Answers to Common Concerns

Common Animal Health Concerns Answered by Dr. Littlejohn


There are a number of causes of bloat but for the most part they can be categorized into either physiological, physical, biological or nutritional.

Physical Bloat: An example would be an obstruction in the esophagus not allowing the animal to ruminate off the rumen gas.  Another would be an animal that has cast itself and can't get into sternal recumbency.  In these cases the bloat comes off quickly once the cause is corrected.

Physiological Bloat: In this instance there is a problem with the innervation of the stomach(s) in that is not allowing it to function properly.  Hardware and vagus indigestion are the 2 more common diagnoses of this type.  In these cases the bloat has a poorer prognosis as the animal does not improve with treatment or relapses at a later date.

Biological Bloat: Is seen in cattle (particularly calves) with an overgrowth of Clostridia bacteria in the digestive tract.  This type is greatly correlated with the diet but usually occurs after some insult to the intestinal tract.  It could also be due to a parasitic overgrowth seen in calves >3wks that are more pot-bellied than bloated.  These cases are treated by treating the potential pathogens in the intestines.

Nutritional Bloat: Bloat caused by the diet.  Examples are grain overload, frothy bloat (seen on lush alfalfa pasture).  It can also be seen when 2 foodstuffs are mixed such as milk or alfalfa hay, and that can develop into a biological bloat.  These cases need to be treated with anitgas products and a change in the diet.

Passing a stomach tube is the first step in determining what kind of bloat it is.  Is it free gas (physical,physiological) bloat or frothy (nutritional, biological) bloat?

With a free gas bloat,  the gas comes off with the passing of a stomach tube usually rather quickly.  The contrary occurs in a case of frothy bloat, where the bloat is comprised of many tiny bubbles that won't form a bubble large enough to be eructated or burped off.  In these cases, an antigas product needs to be used.

Grass Tetany

Grass tetany or "hypomagnesemia" is a condition caused by low blood magnesium.  It can occur in all classes of cattle including pregnant cows but we most commonly see it in cows that have recently calved.

It is usually seen in cattle grazing a lush pasture dominated by grass or green cereal crops.  These types of feed are predisposed to low magnesium and this predisposition can be worsened by the application of manure that is relatively high in potassium.  The potassium competes with the magnesium in being taken up by the pasture and causes a feed that is too low in magnesium.

 To prevent it feed a good quality mineral to your herd year round.  If you are not currently feeding mineral feed it for a month and then get blood work done to see if the levels are adequate and then the feeding rate of mineral can be adjusted if needed.

Vertical Sand Cracks

Vertical (sand) cracks of the hoof have no one single cause.  The most important factors involve the conformation and strength or quality of the hoof.

Abnormal conformation is a risk factor because the stresses and forces acting on the hoof wall are not normal and these cause points of weakness in the hoof.

The strength or quality of the hoof horn is primarily affected by nutrition.  Make sure the herd has adequate levels of copper, zinc, molybdenum, selenium and vitamin E all of which are important in hoof strength.  Where hoof quality can be affected is when levels of copper and zinc are too low, or increased levels of molybdenum and sulphur will cause the copper levels to become artificially low as they bind to the copper and make it unavailable.  Excessive levels of selenium can also be detrimental to the hoof quality.

Animals with a body condition score (BCS) of 4.5-5.0 (on a scale of 1-5) put added stress on the hoof and should have their diet adjusted to decrease their weight.  However, feed changes themselves (significant increase in protein and starch) can lead to laminitis that will weaken areas in the hoof and increase the chance of a vertical crack.

Treatment: Only treat the ones that are lame.  Hoof testers are needed to rule out any other cause of lameness.  I would call on a hoof trimmer or your vet to deal with the hoof.  They will treat the affected claw according to what debriding needs to be done.  In all cases, a block should be placed on the unaffected claw.

Prognosis: The horn of the hoof grows 5mm/month so healing will take some time.  The prognosis is more favourable of course in a non lame lighter weight animal and is strictly case by case.

Prevention: The best way to prevent vertical cracks is through proper conformation and nutrition.  Select genetics (sires) with good feet and legs and cull animals with poor conformation.

Keep the herd in a good plain of nutrition that includes a properly fed vitamin/mineral premix.  Feed the premix at the recommended levels and draw blood on animals to determine if the blood levels are within range.

Vitamin E and Selenium: The reason there is such a difference in levels of vitamin E between products most likely depends on how they are "carried" or what they are "bound" to.  Some supplements need higher levels in order for an adequate amount to be delivered to the animal.  The best advice I can give you is to feed a reputable well supported mineral supplement as per label instructions.  Feed it for at least one month and then check blood levels of the mineral in question.  Take approximately 10% of the herd for a good representation.

With respect to selenium, there are two types.  Selenite (inorganic) and organic.  It is harder to get the selenium level where it needs to be by feeding selenite because it is very unpalatable, whereas the organic selenium is very palatable and easily absorbed by the cow.  

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