Relatinships Between Subclinical Mastitis Traits In The Pennsylvania State University Dairy Herd
Open Access
- Author:
- Lehew, Ryley Paige
- Area of Honors:
- Animal Sciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Chad Daniel Dechow, Thesis Supervisor
Troy Ott, Thesis Honors Advisor - Keywords:
- Mastitis
Cattle
Dairy
Genetics
Somatic Cells - Abstract:
- Mastitis, or the inflammatory infection of the mammary gland, is a major economic and welfare concern within modern dairy operations. The major causes of economic loss in mastitis-affected cows are decreased milk production, medication costs, loss of dumped milk, labor costs, decreased longevity and associated cull costs. Scientists have studied the disease in cattle for decades to better understand and reduce incidences of mastitis. Currently, subclinical mastitis is predominantly detected through the use of a linear somatic cell score, which is a function of the number of somatic cells in one mL of milk. However, the total somatic cells that a cow produces in a day also depends on daily milk yield. We derived a new trait of daily somatic cell output, which ranged from 12 million to 440 billion and with a median of 1.99 billion. To determine the effectiveness of the new and traditional somatic cell measures, we utilized proc mixed and proc glimmix analysis to better understand if linear score, total somatic cells, milk yield or a combination of these factors produces the most effective data to predict mastitis within the Penn State dairy herd. During our analysis, we found that the somatic cell score significantly increased one week before the incidence of mastitis and remained there until two weeks after the mastitis event. This trend was followed by a similar increase in total somatic cell count. A small decrease in milk yield was observed one week before and one week after a mastitis event. The best fitting model for mastitis prediction included both somatic cell score and total somatic cell score. Milk yield was not strongly associated with mastitis. Total daily production of somatic cells is a novel trait that should be explored more fully to improve mastitis diagnosis.