In the quest to raise healthy, productive, profitable calves comes an emerging element: genetics.
Along with the myriad factors dairy producers embrace to raise the healthiest potential offspring, there is growing evidence that calves can inherit disease resistance from their parents. Thus, traits for resistance to diseases like pneumonia and scours may become an increasingly important factor in dairy genetic selection, according to Dr. Isaac Haagen, Assistant Professor of Animal Science at the University of Minnesota.
Haagen shared his thoughts on dairy calf genetic health traits on a recent episode of The Dairy Podcast Show.He discussed data that he gathered during his graduate studies at Pennsylvania State University, which encompassed 15 organic dairy herds from across the United States, ranging in size from about 30 cows to several thousand.
Specifically, he merged the calf health data from those herds, which was gathered via a variety of herd software platforms. Then, using traditional pedigree analysis and a limited amount of genomic data, he was able to determine that, based on that data set, health traits in calves are heritable to a degree similar to more widely monitored traits like Daughter Pregnancy Rate (DPR) and Productive Life – generally, about 5-10%.
Haagen said that rate is similar to the heritability reported by Zoetis for the Calf Wellness IndexTM (CW$TM) in their Clarifide® Plus genomic test. The Clarifide Calf Wellness Index encompasses traits for respiratory disease, scours, and calf livability.
A Canadian study recently published in the Journal of Dairy Science further supports the notion that calf diseases can be controlled in part via genetic selection. In that study, records from more than 62,000 dairy calves from 1,617 Canadian herds spanning 2006-2021 were evaluated.
The Canadian researchers found that heritability for respiratory disease and diarrhea ranged from 2-7%. They also discovered that calves born to the bottom 10% of sires for the traits were 1.8 times more likely to develop respiratory disease, and 1.9 times more likely to develop diarrhea, compared to daughters born to the top 10% of sires.
That group advocated for a national recording system to allow for national genetic evaluation, a concept that Haagen also supports in the United States. He said the evidence is strong enough to make the argument for a calf health specific index among the national traits evaluated by the Council for Dairy Cattle Breeding.
“While 5-10% heritability is a relatively small number, we know from other health traits that even that small number can have an impact over many generations,” Haagen stated.
He added that with any selection index, “we’re really selecting for profitability. With heifer replacement costs generally running as the second or third highest expense on farms, there is value in selecting for healthier animals that are expected to live longer.”
An interesting and related factor in Haagen’s research was an analysis he ran on serum total protein (STP) as a health measure. His findings indicated that, in addition to crucial factors like colostrum delivery, STP also is a heritable trait in calves.
“We found that calves differ in their ability to acquire passive immunity,” he stated. When he and his colleagues separated animals according to breeding value for STP, they found that 4-6% more of the heifer calves in the top quartile would remain in the herd at one year of age compared to the worst calves.
Haagen is continuing his research on calf health genetic traits using 20 years’ worth of data on more than 6,000 calves from commercial Minnesota dairy herds. He hopes the longer range of that data will help him extrapolate lifetime performance evidence related to genetic factors for calves, providing yet more proof of the link between the two.
