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1508 PD: Nutrition and hoof health

John Hibma Published on 16 October 2008

Hoof health is something that many dairy farmers don’t spend a lot of time thinking or worrying about – until they see a few of their cows tip-toeing around the feedbunk or alleyways.

And even then, many will not think that the issue is related to nutrition; rather, that it’s time to call the hooftrimmer to trim a few hooves and maybe check for “the wart.” If you can rule out digital dermatitis, foot rot, bruising or abscesses and your cows are still limping, the culprit is going to be laminitis.

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Laminitis is an inflammation of the lamina or corium of the foot, caused by a disturbance of the blood circulation in that sensitive area. This reduction of circulation will result in edema, hemorrhage and break-down of the corium tissue. On a white-legged Holstein, it’s very easy to spot even a mild case of laminitis – that puffy pinkness just above the hoof at the hairline.

Rumen acidosis is considered to be a predisposing cause of laminitis. When a cow has an acidotic rumen, certain substances are released into the bloodstream that interfere with the blood flow from arteries to veins. A cow’s foot happens to be very vulnerable to this inflammation. Laminitis in dairy cows and heifers is exclusively a nutrition problem caused by poor rumen function. Occasionally you might hear someone blame it on stress; however, even in that case, it most likely was a stress event that disrupted a diet.

Rumen acidosis – and therefore, laminitis – can always be traced back to insufficient dietary effective fiber. More often than not in high- producing dairy cow diets, low fiber is a result of too much concentrate thereby lowering the ratio of fiber-to- concentrate in the ration. A closely related cause comes from finely chopped forages such as haylage and silage or from total mixed rations (TMRs) that have been mixed too long. Slug feeding and feed sorting may also contribute to low effective fiber as could rapid changes in diet or wet feeds.

Rapidly fermented carbohydrates such as corn and barley that are typically found in dairy grain mixes will often result in high levels of lactic acid, which can diminish or stop the efficacy of the fiber-digesting bacteria. This unwanted level of lactic acid is what causes rumen acidosis.

If left unaddressed, this acidotic event can cascade into other problems. As fiber fermentation is slowed, less digesta will flow from the rumen to the abomasum, opening the door for a displaced abomasum (DA). Your fresh cow, who is already under a lot of stress because she wasn’t transitioned properly, is often the cow who gets hit with acidosis. If the cow is left untreated she may also become ketotic as her body mobilizes fat reserves to compensate for the lack of energy. All of this may happen before she shows any signs of foot problems – and you probably have already shipped this cow before laminitis sets in.

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As is often the case, however, a mild case of acidosis may go undiagnosed and several weeks later you’ll have cows with laminitis. You most likely won’t even remember that there was a change in feeds or feeding routines or that the weather was really rainy for a week and no adjustments were made for the wet silage that was fed during that time. Summertime heat and humidity will also cause cows to reduce dry matter intakes and be inclined to sort feeds, which may lead to acidosis. Here in the Northeast I can often tell the cows that freshened during the summer by ones who are limping in the fall.

Cows can develop laminitis at any stage of lactation but it seems the ones most prone to the problem are those in early lactation. Feed rations balanced to support more than 80 or 90 pounds of milk production tend to have higher levels of non-fiber carbohydrates (NFC) – that part of the ration that’s mostly grains or byproducts and low in effective fiber. There’s a limit to how much NFC a cow can consume before the rumen becomes acidotic.

If effective fiber is too low in a ration, the fiber-digesting microbes in the rumen will be overwhelmed by the microbes that ferment sugars and starches. Starches tend to be main contributors to acidotic rumens and a coinciding high NFC. If you can keep nutrient content of a ration within these following guidelines you can usually avoid acidosis:

• starch levels at 25 to 28 percent of dry matter (DM)

• total NFC at 35 to 40 percent of DM

• neutral detergent fiber (NDF) at 30 percent DM

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• total moisture in ration not to exceed 60 percent

• total fat from plant sources not to exceed 0.5 pound

• use a rumen-protected fat source if more energy is required

• include a rumen buffer such as sodium bicarb at 4 to 10 ounces per day

• total crude protein (CP) in ration should remain around 17 percent with properly balanced amino acids

• focus on feeding high-quality forages to keep the rumen mat viable

Then, of course, if you’ve got a well-balanced diet on paper but don’t get it delivered to the cow, you still could be setting yourself up for rumen upsets.

• Avoid overmixing of TMRs.

• Make sure the scales on the mixer are working correctly.

• Make sure cows have adequate feedbunk or stanchion space to eat.

• Make feed available to cows all day.

• Keep feeding schedules consistent.

• Use a particle size separator to check silages and TMRs.

• Don’t forget the water.

With high -producing dairy cows, we often find ourselves walking that fine line of pushing fermentable carbohydrates to the limit while reducing effective fiber to a dangerously low level in order to get the necessary energy into those cows. A carefully balanced and managed feed ration will avoid problems with laminitis. PD

John Hibma
Nutritionist

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