1a.Objectives (from AD-416)
The objective of this cooperative research project is to evaluate the effects of breed of dam on hornfly infestation in beef cattle; the relationships of hornfly infestation to milk production and quality, serum cortisol, and serum prolactin; and the relationship of the promoter region of the prolactin gene to variables measured in this study.
1b.Approach (from AD-416)
The project will consist of 48 crossbred cows sired by Bonsmara, Brangus, Charolais, Gelbvieh, Hereford, and Romosinuano sires with approximately 8 cows per sire breed. Cows will be managed on tallgrass native prairie throughout lactation. Fly counts will be done on pasture prior to milking and fly control treatment every 28 days starting in late May and continuing for 6 milkings or early October. Two native pastures will be used in this research, with cows and pastures located at the USDA Grazinglands Research Laboratory at El Reno, OK, and will be stocked at the rate of 6 acres per animal. Fly control will be done every 28 days prior to milking. Cows will be milked using single cow milking machines, and blood samples will be taken at each milking via jugular venipuncture. Data will be analyzed as a repeated measures design with the main unit breed of cow and subunit time of lactation.
Cooperative research in evaluation of breed and genomic effects of hornfly infestation on milk production and calf preweaning growth was initiated in May of 2011. Blood was collected for DNA isolation from cows in the study, and hornfly counts have been done monthly since the inception of the project. Fly counts will continue through weaning in October, and cows will be genotyped for prolactin polymorphisms in the fall and winter. Since this is the first fly season of the study, there are no results to report.
The ADODR monitored progress of the project through telephone conversations and emails.