Attendance was at an all-time high at the 4-State Dairy Nutrition & Management Conference in Dubuque, Iowa, June 12-13, where more than 500 nutritionists and dairy industry professionals gathered to learn about the latest research. The program planning committee consisted of dairy extension faculty from Iowa, Illinois, Minnesota and Wisconsin, and the intention of the conference was to provide timely research information for dairy industry professionals.

• Dr. Lance Baumgard, associate professor of animal science at Iowa State University, shared “practical lessons learned” about heat stress from the summer of 2011.

After studying the effects of the heat wave that gripped the Upper Midwest of the U.S. in the days before and after July 20, 2011, Baumgard and others worked to identify management characteristics associated with good herd responses to heat stress. This heat wave hit dairy herds particularly hard because of the lack of nighttime cooling coupled with high humidity.

Although milk yield decreased on every dairy in Wisconsin, Minnesota, Iowa and Illinois during that heat wave – an average drop in production of 20.2 percent – there were considerable variations with the long-term responses.

“From a nutrition perspective, clearly the producers who employed a professional nutritionist fared better at almost all the parameters measured,” Baumgard said.

They also concluded that acute responses to the heat wave were fairly similar among barn types, but grazing dairies “did not have near the persistency as compared to the others.”

As expected, utilizing intensive heat stress abatement strategies (fans, soakers, etc.) lessened the acute effects of the heat wave and lessened the length of recovery, particularly when placed in the holding pen and feeding areas.

Cows were also less affected by the heat and recovered more quickly when they were not overstocked. Cows fed Sweet Energy recovered quicker, as did those given rumen modifiers and HydroLac.

Cows in freestall barns tended to recover quicker than those in tiestall barns, but the open-lot grazing producers had the lowest persistency of heat stress symptoms.

He also noted that culling numbers were not influenced by the drought, but the death percentage doubled during July as compared to the rest of the year.

• Dr. Mary Beth Hall, dairy scientist at the U.S. Dairy Forage Research Center, reported that “forage substitute or high-byproduct diets are viable substitutes to feed late-lactating cows when other more traditional feeds are in short supply.”

Hall reported that late-lactation cows can maintain performance while on low-forage, low-starch diets based on byproduct feeds, but producers should be careful to observe their cows to ensure body weight is maintained.

With the diets used in the study, lactating dairy cows were offered varying combinations of forage substitutes. Diets using up to 6 percent wheat straw had good performance without changing body conditioning.

Hall noted that byproducts diets had a higher phosphorous content (about 66 percent higher), which is not desirable for long-term nutritional management of dairy cows, or for environmental impact.

Cows given a more common 60 percent forage diet had similar milk production, had lower intakes, more efficient production and, most importantly, better income over feed costs than cows on the experimental diets.

That being said, the diets using forage substitutes or high byproduct content are “viable substitutes to feed lactating dairy cows when other more traditional feeds are in short supply.”

• Dr. Albert DeVries, associate professor in the Department of Animal Sciences at the University of Florida, shared information about using genomic testing to make better culling and breeding decisions.

There are four main ways to use genomic information, he explained: To identify animals and verify parentage, identify elite cows, mate selection and to make early culling decisions.

DeVries said genomic testing with low-density tests (which measures approximately 8,000 known locations in DNA for information) can be a good value at $40 per test if the information is used correctly to make decisions that lead to alternate breeding or culling.

If a dairy producer is keeping less than 95 percent of the heifer calves, the low-density test is “generally valuable,” he said.

DeVries stated pre-ranking animals before genomic testing makes sense as the animals with the highest parent averages will likely be kept anyway.

“Generally only the bottom third to half of all heifer calves needed to be tested when animals can be pre-ranked … and when the majority of the animals need to be kept.”

He concluded, “The results showed genomic testing, breeding, culling and calf-keeping decisions for cows and heifers are interdependent and not easily summarized in easy rules.” PD

Kelli Kaderly-Boylen is a freelance writer based in Waterville, Iowa.