ANSC 438 Home / Beginning / Milk Composition / Mammary Structure
Mammary Development / Mother & Neonate / Lactation / Mastitis
Lactation Biology
WL Hurley

Welcome to the Mastitis
Detective Cases

Blood agar plate with E coli.

Mastitis is an inflammation of the mammary gland. Mastitis usually occurs in response to:

  • Intramammary infection (IMI) - primarily bacterial infection, but also mycoplasmal, mycotic (fungal), or algal infections. Most mastitis is caused by bacterial infection of the mammary gland.
  • Mechanical trauma, which predisposes the gland to IMI
  • Thermal trauma, which predisposes the gland to IMI
  • Chemical insult, which predisposes the gland to IMI

Prevalence in dairy cattle approach or exceed 25% of quarters at any time. Mastitis is recognized as the most costly disease in dairy cattle. Losses to the US dairy industry alone amount to well over $2 billion/year. Costs of mastitis include:

  • DECREASED MILK PRODUCTION is associated with subclinical or clinical mastitis. Decreased milk production accounts for about 70% of total cost of mastitis. About 10-26% of total milk loss occurs in quarters with subclinical IMI.
  • Milk dumped for antibiotics is the major cost associated with clinical mastitis. Discarded milk and decreased production accounts for about 85% of cost of clinical mastitis.
  • Veterinary costs
  • Labor costs
  • Culling and death costs
  • Lost milk quality premiums due to increased SCC(somatic cell count), decreased milk fat which may occur as a result of IMI, and decreased protein which may occur as a result of IMI.

It is sometimes difficult to initiate mastitis control programs, because 70% of the losses are not visible to the producer (unrealized production potential).


Be a Mastitis Detective - Here is your chance to be a real problem solver. These mastitis cases represent herd mastitis problems that have occurred on dairy farms in the US. They are adapted from real-life herd mastitis cases that were addressed by Dr. Dawn Morin (Department of Veterinary Clinical Medicine, University of Illinois). Your role in these exercises is to act as a consultant and troubleshooter for dairy producers who are experiencing mastitis problems in their herds. You get to be the Mastitis Detective.

The initial information that you receive is analogous to information that you might gather from the producer when they initially call you on the phone to solicit your help. The case study exercises then take you through the process by which you might critically think your way through the problem to a satisfactory solution. You will be given various types of information to help you make these decisions. Some of that information may be relevant to the case and some may not. You will need to make decisions and value judgments about the information throughout the case study.

Be sure you have studied all of the resource sections before completing these cases.


From time to time you will be asked to PRINT THIS PAGE at various steps in the case. Use those pages for writing out your thoughts and responses. These can also act as an archive of your thought process as you move through each mastitis case.

*Please record the time at which you begin this mastitis case.

You may chose to start with either the problem of Farmer Bo Vine or the problem of Farmer Elsie de Koo, or start with familiarizing yourself with the Mastitis Resources pages. See below for the icons to begin your detecting.



Acknowledgments: The author wishes to recognize Dr. Dawn Morin for developing the original mastitis case studies. These cases have been invaluable teaching tools for many years. Lindsay Yorke also is recognized for her insights and help in developing these web-assisted case studies. This project was funded in part by a Teaching Enhancement Grant from the Office of Academic Programs, College of ACES.

Information contained herein is subject to change without notice.
Copyright® 2009 by Walter L. Hurley, University of Illinois, Urbana-Champaign