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Farm & Ranch

Prussic Acid Toxicity

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By Barry Whitworth

As the temperature rises and the ground gets drier, plants in the sorghum family may become toxic. A common scenario for a veterinarian is to receive a call from a frantic rancher who says that his cows are “dropping like flies” or that he has found several dead cows after turning his cattle on to new pasture. One question the veterinarian will probably ask is if the cattle have been grazing Johnson grass.

Hydrocyanic acid (HCN), which is also referred to as cyanide or prussic acid, is a toxin in these plants that causes problems. The toxin is created when the harmless hydrocyanic glycosides in plants are stressed and break down. Once the hydrocyanic glycosides in the plants are damaged, they quickly convert to prussic acid which can kill an animal in minutes when consumed. When cattle ingest the plants high in hydrocyanic glycoside and break them down by chewing, the prussic acid is released in the rumen and absorbed into the blood stream.

Once in the circulatory system, the toxin prevents cells in the body from taking up oxygen. The blood becomes saturated with oxygen, which is why venous blood appears bright red. The clinical signs are excitement, muscle tremors, increased respiration rate, excess salivation, staggering, convulsions, and collapse. The cattle actually die of asphyxiation.

Learn more in the August issue of OKFR!

Farm & Ranch

Disaster Prep

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By Barry Whitworth, DVM

Chances are that livestock producers at some time or another will be affected by a disaster such as a flood, tornado, drought or wildfire. Whatever the disaster, the challenge of any producer is to take care of their animals. Unlike small animals, farm animals tend to be large and require special needs in an emergency. For this reason, it is important to take the time to prepare a “Disaster Preparedness Plan.”

The plan will hopefully create a step-by-step set of guidelines to follow during a chaotic situation that will keep both animals and humans safe. In any disaster situation, the most important thing for a producer is to ensure above all else that his/her family and life come first. A producer should never attempt to risk his/her life or a member of their family’s life to save the life of an animal.

The start of a good disaster preparedness plan begins with evaluating what are the most likely disasters that a ranch or farm might face. For example, a ranch in the far eastern part of the state may not spend as much time with drought preparation as a ranch in the western part of the state. All producers should take the time to research history and look at weather patterns to understand the most likely disasters they could face.

Next, the producer should evaluate their premises to determine the potential risk to the animals. For example, the producer may want to remove the animals from any area that falls in a flood plain during certain times of the year or have an evacuation plan ready in case of an emergency. One should also evaluate the structures on the property. Are the barns or sheds able to withstand strong winds or not? The answer to that question will determine if the animals will be kept in a barn or turned out in a pasture during a storm.

Stacks of lumber and/or tin should be tied down. This will prevent the material from being blown around and possibly injuring an animal. Areas around a barn should be kept mowed and free of dead debris. This will help reduce risk where there is potential for a wildfire.

These questions and more need to be addressed in preparing the plan.

A disaster preparedness plan should also include animal identification. All animals need some form of identification. Brands, microchips and tattoos make excellent identifications since they are more permanent than other forms. Pictures will help identify animals. The producer should have records of ownership in case animals are lost or die in the disaster. This will be important if the producer is receiving insurance or indemnity payments.

It is important to remember that during a disaster power and utilities may be lost. A livestock owner who relies on electricity for his/her animals will need to have a backup source of power. A seven to 10-day supply of feed and water should be kept on hand. Producers may want to prepare an emergency kit. Items that might be included in the kit are halters, ropes, feed buckets, medications, first aid supplies, cleaning supplies, flashlights, batteries, cell phone, radio, feed, hay, water and generator. These are just a few things that a producer might need in an emergency.

An evacuation may need to be part of a producer’s disaster preparedness plan. Moving large herds of animals is probably not feasible. However, producers may wish to evacuate a small number of animals that have exceptional genetics. If evacuation is an option, producers will need to prearrange for an evacuation site. They will need to establish a route.

The truck should be full of gas and the trailer hitched during unfavorable conditions. Producers need to leave early. A producer should keep in mind that traffic may be increased during a disaster. The last thing a livestock owner needs is to be caught in a disaster stuck on a highway.

The producers will need to take feed and hay or prearrange for delivery to the evacuation site. If the animals are to remain on the farm, the producer will need to establish an area that he/she feels is safest depending on what the disaster is. For example, a pasture with no trees would be safer than a pasture with a few trees that animals would congregate under during a severe storm.

Once the crisis is over, the owner should be prepared to deal with injuries and dead animals. Producers need to have a carcass disposal plan ready in advance. Producers need to check with the local and state officials about the laws for disposing of animals. Producers need to realize that there is a chance that some animals will need to be euthanized. Owners need to be prepared to euthanize or contact a veterinarian to this job.

Planning how to deal with a disaster is like writing a will. Most of us think that we have plenty of time to get it done later. Unfortunately, later usually comes earlier than we like, and we get caught in an emergency with no plan. If a producer would like more information about planning for a disaster, they should go to www.prep4agthreats or contact their local county educator.

This article originally appeared in the June 2018 issue of Oklahoma Farm & Ranch. 

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Farm & Ranch

Footrot in Sheep and Goats

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Barry Whitworth, DVM, MPH | Senior Extension Specialist | Department of Animal & Food Sciences | Ferguson College of Agriculture | Oklahoma State University

Foot issues are a common finding in sheep and goat operations. According to a 2011 Sheep Study conducted by the United States Department of Agriculture, footrot was found in 37.3% sheep operations. In the 2009 Goat Study, “symptoms of sores on hoof area with foul odor” were found in 6.6% of all the operations. Some studies indicate the issue increases with herd size.  

Several factors contribute to the disease, but the main bacterium involved is Dichelobacter nodosus. The bacterium is contagious and does not survive long outside the host. However, the bacterium will live for years in the feet of sheep and goats. The bacterium has many strains. In general, they can be classified as benign or virulent. Virulent strains are able to destroy the horn. Benign strains do little or no damage to the horn.

Two other bacteria may play a role in footrot. Fusobacterium necrophorum, which causes foot scald, is a common inhabitant of the digestive tract of ruminants. It does not appear to be contagious. This bacterium usually contributes to the development of footrot. Some experts believe that foot scald is a precursor to footrot. One other bacterium that may contribute to the development of footrot or footscald is Trueperella pyogenes. This bacterium may increase the susceptibility of the hoof to the other two bacteria. This bacterium is found in the environment and is associated with foot abscesses. 

The first sign of foot scald is usually lameness. In foot scald, the space between the claws may appear red, hairless, swollen, and moist. No odor is present, and the condition tends to improve with dry weather.  

In comparison, footrot will have the same clinical signs as foot scald but the signs will be more severe. The space between the claws will be necrotic and the hoof will be affected. The foot will have a foul odor. In severe infection, the hoof wall will separate from the pedal bone. The condition is highly contagious and will spread rapidly through the flock.

Both footrot and foot scald are usually diagnosed on clinical signs. The presence of a foul odor is important to separate footrot from foot scald. A definitive diagnosis is based on culturing the bacteria from the foot.

Several management tools need to be used when dealing with footrot. Studies show a significant improvement in overall herd lameness when lame animals were separated from the flock. Sheep infected with Dichelobacter nodosus that causes footrot continue to shed the organism for a period of time after treatment. If left in the herd, these animals contaminate pastures and facilities which contribute to the spread of bacteria. Lame animals need to be isolated until they are healed.

Research has demonstrated that there is a benefit to early identification and prompt treatment of lame sheep. Sheep need to be observed daily for health issues. Studies show that treatment should be initiated within 3 days of lameness. Any animal found to be lame needs to be treated promptly with a long-acting antibiotic and topical antibiotic. Their feet should not be trimmed at this time. Trimming infected feet delays healing.

Another management tool is the use of foot baths. Using a foot bath during a footrot outbreak has been found to reduce lameness. Copper sulfate, formalin, and zinc sulfate may be used in foot baths, but a 10% zinc sulfate solution is preferred. 

Lastly, significant improvement in a flock can be made by culling lame sheep. Sheep requiring 2 or more treatments should be culled. Removing chronically infected sheep from the flock reduces a significant source of the bacteria which should lower the spread of the disease. Culling will improve the economics of the flock by decreasing labor time and money associated with treating footrot. It is also recommended not to keep lambs from culled ewes with footrot for replacement ewes.

Preventing footrot begins with proper nutrition. Hoof health is influenced by minerals and vitamins. Special emphasis should be placed on ensuring adequate amounts of selenium, biotin, zinc, Vitamin A, and Vitamin E. Hooves should not be allowed to over grow. Routine trimming and examination will ensure a healthy foot. Facility and pasture management play an important role in controlling lameness as well. It was found in a study conducted in the United Kingdom that allowing pastures to rest 2 or more weeks had a high impact in reducing lameness in sheep. Facilities need to be kept clean and dry. Lambing pens need to be cleaned and disinfected between uses. Fences need to be maintained. This prevents neighboring animals from entering the farm which could contaminate the pasture with unwanted bacteria.

Footrot can be a frustrating disease. However, following the above practices should improve foot health. For more information about footrot in sheep and goat enterprises, producers should consult with their veterinarian or the Oklahoma State University County Cooperative Extension Service Agriculture Educator.

References

Reilly, L. A., Baird, A. N., & Pugh D., G. (2002). Diseases of the foot. In D.G. Pugh(Ed.), Sheep & Goat Medicine (pp. 225-227). W.B. Saunders Company

Witt J, Green L. Development and assessment of management practices in a flock-specific lameness control plan: A stepped-wedge trial on 44 English sheep flocks. Prev Vet Med. 2018;157:125-133.

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Farm & Ranch

Why Body Condition is Important in the Cow Herd

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By Marty New

Body condition scores of beef cows at the time of calving have the greatest impact on subsequent rebreeding performance.

One of the major constraints in the improvement of reproductive efficiency is the duration of the post-calving anestrous period. If cows are to maintain a calving interval of one year, they must conceive within 80 days to 85 days after calving. Calving intervals in excess of 12 months are often caused by nutritional stress at some point, which results in thin body condition and poor reproductive performance.

Research has shown mature and young cows that maintain body weight have ample energy reserves before parturition, exhibited estrus sooner than cows that lost considerable body weight and consequently had poor energy reserves. Body weight change during pregnancy is confounded with embryo and placenta growth. Therefore, the estimation of body fat by use of body condition scores is more useful in quantifying the energy status of beef cows. The system of body condition scoring is an excellent estimator of percentage of body fat in beef cows.

The processes of fetal development, delivering a calf, milk production and repair of the reproductive tract are all physiological stresses. These stresses require availability and utilization of large quantities of energy to enable cows to be rebred in the required 85 days.

Added to physiological stresses are the environmental stresses of cold, wet weather on spring calving cows. In normal cow diets, energy intake will be below the amount needed to maintain body weight and condition. As the intake falls short of the energy utilized, the cow compensates by mobilizing stored energy and over a period of several weeks, a noticeable change in the outward appearance of the cow takes place.

Cows that have a thin body condition at calving return to estrus slowly. Postpartum increases in energy intake can modify the length of the postpartum interval. However, increases in the quality and quantity of feed to increase postpartum body condition can be very expensive. Improvement in reproductive performance achieved by expensive postpartum feeding to thin cows may not be adequate to justify the cost of the additional nutrients.

The influence of nutrition before calving is a major factor that controls the length of time between calving and the return to estrus. Thin cows with a BCS score of four or less at calving produce less colostrum as well as give birth to less vigorous calves that are slower to stand.

The impact of quality and quantity of colostrum will effect these calves’ immunoglobulin levels, thus harming their ability to overcome early calf-hood disease challenges. It is much easier to increase condition in cows before rather than after they calve. High nutrition after calving is directed first toward milk production. Feeding cows to gain condition early in lactation therefore leads to increased milk production but has little effect on body condition.

Cows prior to calving and through breeding should have a BCS of five or higher to have good reproductive performance. First-calf heifers should have a BCS of six. Spring-calving cows are still consuming harvested forages and lactating will generally lose one BCS following calving.

Over-stocking pastures is a common cause of poor body condition and reproductive failure. Proper stocking, year-round mineral supplementation and timely use of protein supplement offer potential for economically improving body condition score and reproductive performance.

An efficient way to utilize BCS involves sorting cows by condition 90 to 100 days prior to calving. Feed each group to have condition scores of five to six at calving. These would be logical scores for achieving maximum reproductive performance while holding supplemental feed costs to a minimum.

Body condition scoring has allowed cattlemen to continually evaluate their nutritional program. By evaluating cow condition at strategic times of the year, it is possible to coordinate use of the forage resource with nutritional needs of the cow herd so supplemental feed and hay needs are reduced to a minimum.

This article originally appeared in the February 2016 issue of Oklahoma Farm & Ranch. 

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