Beef Builder and Prime Plus Selection Indexes

Updated Spring 2001

At the completion of each bull evaluation group, two selection indexes are produced – Beef Builder and Prime Plus.  This factsheet provides background information on the indexes, and how to use them to select bulls.

The goal of the indexes is to combine key genetic factors that influence profitability into a number that can be used as a starting point for sire selection.  The indexes are intended to compare the profitability of using a bull for 2 years in a commercial herd of 30 cows.  A portion of heifers are kept for replacements, while the remaining heifers and all males are retained until slaughter and sold based on carcass value. 

Prime Plus rewards bulls that are predicted to sire calves with moderate carcass weights, and good marbling.  The ideal Prime Plus carcass is 700 lbs with AAA marbling and 7 mm of backfat.  This type of carcass is in demand by the restaurant and hotel trade.  Emphasis is also placed on maternal traits, as most heifers are targeted for replacements.

Beef Builder is focused on producing market animals that have high lean meat yield, and larger carcass weights.  This type of carcass is in demand by the supermarket trade.  Fewer heifers are kept for replacement, so there is decreased emphasis on maternal traits.

To create these selection indexes the key factors that influence the profitability of beef production in Ontario are used.  Income is predicted from the sale of finished animals on the rail.  Final carcass composition (weight, yield, marbling) is predicted from the bull’s growth and carcass trait ABCs.  Expenses are predicted from the costs of raising a calf to weaning (calving costs, cow feed costs), as well as feedlot costs (yardage, feed costs).

The traits that are included in the indexes are:

Percentile ranks are also calculated for each bull.  This is a measure of where a bull places for the index compared to all other bulls evaluated in the past 3 years.  The average value for each index is 2000.

It is common to receive questions regarding the use of Beef Builder and Prime Plus Indexes to select bulls.  This section will suggest a method that can be used to use the indexes to your advantage.

1. Assess your needs

There is a lot of information available on evaluated bulls.  Beef Builder and Prime Plus indicate the potential of a bull to be profitable.  However, you need to know which number pertains to you.  Are you targeting production of market animals with a moderate carcass weight, and marbling?  Do you keep a high percentage of replacement heifers?  Then you should likely focus on the Prime Plus index.  Are you targeting production of heavier finishing, higher yielding cattle?  Do you keep fewer replacement heifers?  Then you should likely focus on the Beef Builder index.

2. Look at the index first

Once you have decided which index is for you, it can be the starting point of your assessment of the genetic ability of that bull.  This avoids having to sort through all the individual traits to find the combination that suits you

3. Expand your criteria to individual traits

Suppose you are looking at two bulls with the same index value, as shown in the table below.  They are of equal physical and structural soundness.  They are also priced that same.  Which one would you purchase?  This is where expanding your selection to individual traits becomes important.  Because all the traits are combined to calculate the indexes, these two bulls could have different ABCs for several traits.

Looking at these two bulls, we can see that Bull A would have an increased risk of producing large calves (increased costs due to calving difficulty), and finished progeny would have higher marbling (higher carcass premiums).  Bull B is predicted to reach similar profitability, but in a different way – lower birth weights (lower cost due to reduced calving difficulty), and lower marbling (lower carcass premiums).

These values are based on use in an average cow herd.  In reality, very few herds are exactly average.  By knowing what traits would complement your cows best, you can choose the best bull for your cows.  If you have a herd of smaller, British type cows, that have produced well marbled progeny in the past, then Bull B may be best for you.  However, if you have a herd of larger, Continental type cows, and you have identified marbling of progeny as a weakness, then Bull A may be the best for you.

Keep in mind that these traits were used for illustrative purposes, and birth weight and marbling are not genetically correlated.

Beef Builder and Prime Plus allow you to find the bull(s) that fits your operation, providing the trait emphasis to make a balanced and profit-oriented decision.