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Archive for Somatic Cell Score

Dairy farmers want to avoid mastitis. It’s expensive – antibiotics, lost milk, extra staff time and lost genetics. Furthermore every dairy operations targets to have the food safety and milk product quality that consumers want and deserve. When SCC testing through DHI and subsequently SCC sire proofs became available significant improvement tools were available to dairy cattle breeders. Breeders knew from experience that some cows and cows families were more prone to getting mastitis. Although somatic cell information was a great first step, it wasn’t the total answer. Breeders questioned if SCC could be too low and if very low SCC cows actually have less ability to fight off infectious agents that cause mastitis. So breeders asked the researchers to investigate further.

Canadian Stats Lead to First Mastitis Resistance Ratings

At CDN, breeders and researchers put their heads together in 2007 and decided to ask breeders to report on eight cow health events (Read more: Is Animal Health Important to You?) to get the necessary field information on incidences. For more than five years, 40% of Canadian milk recorded herds have been reporting if a cow has had mastitis and any of the other seven health diseases since her last test day. That information plus her somatic cell scores and genomic profile were combined to develop animal genetic ratings for mastitis resistance that will be released for the first time by CDN (Read more: Mastitis Resistance Selection: Now a Reality!) on August 12, 2014. By using the negative of a mastitis case plus the actual facts on SCC and genomic profile, a new tool will be in the hands of breeders to use in making their selection decisions.

The study of the data collected showed that Mastitis Resistance has a heritability of 12%, similar to the heritability of an important trait like feet and legs and therefore it is possible to improve it genetically. As many discerning breeders suspected, the study showed only a moderate association between a positive genetic rating for SCC and incidence of clinical mastitis in first lactations (44%) and later lactations (58%). SCC genetic indexes are an indication of few mastitis cases but a considerable distance from the accuracy breeders expect.

Mastitis Resistance Sire Proofs

After developing the formula calculating genetic evaluations for mastitis resistance, CDN researchers then compared the results to existing known facts. It was found that Sire Proofs for SCC have a correlation of 80% with Sire Proofs for Mastitis Resistance. That is moderately high but not perfect. And Sire Proofs for Mastitis Resistance were strongly associated with incidence of mastitis in first lactations (85%) and later lactations (90%). Note that the associations for first and later lactations are closer for Mastitis Resistance than they are for SCC.

When CDN publishes the genetic indexes in August, the scale will be 100 for average with a standard deviation of +/- 5. The following table produced by CDN is very interesting.

Source: Mastitis Resistance Selection: Now a Reality! CDN July 2014

Source: Mastitis Resistance Selection:
Now a Reality! CDN July 2014

This table provides for breeders some information details for both clinical mastitis (actual mastitis cases) and sub-clinical mastitis (SCC).  On a population wide basis breed average bulls (100) for Mastitis Resistance will have 92% healthy daughters with an average SCC of 178,000 in their first lactation.  In later lactations an average bull will have 88% healthy and an SCC of 226,000 in second lactation and 292,000 in third lactation. It should be noted that if a bull is used that only has a 91 rating, breeders can expect his third lactation daughters to average 400,000 SCC. In many countries 400,000 is now, or soon will be, the maximum allowable for milk to be accepted for shipment off-farm. As mentioned the numbers in this table are for an average herd. Individual breeders with less mastitis incidence can expect healthier animals and lower SCC average. However herds, with higher than average mastitis incidence, can expect poorer results.

In August Mastitis Resistance sire proofs will be published by CDN for Ayrshire, Holstein and Jersey breeds. Due to the large number of Holstein bulls with proofs and genomic profiles, CDN will publish genomic evaluations for Mastitis Resistance for the Holstein breed.

The Bullvine Bottom Line

CDN Mastitis Resistance genetic indexes will increase the accuracy of selecting animals for their ability to avoid the significant cost of udder disease. It is the tool that breeders have been asking for. It came about when breeders, researchers and genetic evaluation officials collaborated. Look for bulls or cows that are 105 or higher before considering them to be significant breed improvers.




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How often do you select a mating sire for the reasons you typically cull animals, as opposed to what your perceived ideal cow looks like?  Further to our discussion about what the Perfect Holstein Cow looks like we here at the Bullvine started to ask ourselves, “How often do we choose our matings based on what we think the perfect cow looks like? vs. what our true management needs are?” Far too often sire selection is based on the fantasy of breeding that next great show cow or VG-89-2YR instead of facts needed to breed that low maintenance cow that will stay in your herd for many lactations and produce high quantities of milk.  Do your sire selections overlook your management needs?

Speedy Selection. Long-Lasting Problems

Discernment is the hardest part of sire selection.  Seeing your herd for what it is and what its genetic needs are is step one.  Step two is choosing what will work for you almost three years from now when the daughters of the sires you use today will be entering the milking string.  The old adage was “breed for type and feed for production.”  But how many breeding stock animals have you sold recently based solely on conformation?  How many will you be selling in three years based on their type?  What are the revenue sources for your farm now and in the future?  If your answer is “We get our revenue from the milk cheque from as few cows as possible and with as much profit per cow as possible” then selecting for type could mean that your sire selection is out of alignment with your management needs.

How Can You Tell If You Are You Out of Sync?

One place to determine where your herd has issues is to look at the reasons for and the frequency of culling. Every cow that leaves your herd for any reason other than a profitable sale is an indicator of the issues that could be arising from sire selection that is out of alignment with what is going on in your herd.

The Bullvine found the following information on milking age females that are removed from herds:

  • Over 35% of cows in a herd are replaced annually. That is costly!
  • The top known reasons for culling or removing cows are:
    • Infertility  / reproduction                    23.1%
    • Sold for dairy purposes                       21.4%
    • Mastitis                                               13.8%
    • Feet and Legs                                        9.6%
    • Low production                                     7.6%
    • Total    75.5%
  • The other known reasons for culling or removing cows are:
    • Injury               10.0%
    • Sickness           7.0%
    • Old Age           2.4%
    • Diseases          1.8%
    • Bad Temperament      0.9%
    • Difficult Calving          0.9%
    • Conformation 0.9%
    • Slow Milker                 0.6%
    • Total    24.5%

Are You Breeding to Spend Money or Are you Breeding to Make Money?

You may be comfortable with your culling rate especially if it isn’t too far off “normal”. However when you look closely at the cows that remain in your herd how “needy” are they?  Staff time, vet calls, hoof trimming, semen, drugs, supplies, extra time in the dry cow pen and removing cows from herds before they reach maturity – these all add up to significant dollars down the drain.  Therefore, anything that can be done in sire selection to minimize these costs goes right to improving the financial bottom line.  All unbudgeted costs mean less profit. If an animal is culled early, it does not matter where she placed at the local show or that her sire was a popular bull that left fancy udders.  If he also left poor feet and low fertility, that costs you money.

A More Realistic Approach: Breed for the Bottom Line Not Just the Top Number

Often top bulls for total index are put forward to breeders for their use, without regard for the bull’s limiting factors.  The Bullvine doesn’t support that approach.  We recommendation that minimum sire selection values be set for the reasons cows are culled so that sires used in a herd don’t create new problems while the breeder tries to solve the current ones.

Here are the Bullvine we recommend the following requirements bulls should meet to be considered for use by bottom line focused breeders:

  • In Canada
    • Lifetime Profit Index   > +2000*
    • Daughter Fertility          > 100
    • Somatic Cell Score         < 2.90
    • Feet & Legs                      > +5
  • In USA
    • Total Performance Index        > 2000*
    • Daughter Pregnancy Rate          > 1.0
    • Somatic Cell Score                    < 2.90
    • Feet & Legs Composite               > 1.0

* A high minimum value has been set for both LPI and TPI to address the removal of cows for low production and so animals sold for dairy purposes can be in demand for their milk producing ability.


Every dairy breeder wants a superior herd and wants to eliminate the daily annoyances, costs and loss of valuable cows due to infertility, mastitis and feet problems and low production. Breeders should choose the best sires that correct the actual problems that they face in their herd instead of chasing a fantasy that has nothing to do with their reality.

The Dairy Breeders No BS Guide to Genomics


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