Sexually dimorphic stress and pro-inflammatory cytokine responses to an intravenous corticotropin-releasing hormone challenge of Brahman cattle following transportation.

This study was designed to characterize potential sexually dimorphic stress and immunological responses following a corticotropin-releasing hormone (CRH) challenge in beef cattle. Six female (heifers) and six male (bulls) Brahman calves (264 ± 12 d of age) were administered CRH intravenously (0.5 µg of CRH/kg body mass) after which serum concentrations of cortisol increased from 0.5 h to 4 h. From 1 h to 4 h after CRH administration, serum cortisol concentrations were greater in heifers than in bulls. In all cattle, increased serum concentrations of TNF-α, IL-6 and IFN-γ were observed from 2.5 h to 3 h after CRH, with greater concentrations of IFN-γ and IL-6 in heifers than bulls. Heifer total leukocyte counts decreased 1 h after CRH administration, while bull leukocyte counts and percent neutrophils decreased 2 h after CRH administration. Heifers had greater rectal temperatures than bulls, yet rectal temperatures did not change following administration of CRH. There was no effect of CRH administration on heart rate. However, bulls tended to have increased heart rate 2 h after CRH administration than before CRH. Heifer heart rate was greater than bulls throughout the study. These data demonstrate that acute CRH administration can elicit a pro-inflammatory response, and cattle exhibit a sexually dimorphic pro-inflammatory cytokine and cortisol response to acute CRH administration.

Enhancement of the acute phase response to a lipopolysaccharide challenge in steers supplemented with chromium.

The study examined the effect of chromium supplementation on the response of steers to an LPS challenge. Steers received a premix that added 0 (control; n = 10) or 0.2 mg/kg of chromium (n = 10) to the total diet on a dry matter basis for 56 d. Steers were fitted with jugular catheters and rectal temperature (RT) recording devices on d 52. Blood samples were collected and sickness behavior scores assigned to each steer relative to an LPS challenge (0.5 µg/kg) on d 55. Pre-LPS RT were greater in chromium-supplemented than in control steers. Post-LPS RT increased in both treatments, with control steers producing a greater change in RT than chromium-supplemented steers. Sickness behavior scores were greater in control than in chromium-supplemented steers post-LPS (P = 0.03). Cortisol concentrations did not differ between treatments pre-LPS. Post-LPS cortisol concentrations increased but did not differ due to treatment. Concentrations of IL-4 increased post-LPS but were not affected by treatment pre- or post-LPS. Treatment did not affect pre-LPS TNF-α or IFN-γ. Post-LPS TNF-α and IFN-γ increased in both treatments, with chromium-supplemented steers producing greater TNF-α (P = 0.005) and IFN-γ (P = 0.004) than control steers. Pre-LPS IL-6 was greater (P = 0.027) in chromium-supplemented steers than in control steers. Post-LPS IL-6 increased in both treatments and was greater (P < 0.001) in chromium-supplemented than in control steers. These data suggest that chromium supplementation enhances the acute phase response of steers to an LPS challenge, which may expedite recovery.

Innate immune responses of temperamental and calm cattle after transportation.

The objective was to investigate measures of cellular innate immune responses among calm and temperamental Brahman bulls in response to handling and transportation. Sixteen Brahman bulls (344 ± 37 d of age; 271.6 ± 45.5 kg BW) classified as either calm (n=8) or temperamental (n=8) were loaded onto a trailer, transported for 4h to a novel facility, rested 16 h overnight, and then were returned to their original facility after a 4h transport. Blood samples were collected immediately prior to (time 0) and at 24, 48, and 96 h after initial loading for analyses of innate immune and blood parameters. Leukocyte counts did not differ (P>0.05) due to temperament before or after transportation, but neutrophil:mononuclear cell ratios were greater in temperamental bulls compared to calm bulls at 24h. At 24h, expression of peripheral neutrophil ß(2)-integrin decreased among all bulls compared with 0 h (P<0.01). Temperamental bulls had greater glucose and cortisol than calm bulls (P<0.01) at 48 h; whereas calm bulls had elevated neutrophil L-selectin expression, and phagocytic and oxidative burst activity compared with temperamental bulls (P<0.10) at 48 h. The supernatant collected from endotoxin-stimulated whole blood cultures had greater TNF-α concentrations at 48 h than at the other time points (P<0.05), but no temperament effect was observed (P>0.05). In contrast, 96 h after initial loading the supernatant TNF-α concentrations were lower (P<0.05) among all cattle. Lastly, transportation increased neutrophil phagocytosis, oxidative burst, and cell adhesion molecule expression 96 h post-transportation and the effect was more pronounced among calm bulls. These data suggest that neutrophils from calm bulls are more likely to resist microbial invasion at 96 h after transportation than neutrophils from temperamental bulls.

Temperament influences endotoxin-induced changes in rectal temperature, sickness behavior, and plasma epinephrine concentrations in bulls.

This study was designed to determine the influence of temperament on endotoxin-induced changes in body temperature, sickness behavior, and stress hormone concentrations in cattle. Brahman bulls were selected based on temperament score measured 28 d prior to weaning. In dwelling recording devices were used to monitor rectal temperature, and jugular catheters were used to collect blood samples to determine cortisol and epinephrine concentrations before and after LPS administration (0.5 µg/kg body weight). Temperamental bulls had the lowest peak rectal temperature and sickness behavior scores relative to the Calm and Intermediate bulls. Prior to the administration of LPS, Temperamental bulls had greater cortisol and epinephrine concentrations than Calm or Intermediate bulls. Cortisol concentrations increased following LPS administration but were not affected by temperament. Epinephrine concentrations peaked 1 h after LPS administration in Calm bulls. Temperamental bulls did not exhibit an epinephrine response to LPS challenge. These data demonstrate that the temperament of calves can modulate the physiological, behavioral, and endocrine responses of pre-pubertal Brahman bulls to endotoxin challenge. Specifically, temperament differentially affected the rectal temperature, sickness behavior and epinephrine, but not cortisol, responses to LPS challenge.