160 Effect of Diets Containing Soybean Co-Products Formulated for High-Risk Stocker Cattle on Growth Performance, Morbidity and Mortality Associated with Respiratory Disease

Abstract

Abstract The objectives of this study were to determine the effect of including soybean co-products on growth performance and respiratory disease incidence in high-risk stocker cattle. For this study, crossbred beef bulls and steers [n = 272; initial body weight (BW) 230.9 ± 19.7 kg] were purchased from local auction markets at 3 time points (load 1: n = 93 cattle; load 2: n = 91 cattle; load 3: n = 88 cattle). On day 0, cattle were processed (ear tagged, vaccinated, dewormed, ear notched for identification of cattle persistently infected with bovine viral diarrhea virus, castrated intact bulls), stratified by BW and allocated randomly to 1 of 8 pens (0.45 ha). Pens were assigned randomly to 1 of 3 dietary treatments: 1) a control supplement containing no soy co-products (CON); 2) a supplement containing soybean meal (SBM); or 3) a supplement containing soy oil (SBO). All supplements were isonitrogenous and isoenergetic. Cattle were fed supplements (2.45 kg DM/day) and offered bermudagrass hay for ad libitum intake for a 42-day trial. Body weights were taken on days 14, 28, 41, and 42 of the trial. Each morning, cattle were observed for signs of morbidity. If presenting with symptoms, cattle were pulled and rectal temperatures were recorded; if temperature exceeded 40°C, calves were treated according to a standard protocol. Cattle were deemed chronic if they received 3 antibiotic treatments and had an overall average daily gain (ADG) of less than 0.5 kg/d. Statistical analyses were performed using SAS 9.4, with PROC MIXED used for BW, ADG, and antibiotic cost analysis. Body weights were analyzed with the repeated measure of day and for treatment, day, and treatment by day interaction. PROC GLIMMIX was used for morbidity and mortality analyses. There was no treatment by day interaction (P = 0.99) or main effect of treatment (P = 0.86), but there was a day effect (P < 0.0001) with BW increasing throughout the trial. Average daily gain was not affected by treatment (P ≥ 0.42; 0.81 kg/d for SBM, 0.79 kg/d for SBO, and 0.76 kg/day for CON). Overall morbidity and mortality were 71% and 1%, respectively, and were not affected by treatment (P = 0.62 and P = 0.99, respectively). Relapse rates and chronics were not affected by treatment (P = 0.52 and P = 0.51, respectively). Total cost of antibiotic treatments was not different (P = 0.8; $30.37 for SBO, $28.95 for CON, and $28.52 for SBM). While the inclusion of soybean co-products did not affect BW, respiratory disease incidence, or cost of antibiotic treatments in high-risk stocker cattle, further work will focus on haptoglobin, hemocytology, and antibody titer responses during the receiving period.