The effect of feeding a yeast supplement or finely ground fiber during the summer on body temperature, performance, and blood metabolites of finishing steers

Abstract Text:

Crossbred beef steers (n=96) were utilized in a study conducted at the University of Nebraska-Lincoln Agricultural Research and Development Center research feedlot near Mead, NE to determine the effect of feeding Agrimos (Lallemand Animal Nutrition; Montreal, Canada) and 2.5-cm ground wheat straw to finishing steers during the summer on body temperature and panting score in addition to performance, carcass characteristics and blood metabolites. Three treatments with four replications per treatment were set up in a completely randomized design. Treatments consisted of a basal control diet (CON); consisting of 68.5% corn, 20% modified distillers grains plus solubles, 7.5% sorghum silage, and 4% supplement, the inclusion of Agrimos (MOS; 30g/steer daily),  and 2.5-cm ground wheat straw replacing 5% corn (WHT). Cattle were stratified by initial BW between pens and pen was assigned randomly to treatment. Rumen boluses to collect body temperature were inserted on d 21 of the trial after cattle were adapted to finishing diets. Blood was collected in July and August (7 collection weeks) of the trial via jugular venous puncture. There were no differences (P > 0.19) observed for final BW, ADG, and DMI among treatments. Additionally, no difference (P > 0.24) was observed for carcass-adjusted final BW or ADG. Feed efficiency was decreased (P < 0.02) on both a live- and carcass-adjusted basis for cattle fed WHT when compared to CON and MOS. Hot carcass weight, dressing %, LM area, and marbling score were not different (P > 0.36) among treatments. Cattle fed the CON had greater 12^th rib fat depth and USDA yield grade (P < 0.02) than cattle fed WHT and MOS. Both average and maximum body temperatures were greater (P < 0.01) for cattle fed MOS than for cattle fed CON or WHT. There was no difference (P = 0.18) for area under the curve body temperature between treatments.  Panting scores were least (P < 0.01) for cattle fed the WHT when compared to CON and MOS. Time and treatment interactions (P < 0.05) were observed for bilirubin, blood urea nitrogen, calcium, chloride, carbon dioxide, creatinine, potassium, lactate dehydrogenase, phosphorus, total protein, triglyceride, uric acid, red blood cell count, hemoglobin, and hematocrit levels. No effect on animal performance was realized from the addition of Agrimos to the diet, however, body temperature was increased slightly. Adding 5% finely ground wheat straw decreased G:F and reduced panting score but did not affect body temperature.

Keywords: Body Temperature, Feedlot Steers, Heat Stress