Guernsey cows are a unique breed in U.S. dairy.
Besides their docile temperament, Guernsey cows are known for producing milk that’s higher in butterfat and protein. It’s also a natural producer of the A2 beta-casein protein with estimates that as high as 90% of the breed’s animals carry the variant, which is the basis for A2 milk.
But the breed also has unique challenges, especially when it comes to genetics. John Cole, acting director of the USDA’s Animal Genomics and Improvement Laboratory, said the breed has fallen behind in terms of official genetic evaluation.
According to the April 2019 breed parameters from the Council on Dairy Cattle Breeding, the Guernsey breed ranks last in milk pounds — 17,472; near the bottom in pounds of fat and protein; and last in daughter pregnancy rate, heifer conception rate, cow conception rate and livability.
By comparison, the cattle industry is averaging about 27,000 pounds of milk per cow per year, with Holsteins generating the highest average, 26,994 pounds.
Speaking at the World Guernsey Conference in Lancaster, Pa., Cole said genetics and the environment are the biggest factors to a breed’s improvement or breakdown.
“An animal’s total performance is a combination of genetic and environmental factors. You can put the best genetics in the world in a poor environment and that animal is not going to perform well,” he said. “You can put in a mediocre animal in a good environment and that animal will perform above expectations because she’s fed properly, she’s housed properly and she’s treated properly.”
To illustrate the point, Cole displayed a graph that showed 51% of overall gains in dairy total fat since 1957 were a direct result of genetic improvements while 49% could be attributed to better management and the environment.
Cole said the Guernsey breed has become stagnant in terms of genetic improvement. Milk yield has plateaued, and overall fertility has been a challenge. Cole thinks this is because many producers consider Guernsey to be a niche breed, something that’s added alongside Holsteins, Jerseys or Brown Swiss.
Blaine Crosser of Select Sires, who listened to Cole’s talk, said part of the reason the Guernsey breed has fallen behind is because producers have focused more on health traits than production.
In terms of longevity, which the breed is last in, there are likely many causes, but Crosser theorizes that it might have something to do with the breed’s docile nature.
“When something goes wrong with a Guernsey, her response to it is not to fight and win,” Crosser said.
The breed also suffers from a small pool of bulls to choose from.
GENETIC CHALLENGES: John Cole, acting director of the USDA’s Animal Genomics and Improvement Laboratory, said the breed faces challenges in terms of improving genetics and improving herds.
“When the pool of selection candidates is small, you’re less likely to identify an extraordinary animal that’s really going to help move the breed forward,” Cole said. “This is a big concern.”
With genomics, a dairy farmer can test a young calf to get a more accurate prediction of economically important traits.
Guernsey genomic evaluations were started in 2016, Cole said. Data were shared with breed groups in other countries and 2,400 animals were put under genomic evaluation.
The results have been better than expected. On average, he said, reliability has improved 17 points across traits, much higher than expected.
The Council on Dairy Cattle Breeding has genotyped 3,940 Guernseys in its database, he said, a steady number but much lower than the other well-known dairy breeds.
Even though the number is low, Cole said that “the point is that every genotype you put into the database is important. Every cow phenotype that’s associated with that genotype is important.”
Important tool but more data needed
With the limited size of the Guernsey population, it’s difficult to do the kind of preselection that often occurs in Holsteins or other breeds.
Genomics allow a farmer to test young calves to get a more accurate prediction of what it will likely do down the road in terms of production, daughter pregnancy rate and many other traits.
The problem here, Cole said, is that there are only seven young Guernsey bulls under evaluation right now. These bulls, he said, will drive the genetic change in the breed.
“To me, the most important point is you have a very limited pool to draw from," he said.
Cole said that farmers and the industry should not just focus on one or a few bulls to improve the entire breed. He said that other sources of desirable genetics are available.
The Guernsey Global Breeding Program, started by the World Guernsey Cattle Federation in 1992, focuses on getting better genetics into cows and getting better germplasm from overseas into the U.S.
Cole said that other breeds can even be used for crossbreeding, but this must be done carefully. A paper from 10 years ago that genotyped animals from lots of different breeds, dairy and beef, showed that Guernseys and Jerseys were the most genetically alike to each other.
“The point is to think carefully about where you want to bring new genetics from,” he said. But he pointed out that crossbreeding only works when there is a purebred to do the cross to, so too much crossbreeding isn’t recommended.
“We need more high-quality guernsey cows to meet the growing demand," he said.