in a cowherd can be especially disheartening when it hits more than
one animal. Was it a disease, poisoning, or other cause? Will other
animals die or get sick?
One type of sudden death is known as Weak Calf Syndrome. We have already experienced this problem this winter. Calves are born weak and die the day they are born or within 2 or 3 days. No treatment seems to be able to save them. Years ago Dr. Dick Bull and his associates at the Univ. Idaho studied this problem in cowherds across the state of Idaho. They found that cows eating diets low in protein during the last 60 days of pregnancy were the group most likely to give birth to weak calves. Due to the high cost of hay and supplements, many cows are wintering on straw. Some of the grass seed straws may have enough protein for cows, however many of them don’t. Grain straws such as wheat, barley, and oat straw are very low in protein. Baled corn stalks are low in protein. However, if the cattle ‘sort’ out the stalks when fed baled corn stalks, they may be able to select a diet with enough protein. Corn stubble has sufficient protein until the animals have consumed the leaves, cobs, and husks.
I’ve already had quite a few calls about nitrates. In order to cut costs almost anything that grew was baled. Fields of weeds with a little bit of grass were in this group. Some of the weeds that grow in the Northwest are particularly good at accumulating nitrates. If I purchased some weedy grass hay, it might not dawn on me to check for nitrates. Grass hay isn’t usually considered to be dangerous. Even a weedy area in a pretty clean field of grass can cause a problem. Those weeds could all wind up in 1 or 2 large bales. With my luck several cows will gather around those bales and eat enough to get poisoned. All we find is several dead cows while the rest of the herd looks and is absolutely fine. A nitrate test from a feed lab costs $15.00, so it is a good preventive measure. If nitrate-nitrogen (NO3-N) is 2000 ppm or 0.20% or higher don’t feed until you have worked out a plan to gradually introduce it to the animals. Remember that nitrates also cause abortion, so even if no more cows die, you still may lose calves from those cows not eating a lethal dose. However in the situation described above, the chances of probing and analyzing two bales out of a total of 50 are pretty low. You might inspect the bales as they are fed looking for lambsquarter, nightshade, pigweed, or kochia, to name a few. Sudangrass and grain hays may also accumulate nitrates.
Grass tetany kills many cows every year. Most typically it kills the best cows nursing the best calves because the cows are drawing heavily on their reserves of calcium and magnesium to produce milk for those calves. High levels of protein and potassium are associated with grass tetany. Spring grass is especially high in both protein and potassium. If it occurs while the cows are still being fed hay, the amount and type of hay can be adjusted to provide a better balance of those nutrients. It is also prudent to feed a ‘tetany’ mineral that has high levels of magnesium and calcium. The mineral should have no added potassium. Unfortunately magnesium is not very palatable to cows and it can become quite frustrating to find a mix that the cows like, especially on spring range.
Fog fever is
another nutritional disease that can kill calves, yearlings, or mature
animals. It occurs when cattle are moved from dry, mature feed onto
lush pastures. The pastures may be alfalfa, grass, clover, or turnips.
In the dry country of the Northwest this condition usually appears in
the fall when cattle are moved from dry range onto these kinds of pastures.
The pastures are high in protein. Protein is made up of a chain of amino
acids. It appears that a high concentration of the amino acid tryptophan
is responsible for this disease. Most treatments meet with little success
because the animals are dying of respiratory arrest and can’t
be moved to an area where they can treated. If you have this type of
pasture available in the fall, the cattle need to be fed alfalfa hay
or some other source of protein for a week before you turn the cattle
into the pasture. This allows the bugs in the paunch to adapt to the
high protein feed. Another means of prevention is to feed a supplement
that has Rumensin added for several weeks prior to turning into the
Poisonous plants were mentioned previously as a source of nitrates. However there are many plants that have their own chemical compounds that are toxic to cattle. Plants that have been identified in the Northwest include:
Hopefully you have identified areas on your range or pasture that have these plants and can keep cattle out of these areas, spray, or graze the area with animals not susceptible to the toxin present.
White muscle disease is caused by selenium deficiency. It is most typically seen in very young calves. Calves are born weak and rarely survive for more than a few weeks. It is termed white muscle because calcium is deposited in the heart muscle and other areas causing the organ to appear white rather than pink or red. Fortunately we don’t hear of white muscle nearly as much as we did 20or 30 years ago. Most livestock owners are aware of the deficiency of the mineral selenium in their feed and take the steps necessary to prevent this disease. Work reported by Oregon State Univ. in the late 1950’s identified the cause of this disease and the importance of supplementing the trace mineral selenium in the diet of the cows. Most feeds grown in the Pacific Northwest are deficient in selenium, however there are areas that have adequate selenium in their forages. Recent evidence shows that selenized yeast is superior to sodium selenite in providing supplemental selenium. The selenized yeast can be added to any form or source of supplement. High levels of sulfur fertilizer interfere with selenium status of the animals grazing those fields. Oregon State is working on selenium fertilization as a means of providing adequate selenium for grazing animals and animals fed hay from that ground.
On that happy
note I’ll conclude this column. Hopefully your cattle haven’t
died from any of the nutritional diseases mentioned. Management to prevent
these diseases is far more economical than treatment. Feed tests can
identify low protein feed, high levels of nitrates in water and feed,
probability of grass tetany and the presence or absence of
Michael J. Mehren, Ph.D. is a livestock nutritionist from Hermiston, Oregon avoiding the toxins in okra, broccoli, and avocados. He may be contacted by Email at firstname.lastname@example.org.