As genetic research develops over the next 10 years, dairy producers will find more definitive data about sires that will allow them to select their cows based on longevity, udder health, calving performance and a variety of other important genetic data. That information, combined with the growing body of research about enhanced dairy environments, should allow dairies to obtain high production rates and improved dairy cow health.
University of Wisconsin Associate Professor, Kent Weigel, says the AI use of proven sires has led to rapid genetic change within the dairy cow population.

"In the next decade, development of routine genetic evaluations for specific diseases and disorders, such as mastitis, ketosis, displaced abomasum, lameness, and metritis is likely," he says. "Data for these traits can be captured electronically from on-farm computer systems, although trait definitions and recording schemes are not yet standardized across software programs. Nonetheless, the robust structure of AI progeny testing programs seems to allow effective genetic selection, even in the presence of imperfect data recording."
Weigel believes the potential impact of selection for PL and its components on dairy cattle improvement programs should not be underestimated. Since routine genetic evaluations for PL were introduced in 1994, several sires that rank extremely well for PL have achieved elite status, and have produced hundreds of sons, along with tens of thousands of daughters and granddaughters.
"Such changes would not have occurred if genetic data regarding PL had not been available," Weigel says. "We can only hope that the recent introduction of genetic rankings for traits such as DPR and maternal calving ease will achieve a similar impact."
While the capture and analysis of genetic data continues to develop, Weigel says dairy producers can implement some practices that will help them select productive cows.
"The udder is always the place to start evaluating a cow," Weigel says. "Poor udder traits are the biggest problem, followed by poor feet and leg traits. Naturally, cows that avoid mastitis or injury to their udder are going to be in the dairy herd longer. A lot of times, dairy owners focus on the body size of the cow and for some reason they want big cows. At livestock shows, large dairy cattle often place well, even though body size really doesn't affect the productive life of the cow."
Weigel also advises producers to consider their facility when they're selecting cows. It's possible that large bodied cows will not do well in an environment that has small stalls or stanchions.
"A better way to select your cows is use of the Lifetime Net Merit Index provided by the USDA," Weigel says. "There's a lot of data available about sires, but the Net Merit Index makes it possible for producers to look at one number and determine which sire is best suited to their operation."
As a result of research he has taken part in, Weigel says producers should not just consider the pounds of milk a cow produces as they weigh their decision about genetic traits.
"You want to maintain the highest possible income, but you also want to control expense," he says. "You also have to consider the impact of the cow's environment, such as stall size, bedding type, degree of overcrowding. You want cows that produce a live calf without assistance, cycle normally, show visible heat and conceive when they're inseminated. Many cows fail to complete these and other important tasks and leave the herd prematurely."
Weigel noted that progression of dairy cattle genetics was minimal until the 1950s. Because outstanding animals were genetically isolated and their traits were not easily incorporated into other breeding programs, the genetics could not progress.
"When AI became more common, there was intense focus on milk yield in the sixties and seventies," he says. "Linear type evaluation came about in the eighties and that was a step in the right direction. It gave producers guidelines to use in selection of their cows and assign a standard score to an animal."
In the past 10 years, Weigel says the focus on genetic improvements has been on overall cow health. A variety of traits that include longer PL, fertility, calving ease, and resistance to lameness, mastitis and other diseases have been driving breeding programs.
"The focus of dairy cow genetics has gone from just higher milk production to selection for the entire package," he says. "Breeders have realized that a cow that produces a lot of milk but has a tendency to be lame or develop mastitis isn't helping the farmer's bottom line. So when producers select their genetics, they want to consider the entire dairy production package. Consider the expense side of the dairy, including vet bills and replacement costs. Much of that data is now gathered right on the farm through the use of computers, so producers can accurately and thoroughly analyze the traits of a sire's progeny."
With the use of on-farm computers and improved software, Weigel expects data collected through the national milk program will be more accurate over the next 10 years. Current reports, he notes, often don't provide enough details to identify exact reasons why cows are culled.
"Animals can be recorded as 'died,' 'sold for dairy,' or 'sold for beef,' because of low production, mastitis infertility and so on," Weigel says. "From that data, you might conclude that mastitis and infertility are the most common causes of culling on dairy farms. However, reported reasons for disposal can be misleading when one attempts to compare the management level of various dairy farms or to draw conclusions about the genetic merit of certain animals or sire families."
Weigel went on to say that some animals are culled for "multiple offenses," such as difficult calving followed by ketosis and a displaced abomasum.
"She may then fail to breed back in a timely manner and be culled when her daily milk production falls below a profitable level," Weigel says. "The farmer might code here as 'sold for low production' or infertility or disease. The reported reason for disposal is often a vague indicator of the actual problem."
Because of advancing genetic evaluation, significant genetic variations for longevity between sire families has been identified and is available to producers as they select their own genetics. The Lifetime Net Merit Index for 2008 is available at ftp://aipl.arsusda.gov/pub/bulls/evalrpt.txt.
"We can improve longevity directly by selecting families that resist culling or improve longevity indirectly by selecting families that excel for each of its component traits," Weigel says.
Dr. Kent Weigel is Associate Professor and Extension Dairy Genetics Specialist at the University of Wisconsin – Madison, USA. He also serves as Genetic Programs Administrator for the National Association of Animal Breeders. His research focuses on genetic improvement of health, fertility, and survival in dairy cattle using tools such as genomic selection, crossbreeding, reproductive technologies, and data from on-farm computer systems. Dr. Weigel is a key resource person for many companies and organizations within the USA, and he has given lectures to academic, industry, and producer audiences in more than twenty-five countries.