Location: Livestock Issues Research
Project Number: 3096-32000-008-031-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 15, 2021
End Date: Aug 14, 2023
Liver abscesses are a problem in beef and dairy cattle with cost implications related to profitability and animal well-being across multiple sectors of the production chains. Feed-through antibiotics are the primary prevention/intervention strategy; however, consumer perception is driving producers to seek alternatives to antibiotics, thereby leaving producers to search for novel ways to reduce liver abscesses. Currently, the study of liver abscesses is primarily conducted by relying on natural infections that occur in commercial production settings. These studies may require a large sample size to evaluate the effectiveness of various interventions which may be inadvertently biased by a plethora of genetic and/or environmental factors. Therefore, the objective of this study is to develop a model to induce the formation of liver abscesses that is minimally invasive, reliable, and repeatable while attempting to mimic real-world disease etiology. If successful, this model could be utilized to test novel antibiotic alternatives and/or liver abscess reducing compounds in a controlled setting with fewer animals to evaluate efficacy prior to conducting larger scale commercial trials.
Forty weaned Holstein steer calves from a commercial calf ranch or dairy operation in the Texas Panhandle will be randomly assigned to 1 of 3 treatments: 1) Control (n=13), 2) acidotic diet (n=13), or 3) acidotic diet + intraruminal inoculation with F. necrophorum (n=14). The acidotic diet will be comprised of fine ground corn (66%), distillers corn with solubles (25%), cottonseed hulls (5%), and fine ground alfalfa (4%). Upon arrival, an intraruminal bolus that monitors pH will be inserted and calves will be placed in individual pens in an indoor climate-controlled facility and allowed to acclimate for 7 d to a commercial, basic starter ration. On d 0, calves in treatments 2 and 3 will undergo a diet change. Calves will be fed the acidotic diet for 3 days, control diet for 2 days, and the cycle will be repeated 3 times. Boluses monitoring real-time pH will be evaluated prior to the morning feeding, and if a calf reaches a ruminal pH of less than 4.5 for greater than 4 h, the calf will be switched back to a control diet. Following the ration change cycles, the calves in treatment 3 will be intra-ruminally administered with F. necrophorum. Blood will be collected prior to the ration change and every 2 weeks until harvest (43 days post-ration changes). Blood will be used to quantify complete blood cell counts and serum chemistry profiles. Upon harvest, calves will be evaluated for liver abscesses and/or scarring along with an evaluation of the rumen, lungs, and colon. Abscesses will be cultured for Fusobacterium, Trueperella, and Salmonella spp. Histopathology samples will be collected from the rumen to evaluate the differences in architectural features between the treatments. Finally, F. necrophorum will be cultured from ruminal epithelial tissue and colon tissue.