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Newsletter of Penn Dutch Cow Care May 2009

Hi Folks,

Last month I discussed trying not to let cows get into negative energy balance as ketosis can occur. This month I want to talk about the possibility of another problem from the nutritional angle that can attack cows – rumen acidosis. Oftentimes graziers will reflexively say that rumen acidosis only occurs on conventional confinement farms, due to pushing for really high milk production. While rumen acidosis can hit cows pushed hard, believe it or not it can also hit grazing cows that milk more moderate levels. Why?

First, let’s look at what rumen acidosis is and some of the signs when an animal may be experiencing it. The rumen pH should be about ~ 6.8 when normal. The pH tells you how much acid is in a system - whether it is the soil that your crops grow from, your well water or the cow’s rumen fermentation vat.  As the system becomes more acid, the pH number gets smaller. It is also a “log” number so that a drop in from 6.0 to 5.0 is 10 times more acid. The population of rumen bugs is highly varied and each type of bug likes a certain range of pH. Some of the products the rumen creates are dependent on the general rumen ecology, which is affected by the pH. When all the bugs are “happy” there will be a production of acetic and propionic acid, with some butyric acid. These are volatile fatty acids which can migrate through the rumen wall and enter the cow’s general system to help build certain milk components. (Acetic acid generally helps build butter fat). When the rumen pH drops much below 6.0, the normal rumen bugs are unhappy and die off, especially if the pH remains too low for too long.

The pH, being a reflection of the amount of acid present, can be changed very easily by intake of different feed ingredients. To keep the rumen bugs happy, cows chew cud. Chewing cud creates saliva. Saliva has bicarbonate in it, which opposes acid. Therefore, the more the cows chew cud, the more saliva is produced, and this saliva is swallowed when the cow swallows her cud. This then maintains a pH between 6–7 that keeps the important rumen bugs happy. What makes cows chew cud? FIBER. The best fiber for cud chewing is effective fiber like dry hay. You can never have enough dry hay on a dairy farm. It truly is a medicinal feed for cows. Fresh grasses and legumes from pasture also provide a lot of material for cud chewing. But sometimes the effective fiber is not as great. We easily see this when cows shoot “pasture manure” across the walkways at this time of the season.

What is almost the opposite of healthy fiber? GRAIN. The purpose of grain is primarily to provide energy for cows to make lots of milk. In the wild, ruminants do eat grain in the way of seed heads on grasses and the like. So while grain is not entirely foreign to a cow’s system, giving too much hammers the system in a terrible way. How? As grain is fermented in the rumen, lactic acid is produced, which will drop the rumen pH lower and lower unless offset by sufficient fiber intake. The whole science of ruminant nutrition essentially boils down to balancing the amount of fiber and grain going into the rumen to keep the bugs happy and to produce milk. How this is accomplished definitely impacts cow health.

With this in mind, perhaps it can be seen how rumen acidosis can occur not only in confined herds pushed for maximal production but also with grazing herds. In grazing herds that feed grain (which most do to some extent), there must be adequate effective fiber going into the rumen so the cow chews cud as much as possible to maximize saliva production with its bicarbonate. I have seen grazing herds that provide lush spring grass get rumen acidosis by slug feeding grain twice a day at milking times and not providing dry hay but only baleage, or worse, haylage (short chop). Always feed hay before grain.

However, the consequences of rumen acidosis don’t seem to be as terrible in grazing herds as those kept always inside or on concrete barnyards. Why? This is mainly due to the fact that when rumen acidosis occurs, hoof health is almost always impacted. In chronic, low grade rumen acidosis (also called sub-acute rumen acidosis or SARA), sole ulcers will develop on the bottom of the hoof. These are always on the bottom, about 1/3 of the way from the back heel and 2/3 back from the toe tip. These are classic signs of rumen acidosis. On grazing herds that I know that get a hoof trimmer in, sole ulcers are almost never noted. I believe that the give and take of the natural earth underneath the animals as they walk on pasture helps prevent these sole ulcers even if the conditions for rumen acidosis are present. This has been borne out by seeing a few outbreaks of a bunch of cows getting into grain, becoming very ill shortly afterwards, but having no long term lameness issues due to sole ulcers. Other symptoms of rumen acidosis is grinding teeth, irregular light colored manure with grain in it and not chewing cud much. One thing to avoid is graining cows that are skinny to put weight on them – this is a wrong thing to do. Always try to feed the most nutrient dense forages to cows to keep them healthy and maintain good body condition. At least 60-70% of resting cows should be chewing cud at any time.

While last month’s newsletter discussed ketosis (lack of energy) and how to prevent it, there also needs to be an awareness that too much energy coupled with a lack of fiber can severely impact cows in a very bad way. It all comes down to a balanced approach to feeding and not being too extreme in one direction or the other. This is where each and every grazier really should be connected with a nutritionist – the nutritionist being truly interested in proper grazing and basing the ration on the growing grass as the primary ingredient. Do not try to work with a nutritionist that simply pays lip service to grazing to keep your business. It is usually fairly obvious who truly likes to work with grazing herds versus those who don’t. I’ll be happy to give a list of people I know of that work well with graziers as I see the results of nutritional programs on all the farms I visit.

NOTE: Moses B. Stoltzfus, 1846 Georgetown Rd., Christiana, PA 17509 has a springing Jersey-Holstein and a Holstein due in June for sale.

Levi S. King, 523 Valley Road, Quarryville, PA 17566 is looking for a yearling Jersey bull. He can also be contacted at 717-786-9183 on Mondays between 7-7:15pm, fast-time


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