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OSU Extension BEEF Team
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Previous issues of the BEEF Cattle letter
Issue # 690
June 9, 2010
Forage Focus: Pasture Management: June Is a Transition - Rory Lewandowski, Extension Educator, Athens County, Buckeye Hills EERA
June is often a transition time for pasture management. Generally in early June moisture and temperature are still favorable for good cool season grass growth. It is also a time when grasses are maturing if seed heads have not been clipped or grazed off and, even if an earlier clipping was done to remove seed heads; there can be new seed head production. The emphasis in many pasture management systems at this time is quick rotations through pasture paddocks to try to keep up with grass growth and to try to keep seed heads grazed and/or clipped off.
As we get past mid June and into later June our weather pattern often changes. Summer has arrived. It generally becomes warmer and drier. Cool season grass growth slows down. Plants clipped in late June remain in vegetative growth. The emphasis on pasture management now must shift to reflect this change in cool season grass growth. Pasture rotations should be slowed down. Paddocks that were dropped or left out of the spring rotation can now be worked back in to the rotation.
Keep in mind the two important "R's" of pasture management: Residual leaves and Rest period. Do not overgraze pastures as the transition is made from spring to summer. Make sure that leaf cover is left after a grazing pass. In beginning level grazing schools, we generally talk about leaving a residual of at least 4 inches of plant leaves. That leaf cover will provide the plant with a photosynthetic base to continue growing and recover more quickly from defoliation caused by grazing. The residual leaf growth will also provide shade for the soil. Shading will help to keep the soil temperature cooler as compared to exposed soil and it will help to reduce moisture loss due to hot temperatures. Cooler soil temperatures and retained moisture will help cool season grass to grow better longer into the summer period.
Rest period is simply the time it takes the cool season plant to recover or grow back to the target grazing height. Rest period is what dictates how soon a pasture paddock can be grazed again. In our beginning grazing schools we talk about an 8-10 inch beginning grazing height for most cool season pasture mixes. An endophyte infected fescue stand is an exception; and the recommended beginning grazing height is 6 inches. The rest period between grazing passes increases with cool season grasses as the transition is made from spring to summer. Slower growing grass needs a longer rest period to recover after grazing. The exact amount of time needed is related to the residual leaf cover that remains after a grazing pass. Less residual leaf cover translates into longer rest periods.
June is an important time to pay attention to cool season grass growth and make appropriate management changes as we transition from spring to summer.
Summer Storms and Wild Cherry Trees - Rory Lewandowski, Extension Educator, Athens County, Buckeye Hills EERA
Following some of the rain storms and winds that have moved through our area recently, I received a phone call from a farmer who had noticed that a large wild cherry tree had fallen down into a pasture paddock. His question was: 1) how long should cattle be removed from that paddock? And 2) as he cleaned up that tree from the paddock and leaves scattered across the paddock, could those leaves be harmful in a subsequent grazing pass?
As we get into our summer months, occasional storms are likely and this is a situation other graziers could face. As a way of answering these questions, I will review what is known about the toxicity/poisoning potential of wild cherry trees using as a basis for information, a section of a chapter from a book by Burrows and Tyrl, sent to me by Dr. William Shulaw, OSU Extension veterinarian for cattle and sheep.
At issue here is what is termed cyanogenesis, or the potential to produce cyanogenic or hydrogen cyanide (HCN) compounds, sometimes more commonly called prussic acid. Many plants in the Rosaceae (rose) family and specifically in the prunus genus, of which the wild black cherry is a member, have this potential. HCN is not found in the normal plant tissue state. It is only formed when glycosides in the leaves are combined with hydrolytic enzymes in the leaves. These two materials are stored in separate sites in the plant and so HCN is formed only when the barrier separating these sites are broken. This occurs when plant tissue is damaged, through such mechanisms as chewing, frost, or damage to the tree that causes leaves to wilt.
Ruminant animals are very susceptible to poisoning from HCN. Research indicates that the lethal dose for sheep/cattle can be as little as 1 to 4 grams of plant material per kilogram of body weight, or since there are 2.2 pounds per kilogram, 0.46 grams to 1.82 grams of plant material per pound of body weight. To give this some perspective, there are 454 grams in one pound, so this is a small amount. For a 1200 lb cow, consuming 1.2 to 4.8 pounds of wilted black cherry leaves could be a lethal dose.
Signs of HCN toxicity can occur quickly, as soon as 15 to 20 minutes after ingestion. Typical signs are distress, followed by severe weakness to the point where the animal is barely able to stand, or even to the point of collapsing. Animals will exhibit rapid and labored respiration. If they have collapsed there may be kicking/paddling of the legs and/or kicking associated with seizure like symptoms. This entire sequence can progress in 10 to 15 minutes with a high dosage of HCN and up to 45 to 60 minutes with a lower dose. References state that if the animal does not die in the first hour, there is a good chance for recovery.
According to the chapter from the book by Burrows and Tyrl that Dr. Shulaw provided to me, the effects of consuming wilted black cherry leaves are not cumulative. In other words, a cow could consume less than a lethal dose at various times throughout the day and survive, even though the total amount ingested during the day might add up to 4 or even 5 times a lethal dose. The critical element appears to be time, that is, separating each intake event with enough time for the HCN to be processed in the rumen.
The range in what comprises a lethal dose of wilted black cherry leaves reflects the HCN potential of the leaves. There are several factors that influence the HCN potential. Growth stage or maturity of the leaf is important. Young leaves have a higher HCN potential than older leaves. In wild black cherry, the HCN potential may be as high as 2500 ppm in newly emerged leaves, down to around 500 ppm after 6 weeks and then tail off gradually during the growing season down to around 40 ppm after several months. It is thought that a HCN potential of around 200 ppm is the hazard level for ruminant animals. This would suggest that the greatest threat to cattle from wilted cherry leaves is early in the season, but there are other factors that can affect the HCN potential. For example, moisture levels in the leaves are a factor. When a normal moisture/rainfall period is followed by a dry period the HCN potential can increase during the dry period. This would seem to apply to many of our Ohio summers where we have good rainfall through early June and then may be dry until or through August.
Once HCN is formed in the leaves, as would be the case when either a limb from a tree breaks off or an entire tree is felled and the leaves begin to wilt, those leaves present a health threat to cattle. However, HCN is volatile, which means that it dissipates and is loss with time. In particular, once leaves are air dried and have turned brown, they will lose much of their HCN potential. Toxicity is more likely to be retained over a longer time period if environmental conditions are such that leaves remain green and do not dry out.
Alright, time to turn this information into a practical form. Getting back to the questions at the beginning of this article, once a tree or limb from a wild black cherry has fallen into a pasture; ruminant animals must not be allowed to eat the wilted leaves. If it can't be completely cleaned up, remove animals until the leaves have completely dried up and turned completely brown. If, in the cleanup process some leaves are scattered in the paddock, do not let cattle back into the paddock unless the amount of wilted leaves is very minimal and scattered across a wide area or, better yet, the leaves are completely dried and brown.
Summer storms and wild black cherry trees can be lethal mix for grazing cattle. Understanding the potential for HCN poisoning can help the grazier manage the risk.
Poison Hemlock: Have you seen this weed? - Stan Smith, PA, Fairfield County OSU Extension
Each passing year it seems I get a few more calls regarding "this weed that looks like a real tall wild carrot." Indeed, the population of poison hemlock along field edges, in fence rows, around barn lots, and now even growing throughout hay fields seems to have reached new proportions this year.
Poison hemlock is a biennial member of the carrot family - Conium maculatum - which can cause respiratory failure and even death when ingested by livestock or humans. It may, at times, be confused with giant hogweed - Heracleum mantegazzianum - a plant with many similarities and also quickly spreading in Ohio.
In fertile soils poison hemlock may easily grow up to 10 or 12 feet, producing small white flowers that are typical of the carrot family. The plant began flowering around Ohio a few weeks ago. The herb has a smooth, purple-spotted stem; dark, glossy-green and fern-like triangular leaves. It has a fleshy white taproot. Both the leaves and roots have a disagreeable parsnip-like odor.
All parts of the plant are poisonous including the leaves, stems, seeds and roots. Simply handling the plant can cause toxic reactions in humans. Perhaps poison hemlock's most famous claim to fame was when it was used to execute Socrates in 329 B.C.
The taste of leaves and seeds to livestock of poison hemlock is unpleasant, so toxic quantities are seldom consumed when ample desirable feed is available for the animals. Cattle can usually survive poison hemlock if consumed in amounts less than 0.4% of their body weight (4 to 5 pounds for mature cows) although abortions are possible at lower rates. The toxicity of the plant changes little if fermented with silage or dried in hay.
Crossbow and Banvel are fairly effective on small poison hemlock. Taller plants may need to be controlled with glyphosate. Mowing after the plants have bolted and before seed set will prevent seed production.
Hay Technology and Biofuel Grasses Featured at June 17th Hay Day
With hay-harvesting equipment demonstrations, educational presentations on biofuel grasses and a variety of exhibitors, the 2010 Southeastern Ohio Hay Day, Thursday, June 17, promises to be a great opportunity for producers serious about maximizing farm income and exploring new ventures.
Sponsored by Ohio State University Extension and the Ohio Agricultural Research and Development Center (OARDC), the event - free and open to the public - will be held from 4-8:30 p.m. at the Eastern Agricultural Research Station in Belle Valley, Ohio, just off Interstate 71 in Noble County. Dinner will be provided.
The program includes a series of hay-equipment demonstrations (raking, baling, mowing and tedding). Exhibitors include hay-equipment manufacturers, local equipment dealers, Soil and Water Conservation Districts, and OSU Extension.
New this year are presentations on biofuel grasses and warm-season grass production, said Clif Little, OSU Extension educator in agriculture and natural resources. Larry Merry, Belmont County (Ohio) Port Authority, will be on hand to discuss Berger Plant's (also located in Belmont County) plans to use biomass for energy generation by 2013. Also, Little will talk about production of switchgrass (a biofuel source), how to establish it, and the costs to produce it and pelletize it.
The Eastern Agricultural Research Station is located at 16870 Township Road 126 near Belle Valley. Take Exit 28 off I-77. Turn south on State Route 21. Go east (left) on State Route 215 for about one mile. Turn right onto Bond Ridge Road (a township road) and look for signs. The facility is one of 10 OARDC outlying agricultural research stations located around Ohio.
Call 740-489-5300 or 740-732-2682 for more information about the event. OARDC and OSU Extension are the research and outreach arms, respectively, of Ohio State's College of Food, Agricultural, and Environmental Sciences.
Weekly Roberts Agricultural Commodity Market Report - Mike Roberts, Commodity Marketing Agent, Virginia Tech
LIVE CATTLE futures on the Chicago Mercantile Exchange (CME) closed down on Monday. JUNE'10LC futures were down $1.150/cwt at $89.800/cwt. The AUG'10LC contract closed at $87.725/cwt; off $0.900/cwt. Declining beef prices and spillover effects from hogs pressured prices. Cash prices were bid lower by packers on shrinking margins with USDA posting the 5-area average price at $94.53/cwt. Futures traders see nothing but weakness for cash prices at least for the next 10 days as fat cattle were bringing $2-2.50/cwt less than this time last week. USDA placed the choice price at $160.45/cwt; off $0.36/cwt. The struggling European economy looks like it is finally impacting U.S. beef sales even though some export markets are still supporting beef prices. Weakening processing margins could limit how much packers are willing to pay this week. According to HedgersEdge.com, the average packer margin was lowered $6.30/hd from last report to a positive $33.70/hd based on the average buy of $94.15/cwt vs. the average breakeven of $96.86/cwt.
FEEDER CATTLE at the CME closed down on Monday. AUG'10FC futures closed at $108.400/cwt; off $0.475cwt. Feeders followed cattle and other commodities lower. However, losses were cut short on lower corn prices. Compared to a week ago cash feeder prices were $2-$4/cwt lower. Demand is moderate for feeders and low for calves. Estimated volume in Oklahoma City was 13,200 head vs. 9184 this time last year. Last week no sales were held on Monday due to the holiday.
Visit the OSU Beef Team calendar of meetings and upcoming events
BEEF Cattle is a weekly publication of Ohio State University Extension in Fairfield County and the OSU Beef Team. Contributors include members of the Beef Team and other beef cattle specialists and economists from across the U.S.
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Fairfield County Agriculture and Natural Resources