Location: Livestock Issues Research
Project Number: 3096-32000-008-034-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jan 1, 2022
End Date: Dec 31, 2024
To determine if feeding an immunostimulant (Beta-Glucan), to dairy calves will alter their innate immune response to an endotoxin challenge.
Weaned dairy steer calves (n = 40; 200-400 lbs) will be sourced from a commercial calf ranch in the Texas Panhandle. The calves will be transported to the Livestock Issues Research Unit’s Research and Development Complex in Lubbock, TX (d -25 to -21). Upon arrival, calves will be weighed, given a unique ID, placed in indoor individual pens in an environmentally-controlled building, and allowed ad libitum access to water and a starter/grower ration set to meet or exceed NRC requirements. The diet will be formulated to not include any probiotic or immunomodulating feed supplement to prevent confounding the study with the product being examined. Cattle husbandry and building maintenance will be conducted in accordance with SOP LIRU-C1 (Calf Building Monitoring and Care). Accordingly, observations of calf health and attitude will be monitored and recorded daily from arrival to study termination. On d -21 cattle will be randomly assigned to treatments and balanced by body weight. Treatment will be the incorporation of a purified beta-glucan supplement (Aleta, Kemin Industries, Des Moines, IA) at 1 of 4 inclusion concentrations to include 0 g/hd/d (CON), 1 g/hd/d (A) 2.5 g/hd/d (B), and 5 g/hd/d (C). These inclusion rates are based on the assumption that the mean daily intake will be 10 lb/day. Calves will be supplemented with their respective treatment rations for ~ 21 d. On d -1, calves will be weighed, and restrained via halter in a squeeze chute to allow the neck, caudal to the jaw, to be shaved, cleaned, and disinfected. Calves will then be fitted with indwelling jugular catheters (LIRU SOP B1) and rectal temperature monitoring devices (LIRU SOP C2) that will measure body temperature continuously at 5-min intervals. Calves will be housed in individual bleeding pens (LIRU SOP B2) for the duration of the study with access to water and their ration. On day 0, all calves will be challenged intravenously with lipopolysaccharide (LPS; 0.25 µg/kg body weight) via the jugular catheter. Whole blood samples will be collected for serum isolation on d0 at hours: -2, 0, 1, 2, 3, 4, 5, 6, 8, and 24, relative to LPS administration at 0 h. Serum will be isolated and stored at -80oC until analyzed for respective biomarkers. An additional whole blood sample will be collected for measuring hematology parameters (red blood cells, hemoglobin, hematocrit, platelets, and total white blood cells and differentials) at d-21, d-14, d-7 and on d0 at -2, 0, 2, 4, 6, 8 and 24 h relative to LPS administration. A third whole blood sample will be collected at -21, 0, and 24 h relative to LPS administration. Additionally, sickness behavior scores, will be recorded prior to the collection of each blood sample. If at any point, an animal reaches a sickness score > 4 the animal will be removed from the study and treated with an intervention protocol as prescribed the USDA-ARS Program of Veterinary Care and/or with the consultation of the attending veterinarian.