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0908 PD: Consistency is key to peak performance

Charlie Elrod Published on 16 June 2008

After a brief period of excellent milk prices and reasonable feed prices, the dairy industry is once again slipping back toward a break-even mode of production. Hopefully, that won’t be long-lived.

In what will likely be trying times ahead, dairy producers and their advisers need to seek out opportunities to improve the efficiency of nutrient delivery to their cows.

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Consistency is one area in which I believe cows respond very positively. Dr. Larry Chase of Cornell University often equates the rumen of a cow to the fermentation vat at a brewery. So that a particular beer will taste the same year after year, whether it’s produced in California or New York, the brewmasters work very hard to keep the fermentation consistent. That means the same ingredients, of the same quality, in the same proportions and fermented under the same conditions wherever their beer is made.

We need to work toward the same ideal when we are selecting or harvesting ingredients, formulating diets or feeding dairy cows. The rumen bacteria, just like the yeast cells in a brewer’s vat, will respond positively and with improved efficiency to a consistent, high-quality diet. The bugs, in due course, will then do a better job providing the cow with more volatile fatty acids (VFA) for energy and high-quality microbial protein to meet her nutrient requirements for maintenance, growth, production and reproduction. Figure 1*is a simplified scheme for the nutrient requirements of the rumen bacteria.

One of our jobs as dairy producers and nutritionists is to make sure that the ‘pools’ of nutrients required by the bacteria are kept full. That’s why we will often formulate a diet with different sources of starch, for instance, which will have different rates of availability throughout the day. As those various starch sources break down in the rumen, they trickle into the pool and keep the bacteria from going hungry. If one of the pools gets low, the bacteria cannot work at maximal efficiency and the delivery of nutrients to the cow is compromised. It’s like opening up the throttle on your tractor, but choking off the air. The tractor just won’t operate at peak performance or efficiency.

No one is happy with the price of feed ingredients these days (unless you have a bunch of it to sell). Protein feeds in particular are expensive and also not very well utilized by the cow. Most researchers calculate that nitrogen (protein) efficiency is around 35 percent. So, for every pound of protein the cow eats, she can only turn about 5.5 ounces of that into milk protein and tissue. The rest ends up in manure and urine. It’s a fine line to balance protein fractions and ensure there is enough ammonia and amino acids available in the rumen at all times for the bacteria to use and enough amino acids (bypass protein) flowing to the intestine for the cow to absorb directly. Recent advances in controlled release non-protein nitrogen can help us do a better job of this.

Nutritionists in general do a good job of providing adequate supplies of amino acids that are available in the rumen for the starch-digesting bacteria to use. It’s the fiber digesters that we often struggle with. Rumen ammonia levels are highly variable, even in well-balanced diets provided to the cow throughout the day (Figure 2*). Adding urea can help, up to a point. In a recent study from Dr. Chuck Schwab’s lab at the University of New Hampshire, they found that adding urea can help grow more rumen bacteria, up to about 4.5 ounces per cow per day in this particular study. When they moved up to 6.75 ounces, the efficiency of nitrogen use and microbial protein growth fell back off. Even in these diets with lots of urea, rumen ammonia still fluctuated between about 8 and 20 milligrams per deciliter. Here’s where the role for a controlled-release urea comes in.

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By using a controlled-release urea product we can smooth out the dips in the rumen ammonia curve. The fiber-digesting bacteria especially will benefit from this more consistent supply of ammonia, so that they can do what they’re supposed to – breaking down fiber, growing microbial protein and producing VFAs.

The cow then sees a more consistent supply of the nutrients she needs to be healthy and productive. Because the controlled-release urea is such a concentrated protein source, about a quarter pound of supplement can replace about 1.3 pounds of soybean meal or a pound of corn gluten meal. The space created in the diet can then be used however best meets the cow and farm’s priorities. Often, this means filling in with more forage. In other cases, a source of digestible fiber, like soy hulls may fit. In either case, its an opportunity to make a more rumen-friendly diet.

This year is shaping up to have record-high prices for feed, fuel and fertilizer. Dairy producers across the country are going to have to make the most of every input dollar on their farm. That means more attention to timely harvesting to capture all of the nutrients possible from forages. It means storing feeds well to reduce the loss of nutrients that have been paid for with time, fuel and fertilizer.

It also means we should seek opportunities to provide the highest quality nutrients, consistently delivered, to the rumen bacteria on which our cows depend. PD

Figures omitted but are available upon request to .

Charlie Elrod for Progressive Dairyman

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