Last week in this publication we shared concerns for frothy bloat in pastured cattle. As a follow up, in this episode of Forage Focus, Host- Christine Gelley- Extension Educator, Agriculture & Natural Resources in Noble County and Dr. Steve Boyles, OSU Extension Beef Specialist, dig deeper into the causes and possible solutions for frothy bloat occurrences in pastured livestock. Their discussion includes how pasture managers need to be observant of forage growth, weather conditions, and animal behavior to avoid conditions that commonly trigger bloat and to recognize and treat bloat quickly if it occurs.
Dr. Richard Bowen, Professor, Department of Biomedical Sciences, Colorado State University (Previously published online with Colorado State University, VIVO Pathophysiology)
The rumen encases a complex ecosystem containing numerous species of bacteria and protozoa that collectively provide the capacity for efficient fermentation of carbohydrates. Among the major products of such fermentation are volatile fatty acids and lactic acid. Wild ruminants and those raised on pasture consume a diet rich in grasses of one sort or another that consist mostly of cellulose. Cellulose is a molecule that might be called a “slowly fermentable carbohydrate”. In contrast, grains such as wheat, barley, and corn are considered “highly fermentable carbohydrates”, meaning that they can be very rapidly fermented to generate – you guessed it – large quantities of volatile fatty acids and lactic acid. Ruminal acidosis results from consumption of a unaccustomed quantity of highly fermentable carbohydrate, almost always well described as grain overload.
Ruminal acidosis is most commonly a disease of dairy and feedlot cattle, and occasionally sheep in feedlots. All of these animals are typically fed large quantities of grain, because such a diet promotes production of milk and enhances growth. The key point is that animals and their ruminal microbes must be adapted over time to a high grain diet, rather than being acutely changed to such feed, otherwise acidosis commonly ensues. In some cases, animals develop acute acidosis “accidentally”, when, for example, they escape from their pen and get into a store of grain.
Melissa Bravo, agronomic and livestock management consultant
Previously published in Hay & Forage Grower: April 21, 2020)
Here we go again. Another mild winter of heave and thaw with little snow cover to protect the shallow roots and crowns of improved forage crops.
Without that snow barrier, species such as alfalfa and timothy — the most susceptible of our non-native forages — are subject to winter injury, which thins stands. This leaves less competition for weeds to establish and flourish.
– Rory Lewandowski, Extension Educator Wayne County
Originally posted on the OSU BEEF Newsletter
Check beef and dairy cattle for lice infestations during the late winter and early spring months. Although lice can be present throughout the entire year, high numbers of lice are most likely during winter months when cattle have longer, thicker hair coats, which make self-grooming less effective in reducing lice numbers. Hot summer temperatures, and for pasture-based production systems, direct exposure to sun, plus rain showers, all play a role in reducing lice numbers and offer further explanation of why heavy lice infestations are most often seen during winter months.
– Chris Penrose, Extension Educator, Ag and Natural Resources, Morgan County
Originally posted on the BEEF Newsletter
One goal I have had with livestock grazing over the years is to start as soon as I can. I put spring calving cows on stockpiled grass in early March to calve with the hope of not having to feed any more hay. Many years this works but not this year, grass is just starting to grow. The stockpile is about gone and I have started feeding them some more hay but hope to move the group with the fall calving cows this weekend. I then plan on starting a fast rotation around many of the paddocks and hay fields which is actually later than many years.
Originally posted on the BEEF Newsletter
Forage stands will begin spring greenup in the next few weeks, especially in southern Ohio. While winter injury in forages is very hard to predict, this winter has presented some very tough conditions for forage stands. This is especially true of legumes like alfalfa and red clover. Producers and crop consultants should be prepared to walk forage stands early this spring to assess their condition in time to make decisions and adjustments for the 2019 growing season.
Originally posted on the BEEF Newsletter– Mark Sulc, OSU Extension Forage Specialist
As cold weather approaches this week, livestock owners need to keep in mind the few forage species that can be extremely toxic soon after a frost. Several species contain compounds called cyanogenic glucosides that are converted quickly to prussic acid (i.e. hydrogen cyanide) in freeze-damaged plant tissues. A few legumes species have an increased risk of causing bloat when grazed after a frost. Each of these risks is discussed in this article along with precautions to avoid them.
Species with prussic acid poisoning potential
Forage species that can contain prussic acid are listed below in decreasing order of risk of toxicity after a frost event:
- Grain sorghum = high to very high toxic potential
- Indiangrass = high toxic potential
- Sorghum-sudangrass hybrids and forage sorghums = intermediate to high potential
- Sudangrass hybrids = intermediate potential
- Sudangrass varieties = low to intermediate in cyanide poisoning potential
- Piper sudangrass = low prussic acid poisoning potential
- Pearl millet and foxtail millet = rarely cause toxicity
Species not usually planted for agronomic use can also develop toxic levels of prussic acid, including the following:
- Black cherry
It is always a good idea to check areas where wild cherry trees grow after a storm and pick up and discard any fallen limbs to prevent animals from grazing on the leaves and twigs.
Fertility can affect poisoning risk. Plants growing under high nitrogen levels or in soils deficient in phosphorus or potassium will be more likely to have high prussic acid poisoning potential.
Fresh forage is more risky. After frost damage, cyanide levels will likely be higher in fresh forage as compared with silage or hay. This is because cyanide is a gas and dissipates as the forage is wilted and dried for making silage or dry hay.
Plant age affects toxicity. Young, rapidly growing plants of species that contain cyanogenic glucosides will have the highest levels of prussic acid. After a frost, cyanide is more concentrated in young leaves and tillers than in older leaves or stems. New growth of sorghum species following a non-killing frost is dangerously high in cyanide. Pure stands of indiangrass can have lethal levels of cyanide if they are grazed when the plants are less than 8 inches tall.
Animals can die within minutes if they consume forage with high concentrations of prussic acid. Prussic acid interferes with oxygen transfer in the blood stream of the animal, causing it to die of asphyxiation. Before death, symptoms include excess salivation, difficult breathing, staggering, convulsions, and collapse.
Ruminants are more susceptible to prussic acid poisoning than horses or swine because cud chewing and rumen bacteria help release the cyanide from plant tissue.
The following guidelines will help you avoid danger to your livestock this fall when feeding species with prussic acid poisoning potential:
- Do not graze on nights when frost is likely. High levels of toxic compounds are produced within hours after a frost, even if it was a light frost.
- Do not graze after a killing frost until plants are dry, which usually takes 5 to 7 days.
- After a non-killing frost, do not allow animals to graze for two weeks because the plants usually contain high concentrations of toxic compounds.
- New growth may appear at the base of the plant after a non-killing frost. If this occurs, wait for a killing freeze, then wait another 10 to 14 days before grazing the new growth.
- Don’t allow hungry or stressed animals to graze young growth of species with prussic acid potential. To reduce the risk, feed ground cereal grains to animals before turning them out to graze.
- Use heavy stocking rates (4-6 head of cattle/acre) and rotational grazing to reduce the risk of animals selectively grazing leaves that can contain high levels of prussic acid.
- Never graze immature growth or short regrowth following a harvest or grazing (at any time of the year). Graze or greenchop sudangrass only after it is 15 to 18 inches tall. Sorghum-sudangrass should be 24 to 30 inches tall before grazing.
- Do not graze wilted plants or plants with young tillers.
Green-chopping frost-damaged plants will lower the risk compared with grazing directly, because animals are less likely to selectively graze damaged tissue. Stems in the forage dilute the high prussic acid content that can occur in leaves. However, the forage can still be toxic, so feed greenchop with great caution after a frost. Always feed greenchopped forage of species containing cyanogenic glucosides within a few hours, and don’t leave greenchopped forage in wagons or feedbunks overnight.
Hay and silage are safer
Prussic acid content in the plant decreases dramatically during the hay drying process and the forage should be safe once baled as dry hay. The forage can be mowed anytime after a frost if you are making hay. It is rare for dry hay to contain toxic levels of prussic acid. However, if the hay was not properly cured and dried before baling, it should be tested for prussic acid content before feeding to livestock.
Forage with prussic acid potential that is stored as silage is generally safe to feed. To be extra cautious, wait 5 to 7 days after a frost before chopping for silage. If the plants appear to be drying down quickly after a killing frost, it is safe to ensile sooner.
Delay feeding silage for 8 weeks after ensiling. If the forage likely contained high levels of cyanide at the time of chopping, hazardous levels of cyanide might remain and the silage should be analyzed before feeding.
Nitrate accumulation in frost forages
Freezing damage also slows down metabolism in all plants that might result in nitrate accumulation in plants that are still growing, especially grasses like oats and other small grains, millet, and sudangrass. This build-up usually isn’t hazardous to grazing animals, but green chop or hay cut right after a freeze can be more dangerous. When in doubt, send a forage sample to a forage testing lab for nitrate testing before grazing or feeding it.
Species That Can Cause Bloat
Forage legumes such as alfalfa and clovers have an increased risk of bloat when grazed one or two days after a hard frost. The bloat risk is highest when grazing pure legume stands and least when grazing stands having mostly grass.
The safest management is to wait a few days after a killing frost before grazing pure legume stands – wait until the forage begins to dry from the frost damage. It is also a good idea to make sure animals have some dry hay before being introduced to lush fall pastures that contain significant amounts of legumes. You can also swath your legume-rich pasture ahead of grazing and let animals graze dry hay in the swath. Bloat protectants like poloxalene can be fed as blocks or mixed with grain. While this an expensive supplement, it does work well when animals eat a uniform amount each day.
Frost and Equine Problems (source: Bruce Anderson, University of Nebraska)
Minnesota specialists report that fall pasture, especially frost damaged pasture, can have high concentrations of nonstructural carbohydrates, like sugars. This can lead to various health problems for horses, such as founder and colic. They recommend pulling horses off of pasture for about one week following the first killing frost.
High concentrations of nonstructural carbohydrates are most likely in leafy regrowth of cool-season grasses such as brome, timothy, and bluegrass but native warm-season grasses also may occasionally have similar risks.
Another unexpected risk can come from dead maple leaves that fall or are blown into horse pastures. Red blood cells can be damaged in horses that eat 1.5 to 3 pounds of dried maple leaves per one thousand pounds of bodyweight. This problem apparently does not occur with fresh green leaves or with any other animal type. Fortunately, the toxicity does not appear to remain in the leaves the following spring.
Commentary by Dianne Shoemaker/ OSU Extension Field Specialist
Since June 25, 66 more Ohio dairy farms have ceased milking cows. In three months, 3 percent of Ohio’s dairy herds are gone.
Since October 2017 — when there were 2,312 operating, licensed dairy farms in Ohio — 172 farms have quit milking, a decline of 7.4 percent of dairy farms in one year.
On Sept. 25, 2018, Ohio had 1,745 Grade A farms and 395 Grade M (Manufacturing Grade) farms, totaling 2,140 operating dairy farms.
Sadly, these numbers will continue to rise, as too many years of poor milk prices and unpredictable markets for milk, cull cows, breeding stock, and feed take their toll.