Feed Nutrient Uniformity

Feed Nutrient Uniformity
By Dr. Jim White

There are some things you can control to get the most out of your feed materials.

Awhile back I was having dinner with some beef producers when a question was raised.

“What happens if you don’t feed a balanced ration?” queried one of my dinner partners. “Particularly, what happens if you offer mature beef cows forage free choice along with free-choice mineral rather than provide a total mixed ration?” After a typically pedantic nutritionist’s tedious explanation, I summarized with, “I don’t know, but if you feed them at least every other day, it seems to work out OK.”

An initial assumption that we nutritionists make is that when we formulate rations, the animals will be getting a homogeneous mixture of the nutrients required by the “target animal.” We assume that every bite is balanced. It’s a great system if every bite is balanced. But what if every bite is screwed up? We accept that the diet should have the requisite nutrients to support health and performance—too little is unacceptable and likewise having too much is unacceptable. Feed additives in particular have a rather narrow range of usage. For example, AS700 is fed at 350 milligrams per head per day for both the Aureo and Sulfa. That’s not much room for slop.

A number of years ago, I had spoken with my grandfather about some work we were doing with feeding lysine hydrochloride to hogs. He was skeptical. He told me lysine didn’t work. He had tried it a number of years earlier, and it didn't work. Case closed. I maintained that the lysine worked great. The difference was in how the lysine was being fed. My grandfather fed lysine at a pound per day sow supplement, fed once a day to gestating sows. In our research, lysine worked great with blended corn and soy meal-based diets where we were adding lysine to an amino acid spec. Providing the lysine uniformly through the animals’ feed was the key. University work with hogs has further demonstrated that the smaller the animal and the smaller the meal size, the greater the effect of nutrient uniformity or lack thereof.

With that in mind, remember that cattle tend to eat a fair amount per meal, and they tend to eat multiple meals each day. Thus, it seems that the effects of a poorly mixed ration may not be readily apparent. However, we might just be hiding the effect from ourselves. There are any number of cases where animals being pushed for high gains show up with acidosis, bloat and laminitis due to non-uniformity of the ration. This may be due to operator and machinery error, or it could be due to an animal effect.

Everybody using TMRs wants to have adequately mixed feed, but what is a good mix, and what are good mixing practices? Numerically, the official feed-geek method has been to set the target at a coefficient of variation at 10 percent. To derive this you divide the standard deviation by the average. Most hand-held calculators have such keys. In a spreadsheet, you just paste in the functions, and the program crunches away. You know you’re finished when the numbers start screaming.

Feed mix uniformity is influenced by numerous factors. There are some we can control and some we can’t. Those that we usually can control are:
1. Choice of mixer and mixer selection—some models are better than others.
2. Loading accuracy—if the batch calls for 54 pounds of salt, what if only 50 pounds go in? If the wagon scale has a capacity of 12,000 pounds, do you want to weigh out 10 pounds of a feed additive with it?
3. Ingredient loading sequence.
4. Mixing time and speed.
5. Equipment maintenance.
6. Delivery accuracy—is there a huge pile of feed at the end or front of the bunk?

Regardless of the mixer type, the characteristics of the ingredients will have a tremendous influence on mixer performance. I think that the most important ingredient characteristics are stickiness/tack, size, shape and density. Lighter and larger particles tend to move up. Small, heavy material moves down. Rather than cursing material for these properties, you can use them to your advantage. Load the forage first, which will be larger and lighter than the concentrate fraction of the diet. Add liquids last—after initial blending of the dry ingredients. It just is not effective to throw a small addition of a soluble additive—say a couple pounds of buffer—over the top of a wet ration. The buffer is staying where it hits.

What’s the minimum mix time? There’s a topic near and dear to the hearts of feeders. The minimum mix time is determined empirically. That is, you mix feed, measure uniformity, and keep moving mix time up or down until you get the uniformity where it should be. As a feed microscopist, I can look close to see what is in a pelleted feed, but I can't see the uniformity. To measure uniformity you need to take a number of samples and test each one.

Getting a good sample is a challenge. You are going to pull a half a pound of sample from anywhere from a one 1-ton lot to a lot of 200 tons or more. The lab is going to use a couple of grams to analyze it. So there is significant potential variation in just getting the samples. As a rough rule, the higher the forage of the sample, the more difficult it is to get a uniform sample. I am particularly distrustful of grab samples from the top of the bunk on mixed rations, particularly when I am looking for things used at low levels such as feed additives. If the additive comes up low or long, there are accusations and denunciations toward the nutritionist and a bit of panic from the feeder.

When you look at additive uniformity, the first thing to do is validate the source of the additive.

If you must sample bunk rations, the following method is recommended, unless you don’t have enough stress in your life; then I recommend top of the bunk grab samples.

Method to get a representative sample for uniformity testing:
1. Lay large, unopened garbage bags or large plastic sheets across the bunk at random intervals along the distance covered by a single delivery feeding.
2. Using normal delivery practices, fill the bunks, ensuring that the delivery chute passes over the plastic sheets.
3. Collect each sheet with its feed intact, making sure to maintain location identity. Lay sheet with sample on a flat surface.
4. Cut the pile into quarters, using a panel, bar or machete. Pick a pile and quarter the selected pile again. Repeat until you have a sample of 1 to 2 pounds.
5. Place each sample in a clean, uniquely identified/numbered plastic bag.

The objective of the feeder is to provide consistent nutrient intake. A balanced and uniform ration encourages rumen stability, feed intake, and nutrient utilization. But providing a uniform ration requires careful attention to equipment selection, operation, maintenance and management.

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