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Supplementing Energy On Pasture

David P. Price is a consulting nutritionist specializing in feedlot and range cattle

www.cattleandwildlifenutrition.com

Last time we discussed substituting straw for hay. We can do that, but it will require supplemental energy to offset what is not contained in the straw (as well as protein, vitamin A and minerals).

If we are growing heifers on pasture to be bred to calve as two-year-olds, we will likewise need to supplement energy. This is never easy for two primary reasons: 1. Commercial feeds for use on pasture are seldom high in energy, and 2. Related to point #1, high-energy feeds usually carry a substantial risk of acidosis and death loss; bloat or long-term liver abscess.

Acidosis 101. This is remedial education for feedlot operators, but for ranchers the risks of acidosis should be thoroughly understood. Any feed high in starch carries substantial risk for acidosis. Specifically, the rumen bacteria will rapidly break down starch (from grain, potatoes, etc.) and give off lactic acid as one of the byproducts. If the release of lactic acid is more rapid than can be metabolized (by other bacteria), the rumen fluid will turn acid.

The acid will inflame the rumen wall causing rumen papillae to slough off. In this process, tiny “holes” in the rumen wall are created, giving rumen fluid access to the blood. This can cause four things to happen; all of them bad. 1. The acidity of the rumen fluid can change the delicate pH balance of the blood, causing the animal to go into convulsions and die; 2. The rumen fluid can also contain toxins, which if the animal has been previously sensitized; can cause the animal to go into anaphylactic shock and die (instantly); 3. On a lesser scale, the toxins or acidity (the mechanism is not clearly understood) will cause the animal to founder; and 4. Pathogenic bacteria will cause liver abscesses, which can cause death at a much later date.

For all these reasons, feed manufacturers are reticent to sell true high-energy pasture feeds. The salesman may refer to them as high energy, but in most cases they will not be.

20 per cent cubes. Most high-protein cubes run 30 to 40 per cent crude protein, so lower-protein cubes are usually thought to be high energy. In most cases they are not. Most lower-protein cubes will have dehydrated alfalfa or some other high-fibre filler as the base. Dehy alfalfa is a good source of protein, carotene and minerals, but has very little energy.

The reason is obvious. If feed manufacturers were to put a substantial amount of grain in cubes; somebody would put them out unevenly, and lose cows (and then turn around and sue).

Custom cubes. It is possible to get high-energy cubes, but usually it has to be on a custom basis. In this case the feed mill makes them according to your nutritionist’s specifications (and you accept liability for the formula). Surprisingly, we can usually obtain custom cubes cheaper than commercial cubes; most commonly, for 10 to 20 per cent over commodity costs. The reason is the feed mill has no storage or selling costs. The product goes out the door right after it is made (and cooled).

With custom high-energy cubes, feeding is relatively simple and totally “doable,” but requires a conscientious effort to make sure dominant animals do not eat disproportionate amounts. It is a matter of determining how many pounds are required to meet the target weight gain (in heifers) or otherwise needed to supplement the straw (or dormant pasture). We then just spread the cubes out across a big enough area that dominant animals are not able to intimidate more timid ones.

Custom blocks. High-energy blocks can be made, but some very special ingredients are needed for formulation. In addition to calculating nutrient requirements and availability, we must design the formula in order to have good block integrity; while simultaneously designing the palatability to fall within the targeted consumption. The cheap shot is to use palatable ingredients and then add a slug of salt. That is not good. Excess salt over time can increase kidney size, but beyond that, the excess sodium gets excreted on the pasture. For this reason we won’t even discuss mixing salt with grain.

Grain byproducts. As we discussed previously, grain byproducts such as dried distillers grains (DDG), wheat midds or corn gluten can make excellent pasture supplements. Likewise, since they can be bought as raw ingredients, there is usually considerable cost savings. The downside is that considerable infrastructure is required; e. g. a feed truck or wagon and troughs.

The advantage to these products is that while they yield considerable energy, there is very little starch present. Thus, there is much less risk of acidosis. Corn gluten and DDG can contain significant sulphur, which can be toxic if animals overconsume. In an ideal world these products could be added to cubes. The problem is they do not cube well and tend to be crumbly. In that case we’re back to the need for troughs. May as well save the cubing cost and feed direct. As discussed in a previous column, these products do not contain vitamin A or significant trace minerals — and a custom mineral will therefore be required.

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