Grain Overload and Acidosis

 

We don't feed much grain here at the farm.  We are firm believers that cattle were designed to eat grass, hay and other forage.  Our calves receive a small amount of grain over their first winter, as weanlings, just to balance their ration.  Because of this fact, we don't have a problem with grain overload, but it is an extremely important subject for those who are planning on feeding grain to cattle.  In addition, bread loaves, bags of snack chips and fruit can have the same effect as grain feeding. Cattle get sick or even die everyday from receiving too much high carbohydrate products of some kind or another.

Acidosis is the most important nutritional problem that faces feedlot operators and dairy managers on a daily basis.  It also it an important subject for the small herd owner to be aware, particularly if using grain supplements, brewery by-products, fruit or fruit by-products, and bread or snack chip products in a feed program for cattle.

Grains or any easily digestible, low-fiber carbohydrate are subject to fermentation by microorganisms in the rumen of the cow.  When carbohydrates are broken down in the rumen, acids are produced.  When the intake of carbohydrates is particularly high, acid levels increase at a rate faster than they can be neutralized by saliva and this results in rumen acidosis. The severity of the acidosis may range from mild and unnoticed to life threatening. Cows are designed to consume forage, with its high level of plant fiber.  This fiber acts indirectly as a buffer in the rumen because it causes the cow to chew and produce saliva.  The quality of the fiber also affects its ability to act as a buffer; fibrous feed ground too fine will decrease the effectiveness of the fiber in the diet.

Acidosis does not cause just a single set of signs but a variety of conditions, mostly related to either the digestive system, or the feet. Conditions associated with acidosis include

1. laminitis (founder and its associated problems such as sole ulcers, sole abscesses chronic hoof wall changes etc.), lameness

2. polioencephalomalacia  (thiamine deficiency- thiamine is manufactured in the bovine rumen by bacteria;  with sufficient die off of microorganisms, no thiamine is produced and the animal shows signs of brain disease, such as staggering, incoordination and seizures.)

3. sudden death syndrome (probably cases of grain overload)

4. grain bloat

5. transient diarrhea

6 Poor production, reduced appetite, lower milk production

7. liver abscesses

8.  many others

 “Grain overload” is a specific disease that is also called lactic acidosis.  Grain overload is the most extreme of the conditions causing severe rumen acidosis and severe systemic illness.   The condition may lead to cardiovascular collapse, kidney failure, muscular weakness, shock and death.  Acute laminitis may be seen, and this is usually in the animals that are not so severely affected. Furthermore, in the animal dying from grain overload, the feet are the last thing you would be worried about.

This is the most dramatic manifestation of rumen acidosis where rumen pH drops to well below 5, with subsequent inflammation to the rumen wall.  This is most common in cattle that accidentally gain access to large quantities of grain or other readily digestible carbohydrates.   It is also seen in feedlot cattle that are introduced to a heavy grain diet too quickly.  Wheat, barley, milo and corn are readily digestible grains.  Wheat is considered the most digestible, followed by barley, then corn and grain sorghum.   However, processing of the grain affects its digestibility.  Anything that disrupts the outer tough layer of the grain will increase digestibility, and also affect the likelihood of contributing to the development of acidosis. Thus wheat, barley and high-moisture corn are more rapidly digested and likely to be a problem than dry rolled corn, dry whole corn or dry rolled grain sorghum. Oats are in a class by themselves.  Oats are a very fermentable grain, but are much lighter in weight than other grains, and much higher in fiber.  If feeding by volume, a large scoop of dry corn is considerably more grain than the same large scoop of oats.  Thus, owners can be happy feeding their cattle a treat, while giving considerably less actually carbohydrates than if feeding corn, wheat or barley.  However, oats are still highly digestible, and can cause acidosis or bloat just like any other grain if overfed.  Importantly, engorgement with apples, grapes, bread, sugar beets or sour wet brewer’s grain incompletely fermented in the brewery can also cause “grain overload.”            

Cattle accustomed to high levels of grain in the diet may be able to consume 30-45 pounds of grain with only moderate illness, while animals unaccustomed to heavy grain consumption may be acutely ill and die after eating much smaller amounts.  Grain overload is an emergency, as death may occur in 24-72 hours.  Because the condition depends not only upon the level of grain consumed, but the individual animal itself the dilemma is to figure out which animal requires intense therapy (or slaughter),or  supportive therapy only (which may only require restriction of grain and water intake coupled with hay and  exercise.) If the cattle are found still in the process of gorging themselves, it is possible that some animals will become severely ill, while others will not.  Concentrate and water should be withheld, and plenty of good quality hay should be provided for up to 24 hours.  The cattle should be forced to exercise periodically and evaluated for signs of illness or pain upon movement. If the cattle appear normal after 24 hours, they are probably okay, but if even one in the group is ill, the entire bunch should be carefully monitored for another 24 hours, continuing access to hay and water only. Those who have eaten enough concentrate to become seriously ill will generally show signs of illness within 6-8 hours. Treatment of severely ill animals suffering from grain overload is difficult, and may require pumping the stomach, re-inoculation of the rumen with rumen contents from another cow, and intravenous fluids.  Death is common. It may be prudent to treat particularly valuable animals before they are showing signs of illness.

Less extreme cases of illness due to rumen acidosis do not necessarily involve grain overload, but are associated with the feeding of grain or any of the other highly fermentable feeds.  As the pH of the rumen drops, useful bacteria and protozoa that require a more neutral pH die and poisons (vasoactive agents such as endotoxins) are released from their dead cells. These toxins have their affect on the sensitive lamina in the feet, and laminitis may result.  These animals are not necessarily showing signs of illness from the rumen acidosis, but the changes are occurring anyway.  More subtle signs of acidosis may be the animal going off its feed for a day or two.  At this point, the rumen recovers to normal pH, the animal resumes eating carbohydrates, then the acid level drops, rumen acidosis reoccurs, the animal goes off feed for a day or two and the cycle continues.  While certainly this scenario is most common in dairy cattle and beef steers on finishing rations, it can also occur in any cow that consumes easily digestible carbohydrates for any reason.  This includes cattle on show rations, or animals fed as a small group where one or more hog the ration, receiving more than their fair share.  The condition is certainly not limited to adult or near adult animals, but can occur in ruminating calves on creep feed or being fed grain rations to balance their diets .(i.e. balancing high quality alfalfa hay or haylage with corn or barley to supply needed energy for growth.)

The key to feeding grains or similar products is to balance that intake with high fiber forages and watch carefully for indications that the animals may be suffering from subclinical rumen acidosis. Such symptoms may require a change in feed management, such as increasing forage available or decreasing grain amounts.

Tips for the average Highland owner to avoid rumen acidosis if grain is to be fed:

1.If possible, choose a less highly digestible grain such as dry whole corn or dry rolled grain sorghum

2.Limit processing of grain products. Finely ground feeds are more likely to contribute to both acidosis and bloat.

3. Allow free access to high quality forage to make sure that animals are eating lots of fiber and are not hungry when grain is offered.  If the cattle are genuinely hungry then aggressive feeders may overeat.  High quality forage ensures that the cattle are eating it well. Moldy feed or very poor quality hay may not be palatable and go uneaten, and may well make the cattle much hungrier for the grain products.

4. Limit the total percentage of grain in the diet.  A good growth ration may include roughly one pound of dry whole corn for each 100# of body weight when coupled with good quality 50% alfalfa hay.  Calves and yearlings will eat about 2-3% of their body weight in dry matter per day.  This percentage drops as animals age, so that the mature cow may only consume 1.5-2% of her body weight.  1 pound per 100# of body weight will provide something less that 50% of the total feed intake as a grain product when feeding young stock. (Feedlot cattle receive far more of their diet as grain products, with roughage limited to 5-10% of total diet.) The greater the percentage of forage in the diet, the lower the risk of acidosis.

5. Start cattle on grain rations with very small amounts and work up to larger volumes slowly.

6. Feed at the same time every day.

7.If possible, split the daily ration of grain into more frequent, smaller meals.

8.If possible to feed each individual separately, do so.

9. Remember that treats such as apples, pears, bread loaves all add to the grain burden for the day, and will have different fermentation rates.  Substituting grain products on a pound for pound basis, without an introductory period for the new product, may contribute to the development of acidosis.

10.Watch your animals closely.  Any of the following may be an indication of problems with subclinical acidosis.

      a.       Reduced cud chewing.

      b.      Great daily variation in feed intake, the animals go off feed, not necessarily at the same time.

      c.       Manure in the same feeding group varies from firm to diarrhea

      d.      Manure appears foamy with gas bubbles

      e.       Appearance of mucous or mucin casts, and sometimes blood, in the manure

      f.        Increase in fiber particle size (> ¼  inch) in manure

      g.       Appearance of undigested fiber in the manure

      h.       Appearance of undigested, ground (< ¼ inch) grain in the manure

 

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