A bi-monthly news publication of The Ohio State University Extension, Editors: Clif Little and Mark Sulc
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[top] Planned Winter Feeding - Clif Little, Extension Educator, Guernsey County

Winter is fast approaching, are you ready? The single largest expense of keeping livestock is winter-feeding costs. Last year was very expensive and this year with high forage and grain prices it will probable be even more expensive. Livestock owners can reduce and minimize the cost with a little planning.

It sounds strange but feeding hay now might be one strategy to reduce winter-feed costs. One reason for doing this is that we can rest our fescue and orchardgrass pastures and allow them to grow long into the fall, building forage reserves. Secondly, generally speaking, 1st cutting grass hay may be of lower quality than fresh growing pasture and would better match the nutritional status of a mature animal in early to midgestation under no stress of cold or mud.

Next, plan your winter-feed needs now. Do not get caught in late January, February or March needing feed or forage. For example, how much forage does a 1300lb. cow need for 150 days of winter-feeding? Accounting for feeding losses, hay storage losses and adjusting for hay dry matter content (DM), she may need approximately 8373 lbs of hay. For sheep, goats, and cattle fed only hay take the total pounds of livestock times .043 times the number of days you have to feed and this will give you a rough calculation of the pounds of hay you will need to make it through the winter. You can refine this calculation by adjusting for each class of livestock, forage quality, method of feeding, and method of bale storage.

Another method of reducing winter-feed cost is to supplement with an economical grain concentrate. Select a concentrate based on animal nutritional needs, forage quality and economics. Keep in mind that concentrates may increase total dry matter consumption and forage digestibility. The key here is being able to limit feed forage while feeding groups of animals separately. In order to realize the economics of concentrate feeding we may need multiple areas to feed groups of livestock while having the ability to store grain concentrates. With the exception of high fiber based supplements, concentrates are generally best fed daily.

Finally, forage test. Forage testing allows you to feed the best quality to the animals that need it the most. Knowing the nutritional value of forage also allows you to make wise decisions when purchasing forage. Plan now and the winter-feeding period will be less stressful and more economical.

[top]Prussic Acid Poisoning Potential in Frosted Forages- Mark Sulc, Extension Forage Specialist

Jack Frost will certainly arrive this autumn in Ohio, bringing the potential for prussic acid poisoning when feeding specific forage species. Some species, primarily sorghums and closely related species, contain cyanogenic glucosides, which are converted quickly to prussic acid in freeze-damaged plant tissue.

Animals can die within minutes of ingesting forages with high concentrations of prussic acid, also known as hydrogen cyanide. Prussic acid binds to hemoglobin in the bloodstream and interferes with oxygen transfer, causing animals to die of asphyxiation. Symptoms include excess salivation, difficult breathing, staggering, convulsions, and collapse. Ruminants are more susceptible than horses or swine because cud chewing and rumen bacteria help release the cyanide from plant tissue.

Sudangrass varieties are low to intermediate in cyanide poisoning potential, sudangrass hybrids are intermediate, sorghum-sudangrass hybrids and forage sorghums are intermediate to high, and grain sorghum is high to very high.

Johnsongrass, chokecherry, black cherry, indiangrass, elderberry, and some varieties of birdsfoot trefoil also have potential for prussic acid poisoning. Piper sudangrass has low prussic acid poisoning potential, and pearl millet and foxtail millet have very low levels of cyanogenic glucosides.

Plants growing under high nitrogen levels or in soils deficient in phosphorus or potassium will be more likely to have high cyanide potential. After frost damage, cyanide levels will likely be higher in fresh forage as compared with silage or hay, because cyanide is a gas and dissipates as the forage cures and dries.

Young, rapidly growing plants of species with prussic acid poisoning potential will have the highest levels of prussic acid, as the cyanide is more concentrated in young leaves than in older leaves or stems. New growth of sorghum species following drought or frost is dangerously high in cyanide. Pure stands of indiangrass (not common in Ohio), if grazed when the plants are less than 8 inches tall, can have lethal levels of cyanide.

When grazing or greenchopping species with prussic acid potential this fall, follow these guidelines:

• Do not graze on nights when frost is likely. High levels of the toxic compounds are produced within hours after a frost.
• Do not graze after a killing frost until plants are dry, which is usually 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 hard, killing freeze then wait 10 to 14 days before grazing.
• Don’t allow hungry or stressed animals to graze young growth of species with prussic acid potential.
• Graze or greenchop only when sudangrass exceeds 18 inches in height, and sorghum-sudangrass should be 30 inches in height before grazing. Never graze immature growth at any time.
• Do not graze wilted plants or plants with young tillers.
• Green-chopping the frost-damaged plants will lower the risk compared with grazing directly, because animals have less ability to selectively graze damaged tissue; however, the forage can still be toxic, so feed with great caution. Feed greenchopped forage within a few hours, and don’t leave greenchopped forage in wagons or feedbunks overnight.

When making hay or silage from sorghum species this fall, consider the following:

• Prussic acid content 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. It is very rare for dry hay to contain toxic levels of prussic acid. If the hay was not properly cured, it should be tested for prussic acid content before feeding.
• Forage that has undergone silage fermentation is generally safe to feed. To be extra cautious, wait 5 to 7 days before chopping after the forage was frosted. If the plants appear to be drying down quickly after a killing frost, it can safely be ensiled within a shorter time period from the frost.
• Delay feeding silage for 8 weeks after ensiling. If the forage likely contained high HCN levels at time of chopping, hazardous levels of prussic acid might remain and the silage should be analyzed before feeding.

Other common forages such as alfalfa, clovers, and cool-season perennial grasses do not produce toxic compounds after a frost and can be fed safely. The only concern is a slightly higher potential for bloat when grazing legumes within a day or two after a killing frost.

Testing for Prussic Acid Content in Forages
An accompanying article describes the management practices to follow for feeding the sorghum species to livestock after a frost. If doubt remains regarding the safety of the forage, the forage can be tested for prussic acid (HCN) content. But keep in mind that prussic acid is a gas, so it is difficult to detect in samples sent to labs. Sample handling is extremely critical to ensure that the lab test will be representative of what is being fed to livestock.

Obtain a representative fresh sample of the forage to be fed. Collect 1 to 2 lbs of fresh forage from across the field to be grazed. For silage, follow proper sampling protocol to obtain a representative sample. Do not allow the sample to dry. Place in an air-tight plastic bag, freeze the sample, and ship the fastest way (overnight express) in a cooler with an ice pack.

Remember, HCN content dissipates with drying of the sample. So if the sample arrives at the lab drier than the fresh forage that is fed, a false negative result will likely occur.

The following are two labs that will analyze samples as soon as they arrive. Other labs may provide testing for prussic acid, always call ahead to confirm whether the prussic acid test is provided.

The Michigan State University Animal Health Laboratory
Diagnostic Center for Population and Animal Health
Michigan State University
4125 Beaumont Road
Lansing, MI 48910-8104
TEL (517) 353-1683, FAX (517) 353-5096
http://www.animalhealth.msu.edu
Request Procedure 70022

Midwest Laboratories
13611 B Street
Omaha, NE 68144-3693
TEL (402) 334-7770, FAX (402) 334-9121
www.midwestlabs.com

[top]Fall Cutting of Alfalfa- Mark Sulc, Extension Forage Specialist

Every year many Ohio alfalfa producers take a fall cutting. Unfortunately, cutting alfalfa in late September to mid-October can carry serious risk to the health of the stand. Cutting during this period interrupts the process of storage of energy and proteins in alfalfa taproots. When alfalfa is cut during this period and if soil moisture is adequate, the plant will regrow and utilize those precious taproot energy and protein reserves that are needed for winter survival and spring regrowth next year.

Fall cutting may not result in real obvious stand loss, although that can occasionally happen. The more common occurrence is for fall-cut alfalfa stands to suffer some loss of vigor and yield next year that is not so obvious. One could only see such loss of vigor and yield next year if side-by-side comparisons were made within the same field, where strips of alfalfa are cut or not cut this fall. Often, the yield gained by fall cutting is lost in reduced yields the following year.

I realize that some producers are in need of additional hay supplies this year. So how can they minimize the potential for damage from cutting alfalfa stands this fall?

A late fall harvest is a safer alternative than cutting now in late September to mid-October, By late harvest, I mean as close as possible to a killing frost of alfalfa, which happens when air temperatures reach 25 F for several hours. This often does not happen until sometime in November in Ohio. But I recommend this late harvest option only if the soil is well-drained, the stand is healthy, a variety is planted that has excellent winterhardiness, and the soil has good fertility status.

I know that the weather is usually lousy in November for cutting forage, but waiting to get closer to the killing frost will prevent the late fall regrowth that “burns up” energy reserves. Thus, cutting late when fall regrowth is less likely will reduce the risk of loss of vigor next spring.

A fall harvest after a killing frost is relatively safe if the soil is well-drained and there is no history or risk of heaving on that particular soil. Without residue cover, the temperature at the soil surface will fluctuate more, so the potential for heaving injury is greater.

I am often asked whether leaving a large amount of fall growth can harm the alfalfa stand in the winter. The fear is that the alfalfa will “smother itself out”. I have let pure stands of alfalfa go into the winter with a lot of growth, even more than we see this fall, and I have never experienced a problem or seen the crop “smother out”.

Fall management of alfalfa is one of the few controllable factors that will potentially influence the health of your alfalfa stand next year. It could play a determining role in how much yield you get next year. If you don’t need the forage, walk away from it this fall and let it insulate those alfalfa crowns this winter. The stand won’t smother out because of excessive alfalfa growth.

If you do need the forage now and to get through this winter, then taking a cutting in early November or after a killing frost will reduce the risk of injury to the stand. But try to limit late cutting of alfalfa to well-drained soils with good pH and fertility status. Also leave a 6-inch stubble.

Finally, if you do cut alfalfa this fall, leave several different strips or areas within the same field where you do not cut. You might learn something interesting next spring about fall cutting on your farm.