Is the rapid declining generational interval in dairy cattle actually a success?

Is the rapid declining generational interval in dairy cattle actually a success?

I recently read an article in the Hoard’s Dairyman magazine which greatly intrigued me. The title was “Genomics gets high grades on two fronts” and was reporting from a presentation given by Michael Lohuis, vice president of research and innovation with Semex, at the 2019 National Genetics Conference held in conjunction with the National Holstein Convention in Wisconsin.

The part that really piqued my interest was this: Lohis awarded genomics with a grade of A+ in the area of Genetic Improvement, based mainly on the observation that there has been “an additional Net Merit (NM$) $50 per cow per year gain because of the drastic drop in the generational interval in the sire population.

The change in the last 10 years has been nothing short of dramatic. “In 2010, the average age of a bull dam was right at 4 years of age, and now bull dams are just over 2 years of age,” said Lohuis. “Even more drastic of a change has been the bull sires, which went from 7.5 years in 2010 to just over 2 years in 2018.”

Now I’m not a geneticist with a college degree, so maybe I’m not qualified to speak on the topic. Nevertheless, I will stick my neck out. Anyone with a “degree in common-sense” will recognise this headlong dash towards unproven genetics as irresponsible and reckless.

The breathtaking drop in age of AI bulls’ sires and dams reinforces what many of us were already aware of. Many of the young bulls being released today are sired by a young sire with no progeny data, and born from a heifer who never had an udder between her legs. If that isn’t scary enough, there are plenty of bulls in the population today whose maternal lineage is devoid of classification scores and milk records for two or more generations!

Could a bull who has three generations of unproven ancestors behind him turn out to be a great breed improver? Of course, there’s a chance; his DNA is the same, regardless of whether his ancestors were permitted to calve in or not. But even genomic’s most avid supporters should be worried, since the accuracy of genomic evaluations is dependant on the continuation of real data collection in milk records, classification scores, etc. 

My point is not to bash genomics as a breeding tool, but to remind us that, at its best, genomics is only a tool and nothing more. After 10 years of genomic evaluations, the result I see is sky high semen prices,a bottle-necking of the gene pool, and dizzying generational turn-over.

Dairymen are told that their best genetics are always in their heifer pens. Maybe…but how do you know for sure until they’ve had a chance to prove it? The claim of fantastic genetic improvement is overshadowed by the fact that the average lactation in the U.S. is only at 2.4. Statistically cows make their best records in the 4th and 5th lactation, and some will peak at even older ages. We should be asking why all this “genetic advancement” hasn’t made our cows last longer.

In the incredibly tight margins that the U.S. dairy farmer is dealing with, a discussion on longevity should be paramount. Presently it costs more to raise a heifer than she’s worth at the market. Depending on your input cost, a cow needs to milk two lactations before she has fully paid herself off. And even then, she hasn’t reached her full potential. If you want to improve your profitability as a dairy farmer, increase the average age of your milking herd, and decrease the number of replacement heifers you need to feed and house.

In a nutshell, genetic improvement is when you can look at your cow and say “yes, she’s definitely better than her mother was.” She milks more, tests higher, breeds back easier, has better confirmation, etc. Genetic improvement is not a faceless escalating index, but rather a measurable, calculable observation in the barn.

I won’t argue for a second against the fact that great advancements have been made in cattle genetics over the last 50 or so years. At the same time, we must also recognize the huge strides that have been made in cattle nutrition, medicine and management. I have been privileged to visit herds all over the country and have seen some interesting things. An Pacalamar Astronaut daughter who is out-milking her modern, high-indexing herdmates. The Sexation daughter that scores EX-96 in today’s classification system. A farmer’s observation that calves from old bulls seem to be the most healthy.

I could go on, but I think the words of the late Peter Heffering, legendary breeder at Hanoverhill Farms will suffice. Almost 20 years ago, Mr Heffering sat down for an interview with Holstein World and here’s what he had to say about breeding cattle based solely on the index system, a decade before genomics hit the scene:

     When we are breeding Holsteins using the index system, we are convinced that genetics are advancing with lightning speed so a bull’s genetic appeal is lucky to last 6 to 12 months. I believe we are discarding some very good genetics far too quickly.

     Breeding Standardbreds has helped solidify that my thinking is justified. I have watched offspring of great stallions produce world champions for many years. Some of those stallions are between 20 and 30 years old. When these stallions are mated to younger mares with more modern pedigrees, they continue to excel.

     Standardbred racing is much like producing milk. Today the tracks are faster, the sulkies are faster, nutrition is more high-tech than ever, and overall management is superior. The fact is, genetics is not the only reason horses and cattle are performing better.

Take it from the Master Breeder. I rest my case.


Jared Martin