Vet Call: Anaplasmosis

By Dr. Bob Larson, DVM, professor of production medicine
Reprinted with permission from the Angus Journal.

Anaplasmosis is a serious disease that affects cattle in an increasing larger area of the country. A tiny organism called Anaplasma marginale attaches to red blood cells which leads to destruction of those cells and a decrease in the ability of affected cattle to carry oxygen in their blood. If more red blood cells are destroyed than the animal can replace with new cells the blood becomes watery, the animal becomes anemic, and other signs of infection can occur including yellow discoloration of the mucus membranes, fever, depression, dehydration and rapid or difficult breathing. Sometimes affected animals become excited and aggressive when not enough oxygen reaches the brain. Young animals are often able to recover because they can make new red blood cells very quickly, but older animals do not produce new cells very fast and they can quickly become very anemic and have very low oxygen levels in the blood leading to severe illness or death.

Anaplasmosis is primarily transferred between cattle by ticks, but the movement of blood from infected cattle to susceptible cattle can also be accomplished by biting flies such as horseflies, or by human activities such as via blood-contaminated needles, dehorning instruments, tattoo pliers or palpation sleeves. The disease has historically been a problem in the southern parts of the United States but has now spread north so that cattlemen in many important beef-producing areas need to be aware of the problem. In herds that become exposed to the organism, cattle of any age can become infected, but the severity of illness is usually mild in young cattle and increases with age. In cattle that become infected when they are 3 years of age or older, 30% to 50% of animals showing signs of the disease are likely to die. If infected cattle are able to survive they are not likely to have severe problems due to the disease in the future, but they remain as carriers for the rest of their life. In some cases these carrier infections can be eliminated using antibiotic treatment.

The first sign of anaplasmosis in a herd may be the sudden death of adult cattle. If anaplasmosis is identified as a cause of death and disease in a herd, cattle that are obviously sick should be kept as quite as possible and treated with a blood transfusion to replace red blood cells and/or with an injectable tetracycline antibiotic to kill the organism. In addition, healthy animals should be moved away from the affected cattle to reduce the risk of the organism being transferred to the rest of the herd by ticks or biting insects, and low levels of tetracycline can be fed in the mineral mix or supplement to provide additional protection to the herd.

For carrier cattle that don’t appear sick but that are infected with the anaplasma organism, your veterinarian can plan a treatment protocol using tetracycline antibiotics administered over several days to clear the organism. However treatment with tetracycline is not effective for all cattle and those animals that are cleared of the organism become susceptible to re-infection.

The best plan to minimize disease lose due to anaplasmosis depends greatly on a farm’s or ranch’s geographic location and the number of cattle in the area that are infected. In parts of the country where anaplasmosis infection is rare, a strategy to find and treat and/or remove any carrier-animals is recommended. In contrast, in areas of the country where many cattle are infected, an attempt to remove all carriers from a herd will result in a herd that is susceptible to re-infection and the herd may have greater losses than if other strategies had been used to minimize the disease’s effects.

If infected cattle are found in a herd in a part of the country where anaplasmosis is rare, one strategy to minimize disease loss is to test the herd for anaplasmosis infection and to treat any test-positive animals with tetracycline as directed by your veterinarian. This treatment should be at a time of year when the local tick and fly population is the lowest. Because the treatment does not clear infection from every animal, the animals should be tested again about six months after the tetracycline treatment and if a positive is found at this time, it should be considered a treatment-failure and removed from the herd, either by slaughter or by being sold to a herd in an area where anaplasmosis is common.

In contrast, in herds located where anaplasmosis is common, rather than trying to avoid infection, some producers may want to allow infection to occur while the cattle are young in order to minimize obvious sickness and death loss. In some countries young animals are purposefully exposed to the organism allowing them to build immunity at a time in their life when the disease is mild. Although they will be infected for life, they are not likely to suffer severe illness. In some states in the U.S., your veterinarian may be able to obtain an experimental anaplasmosis vaccine that does not prevent infection, but is reported to reduce the risk of clinical signs and death. Producers may also elect to feed low levels of chlortetracycline when the disease is most prevalent to control active infection and use insecticides to control tick and fly populations.

Because the best anaplasmosis control strategy for a particular farm or ranch depends on how likely that herd is to come into to contact with the organism, an important component of a control strategy is a plan to deal with replacement animals. If your herd is free of anaplasmosis and the risk of exposure is low, any replacement animal should be tested before being brought into contact with the herd. A test-positive animal should either be culled or isolated and treated with tetracycline and then re-tested six months after treatment. In contrast, if your herd is infected with anaplasmosis and the organism is common in your area, a test-positive replacement animal is desired, and the greatest health risk is in replacement animals that are not infected with the organism but that will be placed in direct contact with carrier animals. In this situation, one option is purposeful exposure (or vaccination if available) with close monitoring for clinical signs of the disease and quick treatment if disease is detected.

Anaplasmosis control requires a good working relationship with your veterinarian to determine your level of risk and best control strategies. The best control strategy for your herd may be very different from that of your neighbors or cattlemen in other parts of the country.

Dr. Bob Larson is a professor of production medicine with the College of Veterinary Medicine at Kansas State University, Edgar E. and Elizabeth Coleman Chair of Food Animal Production Medicine, executive director of Veterinary Medical Continuing Education, and faculty member with the Beef Cattle Institute. He specializes in the integration of animal health, production efficiency and economic considerations in beef cattle production. This column is reprinted and redistributed with permission from the Angus Journal.

Vet Call: Cold-weather concerns

By Dr. Bob Larson, DVM, professor of production medicine
Reprinted with permission from the Angus Journal.

A high percentage of the U.S. beef herd resides in areas of the country where moderately to extremely cold winter temperatures are common. By planning for winter weather, ranchers can avoid being caught off-guard by extreme events and can manage the typical winter conditions so cattle do not have to continually utilize body fat as an energy source to keep warm, leading to excessive loss of body condition.

Situations that are most likely to cause cold stress are: Cattle with thin fat cover and short hair coats (due to movement from a warmer environment to a colder environment, or extremely cold temperatures early in the fall/winter season); cattle with wet hides, or high wind speed accompanying cold temperatures. Wind chill is a better predictor of cold stress than temperature alone because cold wind draws heat away more quickly than still air at the same temperature. Wet or mud-caked hair losses its ability to insulate the animal and a wet winter hair coat only provides as much protection from the cold as a typical summer hair coat. If cold wind is combined with a wet hair coat (as can occur during a winter storm), the effects can be very profound.

Adult cattle with a dry hair coat, adequate body condition, and abundant, adequate-quality forage can withstand most winter situations, especially if they have the ability to find protection from wind and have been exposed to moderately cold conditions for several weeks which allows them to acclimate by growing a thick winter hair coat and increasing feed intake. As temperatures drop, cattle increase heat production which means the number of calories they need for maintenance increases. This increase is met by consuming more feed and moving it through the digestive tract faster, but the cost of this faster movement is that feed is not digested as fully. The effect of needing increased calories for maintenance at the same time that feed digestibility is decreasing means that if cows do not have access to plenty of digestible feed, they will have to “burn” body fat as a calorie source.

Another factor that can limit feed intake in winter conditions is if water sources are frozen or unavailable. If feed intake cannot keep up with energy demands, and body fat is mobilized to meet energy demands, then the cows will have less fat insulation and will be more susceptible to cold temperatures, causing a viscous cycle that can lead to cold stress and even more weight loss.

Cold weather brings a special concern with bulls because of the potential to have frostbite damage to the scrotum and testicles. It is very important that bulls have protection from the wind and adequate bedding if they are housed on concrete or dirt.

Cold temperatures have the greatest potential to cause serious problems in young calves, particularly calves in the first day of life. Because calves are born wet, have thin skin and very little body fat, they lose body heat very rapidly and if they are not able to become dry, can quickly become severely cold stressed. Contact with snow or wet ground will increase the amount of time that a calf stays wet and in danger. Body temperature of newborn calves can drop to dangerously low levels in 3 hours or less.
Calves are born with a body temperature of about 100˚F. When exposed to a cold environment, calves are able to produce heat in two ways: shivering and the heat production of brown fat (fat that surrounds the kidneys of a new-born), and they can conserve heat by reducing blood flow to the body surface and extremities (feet, ears, etc.). In early stages of cold exposure, calves will shiver vigorously and have a fast heart rate and breathing rate. If that does not keep the body temperature up, the calf’s body sends less blood to feet, ears and nose in an effort to minimize heat loss. Severe cold stress occurs when the body temperature drops below 94˚F. At this temperature, the brain and other organs are affected and the calf becomes depressed, unable to rise, unwilling to suckle, and will temporarily lose the ability to shiver. The good news is that if the calf can be warmed up and its body temperature can begin to rise, the shivering response will return and the core body temperature will slowly increase.

During periods of cold or wet weather, newborn calves (less than 1 to 2 days of age) should be checked every few hours with a thermometer and any calf with a below-normal temperature, even if it appears OK, should be warmed. Calves suffering from cold stress must be warmed so that body temperature can rise above 100˚F. If body temperature has not dropped too far, putting the calf in the cab of a pickup out of the wind and rain or snow will warm the calf. In more severe cases the calves can be placed in warm water, specially designed warming boxes, or near a heat source such as an electric blanket, heat lamp, or hot water bottles. To avoid skin burns, the heat source should not exceed 108˚F. In addition to an external heat source, cold-stressed calves should be fed warm colostrum, milk, or electrolyte fluid with an energy source using an esophageal feeder.

Prevention of cold stress involves management to ensure that calves can be born in a short period of time and both the calf and dam can stand shortly after calving so that they can bond and the calf can begin suckling. Anything that prolongs calving or reduces the chance that a calf will suckle soon after birth should be addressed by management changes. Calving difficulties are minimized by proper heifer development, proper bull selection for calving ease, and proper nutrition so that heifers and cows calve in a body condition score of 5 to 6 on a 9-point scale. Cows with large teats or that are not attentive mothers should be culled.

Use of pasture as the primary forage source during calving encourages cows to keep spread apart and minimizes development of muddy areas. If the herd forage plan includes feeding hay, consider feeding hay in early to mid-gestation and saving stockpiled pasture for the calving season. If supplemental hay and grain are fed during calving, these should be provided at locations that are separate and distant from water sources and windbreaks. I discourage the use of bale rings in calving and nursery pastures and suggest that if using large round bales, they be unrolled and the feeding area changed with each feeding. Unrolled bales will have greater hay waste, but reduced chance for mud caused by concentrating the herd into small feeding areas, and unrolled hay provides bedding for newborn calves so that they are not in direct contact with the ground.

In addition to monitoring the weather forecast for severe winter weather events and to be alerted to times when additional feed is needed, minimizing the effects of cold temperatures on newborn calves involves planning ahead and considering calf comfort and protection when making heifer development, bull selection, nutrition and pasture-management decisions. Making sure that cows will have adequate access to forage and water even in situations with significant snow cover is necessary to provide sufficient calories to maintain body fat and heat production. Protecting the cow herd (and bulls) from winter wind and providing bedding if on concrete or mud/dirt will minimize the effects of severe weather.

Dr. Bob Larson is a professor of production medicine with the College of Veterinary Medicine at Kansas State University, Edgar E. and Elizabeth Coleman Chair of Food Animal Production Medicine, executive director of Veterinary Medical Continuing Education, and faculty member with the Beef Cattle Institute. He specializes in the integration of animal health, production efficiency and economic considerations in beef cattle production. This column is reprinted and redistributed with permission from the Angus Journal.

Vet Call: The role of the veterinarian in your business

By Dr. Bob Larson, DVM, professor of production medicine
Reprinted with permission from the Angus Journal.

Many people impact the success of your ranching business, including your customers, your lenders and your suppliers. One of the important suppliers for cow-calf producers is the local veterinarian. Veterinarians can provide important advice and service to improve ranch income, decrease costs, provide protection from losses due to disease, and offer options for marketing high-health cattle.

Ranch income is primarily derived from the sale of calves either at weaning for commercial operations or as breeding bulls or heifers for seedstock producers. Commercial ranchers can increase their income by increasing the pounds of calves at weaning and seedstock operations the number of marketable breeding animals from the same land and cow resources by increasing the reproductive efficiency of the herd. Veterinarians can provide advice and services to monitor and evaluate heifers, cows, and bulls so that a high percentage of the herd is able to successfully mate at the start of each breeding season.

Nutrition has an important impact on whether or not growing bulls and heifers reach puberty at an appropriate age and your veterinarian may be able to provide you with appropriate diets to meet targeted weight gain goals. Genetics also strongly influences whether developing bulls and heifers reach puberty by target ages, and your veterinarian is a valuable resource when considering selection and culling decisions. By doing breeding soundness examinations of bulls and heifers near yearling age, your veterinarian can help you identify the individuals that reach puberty at the time and with the amount of feed resources that you have identified to meet your ranch goals.

Doing breeding soundness examinations of mature bulls prior to the start of each breeding season allows your veterinarian to remove bulls that may fail during the breeding season due to foot or leg problems, other health problems, or reproductive tract problems. Although the reproductive tracts of mature cows are not routinely evaluated before the start of each breeding season, managing and monitoring the cows to confirm that a high percentage of the cows calve early enough in the calving season and in good enough body condition to resume fertile cycles by the start of the breeding season helps to ensure that herd reproductive efficiency will be high.

Monitoring body condition scores of the cow herd and rainfall amounts as predictors of future forage production potential allows your veterinarian to provide advice on a changing year-by-year basis to alter stocking density, timing of weaning, and supplementation strategies to ensure that cows enter the calving and breeding seasons in good body condition. The land base and herd size dictate much of the cost-side of cow-calf production and making sure that a high percentage of the cow herd becomes pregnant early in the breeding season allows those costs to be spread over a large number of marketable calves. By using body condition scores collected at several key points in the production cycle, your veterinarian can help you fine-tune the management of your herd based on the ranch forage-base, and the availability of cost-effective supplements or grazing alternatives, and the optimum cow size and milking ability for your herd.

While every production year is expected to generate income from the sale of calves and to incur expenses associated with pasture and supplementation costs as well as cow depreciation and bull costs, significant losses due to disease are expected to be a rare event for cattle operations. Losses that are expected to occur rarely if at all but that could have a devastating impact on the financial status of a ranch if they did occur must be managed with cost-effective risk management strategies. Because disease losses do not occur every year, providing no defense may appear to be a sufficient and very low-cost management strategy in the short-run. However, over a longer time-frame, it would be very unusual for a herd with minimal disease protection to avoid devastating financial losses due to disease at some point in the future. Your veterinarian can provide valuable information about the likelihood that your herd could suffer losses from various diseases and the expected magnitude of those losses should your herd be exposed. By considering the likelihood of a disease, the magnitude of losses associated with that disease, and the effectiveness of available control strategies, your veterinarian can work with you to optimize the disease risk management of your ranching business.

Marketing of cattle, whether feeder calves or breeding animals, increasingly includes information about health status. When considering the optimum herd health program from a marketing standpoint, the risks that down-stream buyers face and their willingness to purchase from suppliers who can reduce that risk must be considered. For example, your herd may have very low risk for a disease and incurring expenses through diagnostic testing or herd certification may not reduce your herd’s already minimal risk, but the costs could easily be offset by customers willing to pay for that low disease risk. Increasingly, you must think of your down-stream customers as you work with your veterinarian to plan a health program that not only meets the needs of your herd but also provides a cost-effective marketing advantage.

A successful cattle business requires a combination of cattle and business expertise. Many successful ranchers count on a trusted team of advisors and suppliers to help them improve the profitability and sustainability of their ranching businesses. Finding and working with a local veterinarian who can provide assistance to increase income, control costs and manage risks should be a goal of every cattle producer.

Dr. Bob Larson is a professor of production medicine with the College of Veterinary Medicine at Kansas State University, Edgar E. and Elizabeth Coleman Chair of Food Animal Production Medicine, executive director of Veterinary Medical Continuing Education, and faculty member with the Beef Cattle Institute. He specializes in the integration of animal health, production efficiency and economic considerations in beef cattle production. This column is reprinted and redistributed with permission from the Angus Journal.