Calf scours. Two words that even the most experienced cattleman dreads to hear during the calving season. I've read articles that name calf scours as the single most important cause of early calf sickness and death. It is unlikely that any single factor brings about calf scours. Likewise there is no single "silver bullet" medication or vaccination that will stop or prevent calf scours. Prevention of calf scours or minimizing the occurrence of calf scours depends upon management. Proper management depends upon understanding the complexity of calf scours and how various factors interconnect.
In plant pathology, we talk about the disease triangle; 3 conditions that are necessary for a disease to develop and manifest symptoms. We can use the same concept to help explain how calf scours develop and the severity of calf scours. The three sides of this disease triangle are: a susceptible animal, the disease organism, and environmental conditions conducive to the disease. When all three sides of the triangle are present, calf scours is going to appear and is likely to be severe unless quick action is taken. Let's examine each of the triangle sides in a little more detail.
There are factors that will pre-dispose a calf to scours. Some of those factors include: a difficult birth, poor nutrition of the mother cow, poor health of the mother cow, and slow and/or low intake of colostrum by the calf. When a cow is in a state of poor nutrition or poor health colostrum quality and milking ability are affected. This has a negative impact on calf health. Remember that a calf is born without a functioning immune system. Immunity and resistance to disease is passed on through the colostrum of the mother. The calf must ingest colostrum shortly after birth and in sufficient quantity to gain this passive resistance.
There are a variety of infectious agents or disease organisms that can cause calf scours. They may be classified as bacteria, viruses, or protozoa. The most common bacteria associated with calf scours is E. coli (Escherichia coli). These bacteria produce toxins in the intestines that damage the cells to the extent that fluids are lost, leading to the symptoms of diarrhea. E. coli related calf scours generally appears with very young calves, developing as soon as 16 to 24 hours after birth. The most common viruses responsible for calf scours are coronavirus and rotavirus. Both of these viruses will infect cells that line the digestive tract and damage those cells so that milk can not be digested or absorbed. Again the symptom is diarrhea. Generally when these viral agents are the cause of calf scours it appears when the calves are near a week of age or older. Another causal agent is protozoa, possibly cryptosporidium or coccidia. Once again, the cells lining the digestive tract are affected, leading to decreased digestion and absorption of milk along with diarrhea. Calves infected with cryptosporidium are generally in the one to three week age range. While coccidiosis is more often seen in weaned calves it can be associated with calf scours in calves at three to four weeks of age, particularly if those calves are under some kind of stress. It should be noted that it is possible that an outbreak of calf scours could be the result of mixed infections involving a combination of infectious agents.
Environmental factors can play a big role in the development of calf scours. Mud, heavy snow, cold temperatures and rain can all be stressful to a newborn calf. Each one alone, or especially in combination, can decrease a calf's resistance to disease. Other environmental factors that can set up an outbreak of calf scours include overcrowding, contaminated lots, calving heifers and cows together, wintering and calving in the same area. These are all conditions that increase the calf's exposure to infectious agents that cause scours.
While knowing the cause of the scours outbreak and the disease organism responsible for the outbreak may be helpful for future management intervention, the treatment is similar regardless of the cause. 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.
Antibiotics and sulfa drugs are commonly given as an oral treatment to calf scours, but 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."
Prevention or minimization of scours on the farm depends upon management. Here are some key management practices to keep in mind:
* Provide good nutrition to pregnant cows. The last trimester is especially crucial. Remember that heifers that have not reached their full adult size have an additional nutritional requirement for growth. Cold and/or wet weather can increase the energy requirements. Failure to meet nutritional requirements will result in a weak calf at birth, predisposed to early calf hood disease.
* Calving Management. If at all possible, heifers should calf in advance of the cow herd and preferably in a separate location. Cows should be managed to minimize the transmission of scours causing organisms. The "Sandhills Calving System" serves as an example. In this system calves are segregated by age so that older calves don't pass germs to younger calves and pregnant cows are regularly moved to uncontaminated calving pastures. When the first calf is born, all cows are moved to the first calving pasture. Calving continues in this pasture for two weeks and then the remainder of the pregnant cows are moved to the second calving pasture while the cow/calf pairs remain in this first calving pasture. Thereafter, in each subsequent week the pregnant cows continue to move to a new calving pasture while cow/calf pairs remain in the pastures where they have birthed.
* Minimize environmental stress. Strive to provide a dry, clean environment for the calf to be born into. Provide protection from the wind in the form of windbreaks during severe cold weather. Minimize calf exposure to mud and manure.
* Care of the newborn calf. The single most important factor is that the calf ingests colostrum soon after it is born. All other prevention management becomes much less effective if this is not accomplished. The calf should ingest 5-6% of its body weight in colostrum within 6hours after birth. As a secondary factor, most newborn calves may benefit from a Vitamin A injection early in life to boost resistance to scours.
* Vaccination. While there is no universal vaccination program, there are some effective scour vaccines that are available. Vaccines are not a replacement for other good management practices, particularly colostrum ingestion. They can be another piece in a scours management package.
Scours outbreaks can be devastating. Understanding the factors that come together to bring about an outbreak is a step in developing a management plan to minimize the occurrence and severity of calf scours during the calving season.
Calf Scours: Causes and Treatment. Hanson, D. Beef Cattle Handbook, BCH-3056
Calf Scours: Causes, Prevention, Treatment. Stoltenow, C., Vincent, L. North Dakota State University Extension publication AS-776
Calf Scours Simplified. Bagley, C. Utah State University Extension Animal Health Fact Sheet AH/Beef/25
Sandhills Calving System Prevents Diarrhea. University of Nebraska-Lincoln Veterinary Extension Timely Topics
EDITOR's NOTE: Many of the concepts discussed above, primarily those relating to the long term benefits of good cow and calf nutrition, will be a focus of the 5 part Ohio Beef School being hosted in 17 Ohio Counties on consecutive Thursday's beginning February 3. Find details, and a current listing of the host sites in the December 8, issue # 714, of the Ohio Beef Cattle letter.