Location: Livestock Issues Research
Project Number: 3096-32000-008-018-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Sep 15, 2017
End Date: Sep 15, 2022
The specific objective of this experiment is to determine if feeding the Purina Beef Wellness Pack or PMI Commence will mitigate some of the negative effects associated with an acute endotoxin challenge in beef cattle.
Beef calves (n=16 steers and 16 heifers) weighing between 300 and 600 lbs will be transported from the Purina Research Beef Herd in Gray Summitt, MO to the USDA-ARS Livestock Issues Research Unit. Prior to arrival, calves will be assigned to 1 of 2 treatment groups: 1) Control group fed a standard grower ration and 2) calves who received the same grower ration with the addition of a PMI Beef Wellness Pak at 1 oz./hd/d. Post-weaning, all calves will remain on their respective treatment diets for the duration of the study. Calves will be vaccinated 21 d prior to weaning and at weaning with a combination 5-way respiratory modified-live virus vaccine. No bacterin will be administered during vaccination. On d -15, a blood sample will be collected from each calf and will be analyzed for BHV-1 titers. Nasal swabs will also be collected to determine BHV-1 shedding. On d-3, temperature recording devices will be inserted in all calves. Upon arrival in Lubbock calves will be placed in holding pens overnight and maintained on their respective diets (d -1). On d 0, calves will be weighed, and then challenged with approximately 1 x 108/mL PFU of BHV-1 in 1mL phosphate buffered saline in each nostril using an atomizer attached to a syringe. A 9 mL blood sample will be collected for serum, and a 4 mL blood sample will be collected for hematology. Prior to BHV-1 challenge, nasal swabs will be collected to evaluate potential viral shedding and a nasal lesion score will be assigned. After the BHV-1 challenge, calves will be moved to outdoor pens and monitored daily. On d 3, calves will be weighed, and then restrained via halter in a squeeze chute to allow the neck to be shaved, cleaned, disinfected, and fitted with jugular catheters and blood samples for serum and hematology collected. Mannheimia haemolytica (MH) will then be administered intra-tracheally at a targeted dose of 1.0 x 107 in 100 mL of media. Calves will be monitored frequently for 72 hours post-MH challenge and a clinical exam will be performed including an animal sickness score. Calves will be assigned a nasal lesion score on d 0, 3, 6, 10, and 17. At 24, 48 and 72 hours post-MH challenge, a respiration rate will also be recorded. Calves will be assigned a clinical health score prior to BHV-1 and MH challenge and at 24, 48 and 72 hours post-MH challenge while in the bleeding stalls. After the MH challenge, blood samples for serum will be collected every h for 8 h, and at 12, 24, 36, 48, 60, and 72 hours post-MH challenge. Whole blood will be collected every other h for 8 h following the MH challenge and analyzed for hematology and again at 12, 24, 36, 48, 60, and 72 h. Following the 72-hour blood collection, calves will be removed from their stalls, body weights collected, a nasal lesion score assigned, nasal swab collected, treated with an antibiotic, and indwelling jugular catheters removed. Calves will then be moved to the outside pens where they will be maintained in their respective diets. Calves will be monitored daily for signs of illness until shipped to a collaborator. Blood samples, nasal swabs and body weights will be collected again on day 7 following the bacterial challenge.