ± 0.28, rbST125 = 1.87 ± 0.28 optical density). Although treatment tended to affect postpartum β-hydroxybutyrate (control = 747.5 ± 40.2, rbST87.5 = 753.2 ± 40.1, rbST125 = 648.8 ± 39.7 µmol/L), it did not affect liver contents of total lipids, triglycerides, or glycogen. Incidence of metritis among rbST125 cows was reduced compared with that in control cows (control = 23.1, rbST87.5 = 18.0, rbST125 = 7.8%). Treatment of dairy cows with 125 mg of rbST improved innate immune responses and IgG concentration, with limited effects on metabolism.