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 Home>Crops & Livestock>Livestock>Dairy>Genetics>

Take a Look at Fluid Merit Dollars (FM$) as a Sire Selection Criteria

Introduction
Choosing the ‘right’ sires to produce the most profitable daughters in an A.I. breeding program is always a challenge. That challenge can be even more daunting than ever with so much information available today on so many traits. The USDA Dairy Sire Summaries now include three selection indexes that can be very useful in simplifying sire selection. These are called Net Merit Dollars (NM$), Cheese Merit Dollars (CM$) and Fluid Merit Dollars (FM$).

What is a selection index?
A selection index is a tool that combines sire summary information or Predicted Transmitting Ability (PTA) on several different traits into one measure. A selection index accounts for the economic value of each trait in the index and the genetic relationships among all traits in the index. The value of a selection index comes from the fact that it optimizes genetic improvement for each trait in the index according to its potential economic value to the farmer. Two well-known examples of dairy sire selection indexes are the Type-Production Index (TPI) from the Holstein breed and the Jersey Performance Index (JPI) from the Jersey breed. Both of these indexes place a great deal of emphasis on production traits as well as overall type of conformation traits. Both are very useful if some of your animals are being sold as breeding animals; however, if your income is solely generated from the sale of milk, the USDA merit indexes may be more appropriate as sire selection criteria.

Why use a selection index?
When you ‘select’ a sire to breed to your cows, you don’t just select his desirable characteristics. You select ALL of his characteristics. Attempting to set minimum levels of performance for numerous traits can be difficult, time consuming and extremely limiting. For example, if you attempted to ‘select’ only sires that were above a certain minimum level for milk production, component production, type and calving ease, you might find very few bulls that meet all of those criteria. An index can take into account all of these traits as well as other traits by weighing each trait based on its economic value relative to the other traits in the index.

How do you use a selection index?
The first step is to identify your milk market; then choose the index that best matches that market. For example, JPI and TPI both focus on the value of milk used to manufacture cheese. The major difference among the USDA Merit$ indexes is the value each index assigns to milk protein. Cheese Merit$ places more emphasis on protein production than either NM$ or FM$. Fluid Merit$ places more emphasis on milk production than on protein or fat yield. Producers in Louisiana and Mississippi are paid for their milk based solely on skim and fat content of the milk. Therefore, FM$ should be a more appropriate sire selection criterion in the Southeast milk market than either NM$ or CM$.

What other traits are included in the FM$ index?
Several production factors as well as type, longevity, health and reproductive traits are part of the FM$ index. These include milk, fat and protein yield as well as Productive Life (PL), Somatic Cell Score (SCS), Udder Composite (UDC), Feet & Leg Composite (FLC), Body Size Composite (BSC), Daughter Pregnancy Rate (DPR), Service Sire Calving Ease (SCE) and Daughter Calving Ease (DCE).

Production Traits
Production traits included in the FM$ index are milk, fat and protein. The relative value of each production in the FM$ index, along with the relative value of each of the remaining traits in the index, is given in Table 1.

Productive Life
Productive Life is measured as the number of months a cow is in production up to 7 years of age. For cows younger than 7 years old, DHI information can be used to predict how  many months she will produce by the time she is 7. Only the first 10 months of each lactation contribute to months of productive life, and cows receive no additional credit for production past 7 years of age. PL contributes economic value to the dairy by lowering replacement costs and increasing the percentage of mature milking cows in the herd.

Somatic Cell Score
Somatic Cell Score is an indirect measure of the levels of both clinical and subclinical mastitis. SCS is easily measured through the DHI electronic somatic cell count (SCC) program. Sire selection to reduce SCS adds economic value to the dairy by reducing the incidence and costs of mastitis in a dairy herd.

Composite Traits
Udder (UDC), Feet and Legs (FCS) and Body Size (BCS) Composite Scores all are combinations of linear traits. Linear traits can provide additional information about potential incomes and expenses. Instead of trying to use PTAs for all 17 linear traits in a selection index, composite scores combine a subset of traits based on the relative value of each trait.

Daughter Pregnancy Rate
Some bulls tend to consistently produce daughters that more readily conceive. Daughter Pregnancy Rate (DPR) is a measure of cow fertility inherited from the sire. There are several advantages of improved DPR: lower breeding costs, higher peak and total lactation milk production and more heifers born for replacements.

Calving Ease Traits
Every lactation begins with a birth, and difficult births can lead to reduced production, delayed reproduction, early culling of the cow and even death of either the cow or the calf or both. Reducing the number of difficult births in a dairy herd can have both short-term and long-term impacts on income and expenses. Selection for calving ease traits will contribute to the economic value of a dairy herd by lowering the number of difficult births in the herd. Service Sire Calving Ease (SCE) is a direct measure of a bull’s ability to sire calves that do not contribute to calving difficulty in the cows with which the bull is mated. Daughter Calving Ease (DCE) is a measure of a bull’s ability to sire daughters that exhibit less calving difficulty. Selection is important for both of these traits to reduce the effects of difficult calving in a herd.

Table 1. Relative weights assigned to various components of Fluid Merit$ from August 2003.

Trait

Relative Weight (%)

Milk

24

Fat

22

Protein

9

Productive Life

11

Somatic Cell Score

9

Udder Composite

7

Feet &Legs Composite

4

Body Size Composite

3

Daughter Pregnancy Rate

7

Service Sire Calving Ease

2

Daughter Calving Ease

2

 

What level of Fluid Merit$ should be used for sire selection?

Table 2 shows the August 2004 USDA Sire Summary figures for FM$ for 607 active Holstein A.I. sires.

Table 2

Average FM$

+369

70th Percentile (Top 30%)

+448

80th Percentile (Top 20%)

+475

The best way to use Fluid Merit$ as sire selection criteria is to establish a minimum level for sires being considered for use in your herd. Setting a minimum selection criteria at the lower percentile (70th) will result in slightly lower genetic progress overall but will allow selection from a larger group of sires (182 vs 121). This may or may not also have the advantage of lowering semen costs.

Selecting sires in either the 70th or 80th percentile for Fluid Merit$ will ensure genetic progress for all the traits in the index relative to our current understanding of the economic importance of each trait.

Last Updated: 9/16/2013 11:52:31 AM


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