Genetic Considerations for Beef Cattle Production in Challenging Environments

Non-Technical Summary: Outcomes or projected Impacts: If genetic variation for Infectious Bovine Keratoconjunctivitis, Bovine Respiratory Disease Complex and cattle ticks can be better quantified from Objective 1, this information could be utilized by beef producers to identify cattle genetic types that express resistance to these maladies with a subsequent increase in herd productivity being achieved at a lower cost. Participation by multiple states in Objective 2 will provide the large number of records needed to appropriately analyze reproductive data and calf survival and allow for better breeding recommendations to producers. Data and DNA collected in Objective 3 will allow for characterization of new genetic markers as well as provide phenotypic data for potential discovery of new genes of interest that influence beef production. If genetic variation of hair coat type (length and color intensity) and its influence on production traits can be quantified in objective 4, cattle producers in the Southern region, as well as other tropical and sub-tropical regions, can utilize this information in breeding programs. <P> Approach: Methods: Objective 1a. Calves will be evaluated for evidence of Infectious Bovine Keratoconjunctivitis during the preweaning period. Objective 1b. Cattle will be vaccinated for bovine respiratory disease (BRD) at various locations at the ages according to their standard operating procedures. Participants may use killed or modified live (MLV) vaccines at their respective locations, but the same killed and MLV vaccines from a single manufacturer will be utilized across locations. All calves will have known sires. Weight, rectal temperature and blood serum will be collected on calves at the time the booster vaccination of a killed vaccine is administered or the time a single MLV is administered (Day 0). Weight, rectal temperature and blood serum will also be collected 28 days later. Sera will be frozen and banked for later assays as funding allows. Genomic DNA will also be collected and stored for future use as genetic markers for immune function and health become available. Objective 2. Reproductive and maternal data for heifers and cows will be collected at respective locations that will normally be collected. Objective 3. DNA samples will be collected from pedigreed populations of cattle (purebred and crossbred) from various units throughout the Southeastern United States in conjunction with all objectives. Whole blood will be harvested in purple top tubes, transferred to two 2 ml cryotubes and stored in a -80 degrees C freezer at each location until testing is determined. Whole blood or tissue samples will be taken from each animal including calves dead at birth. Data on each animal will include individual, sire, and dam identification, breed or breed type, and location. Objective 4. Cattle will be evaluated at key points during the production cycle. Bull and heifer calves will be evaluated at weaning and up to a year of age. Heifers will be evaluated at first breeding and cows will be evaluated at the start of the breeding season each year. At each time point rectal temperature, and surface temperature if possible, will be measured for each animal using a rectal thermometer and a hand held infrared thermometer, respectively. Surface temperature will be measured at three locations on the animal, the rump, over the ribs and the shoulder. Respiration rate will be determined by visual observation and counting of breaths taken and adjusted to breaths/minute. All temperatures and respiration measures will be done with the animal in the chute, but not squeezed, and in the shade. At each evaluation animals will also be scored for hair coat length and luster.