Location: Livestock Issues Research
Project Number: 3096-32000-008-13-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jun 16, 2016
End Date: Jun 1, 2019
The main objective of this project is to determine if supplementing the diet of growing beef calves with a chelated Zinc-Methionine (ZinMet) or an inorganic zinc (Zn) source will mitigate the negative impacts of a controlled bovine respiratory disease challenge and improve beef cattle health.
The respiratory disease challenge phase of the study will be conducted at the USDA ARS' Livestock Issues Research Unit (LIRU) in Lubbock, TX. After a minimum 30 d of supplementation, 32 heifers will be transported to LIRU's Bovine Immunology Research and Development Facility by USDA staff and equipment. Upon arrival, cattle will be placed in holding pens overnight where they will be maintained on their respective treatments (8 head per pen, 4 pens total) and fed twice daily. The following day, calves will be weighed before feeding and fitted with indwelling temperature recording devices. A blood sample will be collected and analyzed for BHV-1 titers and serum Zn concentrations and cattle will be subsequently challenged intranasally with approximately 4.0 x 10^8 plaque forming units of BHV-1. One mL of BHV-1 culture will be administered in each nostril using an atomizer attached to a syringe. A nasal lesion score will be assigned at this point and cattle will be returned to their outdoor holding pens within their respective treatment diets. Nasal lesion scores will be assigned by trained observers. Following the BHV-1 challenge, cattle will be monitored for clinical signs of illness and assigned a sickness score daily for 72 hours. Three days post-BHV-1 inoculation, all calves will be processed through the working facility and restrained via halter, while indwelling jugular catheters are inserted for serial blood sample collection and a nasal swab collected for measurement of viral shedding. Following these procedures, a nasal lesion score will be assigned and all calves will be challenged intratracheally with 50 mL of 1x 10^7 colony forming units of Mannheimia haemolytica (MH)/mL. Cattle will be monitored frequently for 48 h post-MH challenge, and a clinical exam will include an animal sickness score and respiration rate. Calves will be fed twice daily at 8 am and 4 pm and clinically examined daily at the AM feeding. Water disappearance will be recorded daily. Feed delivery will be recorded and remaining feed weighed after the last day of the challenge. After administration of the MH challenge, 9-mL blood samples for serum will be collected at 0 (i.e., immediately before the MH challenge), 1, 2, 3, 4, 5, 6, 7, 8, 12, 24, 36, 48, 60, and 72 h relative to the challenge. Additionally, a 4-mL sample of whole blood will be collected in EDTA-coated vacutainers for measurement of complete blood counts prior to BHV-1 and MH administration and again at 0, 2, 4, 6, 8, 12, 24, 36, 48, 60, and 72 h relative to the MH challenge. Following the 72 h sample, all calves will be removed from the stanchions and jugular catheters and temperature recording devices will be removed. Also, a nasal swab will be collected and a nasal lesion score will be assigned. Calves will be treated with an antibiotic specific to MH (Nuflor) and will be returned to the outdoor holding pens. The following day, cattle will be returned to the collaborator site along with a transfer of their health records. Cattle will be weighed before feeding and a nasal swab will be collected weekly for 2 weeks at the collaborator site. Thereafter, cattle will be returned to the cattle owner.