A vaccine-induced acute-phase reaction increases plasma leptin concentrations in beef cattle

Abstract Text: The objective of this experiment was to evaluate if a vaccine-induced acute-phase reaction also results in increased plasma leptin concentration, which would explain a potential DMI decrease in vaccinated beef cattle. Twelve yearling Angus x Hereford calves (9 steers and 4 heifers) were ranked by sex and BW, and allocated to 2 groups (6 calves per group, 4 steers and 2 heifers). Groups were assigned to a crossover design containing 2 periods of 14 d, and the following treatments on d 0 of each period: 1) vaccination against Mannheimia haemolytica (VAC; One Shot; Pfizer Inc., New York, NY), or 2) saline-injected control (CON). Calves were maintained in individual pens, offered grass hay for ad libitum consumption, in addition to 1.3 kg/daily (DM basis) of a corn-based supplement. During period 1, hay and concentrate intake were evaluated daily. During period 2, blood samples were collected prior to (0 h) and at 2, 4, 6, 8, 12, 16, 24, 36, 48, 60, 72, 96, 120, 144, 168, 240, and 336 h after treatment administration. All samples were analyzed for plasma haptoglobin concentration. Samples collected from 0 to 36 h were also analyzed for plasma cortisol, whereas samples collected from 0 to 96 h were analyzed for serum NEFA and plasma leptin concentrations. Values obtained at 0 h served as covariates within each respective analysis. Treatment x day interactions were detected (P = 0.05) for hay and total DMI, given that these parameters were reduced (P ≤ 0.02) in VAC compared with CON on d 0 and 1. Mean plasma cortisol was greater (P ≤ 0.01) in VAC compared with CON (39.8 vs. 26.3 ng/mL, respectively; SEM = 2.4). Treatment x hour interactions were detected (P < 0.01) for all other blood variables. Serum NEFA concentration was greater (P ≤ 0.03) in VAC compared with CON at 16, 24, 48, and 72 h. Plasma haptoglobin concentration was greater in VAC compared with CON at 8 h, and from 16 to 120 h. Plasma leptin concentration was greater (P ≤ 0.05) in VAC compared with CON beginning at 6 h relative to treatment administration. In conclusion, plasma leptin concentration was increased during a vaccine-induced acute-phase reaction, and may explain the decrease in DMI observed herein in vaccinated cattle.

Keywords: Acute-phase reaction, feed intake, leptin, vaccination