Diagnosis of Subclinical Mastitis Using Different Methods, with Isolation of Different Causative Organisms from Cow's Milk

Abstract

Milk is a nutritious food containing many essential nutrients. This composition is changed by physiological factors and the health status of the mammary glands. Milk is a good medium for the growth of a wide diversity of microorganisms, the consumption of contaminated milk may lead to food-borne diseases. Investigation of the bulk tank milk (BTM) is an accurate and effective approach for evaluating the milk quality at the herd level, and it is particularly useful for the detection and identification of mastitis pathogens in cows, less expensive, more convenient, and faster than testing milk samples from individual animals or groups of cows. Most countries set critical limit for bulk tank milk somatic cell count (BTSCC), above which milk cannot be collected from the farm, other countries adding total bacterial count of bulk tank, while others including other parameters in the evaluation of bulk tank milk. Mastitis is a global problem and it is the most significant disease of dairy herds; it has massive effects on economy especially in developing countries. It causes changes in milk composition and not only affects the milk quality, but also affects its suitability for processing. Most mastitis pathogens represent major public health hazards. Subclinical mastitis is characterized by no visible changes in milk or udder which reflects its importance than the clinical form. The first step in control of mastitis is the early diagnosis of subclinical type depends on the compositional changes that act as biomarkers of udder inflammation. Screening tests including CMT and SCC are the most common standards for diagnosis of mastitis. Various studies reported that the measurement of enzyme activities seems to be a suitable diagnostic method for identifying infected mammary glands in early lactation, while other investigators reported that positive diagnosis of subclinical mastitis should fulfill two criteria a positive bacteriological test and an inflammatory change.