By Connor Lynch
Like everything else in farming, the breeding of dairy animals has been radically transformed by technology. But transformation can have unintended consequences.
Dave McDiarmid, a third-generation Eastern Ontario dairy farmer takes an active interest in how he breeds his animals. He tracks the Pro-Dollars index and the Lifetime Performance Index, and dabbles a bit in the German Relativ-Zuchwert Gesamt, or RDZ. He’s breeding more for fat these days, given how the Dairy Farmers of Ontario’s milk component ratios are shifting. “It used to be you’d make the most money with a 2.35 ratio (and) less the lower it is,” he said. “Now they’re gonna make it better if you have a lower ratio.”
It’s mainly three technologies that have changed how he breeds his animals: embryo flushing, artificial insemination and genomics. Genomics brought a microscope into the barn, letting producers hone in on specific genetic traits they wanted and avoid undesirables. According to the Canadian Dairy Network, genomics has more than doubled the average rate of genetic gain in Canadian Holsteins. But in a business already heavily reliant on selective breeding, genomics introduces an unprecedented level of specificity. Genomics can be used to prevent inbreeding; but when inbreeding is desirable, genomics can intensify it.
Before genomics, producers had to wait for a proof on a bull before they knew if it was worth breeding. Now they can know shortly after it’s born. Shorter selection time between generations speeds up rates of genetic gain, but speeds up rates of inbreeding.
Inbreeding is something the industry has long been talking about. The average inbreeding level of Holsteins was less than one per cent in the 1970s but almost eight per cent of Holsteins by 2018, according to Canadian Dairy Network data.
“For the last five years, everyone’s been talking about inbreeding rates and things getting out of control,” McDiarmid said. “There’s still a diverse population of Holsteins. I’m not concerned.”
The looming question, however, is how much inbreeding is too much? Guelph-based Boehringer-Ingelheim veterinarian Dr. Robert Tremblay has never gotten a clear answer, nor have the farmers he’s asked. It’s not evasiveness. Tremblay asked a geneticist what a good number might be, and the honest answer was, essentially, that nobody knows. “And given our understanding may be incomplete, making dogmatic statements about what (a cap on inbreeding rates should be) may be pretty indefensible.”
Dairy farmer Todd Nixon is familiar with these technologies and how they’ve shaken up breeding. Artificial insemination companies own most of the high-end females these days, he said. “There’s not nearly as many farms playing in that genetics game to try and make bulls.” Breeding beef animals to their bottom-end dairy cows has also helped increase the rate of gain of genetic progress but has further narrowed the range of animals that successfully reproduce. Most indexes have an inbreeding coefficient telling you how much a given animal is inbred.
Dogs are the obvious example when it comes to concerns about inbreeding. Purebred animals are notorious for health issues as negative recessive traits emerge without fresh genetic material. Genomics has created opportunities to narrow the gene pool of the dairy sector but so far has given the industry ways to avoid the side effects.
OMAFRA dairy genetics specialist Marlene Paibomesai said that interest in genotyping exploded shortly after it was introduced in 2008. In 2019 alone, 53,000 Canadian-born heifers were genotyped, meaning their genetic attributes were recorded and filed in a database. Before genomics producers were, in a sense, breeding blind. Not all traits can be known just by looking at an animal, and potentially lethal recessive traits can crop up in the offspring of perfectly healthy animals.
In wildlife population management, genomics has been used to increase genetic diversity because it allows wildlife managers to avoid inbreeding animals, Paibomesai said. But the dairy industry, at least sometimes, wants inbreeding.
The problem with inbreeding is twofold, according to Paibomesai. Genetic diversity is more easily lost than gained and if traits are lost because they don’t matter now, that doesn’t mean they won’t matter in the future. Particularly for something like disease resistance, if all of a sudden you can’t breed an animal that isn’t vulnerable to a particular bacterial infection, it’ll become a big problem that can be difficult to solve.
Genomics is also a young science, she said. “It’s only been 10 years. (We’re) really still learning how to utilize this.”
Inbreeding as a term has a bad reputation, said Julien Chabot, a Semex Sire Analyst. Line-breeding has emerged as an alternative. When the plan going in is to breed two closely-related animals and the progeny comes out well, that’s line-breeding, he said. Back in the day “Superior animals were few and far between,” Chabot said. “When you found one, you bred the hell out of it.” Embryo flushing and the use of artificial insemination meant one bull and one cow could produce exponentially more offspring than they could naturally. These days, some of the company’s best bulls, he said, are as much as 20 per cent inbred.
In the late 1990s, Chabot recalled, three related bulls gave rise to as many as 400 sons. These days, to get 400 sons, they’d breed as many as 50 different sires. Modern breeding can be intensely complicated, and many farms rely entirely on company representatives to manage their breeding programs, Chabot said.
Further mollifying concerns is the increasingly global nature of the dairy breeding industry. The advent of semen straws and extracting embryos removed the need to physically bring a bull to a farm to breed it, turning a regional activity into a global one. As well, genomics has increased the ability of industry to avoid inbreeding. Inbreeding levels can drop in a generation by matching distantly-related animals, which can be known with greater precision than ever, Chabot said. Simply put, he argued, there’s not a significant concern that the dairy industry, in general, will run out of diversity any time soon.
But some animals have already made enormously outsized contributions to the gene pool.
Round Oak Rag Apple Elevation was a bull that really “pushed the Holstein breed,” in the 1950s, said Dave McDiarmid. According to a study in the Journal of Dairy Science published back in 2015, Elevation was the direct ancestor of 51 per cent of Holstein bulls in North America.
Elevation was one of three bulls that was directly related to every bull on the continent at the time, and its ancestors had an even bigger impact on the gene pool. Every single Holstein bull in North America in the 2015 was the direct descendent of just two bulls from back in 1880, according to the study.
As Brian Van Doormaal, general manager of the Canadian Dairy Network, pointed out in a 2017 article, there are desirable outcomes from inbreeding animals. Properly done, inbreeding increases the odds of getting desired traits. But he also noted that inbreeding is “more and more difficult to manage these days.”
Noted dairy farmer Dave McDiarmid: “As an industry, it’s just about pushing the numbers. If we keep inbreeding and don’t have any problems, we’ll keep going.”
Dairy cows are increasingly inbred. Have we gone too far?
By Connor Lynch