Calf scours or diarrhea is among the leading causes of early calf hood death. Calf scours seemed to be prominent in a number of herds during February and March of 2008. If you remember what our weather was like during this period, you will recall it was rainy and cool as cattle and cattleman alike battled mud and bone-chilling conditions. In fact, rain and mud lead to hypothermia, lower the calf's ability to resist infections, and can open the way for scours or diarrhea to occur.
There are a number of infectious agents that are responsible for diarrhea in calves, among them viruses and bacteria. The most common viruses associated with calf scours are rotavirus and corona virus. Both of these viruses infect and destroy the cells that line the intestinal tract. The calf looses the ability to digest and absorb milk. If the calf survives, this damage can be repaired but meanwhile the calf experiences serious fluid and electrolyte (generally potassium, sodium, chlorine and bicarbonate) loss from the accompanying diarrhea that leads to severe dehydration and acidosis.
The most common bacteria associated with calf scours/diarrhea is E. coli (Escherichia coli). This bacteria releases a toxin that damages the cells lining the gut, causing the normal absorptive capacity of the intestine to change and result in fluids and electrolytes being secreted and lost. This type of calf scours is generally seen only in very young calves up to about 5 days in age. There are also species of Salmonella bacteria associated with calf scours.
Under less severe cases of diarrhea or in early stages of diarrhea, calves exhibit loose stools, dryness of mouth and some loss of skin elasticity due to dehydration. More severe or prolonged diarrhea leads to worse dehydration and chemical imbalance in the body. Symptoms include: eyeballs beginning to sink into the eye sockets, calves become weak and lethargic, calves may be unable to stand, body temperature drops to below normal, and loss of nursing reflex. At this point, if calves are not treated they can move into coma, shock and then will die.
The most important treatment for calf scours/diarrhea is to replace the fluids and electrolytes that the body is losing. There are numerous commercial products available that can rehydrate the calf, correct pH imbalances and replace lost electrolytes. You may want to consult with your veterinarian as to a specific product and recommended volume/mixture to use in treatment of sick calves. A key point is to start fluid replacement early on while calves are still standing and have a nursing reflex. If the calf will nurse from a bottle, electrolytes can be provided in this manner. If the calf refuses to nurse from a bottle, replacement fluids and electrolytes will have to be given by using an esophageal feeder probe/tube. Again, you may want to consult with your veterinarian about the proper use and placement of an esophageal tube. Keeping calves hydrated will help the calf to maintain vigor, enable the calf to continue to nurse, and help the calf to maintain its body temperature. Once a calf loses the ability to stand and suckle, the only recourse is intravenous (IV) treatment.
While antibiotics and sulfa drugs are commonly given as an oral treatment to calf scours, it has been found that this is not effective treatment and may even be detrimental. According to an article on calf scours by Don Hansen, Extension Veterinarian at Oregon State University, ". . . antibiotics and sulfa drugs given orally alter the normal population of organisms in the gut and sometimes predispose to super infections or fungal infections. Some antibiotics, when given orally, actually inhibit glucose absorption and alter the cells that line the gut wall. In these cases, continued oral use actually prolongs diarrhea."
Early fluid replacement treatment can be effective, but prevention of calf scours is, of course, preferable. Prevention goes back to management and understanding how scours can develop. Think of a triangle, with each leg of the triangle representing a factor that needs to be present for scours to develop. There are three: a susceptible animal, an infectious agent/organism and a favorable environment. Management practices that can reduce or break any of these legs of the triangle can reduce the severity of, or prevent scours from developing. A calf that is able to ingest a good quantity of colostrum, 5-6% of the calf's body weight within the first 6 hours after birth, is less susceptible to scours than a calf that nurses late or only ingests a small amount of colostrum. Vaccination programs that include an initial shot and a follow up booster to cows 6-7 weeks before calving boost antibody levels in the colostrum to provide added protection against early calf hood diarrhea/scours. Anything that can be done to keep the calf dry and relatively warm can go a long way in reducing a favorable environment for disease organisms and help to prevent occurrence of scours. Mud is the enemy in this regard.
Another management practice that should be followed as a preventative measure is to make sure that new replacement animals are NOT introduced into the herd within the two months prior to calving to two months after calving window. These animals could carry and introduce disease organisms that calves have no protection against from colostral antibodies.
Calf scours can be a disheartening experience during the calving season. Wet, muddy conditions increase the chance of calf scours. Anything the cattleman can do to provide warmer, drier conditions can help to prevent scours, along with making sure that a good first meal of colostrum is ingested soon after birth. Once scours develop, the most effective treatment is replacement of fluids and electrolytes.
References:
Calf Scours: Causes and Treatments, Don Hansen, Cattle Producer's Library, CL646.