Sexual dimorphic innate immune response to a viral-bacterial respiratory disease challenge in beef calves

Authors: Sanchez, Nicole; Broadway, Paul; Carroll, Jeffery - Jeff Carroll

Submitted to: Veterinary Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2022
Publication Date: 12/15/2022
Citation: Sanchez, N.C., Broadway, P.R., Carroll, J.A. 2022. Sexual dimorphic innate immune response to a viral-bacterial respiratory disease challenge in beef calves. Veterinary Sciences. 9(12). Article 696. https://doi.org/10.3390/vetsci9120696.
DOI: https://doi.org/10.3390/vetsci9120696

Interpretive Summary: Bovine respiratory disease is the leading cause of illness and death in cattle and costs producers $800 to $900 million each year. Yet, few advances have been made over the past 30 years in reducing the negative effects of this disease. Things such as breed, and temperament have been shown to affect immune responses to infection. However, there is limited information on the effect of sex on the immune response to bovine respiratory disease. Thus, a study was conducted where castrated male (steer) and intact female (heifer) calves were given a respiratory disease challenge. In response, heifer and steer calves produced distinct immune responses. Steers produced a stronger early immune response while heifers appeared to have a later or delayed response to the challenge. This suggests heifers may be more resilient to the viral-bacterial challenge compared to steers. Therefore, the sexually dimorphic immune response should be considered when monitoring cattle for symptoms of bovine respiratory disease. This information will be of interest to cattle producers, veterinarians, and scientists interested in bovine respiratory disease.

Technical Abstract: To evaluate a potential sexual dimorphic innate immune response to respiratory disease, 8 steers (castrated males) and 7 heifers (intact females; 280 ± 4 kg body weight) were subjected to a combined viral-bacterial respiratory disease challenge utilizing bovine herpesvirus-1 (BHV-1; intranasal; 1.0 x 10 exp 8 PFU/mL/nostril) and Mannheimia haemolytica (MH; intratracheal; 1.3 x 10 exp 7 CFU/head) administered 72 hours after BHV-1 at 0 h. Following MH administration, serum was collected and analyzed for cytokine concentrations, and whole blood was analyzed for hematology. Body temperature, measured via indwelling rectal or vaginal temperature monitoring devices, was lesser in heifers compared to steers (39.60 vs. 40.06 ± 0.11degree C; P < 0.01). There was a tendency (P = 0.09) for a sex × time interaction for total white blood cells, such that they were lesser in heifers compared to steers at –72 h but were greater in heifers compared to steers from 36 to 60 h post-MH challenge. Neutrophils were lesser in heifers compared to steers from 0 to 4 h, at 6 h, and from 8 to 12 h but were greater in heifers compared to steers at 168 h (P = 0.02). Lymphocytes were greater in heifers compared to steers at 12 h and from 36 to 60 h post-MH (P < 0.01). The neutrophil:lymphocyte ratio was lesser in heifers compared to steers from 2 to 36 h post-MH but was greater in heifers compared to steers at 168 h (P < 0.01). Monocytes were greater in heifers compared to steers from 24 to 60 h post-MH (P < 0.01) while eosinophils were greater in heifers compared to steers at 48, 60, and 16 8h (P = 0.05). Serum IL-4 was lesser in heifers compared to steers (2.8 vs. 14.7 ± 2.7 pg/mL; P < 0.01), and there was a tendency (P = 0.10) for heifers to have lesser IL-6 concentrations. Non-esterified fatty acid concentrations were lesser (P < 0.01) in heifers compared to steers from 2 to 4 post-MH challenge. Additionally, urea nitrogen concentrations were greater (P < 0.01) in heifers than steers at 36 and 60 h, yet lesser at 168 h. These data demonstrate distinct differences in the innate immune response following a respiratory disease challenge such that steers produced an early response while the response in heifers was delayed.