Whenever two or more breeders get together they talk ‘bulls’. Which ones are you using? Why? What results are you seeing?  Do your results match what his proof says he will do? More recently talk has been about genomic indexes and if, when proven, bulls’ proof will match the genomic index. So why is this talk so important? Today half the semen being sold is from genomically evaluated bulls. And quite simply it is because 90% of the improvement in herd comes from the sires used in a herd or a population. Some may disagree saying that cow families are extremely important. However in the majority of herds a cow has one to two heifers and not all of those heifers will calve at least once in the herd. So which sires and how they are used will make the difference between genetic progress or genetic backsliding.

Before Bull Proofs

Before Bull proofs, well in fact before BLUP bull proofs, genetic progress was limited at best. Breeders used cow families to select their bulls from. often crossing cow families to get the result they wanted. In the history books we read about the successes but there were in fact more failures than successes. BLUP indexes (1970’s) were the first accurate genetic measurements available and they started the upward climb genetically. Today we take for granted that proven bulls will do what the proofs say they will do. How fortunate we are that the animal breeding industry has dedicated researchers that made the study and application of cattle breeding their careers. We no longer need to hope that the bull we choose will click with our herd. We have the facts to base our decisions on.

Mating Programs

A.I. organizations for many years now have provided services to interested breeders on which sires should be used in a herd or on which cows a sire will work best. As we all know many breeders use these services, at least as a guide, while other breeders wish to retain sire selection to their own system.

One key factor in mating programs, no matter who offers it or if a breeder has his own is what results a breeder wishes to achieve. Breeding is not simply using top ranked sires. It is about taking the cows in your herd and mating them to a sire to achieve your goals. Even the very elite sires have limitations. Doubling up their limitations with cows will the same limitations is not progress.

How Accurate

Until heifers and cows had genomic results, breeders often selected bulls based on their genetic indexes and females on their phenotypic information (yields and classification). Now with genomic values breeders know with 65-70% accuracy a female’s genetic merit and that plus their phenotypic information, if a breeder wants to use it, represent the female side. For bulls their genetic indexes are the most accurate information to use. The only difference between genomic indexes and a daughter proven bull in addition to the genomic index is the accuracy / reliability of the information 70% vs 90+%.

Corrective Mating

Breeders need to ask themselves if they want a solid herd for the traits of importance to them.  In which cases using a corrective mating strategy is likely the way to go. Most A.I. mating services are based on this strategy. You take each cow or group of cows and you determine their limiting factors. Traits like low milk yield, low %F, high SCS and weak fore attachment. The program searches for the bull or bulls that correct the limitations that the females have. By breeding this way breeders wanting a uniform herd with reasonably high genetic merit for most traits can be achieved within 5-6 generations of females.

An example of corrective mating would be if you have a typical Baxter daughter you would look for a bull that would, at least, improve %P, wide front teats and daughter fertility. Most breeders whose major income source is the milk check would be satisfied to achieve those corrections.

Complimentary Mating

There are breeders that take a different approach to improving their herd. These breeders are not so concerned about having a very uniform herd. They want to have a herd that excels for certain traits. Traits like show type, fat & protein yield and longevity.  Breeders practicing this strategy will first off select bulls that sire daughters that build upon the breeder’s priority areas. The example where we often see this practiced by breeders are those who participate in showing. They always make sure the bulls they use leave daughters with style and stature. But there are other examples. For instance breeders that have the goal of having a least half their cows complete five lactations and 125,000 lbs of milk. These breeders are willing to give up on items of lesser importance to them to achieve their big ticket traits.

An example of complementary mating would be if you have a typical Baxter daughter you would look for a bull that would build on Baxter’s genetic strengths in milk yield, fat yield, median suspensory, heel depth and herd life. Breeders planning to derive significant income from the sale of breeding stock will want to have available for sale stock that excel above average.

Plan for Improvement

So many traits and various methods of expressing indexes can make the job of reading and understanding a challenging one. The Bullvine provides the following table to show where indexes are relative to the cows in North America:


It is important to use bulls that are significant improvers if a breeder wishes to make advancement. For cows or heifers that already have high indexes it takes a significant improver bull to even holder these females at their current indexes. Remember that if a cow is -0.5 for Daughter Pregnancy Rate (in Canada 95 for Daughter Fertility) it takes using a bull that is +1.5 (110 in Canada) to even get the resulting calf to be above average.

The Bullvine Bottom Line

First know what you want to achieve from the matings in your herd. Make sure that you or your advisors base sire selection on corrective mating to limit faults. Use complimentary mating to enhance the strengths already present in your females.  Every journey has a starting point and an end point. The route to get to the end is the breeder’s choice.

The Dairy Breeders No BS Guide to Genomics


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