Guide to the Sustainability Index

This is the average percentage of cows tested individually for milk urea nitrogen (MUN) that had a result of less than 5 mg of nitrogen per dL OR more than 18 mg per dL in the last 12 months prior to the index calculation. 

How to recognize these animals? Cows exceeding these thresholds are more likely to show a feed intake problem or have fertility problems. 

The general principle of the Management Score is to evaluate if the genetic potential of cows to produce milk in a herd is well expressed. 

Why use the Management Score in the calculation of the Sustainability Index? The objective is to isolate the “environment” portion of the popular genetic formula: Phenotype = Genetics + Environment. The environment is influenced by various factors such as housing, management, and various other practices. In other words, we can evaluate if the animal is comfortable and in good condition.

How is the herd Management Score calculated? 

1. A quantity of milk produced at 305 days and corrected for fat and protein is calculated for each cow in the herd and is expressed in kg of corrected milk at 305 days. 
2. An Estimated Breeding Value (EBV-milk) for milk is corrected for fat and protein for each registered cow in the herd and is expressed in kg of corrected milk at 305 days.
   Thus, the individual Management Score for each cow = Amount of corrected milk at 305 days – EBV – Corrected Milk. 
3. To compare the management of the herd to other Canadian herds, one must have the average value for other cows in Canada.  
4. This is done by calculating the average management scores for each parity group (1,2,3+) and breed (HO, JE, AY, BS). 
5. Then for each cow, the average of the population Management Scores for her lactation group and breed are determined. This allows us to center the values of the Management Scores of the cows around zero.
6. For each herd, the average of the centered Management Scores of all cows in the herd is calculated, which gives the Management Score of the herd. 

In summary, if the herd Management Score is negative, the herd is below the national average. If it is zero, it is on the Canadian average and finally, if it is positive, it is above average. 

Depending on your province’s availability, the Transition Cow Index provides a quick and objective assessment of the success (or failure) of the strategy in place for cows in the transition period. 

1. The model first calculates the expected production for the upcoming lactation based on many factors including, among others:  

• • 305-day production from the previous lactation 
  • The lactation number 

1. • Age of the cow  
   • Milking frequency  
   • Number of days dry 
   • Calving month
     
     
2. The model then calculates a projected production for the lactation that is about to start, taking the production at the 1st test as a reference point.
   
3. The Transition Cow Index = expected production – projected production 

The Transition Cow Index can only be calculated for cows that are in their 2nd or later lactation since the previous lactation is used to establish the expected production.