The sickness response in steers with induced bovine respiratory disease before and after treatment with a non-steroidal anti-inflammatory drug

Abstract

Bovine respiratory disease (BRD) is the most common disorder in North American beef cattle. This work aimed to describe the BRD sickness response, identify measures to improve detection, and assess effects of a non-steroidal anti-inflammatory drug (NSAID). We hypothesized that BRD challenge would induce a sickness response, with an NSAID and antibiotics attenuating this more than antibiotics alone. Challenged steers (BRD) were infected with a respiratory virus (d 0) and bacteria (d 5) and No-challenge steers received sterile medium. All were treated once with antibiotics, and half also received one 0.5mg/kg NSAID dose (d 8). After applying inclusion criteria, sample size was five BRD-No NSAID, four BRD-NSAID, two No-challenge-No NSAID, and three No-challenge-NSAID. Clinical examinations were performed daily, loggers tracked fever (d 3–10) and lying (d 0–13) continuously, dry matter intake (DMI) was recorded/24h (d 0–12), grooming was assessed for 20min/d (d 4, 6–11, 13), and mechanical nociceptive threshold (MNT) testing evaluated hyperalgesia (d 4, 6, 7, 9, 10, 13). Average daily gain (ADG) was calculated from end-of-study and baseline BW. Clinical signs occurred d 2–11, peaking on d 5. Sickness response components peaked on different days. Compared with No-challenge, BRD had fever d 3–7 (up to 2.1°C higher on d 3; P<0.001), lower DMI d 2–10 (88% less at the lowest point on d 5; P<0.001), lower ADG (88% less; P=0.002), higher total lying time (up to 11% higher on d 3; P=0.014), longer lying bouts d 3–5 and d 9 (up to 87% higher on d 4; P=0.002) and a tendency for fewer lying bouts (22% less; P=0.072). Compared with No-challenge, BRD groomed less (58% lower; P=0.016) and had hyperalgesia (44% lower MNT; P=0.002). The NSAID had no effect (P≥0.108) except for an interaction involving total lying time (P=0.050), possibly because of experimental design limitations or poor efficacy. In summary, the sickness response began within 2 d of challenge, persisting for up to 10 d. Some aspects mirrored fluctuating clinical signs and appeared early (DMI, fever); others reflected disease in a relatively invariable manner (lying bout number, hyperalgesia, grooming). The most persistent changes lasted for ≥5 d (DMI, fever, hyperalgesia, and grooming). Sickness response components that occur early, persist and mirror clinical sign progression may be better for BRD detection; from this perspective, DMI was the most promising.