The Milk Producer - December 2010 - (Page 38)

APPLIEDSCIENCE By Kristen Reyher, Daniel Scholl and Ian Dohoo Debate still unresolved Do certain types of bacteria cause a mild udder infection that can ward off more serious mastitis? Researchers are seeking answers coagulase-negative staphylococci (CNS) and Corynebacterium bovis. CNS make up the most common group of bacteria infecting udders of lactating dairy cows in Canada and several other countries. Mastitis caused by CNS, typically mild or subclinical, is most commonly associated with increased milk SCC. Similarly, infections with Corynebacteria spp., also common minor bacteria, cause moderate SCC increases with minimal to no milk production loss. Investigation launched Minor bacteria CNS are the most common group of bacteria found in udders of lactating cows in Canada and several other countries. D airy scientists have long classified mastitis-causing bacteria as either major or minor. Minor bacteria can still cause an intramammary infection and increase somatic cell count (SCC). However, the affected cow is likely to have only a mild reaction and experience just a slight decrease in milk production, although even increased production has been noted. Some research has also suggested a minor bacteria infection could protect the cow’s udder from a much more serious case of mastitis caused by a major bacteria strain. Scientists have identified more than 100 different bacteria that can cause mastitis infections. Among them, only a few species of staphylococci, streptococci and coliforms—all major bacteria—are common enough to impact your herd economically. These major mastitis-causing bacteria are classified as either environmental or contagious. They are usually considered more virulent 38 | December 2010 | MilkPRODUCER and damaging to udders than minor mastitis bacteria (see Table 1). LowSCC herds may be more susceptible to environmental mastitis caused by Escherichia coli, which are becoming more important, while Streptococcus agalactiae is rapidly disappearing. Increasing evidence also suggests some bacteria, considered non-pathogenic until recently, are becoming more common as primary mastitis causes. These minor bacteria include Over the past 30 years, several studies have looked at minor bacteria effects on major bacteria infections. Most identified minor bacteria present in the udder as protection against infection from experimentally introduced major bacteria. Natural infections, however, may behave differently. Since the question of how minor bacteria affect major bacteria infections is still open to debate, shedding more light on the subject is the goal of research by Dr. Kristen Reyher, from the Atlantic Veterinary College, University of Prince Edward Island, and colleagues. They are analysing extensive data collected on Canadian dairy farms by the Canadian Bovine Mas- Table 1. Characteristics of Major and Minor Mastitis Bacteria The Major Mastitis Bacteria Can cause a serious reaction, high SCC, milk drop, even death of the cow Staphylococcus aureus Streptococcus uberis Escherichia coli Streptococcus dysgalactiae Klebsiella spp. Streptococci spp. The Minor Mastitis Bacteria Cause a mild reaction, slight increase in SCC, slight decrease or perhaps even increase in production Coagulase-negative Staphylococci Corynebacteria spp.

Table of Contents for the Digital Edition of The Milk Producer - December 2010

The Milk Producer - December 2010
Contents
Editor's Notes
DFO Chair's Message
Dairy Update
Industry Roundup
DFO Promotion
Back to Basics
Research
Applied Science
Index
Markets
New 'N' Noted
Back Forty

The Milk Producer - December 2010