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Canadian Bovine Mastitis Research Network

All about Mastitis  I  Milk Quality

Culling Resulting From Mastitis  I  Clinical Mastitis  I  Bacteria Causing Clinical Mastitis  I  Non Clinical Infections
I The Verdict  I  It Is Not too Late to Do Better

Milk Quality and Udder Health

How is Quebec doing?  How does Quebec compare with the rest of Canada in terms of milk quality and udder health?

Quebec has a lot to be proud of. We have the best poutine in the world, we have the best singer in the world, we have the most beautiful women in the world and, of course, we also have the most beautiful dairy cows in the world! Quebec is also the province with the most dairy farms, the highest quantity of milk produced and… the highest average somatic cell count (SCC) in the country. Oops! It’s nothing to brag about, but we shouldn’t bury our heads in the sand either!
The SCC is, of course, the first indicator that comes to mind when discussing milk quality. It has been relatively stable in Quebec since 2003. The weighted average ranges between 249,624 SC/ml (2005) and 261,986 SC/ml (2003) (see Table 1).
Table 1. SCC weighted annual average and percentage of milk complying with the standard in Quebec
Amount of milk up to standard (%)
Source: FPLQ.
Over the same period of time, the amount of milk meeting the somatic cell standard of 500,000 CS/ml varied from 94.14% (2003) to 96.13% (2007).
Diagram 1. Evolution of SCC Average per Province (1999 - 2009)

Source: Canadian Dairy Information Centre, www.dairyinfo.gc.ca
Note: The average is calculated using the method of mobile average for the last 12 months

Diagram 2.
 Source: Valacta 2009 with the agreement of CanWest DHI.
 Diagram 3. Evolution of the main involontary culling reasons
Source: PATLQ (1980-2004) and Valacta (2005 and following) Annual Reports.  Compilation by Rodrigue Martin, agronomist, MAPAQ.
Comparing the top four milk producing provinces in Canada (Quebec, Ontario, Alberta and British Columbia) shows that Quebec has had the highest SCC for at least 10 years (see Diagram 1).
However, it is important to note that the variation among farms is much higher than among provinces. Diagram 2 shows the distribution of herd SCC’s between the 10th and the 90th percentiles in each of the four provinces.
Although it is cause for concern, the disparity between Quebec and the other provinces is not insurmountable. In 2008, 35.6% of analyses conducted on milk shipped by Quebec herds had an SCC lower than or equal to 200,000 SC/ml. That means that there are many producers out there who exceed standards a great deal.
Culling Resulting From Mastitis
It is generally recognized that the first lactation pays for most husbandry costs and that subsequent lactations generate profits.
Involuntary culling rates impact farming revenues by shortening the productive lifespan of certain subjects. In some cases, a high involuntary culling rate might force the producer to purchase animals, which not only represents additional costs, but also appreciable risk to herd biosafety.
Culling associated with mammary infections has progressed quite significantly over the last 30 years (see diagram 3).
Clinical Mastitis
At every lactation, it is generally observed that one out of every five cows suffers from clinical mastitis. In other words, it means that for a herd of 100 cows, 20 will show symptoms of mastitis during the course of a year. According to the data from the National Cohort of Dairy farms of the Canadian Bovine Mastitis Research Network (CBMRN), the incidence rate of clinical mastitis is precisely 28% in Quebec. This rate is higher than the average in Alberta farms (22%), but much lower than in the Maritimes and Ontario (36%).
Our data also show that the rate of clinical mastitis is generally higher in tie stall farms, which are the most common in Quebec, than in free stall farms.
As was the case for SCC’s, variations in clinical mastitis from one herd to the next are much greater than variations between provinces. For example, recent Cohort data show a spread of 3 to 110 cases per 100 cows per year. For the best and the worst 25% of these herds, the number of cases vary from approximately 15 to 39 per 100 cows per year.
Of course, part of this variation can be explained by differences among producers in detecting mastitis cases and in record keeping. For example, one producer may feel that the mere presence of clots in the milk is not a sign of clinical mastitis, while another producer may feel it is.
Still, the most credible hypothesis to explain such large variations among Quebec herds probably has to do with the implementation of udder health management practices.
Bacteria Causing Clinical Mastitis
The same bacteria flourish everywhere in Canada, but not in the same proportions. We canfight against those bacteria with the help of various management practices.
When milk samples from cows presenting mastitis symptoms are analyzed, the most common bacteria found in Quebec farms is Staphylococcus (Staph.) aureus with 17.8% of cases. This percentage of Staph. aureus is the highest in Canada. It is 15.4% in Ontario and 13.4% in the Maritimes (Table 2).
Table 2. Prevalence of Clinical Mastitis per Pathogen per Province (%)
Staph. aureus
E. coli
Strep. spp.
Strep. uberis
Strep. dysgalactiae
No growth
Staph. aureus is contagious, which means that it can be transmitted from one cow to the next. It is a stubborn enemy which has proven quite troublesome for local producers. However, Western Canada producers seem to have found effective ways to keep it at bay. In fact, Staph. aureus is not the bacteria which causes the most problems in Alberta. It is found in only 5.9% of clinical mastitis samples.
Environmental bacteria are the most troublesome in Western Canada, where the main culprits are E. coli and environmental streptococci. Here at home, although less prevalent than Staph. aureus, these bacteria still wreak considerable havoc. Streptococcus (Strep.) uberis, Strep. dysgalactiae (a bacteria considered to be both environmental and contagious), other Strep. spp. and E. coli are each found in around 8% of clinical mastitis cases. The same is true in Ontario and in the Maritimes.
That being said, it is important to point out that E. coli is the strain most often found in mastitis cases presenting severe symptoms (31% of the cases of severe clinical mastitis). In addition, it is generally recognized that E. coli is probably involved in a large portion of clinical mastitis cases where no pathogen was identified (no significant growth) since this bacteria is often rapidly eliminated by the cow’s immune system.
Non Clinical Infections (without visible symptoms)
Even in the absence of visible signs of mastitis, intramammary infections (IMI) cause an increase in SCC’s as well as important production losses, mainly because of damage to mammary secretory cells.
Based on Cohort farms of the CBMRN, it is estimated that almost one out of every five (18%) quarters is infected with mastitis causing pathogens. And yet, less than 0.5% of these quarters show visible symptoms such as abnormal milk (clots, flakes, watery milk), swelling or fever.
Coagulase-negative staphylococci (CNS) are most often involved in subclinical intramammary infections, followed by a close cousin, Staph. aureus, particularly on Quebec farms. The pattern is more or less the same at the national level, except in the West where Corynebacterium takes second place behind CNS, and where Staph. aureus is far less significant.
The Verdict
It is tempting to compare ourselves with other Canadian provinces as we just did for SCC, clinical mastitis and subclinical mastitis. However, it would be risky to draw any conclusions. There are too many differing factors among provinces, starting with the relative size of dairy farms commonly found in each province. It has a great impact on management practices implemented by producers and therefore, on mastitis pressure and milk quality.
It is more useful to make comparisons among ourselves and see that many dairy farms in Quebec have a good showing in udder health, as evidenced by both SCC’s and the number of clinical mastitis cases. The current level of knowledge in mastitis prevention seems to allow a lot of dairy farmers to succeed, and one could surmise that some of the problems encountered with udder health have to do with the failure to implement known principles.
Table 3 gives an overview of the adoption rate of several management practices that are recommended to fight against mastitis.
Table 3. Adoption of Udder Health Management Practices by Quebec Farmers
Mastitis management practices
% of producers using the practice
Have written milking procedures
Use teat dipping before milking
Wash all teats before installing milking unit
Dry teats before milking
Forestrip all cows
Wear latex gloves during milking
Clean gloves during milking with a disinfectant or water
Milk in sequence, disinfect the milking unit or use a different unit for cows with chronic mastitis
Other practices
Test cow for mastitis before purchase
Burn or shave udder hair
Dry treatment for at least 90% of cows
Source: CBMRN.
This table only lists a short selection of basic practices that are recommended to promote udder health and quality milk in dairy herds. Some are implemented by all producers in Quebec while others are not as diligently followed. For example, it would seem that washing teats prior to milking is well integrated in milking habits. However, wearing and washing gloves during milking just does not seem to be popular here. And yet, it is a simple and low-cost practice that can contribute to reducing the risk of spreading contagious bacteria from one cow to the next during milking.
All producers have adopted at least some of those practices, but how many have indeed implemented most if not all of them? Another problem is that a given practice may be implemented with more or less success. For example, if everyone cleans the teats before milking, it does not necessarily mean that all teats are really clean when the time comes to attach the milking unit. That is probably the weak point of the formula and that is where we need to act in order to generate a significant improvement in the short term.
It Is Not too Late to Do Better
Improving milk quality and udder health at the provincial level is no small task, but it could be accomplished easily by increasing the adoption rate of recommended practices against mastitis at the farm. If some have succeeded, there is no reason why everyone could not succeed as well.
Other jurisdictions have already performed this exercise. For example, the Netherlands and Australia have achieved significant SCC reductions with the help of programs that simply promoted the implementation of existing knowledge. Here, in Quebec, key organizations have already mobilized and are busy developing a wide range of tools and activities designed to equip dairy producers with solutions to achieve optimal udder health and quality milk.
If everyone puts their shoulder to the wheel and works together, this amazing feat becomes possible!

This article was published in Le producteur de lait québécois in November 2009.
Written by Julie Baillargeon, agronomist, transfer agent, CBMRN, Jean Durocher, veterinarian, coordinator of dairy herd health, Valacta, Jérôme Carrier, consulting veterinarian, AMVPQ, Simon Dufour, veterinarian, doctorate candidate, CBMRN, Anne-Marie Christen, M. Sc., transfer project manager, CBMRN, and Daniel Scholl, scientific director, CBMRN, and full professor, Faculté de médecine vétérinaire, Université de Montréal.



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