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Change to TPI formula - effective April 2011
Following a recent vote by the Holstein Association USA, Inc. board of directors, a new Total Performance Index (TPI) will be implemented with the April 2011 national genetic evaluations. Discussions regarding the TPI formula were re-opened following a resolution brought forth at the 2010 Holstein Association USA Annual Meeting in Bloomington, Minn. The resolution, submitted by the Wisconsin Holstein Association and affirmed by the delegates, asked the board of directors to "re-evaluate the TPI formula and raise the type contribution to a level that more accurately reflects what breeders desire for a balance of type and production." The TPI formula was last amended in January 2010.
In summary, the April 2011 TPI formula removes 5 percent weighting from Productive Life (PL), and adds a 1 percent emphasis to PTA Protein (PTAP), 2 percent to Udder Composite (UDC), 1 percent to Feet and Leg Composite (FLC) and 1 percent to Daughter Pregnancy Rate (DPR). The complete formula appears below:
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| *The value 1832, adjusts for our periodic base change, allowing TPI values to be comparable across time |
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PTAP |
= PTA Protein |
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PTAF |
= PTA Fat |
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PTAT |
= PTA Type |
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DF |
= STA Dairy Form |
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UDC |
= Udder Composite |
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FLC |
= Feet & Legs Composite |
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PL |
= PTA Productive Life |
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SCS |
= PTA Somatic Cell Score |
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DPR |
= PTA Daughter Pregnancy Rate |
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DCE |
= PTA Daughter Calving Ease |
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DSB |
= PTA Daughter Stillbirth |
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Weighting of Major Categories |
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Production |
43% |
(+1% from January 2010 TPI formula) |
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Health & Fertility |
29% |
(-4%) |
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Conformation |
28% |
(+3%) |
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Analysis of the Formula Changes on Top 100 TPI Bull Averages
The table below compares the averages of the top 100 TPI bulls (having at least 85 percent reliability to qualify for the Top 100 list), comparing the new April 2011 TPI formula, the previous TPI formula (January 2010), and also the Net Merit (NM$) formula. As the table illustrates, the April 2011 formula results in higher averages for all type traits, addressing the issues raised by the delegate resolution. It also shows slight increases in the averages of all production traits. The new TPI formula places significantly more emphasis on type traits than the Net Merit $ formula, results in a higher average for PTA Milk, comparable averages for pounds of fat and protein, and slightly lower averages for the health traits. |
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| Average PTAs of Top 100 Bulls, Selected by Different Indexes |
| Trait |
New TPI
(April 2011) |
Previous TPI |
NM$ |
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| PTAT |
1.57 |
1.51 |
0.79 |
| Stature |
1.28 |
1.16 |
0.19 |
| UDC |
1.30 |
1.25 |
0.62 |
| FLC |
1.32 |
1.26 |
0.98 |
| Dairy Form |
0.96 |
0.89 |
0.15 |
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| Milk |
937 |
912 |
750 |
| Fat |
48 |
47.5 |
48.8 |
| Protein |
32.7 |
31.6 |
31.3 |
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| Productive Life |
3.26 |
3.49 |
3.88 |
| Daughter Pregnancy Rate |
0.56 |
0.70 |
1.07 |
| Somatic Cell Score |
2.79 |
2.78 |
2.76 |
| Daughter Calving Ease |
6.81 |
6.86 |
6.91 |
| Daughter Still Birth |
6.94 |
6.89 |
6.86 |
In an earlier announcement, Holstein Association USA released the new trait weightings for the April 2011 Total Performance Index (TPI)SM formula. They included the removal of five percent weighting from Productive Life (PL), and the addition of an extra one percent emphasis to PTA Protein (PTAP), two percent to Udder Composite (UDC), one percent to Feet and Leg Composite (FLC) and one percent to Daughter Pregnancy Rate (DPR).
In order to keep the mean TPI and its spread (standard deviation) constant, we need to update two values, i.e., the 1815 (to update the mean) and 3.7 (to equalize the spread). The new updated values are 1832 and 3.8.
Currently, the cows born from 2003 to 2007 have an average TPI of 1297, with the top cow having a TPI of 2333. If we were to change just the trait weightings, all cows would drop a little and the top cow would drop by 49 points. By updating the formula with the values 1832 and 3.8, our TPI values will be directly comparable to the old values, allowing breeders to more easily see how the change in trait weightings impacted each individual animal.
| TPI values for cows born between 2003 and 2007. |
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Average |
Standard Deviation |
| December 2010 TPIs |
1297 |
204 |
| April 2011 TPI *
with as the multiplier and as the constant |
1297 |
204 |
The updated April 2011 TPI formula appears above. |
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