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

Professional Animal Scientist, Apr 2003 by Rivera, J D, Duff, G C, Galyean, M L, Hallford, D M, Ross, T T

Following processing, cattle were moved to their allotted pens and fed approximately 30 kg of wheat hay top-dressed with approximately 18 kg of the receiving diet per pen. Cattle received the wheat hay for a period of 7 d, after which they were offered only milled feed. Cattle were monitored daily for signs of bovine respiratory disease (BRD), and animals displaying clinical symptoms (lethargy, depression, and nasal or ocular discharge) were removed and taken to the processing area for a more thorough examination. If rectal temperature was > or =39.7[degrees]C, the animal was treated with 10 mg/kg of BW of tilmicosin phosphate and 20 mL of long-acting penicillin (300,000 IU of procaine penicillin/mL; Agri-Laboratories, St. Joseph, MO). Following treatment, cattle were returned to their pens. If an animal continued to display symptoms 3 d following initial antibiotic treatment and had a rectal temperature of =39.7[degrees]C, it was treated with florfenicol (6 mL/45 kg of BW; Nuflor(R); Schering Plough Animal Health) and returned to its pen. If the animal did not respond to three antibiotic treatments, it was removed from the experiment and classified as chronic.

Weekly feed samples collected from feed bunks were composited to determine DM, NDF, ash, and CP content of delivered feed (Goering and Van Soest, 1970). On d 14 and 28, cattle were weighed, and orts were collected from each bunk to determine DMI for each 14-d period. Dry matter intake was used in conjunction with ADG to determine gain efficiency. Performance data (BW, ADG, DMI, and gain efficiency) were analyzed using a fixed effects model and PROC GLM of SAS, with pen within treatment as the testing term. Cattle that were treated once for BRD were classified as morbid, and those receiving antimicrobial therapy more than once were classified as retreated. Health data (morbidity, retreatment, and chronic animals) were analyzed using a categorical model (PROC CATMOD of SAS). Medicine cost for each animal was calculated (medicine cost per treatment group / number of animals in each treatment group) and analyzed as a linear model. Pre-planned feed delivery vs the average of injection and oral drenching and injection vs oral drench contrasts were evaluated.

Results and Discussion

Experiment 1. No effect of vitamin E was detected for ADG or B W (Table 2). Average daily gain was less across all treatments following the IBRV challenge than before; however, it is unclear whether this was a result of the immune response of the animals or the added stress of sampling the cattle daily. Similarly, no effect of vitamin E was noted for DMI (Table 2) for d 0 to 7; however, a linear trend (P

It is not clear why vitamin E supplementation increased the inflammatory response, but this increase in febrile response may help explain why vitamin E has been reported to positively affect humoral immune response (Rivera et al., 2002). During an inflammatory response, blood flow increases to the area of infection to allow more neutrophils, macrophages, and B and T cells to the area (Tizard, 1996). This could result in greater production of antibodies specific for that infection. Smith et al. (1997) determined that supplementation of vitamin E and Se resulted in a greater influx of polymorphonuclear neutrophils into milk following an intrammmary bacterial challenge. One poly-unstaturated fatty acid within cell membranes is arachidonic acid. Vitamin E is thought to control peroxidation of arachidonic acid and its unstable metabolites (Peters, 1986). Arachidonic acid can be metabolized to prostaglandins and leukotrienes. Both these metabolites are important in stimulating an inflammatory response (Kuehl and Egan, 1980). Additionally, the decrease in DMI observed in the present study also could be explained by the fact that the inflammatory response is associated with a decrease in appetite (Tizard, 1996).