Genetic Trends for Fullblood, Simbrah, and Hybrid Simmental Populations

Genetic Trends for Fullblood, Simbrah, and Hybrid Simmental Populations (1993-2013)
By Jackie Atkins, Ph. D., Director of Science and Education

 In the April edition of the Register, we published an article reviewing the genetic trends of Purebred Simmental cattle from 1993 to 2013.  Due to space restraints we were unable to dig into similar data for Fullblood, Simbrah, and hybrid Simmental populations but wanted to showcase this data here on the tREG blog. Please note during your reading —  SimAngus™ cattle make up the overwhelming majority of the hybrid population.  The following information is not meant to compare one population to the other, rather we can use this data to see how each section of SimGenetics is doing, where our strengths are, and find what we need to improve for future breeding stock.

The tables below provide the average EPD values for Fullblood, Simbrah, and hybrid Simmental cattle born in 1993, 2003, and 2013 for the following traits: Calving Ease (CE), Birth Weight (BW), Maternal Calving Ease (MCE), Stayability (STY),  Maternal Weaning Weight (MWW), Milk (MLK), Docility (DOC), Weaning Weight (WW), Yearling Weight (YW), Carcass Weight (CW), Yield Grade (YG), Marbling (MRB), Back Fat (BF), Ribeye area (REA), and Shear Force (SF).  As you can see, most traits are moving in the right direction in all three populations. Slide1.GIF

In the rest of this story, we will take a closer look at each group.  Please note, the EPDs in Figures 1, 3, and 5 have been standardized (divided by their standard deviation) so that we can compare one trait to another.  In these same figures, we took the liberty of setting all traits to zero for animals born in 1993, so that we can see the relative change in selection pressure for each trait in the last 20 years.

Fullblood: The Fullblood population has seen an increase in calving ease and decrease in birth weight over the last 20 years while maintaining steady growth traits (weaning weight, yearling weight, and carcass weight).  While most of the carcass traits have remained relatively constant shear force has improved over the past 20 years.  The remaining carcass traits represent an area to focus some selection pressure.  Maternal calving ease has not improved in the Fullblood population and while stayability initially increased (up to 2001), in the last decade stayability has been relatively constant (Figure 1).  Again, this may represent an area to try to improve in the future. Both the All Purpose Index ($API) and the Terminal Index ($TI) have increased in the Fullblood population resulting in an average increase in profit/exposure of $19.00 for $API and  $4.30 for $TI (Figure 2).  Of note is the drop in registered Fullblood cattle in the ASA database from 9,748 head in 1993, to 913 head in 2013.  This makes it more difficult to improve genetics when there is a smaller and smaller pool of animals for breeding stock.

Slide5.GIFFigure 1.  The genetic trends in the Fullblood population for animals born in 1993 through 2013.  Each line represents the standardized EPD (the average EPD for each trait divided by the standard deviation of that trait).  The year 1993 was set to zero for easier comparison between the traits.

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Figure 2.  Average profit indices in the Fullblood population based on year of birth.  The All Purpose Index (API; best if keeping replacement heifers) and the Terminal Index (TI; best if all calves will be harvested) are in actual units.

 

Simbrah: Clearly Simbrah populations have excelled in growth traits like weaning weight and yearling weight in the last 20 years (Figure 3).  There has been less change in birth weights and calving ease although these traits are moving in the right direction and maternal calving ease has improved quite a bit especially in the last decade.  Marbling and yield grade have also improved especially in the more recent years which is likely reflected in the $7.00 increase in $TI over the last 10 years.  The average $API has also improved in the last 20 years from $55.20 to $70.20 profit per exposure (Figure 4).  Similar to the Fullblood population (although not as extreme), there has been a significant drop in the number of registered Simbrah cattle in the ASA database in the last 20 years (see table for numbers).  This adds a challenge to Simbrah breeders as they select breeding stock from a smaller and smaller pool of animals.

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Figure 3.  The genetic trends in the Simbrah population for animals born in 1993 through 2013.  Each line represents the standardized EPD (the average EPD for each trait divided by the standard deviation of that trait).  The year 1993 was set to zero for easier comparison between the traits.

Slide3.GIF

Figure 4.  Average profit indices in the Simbrah population based on year of birth.  The All Purpose Index ($API; best if keeping replacement heifers) and the Terminal Index ($TI; best if all calves will be harvested) are in actual units.

 

Hybrid:  The hybrid Simmental population (again mainly SimAngusTM) has made marked improvements in calving ease (and birth weight) in the last 20 years while increasing weaning weights and yearling weight (Figure 5).  Yield grade has remained relatively constant while marbling has had a dramatic increase.  All of these improvements are reflected in an average increase in API of $49.50 per exposure and $18.80/exposure improvement in TI (Figure 6).  Unlike the Fullblood and Simbrah populations, there has been a nearly doubling of hybrid Simmental cattle in the ASA registry since 1993.

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Figure 5.  The genetic trends in the hybrid Simmental population for animals born in 1993 through 2013.  Each line represents the standardized EPD (the average EPD for each trait divided by the standard deviation of that trait).  The year 1993 was set to zero for easier comparison between the traits.  Note, the marbling line continues to rise up to 1.34 by year 2013 (off the chart).

Slide9.GIF

Figure 6.  Average profit indices in the Simmental hybrid population (largely SimAngusTM) based on year of birth.  The All Purpose Index ($API; best if keeping replacement heifers) and the Terminal Index ($TI; best if all calves will be harvested) are in actual units.

 

In summary, breeders of SimGenetics have a lot to be proud of in the past 20 years.  We hope you can use this data to help market your current genetics and make decisions to continue to improve the SimGenetic populations in the next 20 years.

Get more Science and SimGenetics information on the Science Forum with Drs. Jackie Atkins and Lauren Hyde. 

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