‘Balanced Breeding’ has been promoted and followed in dairy cattle breeding for at least the past forty years. It is when the important traits that breeders desire to improve are combined in what is called a total merit index. All the traits in the index are weighted according to their relative importance for the breed but not for individual breeders. An example could be applying a weighting of 5% for SCS in an index and expecting that all bulls in the top hundred for that index will be improvers for mastitis resistance. On average, there is increased total genetic merit but not an increase for all trait in the index.
Reality Check Time
Here’s the question The Bullvine puts to you – “Is using total merit indexing (aka balanced breeding) the best way to select and mate animals to achieve maximum genetic gain for profit? It could very well be that using balanced breeding gives breeders false hopes of improving all traits in the total merit index.
Check the Facts
If you say it isn’t so, then do this quick check. How many top (25x) daughter-proven US Holstein sires are above 2.90 for SCS and less than 2.0 for DPR? The truth is that that number is higher than you might guess it to be. For TPI there are seventeen (68%), for DWP$ there are sixteen (64%) and for NM$ there are twenty-two (88%) sires that are higher for SCC and lower for DPR than those levels. The Bullvine chose those levels because they are the index values needed to improve a herd that is average for mastitis resistance and fertility.
Furthermore, it is not just US Holstein sires or US total merit indexes. 80% of the top ten LPI Canadian proven Jersey sires, 60% of top ten Pro$ Canadian proven Jersey sires, 80% of top ten LPI Canadian proven Holstein sires and 100% of the top ten Pro$ Canadian Holstein sires are not rated as significant breed improvers for resistance to mastitis and daughter fertility.
The truth is that, by using a high-ranking sire based on North American total merit indexes, a breeder can only in about 30% of the time expect to achieve meaningful improvement in resistance to mastitis and female fertility.
What does Genetic Theory Tell Us?
When practicing single trait selection, breeders can expect to make 100% of the possible genetic gains from a given sire mated to a given dam. Table 1 shows the possible gain for each trait as the number of traits selected for is increased.
Table 1 – Expected Genetic Response
|# of Traits Selected For||Average % of Genetic Gain Achieved for Each Trait|
Of course, the genetic gain achieved is also a function of the merit of the parents. A sire needs to be 1 Standard Deviation above the breed mean (67%RK) before his progeny will exhibit improvement when he is mated to average females. If a female in the top 1% of the breed (99%RK) for a trait is mated to a 67%RK sire their progeny will be 83%RK. Some breeders mistakenly feel that if they mate their 99%RK cow to a slightly above average sire (60%RK) that the progeny will retain the breed leading genetic merit of the dam. It just isn’t so.
Total merit indexes usually contain a dozen or more traits and as can be seen from Table 1, on average, for each of twelve traits the maximum gain possible will be 29% of what would be possible if single trait selection was practiced for each trait.
Bulls of the Past
Total merit indexes were partially implemented so there could be one ranking system for animals in a breed. Before there were total merit indexes marketers were all claiming to have the #1 sire – albeit they may have been #1 for type or production but not #1 overall.
Before total merit indexes, sires were known for what they did best – Marquis (type), Bell (milk yield), Fond Matt (udders), Sheik (% Fat), Rudolph (calving and fertility), Duncan Lester (production), Gemini (type), etc. Most often a sire’s weaknesses were ignored by breeders. So total merit indexes were good as they positioned a sire in the breed according to a combination of his strengths and weaknesses.
Dairy Cattle Breeding in 2025
2025 is less than three generations of cattle into the future. Profitable cows then will need to yield more lifetime profit that our cows do now. How will that come about? It will be by having cows that generate more revenue and decrease some costs. For farms that produce 95% of the milk, cows will generate more revenue by the uniqueness of the milk (i.e. %F, A2A2, BB, … etc.) and by reducing costs by having superior genetic indexes for traits like feed efficiency, productive life, disease resistance, fertility, mobility and milk ability.
Future Focused Selection
Selecting for the six cost reducing indexes mentioned above will slow genetic progress to 41% (see Table 1) of what is possible. The best route for a breeder to follow is to identify the three limiting traits in the herd and to select primarily for those three traits. That way the herd would make 40% more genetic improvement for those traits.
A.I. centers are already doing this when selecting the sire that they mate to a bull dam. They identify the dam’s three most limiting traits and find the bull that does the best job of improving those three traits. They are having excellent success at producing top young sires using this method of breeding. A.I. sire analysts may use a total merit index (i.e. TPI, NM$, JPI, …etc.) to narrow down the list of sires to be considered but they require that a service sire for the bull dam be outstanding (95+%RK) for the dam’s limiting traits.
The Bullvine Bottom Line
Breeding for a balance for a host of traits, some of which do not need to be significantly improved in a herd, is not the way of the future. To maximize the rate of genetic improvement in a herd, breeders will need to identify their 3 most limiting traits and then find and use the best sires for those three traits. In the future, focused breeding on the traits needed to maximize a herd’s future profit rather that a balance of traits will lead the way.