meta Genomic Young Sires vs. Daughter Proven Sires: Which one is best for Reliable Genetic Gain? :: The Bullvine - The World's Leading Dairy Magazine

Genomic Young Sires vs. Daughter Proven Sires: Which one is best for Reliable Genetic Gain?


The Bullvine is often asked, “How can using genomic sires be better, if the genomic sire’s reliabilities are not as high as those for proven sires?” So in typical Bullvine style we set out to answer that question.  The following is our answer…

Single Trait – Fat

Bullvine wanted to keep this comparison as simple as possible.  To do this we used one trait, in this case fat yield, knowing that breeders do not select for one trait only. The results apply to all traits.

Females in Your Barn

You have a virgin heifer and a seven year old cow that are both indexed at 100 kgs for fat yield.  Both have been genomically tested and the cow is milking in her fourth lactation.  The heifer’s index is 67% Rel.  and the cow is 82% Rel.

TABLE 1: Females

Born Fat Index % Rel Regressed Fat Index
Heifer 2012 Jan 10 100 67 67
Cow 2005 Jan 16 100 82 82

 

Sires

Three sires you might consider using for breeding these females could be:

TABLE 2: Sires

Born Fat Index (kgs) % Rel Regressed Fat Index
Oman March 08, 1998 82 99 81
Supersire Dec 28, 2010 116 67 78
Pride January 27, 2012 135 69 93

 

Index of Calves

What will be the fat indexes for the resulting calves? (Add parents together and divide by two)

TABLE 3: Regressed Fat Indexes for Calves (kgs)

DAMS SIRES
OMAN SUPERSIRE PRIDE
Heifer 74 72.5 80
Cow 81.5 80 87.5

These values are the expected average fat indexes.  And, yes, there will be less variation amongst the progeny for Oman and the cow.  The most variability amongst the progeny can be expected for the heifer when mated to Supersire or Pride.

Therefore, the short answer for which bull to use, is Pride. Pride will maximize the calf’s fat yield index.

Rate of Genetic Gain

Determining genetic gain is a principle taught to all college genetic students.  The formula is:

Let’s simplify this:

Accuracy                              =             Reliability

Selection Intensity          =             Determined by where the animal ranks in the population (all these animals are in the top 1% of the population so their selection intensity is identical)

Genetic Variation             =             Standard Deviation of fat yield indexes (common for all the animals in the example)

Generation Interval        =             The average time between the birth of the parents and the birth of the calf.

Generation Interval is the place where the numbers for the heifer and the sires, Supersire and Pride, are much smaller (in years) than those for the cow and Oman.

TABLE 4: Generation Interval (years)

DAMS SIRES
OMAN SUPERSIRE PRIDE
Heifer 8.5 2.5 2.0
Cow 11.5 5.5 5.0

Since the numbers for fat index in TABLE 3 are all similar, dividing them by a larger vs. a smaller generation interval greatly affects the outcome for genetic gain.

For the cow and Oman dividing 81.5 (Fat Index) by 11.5 (Generation Interval) gives a much smaller gain than for the heifer and Pride (80 divided by 2.0).  In fact it is much different 7.9 compared to 40.

That’s the reason turning generations more quickly, using genomics, gives the faster rates of annual genetic gain. (Read more: The Genomic Advancement Race – The Battle for Genetic Supremacy)

The Bullvine Bottomline

Genomics gives you more speed.  No question.  If you’re worried about speed being dangerous, spread the risk by using multiple (not one) high indexing genomic sires where you might have only used one or two proven sires in the past.

 

 

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Comments

  1. I don’t think that the variation in the progeny of one genomic sire is necessarily more than that of one proven sire. However, the average compared to the expected outcome (genomic proof) will have more variation for a genomic sire than a proven sire. This means there will be more variation in progeny from a group of genomic sires than a group of proven sires.

    A proof doesn’t indicate the range possible for progeny but only the average, so a proven sire may have a high average but also wide variation meaning there will be some outstanding progeny but also some poor progeny.

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