Upgrade of the Multiple Trait Prediction Method (MTP)

Context

 
Since the implementation of VISION2000, many clients have noticed that the projections for some cows were overestimated.
 
Two situations explain this overestimation:
 
1: Some cows had similar milk weights for two or more tests (ex: 50 kg on test 1, and 50 kg on test 2). Also, some cows had their highest daily production on the 3rd or 4th test of the lactation. MTP estimates the shape of the lactation curve based on the individual animal’s data and the reference curve. In the above mentioned cases, the data from the animal was more important than the reference curve and MTP projected the lactation curve as a flat line or with an upward slope. The overall effect was to get high and often overestimated projections.
 
2: Other cows had very high production on their first test. Production would then rapidly decline. Also, some cows had no observations in the ascending phase of the curve. In these situations, MTP determined that the peak of the lactation occurred at day 5, with a very high peak milk production (up to 100 kg and more, in some cases). In these cases, we would see an inverted lactation curve lacking an ascending phase.
 
Solution
 
A solution was proposed by Dr. Schaeffer and Dr. Moore. The modification puts more emphasis on the reference curve. Concretely, MTP now estimates the animal’s production at 5 days in milk using her first test production and the appropriate reference curve. This value is used throughout the lactation. The overall effect is to generate an ascending phase in the lactation curve. This modification greatly diminishes the tendency towards an inverted curve with very high peak milk production occurring at day 5 of lactation.
 
Also, based on each new test for the animal (the latest available test), MTP uses the production and the reference curve to establish the production level that the cow will have at day 305. This modification generates a descending phase, thus avoiding flat line lactation curves with high projections.
 
In this document, the modification is called MTP ++

Transition from MTP to MTP ++

 
The month of April is a transition period between the two methods. It is possible that some cows will have large differences in their projections. In large part, this will affect those cows whose production followed a pattern similar to that previously described.
 
Also, cumulative production for the cows will be computed according to the new method. Remember that the MTP approach uses every test after calving, and this each time that we compute the cumulative production on a test day. So, in the extreme cases of cows that declined rapidly in production after the first test, it may be possible to have cows with cumulative production lower than it was the month before. However, this should be limited to a small number of cows.
 
Advantages of MTP ++
 
MTP ++ brings :
 
More accurate and stable projections
Better estimation of the cow’s lactation peak
Easier to understand cow profiles
Better consistency between cumulative production and projections
More accurate and more stable current averages by parity, and for the herd