Dairy producers are offered many opportunities to try new products and technologies.  While new opportunities frequently promote their positive aspects, it is important to consider any potential negative aspects.  What do you think that your response would be if you had to choose between these 2 products?  Both products have the same cost to purchase and the same implementation protocol.

  • Product 1: Increase production by 5.9% but would also increase the incidence of mastitis by 26%? 
  • Product 2: Increase production by 5.6% but would also decrease the incidence of mastitis by 12%?

Pretty easy choice?  How excited would you be to try Product 1 on your cows even if Product 2 didn’t exist?

You may think that there is no way that such a product exists in the dairy industry, but it absolutely does.  Table 1 and 2 below list the top 10 Jersey sires for Cheese Merit (CM$) that have >=50 daughters included in their CDCB Mastitis evaluation.  Listed for each bull are his PTAs for fat, protein, mastitis, and how many dollars the value of the mastitis PTA contributes to the CM$ PTA.  The tables below also contain the expected daughter deviation, which is how the daughters of these bulls are expected to perform as a percentage of the breed average, for combined fat and protein and mastitis. 

All the bulls on these lists are much better than the breed averages for both PTA fat and protein.  Given the breed average of 1,811 pounds for combined fat and protein1 we can see that the daughters of these bulls will average right at 6.1% better than the average cow for combined fat and protein yields.

The PTAs for mastitis are a different story.  Since CDCB indicates that the average incidence for mastitis in their evaluations is 11.7%2, this means that the daughters of these bulls in Table 1 will have 26% more mastitis than daughters of the breed average bull!  As you can see, we have sorted this list of the 10 top proven CM$ bulls based upon their CDCB mastitis PTA to create our Products 1 and 2.  Wow!

How can it be possible that using 5 of the 10 very top bulls in the breed would result in such a dramatic increase in mastitis incidence?  Simply put, the weight given to mastitis in the CM$ formula is 0.59%3.  The last column in Tables 1 and 2 shows what the mastitis PTA contributes to each bull’s CM$ PTA.  As you would expect, if a trait contributes <1% of the index, a bull can be a breed leader or a breed laggard for mastitis and it really doesn’t matter to his CM$ PTA.

Table 1.  These bulls are in the Top 10 proven bulls for CM$.  This is illustrating the Product 1 scenario.  These bulls will produce daughters that are expected to produce 6.8% more fat and protein pounds than the breed average but also are expected to experience 26% more mastitis than the breed average.

NaabCM$CM$ RankPTA
Combined Fat & Protein
CFP %
Increase
PTA MastitisMastitis % ChangeMast CM$
551JE1650$77111377.6%-2.824% $    (5.65)
11JE1339$65841287.1%-2.622% $    (5.25)
14JE769$5786995.5%-0.54% $    (1.01)
7JE1471$56071337.3%-2.925% $    (5.85)
200JE1035$55381156.4%-6.556% $  (13.11)
Averages$624 1226.8%-3.126% $    (6.17)

Table 2.  These bulls are in the Top 10 proven bulls for CM$.  This is illustrating the Product 2 scenario.  These bulls will produce daughters that are expected to produce 5.5% more fat and protein pounds than the breed average and are expected to experience 12% less mastitis than the breed average.

NaabCM$CM$ RankPTA
Combined Fat & Protein
CFP %
Increase
PTA MastitisMastitis % ChangeMast CM$
200JE01045$72821086.0%1.3-11% $      2.62
 11JE1259$68031297.1%1.2-10% $      2.42
7JE1630$64251236.8%-0.11% $    (0.20)
7JE1266$5389502.8%2.6-22% $      5.25
 11JE1212$52870884.9%2.2-19% $      4.44
Averages$623 1005.5%1.4-12% $      2.91

In formulating DWP$ for Holsteins and Jerseys, we used literature values for the economic values and the incidences from our database of large herds that had SOP in place to ensure consistent disease recording.  Coupled with feedback from our customers, this results in an index that places a much higher weight on udder health and on mastitis in particular.

When we look at the DWP$2020 Lifetime Validation Study, it is evident that the index places a lot of weight on mastitis as the best 25% of cows for DWP$ were 9 STA points better for mastitis as compared to the bottom 25% of cows for DWP$. 

Figure 1 shows the actual mastitis incidence for cows in the top and bottom 25% for DWP$ in each lactation of the lifetime validation study.  As expected, the incidence of mastitis increases substantially by parity.  Evaluating data such as these are difficult because the number of cows that survived to the end of each parity is markedly different between the 2 groups.  However, it is absolutely clear that we cannot afford to decrease the genetic ability of cows to resist mastitis if we intend to have a higher percentage of our herds at mature production levels.

Figure 1. Actual mastitis incidence by lactation for cows in the top and bottom 25% for DWP$.


Abbreviations:

  • CDCB Mastitis evaluation: Council on Dairy Cattle Breeding
  • CFP: Combined fat and protein
  • DWP$: Dairy wellness profit dollars
  • GPTA: Genomic predicted transmitting ability
  • PTA: Predicted transmitting ability
  • NAAB: National Association of Animal Breeders
  • STA: Standardized transmitting ability
Text and picture: Daniel Weigel

References:

  1. https://queries.uscdcb.com/eval/summary/Bmean_bases_het.cfm
  2. https://www.uscdcb.com/wp-content/uploads/2019/07/JE-Health-Presentation-2.3-Laura-Jensen.pdf
  3. https://www.ars.usda.gov/ARSUserFiles/80420530/Publications/ARR/nmcalc-2021_ARR-NM8.pdf

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