Location: Livestock Issues Research
Project Number: 3096-32000-008-14-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Feb 1, 2017
End Date: Jan 31, 2019
The objective of this study is to evaluate the effect of a various live yeast/yeast cell wall product supplementation on innate immunity and pathogen migration and translocation in weaned dairy calves following an oral Salmonella challenge.
Weaned dairy calves (n =20; ~250-300 lbs; all same sex) will be sourced from a commercial calf ranch in the Texas Panhandle area. Calves will be housed and processed in accordance to the prescribed procedures of the calf ranch. Calves will be pre-screened to select calves that are not shedding Salmonella and that have not been treated for illness (d ~-28). Calves will be transported to Lubbock, TX (d -22), a body weight will be recorded and randomly assigned to 1 of 5 treatment diets consisting of a basal starter ration (CON; A), basal ration + the inclusion of 4 different yeast supplements (B,C,D, and E). Calves will be individually housed in an environmentally-controlled facility with ad libitum access to treatment diets and water for the duration of the study. Calves will remain on their respective treatment diets for the duration of the study. On d -1, a rectal swab and body weight will be obtained, and calves will be fitted with an indwelling rectal temperature recording device and a jugular catheter. Calves will be returned to their pens and allowed to acclimate overnight. On d 0, calves will be orally inoculated with 1.0 x 10 exp 6 CFU of Salmonella Typhimurium via a bottle containing bacterial culture combined with milk replacer. At time 0 (d0) and every 8 h thereafter, a whole blood sample and a serum sample will be obtained. Whole blood samples will be utilized to analyze hematology, and serum will be used to analyze cytokines. Rectal swabs will also be collected daily to monitor fecal shedding of Salmonella. Also, visual evaluation of sickness will occur daily by a trained observer on a 4 point scale (1 = normal maintenance behaviors; 2 = calm, but head is distended and increased respiration; 3 = clinical signs of sickness and increase respiration with drool; 4 = lying on side with labored breathing and frothing at the mouth). Feed disappearance will be monitored daily. On d 2, calves (n=2) from each treatment will be humanely euthanized. Animals will be weighed and tissues samples will be collected during necropsy. Tissues to be collected include: mesenteric lymph node, subiliac lymph node, ileum, jejunum, duodenum, transverse colon, cecum, liver, kidney, rumen fluid and synovial fluid. Additionally, ileum tissue will be collected for histology analysis. Ileum and rectum samples will be collected for storage in the event microbiome and/or metabolome is needed for analysis. Each tissue will be homogenized, weighed, and Salmonella will be quantified utilizing selective media. Each tissue will also be enriched to identify Salmonella present below the limit of quantification. The necropsy process will be repeated for the remaining calves on d 4 post-inoculation.