55 Maternal bovine appeasing substance improves feeding behavior, growth performance, feed efficiency, and health indicators in weaned feedlot heifers.

Abstract Previous studies have demonstrated that maternal bovine appeasing substance (mBAS) enhances growth while alleviating stress and illness in weaned calves. The current study builds on previous work to investigate the impact on individual metrics such as feeding intake, feeding behavior and feed efficiency. This pilot study aimed to evaluate the effects of a mBAS (FerAppease; FERA Diagnostics and Biologicals, College Station, TX) on feeding behavior, growth, feed efficiency, health and stress indicators in weaned beef cattle. Twenty-two Angus-influenced heifers (315.2 ± 30.76 kg of BW) were abruptly weaned, sampled, and randomly assigned to either a 10-mL mBAS (n = 11) or a placebo (CT; n = 11), followed by 1-hour transportation in separate trailers. Groups were then housed over 27 days (d) in two feedlot pens located 148 meters apart, with ad libitum access to water and feed. Data collection occurred at multiple sampling events: twice before treatment and immediately before transport (d 0; baseline), after transport following a 2-hour fasting period, and on d 14 and 27. On d 14, groups swapped pens in order to minimize pen effects. Behavioral assessments included dry matter intake (DMI), bunk attendance (BA) duration and frequency, feeding rate, activity, rumination and chute exit speed (ES). Physiological indicators included salivary cortisol, red blood cell (RBC), white blood cell (WBC) and neutrophil-to- lymphocyte ratio (N:L). Growth performance was evaluated using body weight (BW), shrunk BW (prior- vs. post-transportation) as well as average daily gain (ADG) and gain-to-feed ratio (G:F) for the 0-14, 14-27, and 14-27 periods. DMI, BA duration, and BA frequency were recorded daily using the Vytelle® feed bunk system, while activity and rumination were continuously monitored via an ear data logger; data was averaged weekly. A mixed-effects model (MIXED) including treatment, sampling events and their interactions were included as fixed effects; sampling events were included as repeated measures for behavioral and physiological parameters. No differences (P > 0.10) were observed for DMI, ES or salivary cortisol. Reduced (P < 0.05) BA duration in weeks 2 and 3, alongside increased (P < 0.05) BA frequency and feeding rate in week 3 were found for mBAS than CT heifers. There was a tendency for lower shrunk BW (P = 0.09) and greater (P = 0.08) ADG0-27 in mBAS than CT heifers. Greater (P < 0.05) G:F14-27, G:F0-27 and ADG14-27 were observed in mBAS compared to CT heifers. Lower (P = 0.05) N:L ratio and a tendency for reduced (P = 0.06) WBC were also found for mBAS than CT heifers. These findings suggest that mBAS at weaning enhanced adaptation to the feedlot, as evidenced by improved immune response, feeding behavior, growth, and feed efficiency, warranting further large-scale studies to confirm its efficacy under commercial conditions.