Feeding productive dairy cows is balancing act
ARLINGTON - The ingredients dairy farmers feed their cows impact overall cow health so much that Dr. John Goeser believes that universities should merge veterinary science with nutritional science. Goeser, an adjunct assistant professor in the UW-Madison Dairy Science Department, is also the nutrition director at Rock River Lab, Inc.
He joined several other speakers last week at two sessions on dairy nutrition sponsored by the Professional Dairy Producers of Wisconsin (PDPW.)
In his position at the commercial feed testing laboratory he sees what’s happening on dairy farms and how it’s affecting cows. In 2016 many farmers were experiencing listeria and salmonella in their cows.
He related the story of one Wisconsin dairy farm that switched from their 2015 to their 2016 high moisture shell corn and saw their cows drop precipitously in production, from a normal high of 90-plus pounds per cow per day. It was enough to get the farm’s attention – the cows dropped 100,000 pounds of milk production in a month. When they looked for a reason, they found that the corn was high in wild yeast and mold. The problem was diagnosed by testing the total mixed ration (TMR.)
They tackled the problem by adding commercial yeast products and mold inhibitors to the feed, which added a cost of 10 cents per cow per day and the cows came back to about 86 pounds per cow per day, he said.
Though the industry outlook for milk prices isn’t good into the coming year, Goeser told the farmers and nutritionists in attendance at the Arlington Agricultural Research Farm that feeding the cows carefully and monitoring things like mold, yeast and aflatoxins in their feed can show results on the bottom line. It can mean the difference between finding or losing several pounds of milk production per cow and a positive versus a negative margin.
Feed gets “dirty” he noted, at harvest, and during fermentation and at feed out. He showed data from his lab on the amount of “ash” or dirt that is in feed. In 2010, samples averaged 8-8 ½ percent and today it is 10-11 percent and the trend has been up every year. That’s important because pathogens like yeast, mold, mycotoxins and bacteria live in the soil. The more soil in the feed means there are more of those hitchhikers along to wreak havoc on the feed – and eventually the cow.
Bearing that out, he showed a chart of samples tested for fungal loads at his lab; both yeast and mold in feeds and TMR samples are on an upward trend since 2014. He speculated that reduction in tillage may play a role in this trend.
Goeser said that yeast fed in commercial products are designed to be good for cows but wild yeast generally have a negative effect on rumen metabolism and should be prevented from taking over the feeds. He notes that we have a lot to learn about fermentation but we do know that we need to get the air out and drop the pH to get the feeds acidified as soon as possible. Molds and fungi are born in the field and in silage if there is aerobic instability.
Some bad actors in the feed – aflatoxins, mycotoxins -- are produced when plants are stressed. “Once present they will be there,” he said. “Fermentation won’t knock them back.” Research is suggesting that these various toxins affect different organ systems in the cow. Some suppress the immune system or reproduction. Some target the liver and kidney. “Very rarely do we have only one toxin present.”
The levels of these toxins found in feed depend on the growing season. Goeser showed a chart with large numbers of samples, dating from 2011-2016 and last year’s corn was double the (1 ppm) threshold in large numbers of samples. The chart is black with data points above the threshold for 2016.
Toxins down this year
However, Goeser noted that toxins in this year’s corn are down significantly. “It looks like cleaner feed.” Balancing that is the fact that many of the samples the lab has tested are very dry – he called them “dry moisture corn” – and they are not going to ensile or ferment.
“October was dry and warm and 16-percent-moisture corn just isn’t going to ferment,” he said. Corn that gets harvested at 24-25 percent moisture may still ferment but if it’s less than 23 percent, he said it won’t “soften up” and he advised grinding it up as small as possible.
He encouraged farmers to keep an eye on bacterial contamination in their feed as well, which comes mostly from manure. “Don’t put manure on your growing crops. After the alfalfa comes off you may have a day or two to put manure on it but if that alfalfa starts to grow back and then you apply manure, you’re inoculating all those plants.”
Challenges for dairy managers also come when feeding the stored forages and corn. When silage is re-exposed to air, yeast will reproduce by feeding on sugars and carbohydrates and then start to eat lactic acid. When that happens the pH goes up and when it reaches a certain level, bacteria start to grow.
Dairy cows can ward off certain bacterial challenges if they are not stressed by other factors, he said, like overcrowding or poor cattle handling methods, but if they are also enduring environmental stress they can experience a “perfect storm.”
Goeser further noted that some research is showing that bacteria can “sense” the stress hormones given off by a cow when she’s got problems and this allows them to take advantage of her.
He gets questions all the time about what additives are best to add to dairy rations. Some are useful for binding toxics, boosting the immune system of out-competing pathogens. His advice is to always “test before throwing 10-15 cents per cow per day into a ration. It takes a comprehensive approach.”
The most critical time is harvest and the decision-maker should be on the packing tractor, at the silo or on the bagger, he said, so they can make key decisions about the crop. If it’s too wet there will be ineffective fermentation; if it’s too dry there will be too much air in the feed. “You need to watch the crop coming in and make key decisions,” he advised. Another piece of advice at harvest is to use a research-proven inoculant.
Not your Daddy’s fiber
Dr. David Combs, a professor of dairy science at the UW-Madison, talked with the group about new technologies and innovations in forages that have improved feeding programs for livestock. On the plant side, brown mid-rib (BMR) was a natural mutation in corn that led to improved digestibility of fiber. Alfalfas have been developed with reduced lignin – some by natural breeding and some with genetic modification – and those have led to improved NDF (neutral detergent fiber) digestibility.
Even grasses have been improved for use in high-producing dairy cows, he said, and some of them have higher digestible fiber than alfalfa or corn silage.
The improved fiber digestibility of BMR corn, Combs said, has been shown to increase milk production by 2-3 pounds per cow per day. The reason some of these newer forages can do that is that “every mouthful the cow takes is effectively utilized or she can eat more,” he said.
However, while crops have been improved genetically, that only accounts for about a third of the fiber digestibility in the eventual feed. Two thirds is due to environmental conditions like moisture, growing temperatures and sun intensity. “California dairy producers like the high elevation alfalfa crops because of the growing conditions there,” he noted.
There have also been advances in laboratory testing and analysis of feeds including one that tests for indigestible fiber – uNDF-240 – and one that simulates the cow’s digestive tract to predict total digestibility. That test is called the total tract NDF digestibility or TTNDFD.
Values vary widely
The reason such tests are important Combs said is that fiber digestibility varies widely in forages. “There’s a huge difference and a lot of energy can be left on the table,” he said. Alfalfa hay and silage can vary from 25-70 percent of NDF; corn silage varies from 25-80 percent and grass hay and silage varies from 15-80 percent. “Two units increase in dietary TTNDFD can potentially increase milk yield by a pound.”
Combs noted, and some farmers in attendance confirmed, that garden chippers are being used in the field just before harvest to determine the fiber digestibility of the crop so the farmer can use that information to determine how to use that feed and which group of animals to feed it to.
In corn silage, 25-30 percent of the energy comes from the fiber portion of the feed. In addition, milk fat will increase in cows as fiber digestibility is improved. As margins continue to be tight on the dairy farm, Combs added that corn grain can be pulled out of the ration “if you have more digestible forages.”