Total merit indexes – NTM vs. TPI 

Total merit indexes like NTM (Nordic Total Merit), TPI, NM$ index, PLI, BPI among others are important genetic selection tools. The indexes differ by the traits covered and by the weight allocated to the specific traits. 

Let’s look at the traits included in TPI and NTM and compare the weights of different traits for Holstein. 
NTM places 53% of the total weight on health and reproduction traits, while TPI puts only 28%. NTM has the traits that are not covered by TPI – Hoof health (3%), General health (4%), Calving direct (6%), Youngstock survival, calf survival in the early and late rearing periods (5%). Daughter fertility has similar weights in TPI and NTM, while Udder health and Calving maternal have higher weight in NTM. It is important to note that Udder health index in NTM is based on the registrations of clinical mastitis – direct selection, while TPI has SCS as indirect selection tool. TPI has higher weight on longevity, as TPI does not have most of the health traits that are included in NTM, so Longevity is used as indirect selection tool for better health in TPI.

As for production, TPI has higher weight on Production 38%, while NTM has lower weight on Production traits – 30% with Production (28%) and Growth (2%). 
If we look at conformation & workability traits, TPI has higher weight on conformation traits than NTM: in TPI Frame, Udders, Feet & Legs together have the weight of 26%, while in NTM – Frame has no weight and Udders and Feet & Legs have a total weight of 13%. Milkability and Temperament are not included in TPI. However, TPI puts 8% weight on feed efficiency. 
 Trait
 NTM
 TPI
 Production
 28
 38
 Growth
 2
 -
 Daughter Fertility
 11
 13
 Calving Direct
 6
 -
 Calving Maternal
 6
 3
 Udder Health / SCS
 13
 5
 General Health
 4
 -
 Hoof Health
 3
 -
 Longevity
 4
 4 (PL) + 3 (LIV)
 Youngstock Survival
 5
 -
 Feed Efficiency
 -
 8
 Frame
0
9
 Feet & Legs
4
6
 Udder
 9
 11
 Milkability
 3
 -
 Temperament
 1
 -

Table: Weights of different traits in NTM and TPI (Holstein)
All in all, NTM includes 14 main traits, while TPI has nine traits. NTM offers extra when it comes to health and reproduction traits compared to TPI and this group of traits has high economic importance for achieving profitable and sustainable dairy production. 

With higher weight placed on health and reproduction traits and the focus on direct selection in general and for health traits in particular, NTM is a much stronger and more reliable tool for commercial dairy farmers, as NTM delivers the well-balanced breeding goal for improving production, health, reproduction performance and functional conformation. 

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