Effects of Copper Oxide Bolus Supplementation on Performance of Stocker Calves Grazing Endophyte Infected Tall Fescue

Abstract Text: Loss in performance of cattle grazing endophyte-infected tall fescue [Lolium arundinaceum (Screb.) Darbysh; E+] has been quantified in a number of studies.  Evidence also suggests lowered Cu status in cattle consuming the fungal endophyte associated with E+.  Therefore, an experiment was conducted to examine the effects of copper oxide bolus supplementation on performance of stocker calves grazing E+.  On September 8, 2014, commercial Angus stocker calves (n = 21; 263.7 ± 38.01 kg LW) were stratified by calving date, body weight, and sex, and allocated randomly to 1 of 3 treatments.  Treatments consisted of an intraruminal bolus containing 12.5 g of CuO needles on d 1 (CB), the same bolus on d 1 and d 30 (CB2), or no bolus (Control).  All boluses were administered using a balling gun.  Calves were then rotationally grazed on E+ pastures for the entirety of the 60-d trial.  Performance was measured and blood was collected at 30-d intervals.  Intraruminal CuO bolus supplementation did not affect (P ≥ 0.21) 30-d weight, 30-d ADG, 30-d gain, final weight, total ADG, or total gain.  White blood cell count on d 30 (P = 0.08) and d 30 WBC change (P = 0.07) tended to be higher in calves administered CB vs. CB2.  Also, platelet change at d 30 tended (P = 0.08) to be lower and total platelet change was lower (P = 0.01) for CB vs. CB2.  Lymphocyte change at d 30 tended (P = 0.09) to be higher for CB and CB2 relative to controls.  Calves receiving either 1 or 2 CuO boluses had lower (P = 0.05) total RBC change and tended (P = 0.07) to have lower total hemoglobin change compared with calves receiving no CuO bolus.  Therefore, supplementation with an intraruminal bolus containing 12.5 g of CuO may not affect performance of stocker calves grazing endophyte-infected tall fescue.  However, administration of CuO boluses may affect some blood parameters depending on dosing rate and time of administration.

Keywords: copper oxide, calves, tall fescue