T. T. Ross

Effects of bacterial lipopolysaccharide injection on white blood cell counts, hematological variables, and serum glucose, insulin, and cortisol concentrations in ewes fed low- or high-protein diets.

Bacterial lipopolysaccharide endotoxins (LPS) elicit inflammatory responses reflective of acute bacterial infection. We determined if feeding ewes high-CP (15.5%) or low-CP (8.5%) diets for 10 d altered inflammatory responses to an intravenous bolus of 0 (control), 0.75 (L75), or 1.50 (L150) μg of LPS/kg of BW in a 2 × 3 factorial arrangement of treatments (n = 5/treatment). Rectal temperatures, heart and respiratory rates, blood leukocyte concentrations, and serum cortisol, insulin, and glucose concentrations were measured for 24 h after an LPS bolus (bolus = 0 h). In general, rectal temperatures were greater (P ≤ 0.05) in control ewes fed high CP, but LPS increased (P ≤ 0.05) rectal temperatures in a dose-dependent manner at most times between 2 and 24 h after the bolus. Peak rectal temperatures in L75 and L150 occurred 4 h after the bolus. A monophasic, dose-independent increase (P ≤ 0.023) in serum cortisol occurred from 0.5 to 24 h after the bolus, with peak cortisol at 4 h. Serum insulin was increased (P ≤ 0.016) by LPS in a dose-dependent manner from 4 to 24 h after the bolus. Insulin did not differ between control ewes fed high- and low-CP diets but was greater (P < 0.001) in L75 ewes fed low CP compared with high CP and in L150 ewes fed high CP compared with low CP. Increased insulin was not preceded by increased serum glucose. Total white blood cell concentrations were not affected (P ≥ 0.135) by LPS, but the neutrophil and monocyte fractions of white blood cells were increased (P ≤ 0.047) by LPS at 12 and 24 h and at 24 h after the bolus, respectively, and the lymphocyte fraction was increased (P = 0.037) at 2 h and decreased (P ≤ 0.006) at 12 and 24 h after the bolus. Red blood cell and hemoglobin concentrations and hematocrit (%) were increased (P ≤ 0.022) by LPS at 2 and 4 h after the bolus. Rectal temperatures and serum glucose were greater (P ≤ 0.033) in ewes fed a high-CP diet before LPS injection, but these effects were lost at and within 2.5 h of the bolus, respectively. Feeding high-CP diets for 10 d did not reduce inflammation in ewes during the first 24 h after LPS exposure but may benefit livestock by preventing acute insulin resistance when endotoxin exposure is mild.

Technical note: comparison of salivary and serum cortisol concentrations after adrenocorticotropic hormone challenge in ewes.

An ACTH challenge was conducted to determine if salivary cortisol concentration reflects serum cortisol concentration in ewes. Twelve yearling ewes (64.0 +/- 1.2 kg) were administered ACTH (100 IU, intravenously) or saline. Serum and salivary samples were collected at 30-min intervals for 2 h before ACTH administration, at 15-min intervals for 2 h after treatment, and at 30-min intervals for an additional 3 h, and cortisol concentration was determined by RIA. Although ewes responded to ACTH and saline, cortisol concentration was greater (P < 0.001) in ACTH-treated ewes from 15 to 120 min and tended to be greater (P = 0.054) at 150 min after challenge in serum. In saliva, cortisol concentration was greater (P < 0.001) in ACTH-treated ewes from 30 to 120 min and tended to be greater (P = 0.092) at 15 min after challenge. No difference was observed between ACTH-treated ewes and controls for time to peak serum cortisol concentration (P = 0.126) and time to peak salivary cortisol concentration (P = 0.109), or between saliva and serum for time to peak cortisol concentration (P = 0.220) and return to baseline cortisol concentration (P = 0.341). The serum (P = 0.009) and salivary (P = 0.050) cortisol areas under the curve between 0 and 150 min were greater for ACTH-treated ewes than controls, and serum (P = 0.002) and salivary (P < 0.001) cortisol return to baseline concentration was longer for ACTH-treated ewes. The correlation coefficient between serum and salivary cortisol concentrations was 0.88 (P < 0.001). These data indicate that salivary cortisol concentration is closely related to serum cortisol concentration and that the former may represent a suitable noninvasive alternative to blood collection for measurement of cortisol in sheep.

Effects of Graded Levels of Vitamin E on Inflammatory Response and Evaluation of Methods of Supplementing Vitamin E on Performance and Health of Beef Steers1

Two experiments were conducted evaluating dietary level of vitamin E and methods of delivering vitamin E to beef cattle. In Exp. 1, 16 beef steers were used to examine effects of 0, 285, 570, or 1,140 IU of vitamin E/d per animal on performance, febrile response, and metabolic responses following intranasal exposure to infectious bovine rhinotracheitis virus (IBRV). In Exp. 2, 120 steer calves were used to evaluate efficacy of three methods of delivering vitamin E on performance and health during a 28-d receiving period. Treatments were an oral drench of vitamin E, a subcutaneous injection of vitamin E, or supplemental vitamin E added to the 70% concentrate diet. No effects (P>0.10) of vitamin E concentration on ADG, BW, DMI, or serum metabolites were observed in Exp. 1. A linear increase (P<0.10) in rectal temperature was detected on d 2 and 3; cattle that received the greatest level of vitamin E had the greatest and most rapid increase in rectal temperature overall (P<0.02). In Exp. 2, no effects of delivery method were evident for ADG, DMI, or gain efficiency. Cattle receiving a drench or injection had a lesser (P<0.13) percentage of morbidity (85% vs 95%) than those receiving dietary vitamin E. Results suggest that supplemental vitamin E may increase the inflammatory response to a viral pathogen and that providing vitamin E by injection or oral drench may be more beneficial than feeding vitamin E.

Technical note: Effects of rumen passage on fluoxetine bioavailability in serum and effects of fluoxetine on serum prolactin concentration and demeanor in ewes.

Sheep are becoming increasingly important in medical research. The objective of the present study was to identify changes in bioactivity of fluoxetine during ruminal passage in ewes, and to examine the effects of fluoxetine administration on demeanor and serum prolactin concentration. Twelve mature ewes were administered saline (control), daily oral fluoxetine (40 mg), or alternate-day oral fluoxetine for 10 d. Four additional ewes were fitted with rumen cannulas and administered daily fluoxetine by abomasal deposition. Serum samples were collected daily for 15 d. Serum fluoxetine concentrations (ELISA) were greater (P < 0.001) in ewes in all fluoxetine treatments compared with controls on d 2. Serum fluoxetine concentrations in ewes receiving daily abomasal dosages were greater (P < 0.007) than those in controls on d 2 to 12 and were greater than those in ewes receiving daily or alternate-day oral fluoxetine on d 3 to 12. Serum prolactin concentration (RIA) did not differ (P = 0.137) among treatments and was only weakly correlated with serum fluoxetine concentration (r = 0.20, P = 0.041), and regression analysis revealed that very little variation in serum prolactin concentration was due to serum fluoxetine concentration (R(2) = 0.04, P = 0.082). Demeanor ratings on d 1 to 12 remained at normal in all treatment groups (P > 0.362). However, in ewes that had received an abomasal dosage of fluoxetine, demeanor scores decreased (P < 0.029) on d 13 and 14 before returning to normal on d 15 (P = 0.397). This study indicates that mature ewes may provide a suitable model for the study of fluoxetine, but that a larger oral dosage may be required relative to the human dosage to overcome partial loss of bioactivity during ruminal passage.