Monday, August 3, 2015

Genetics for Today's Cattlemen (and Women): Texas A&M Beef Cattle Short Course 2015

Tonya Amen
Genetic Services Director, Angus Genetics Inc.

How do you make genetic change in your herd? By choosing the parents (bulls, replacement heifers, etc.). What tools do you use to make those decisions?

Performance is determined by genetics and environment. Environment can be defined by everything that happens from conception to slaughter that is not controlled by environment. Genetics can be split into additive effects and non-additive effects.

The Evolution of Livestock Measurement
  1. Average Daily Gain
  2. Within Herd Ratios
  3. Expected Progeny Differences
  4. Economic Indexes
  5. Genomics
An EPD is the best estimate of that animals worth as a parent. 
Let's consider an example.
Bull A has a weaning weight EPD of 60 lbs.
Bull B has a weaning weight EPD of 40 lbs. 
If we breed both bulls to a large number of cows in the same environment, Bull A's calves will weight 20 lbs heavier on average.

That 20 pound difference can mean $6,000 difference in the farmer's or rancher's take home pay (30 calves per bull, current market prices).

EPDs are used to shift the population. We still have low performers and high performers, but the average of the group is different.

Accuracy is a measure of how much data went into estimating that EPD and how much we can expect that EPD to change in the future when we collect more data. A pedigree estimate EPD is half of the sire's EPD and dam's EPD, and AAA assigns an accuracy of 0.05. Full siblings (flush mates, etc,) are assigned the same pedigree EPD (average of sire and dam) at birth. But, these full siblings can share no genes in common, so this best estimate does not reflect the true difference between these full siblings. A pedigree estimate calving ease EPD with accuracy of 0.05 can increase or decrease by 7.8.

What is the challenge with classic EPDs? It takes a long time to get enough data to produce higher accuracy (more reliable) EPDs. 

Calving ease direct is a measure of how easily a sire's calves are born. Calving ease maternal is how easily a sire's daughters deliver their calves.

From 1990 to 2003 93% of heifers calved with no problems, but during this same period about 2% were very difficult births. Since 2004, 96% of heifers calved with no problems and the percentage of hard pulls were cut in half.

Since 1992, mature weight in Angus has basically leveled off (increase is slow), birth weight has decreased, but weaning weight and yearling weight continue to improve in a straight line year after year.

Genomic-enhanced EPDs allow commercial breeders to buy animals with more confidence and allow seedstock breeders to sell animals that will perform to their customers expectations.

Don't look at genomic scores and genomic-enhanced EPD, you are double counting the genomic information and giving it more weight than it deserves. Look at the genomic-enhanced EPD!

Amen stated, "Genomics allows us to peak under the hood earlier in the life of the animal."
Genomics gives the same information as 9 to 21 progeny. It is like buying a bull with 21 progeny with calving records.

Profit = Revenue - Expense
EPDs have been really helpful in increasing outputs. Economic selection indexes can improve outputs, revenue, inputs and expense.

Keep in mind $B is a terminal index. If you are a commercial cow-calf producer selling your cattle at weaning, you are not getting paid for performance in the feedlot or on the rail. $W is important index is cow-calf settings.
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