With increased consumer demand for higher fat dairy products we are seeing our milk marketers and dairy farmers adjust rapidly to try to fill this need. Increased scrutiny is being placed on Fat production in genetic plans across the Western Provinces, but what exactly do a bull’s proof numbers for fat mean?

In this example we will look at the popular Genomax bull Yamaska’s production proof. His proof shows 119 KGS of Fat with a +.61% Deviation. These numbers are estimated breeding values, and since an animal transmits on average half his breeding value, Yamaska daughters are expected to produce 59.5 KGS (119 divided by 2) more Fat per 305 day lactation than daughters of a 0 KGS Fat bull on a mature basis. Further, if Yamaska is mated to a female with an EBV for Fat of 60 KGS, the daughter of this mating would be expected to produce 119+60 = 179 then 179/2 = 89.5KGS more Fat per 305 day lactation when compared to the average cow in Canada, under average management.  If the management level in your herd exceeds average, this will be a conservative estimate.

Similarly for Fat % Deviation, a sire like Yamaska with a +.61% deviation would be expected to sire daughters with a Fat percentage .30% higher than a zero rated bull. Mating Yamaska to a Cow with an EBV for Fat % of +.20% we would expect that offspring to yield .61+.20 = .80 then .80/2 = +.40%. We expect this offspring to produce milk with a fat percentage .40% higher than the average cow in Canada under average management.

 

Source : CDN.ca article “How do Production Proofs Relate to Average Daughter Yields?” 23-Jan-2017

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