Infectious agents may cause initial damage to the intestine, but actual death from scours usually results from dehydration, acidosis, and loss of electrolytes. Identification of infectious agents which cause scours is essential for implementing effective preventive and treatment measures.

Causes of Scours in Calves

Any type of digestive upset can cause diarrhea in calves. Infectious agents (bacteria and viruses) can attack the lining of the gut, causing water loss through the damaged wall. The known causes of scours are grouped into two categories: (1) noninfectious causes, and (2) infectious causes. The noninfectious causes are often referred to as “predisposing” or “contributing” factors. Whatever they are called, there is a dramatic interaction between noninfectious causes and infection. Any effort to prevent infectious causes is usually fruitless unless serious control of contributing (non-infectious) factors is part of the overall program.

Noninfectious Causes of Scours

Noninfectious causes are best defined as flaws in management which appear as nutritional shortcomings, inadequate environment, insufficient attention to the newborn calf, or a combination of these. The most commonly encountered noninfectious problems include:

• (Inadequate nutrition of the pregnant dam, particularly during the last third of gestation. Both the quality and quantity of colostrum are adversely affected by inadequate intake of energy and protein. 
• Inadequate environment for the newborn calf. Muddy lots, crowding, contaminated lots, calving heifers and cows together, wintering and calving in the same area, storms, heavy snow or rainfall, etc. are stressful to the newborn calf and may increase the chance for easy exposure to infectious agents. The wet and chilled newborn calf can become chilled quickly, become severely stressed and frequently lacks the vigor to nurse in life.
• Insufficient attention to the newborn calf, particularly during difficult birth or adverse weather conditions. The calf is born without scours-fighting antibodies. The calf will acquire these antibodies only by nursing colostrum early in life. Any effort to prevent scours by vaccinating cows is wasted unless the calf nurses colostrum, preferably before it is 2 to 4 hours old. As the calf grows older, it loses its ability to absorb colostral antibodies by the hour. Colostrum given to calves 24 to 36 hours old is practically useless; antibodies are seldom absorbed this late in life.

Infectious Causes of Scours

Infectious causes of calf scours are caused by the following:

• Bacterial (Escherichia Coli, Salmonella spp., Clostridium Perfringens, and other bacteria)
• Viral (Rotavirus, Coronavirus, BVD virus, IBR virus
• Protozoan parasites (Cryptosporidium, Coccidia)
• Yeasts and molds.

Bacteria, such as Escherichia coli and Salmonella, are common in newborn calves (usually younger than 2 weeks old), although Salmonella can affect cattle of any age. Viruses, such as Rotavirus and Coronavirus, commonly affect calves in their first few weeks of life (usually 1 to 3 weeks). Parasites, namely Coccidia and Cryptosporidium parvum, can cause diarrhea in young calves (usually older than 2 weeks old). Calves can be infected with multiple infectious agents at the same time—for example, Rotavirus, Coronavirus, and Cryptosporidia. Some of these organisms can also cause disease in people working with calves.

Treatment of Scours in Calves

Treatment of calves for scours is very similar regardless of cause. Treatment should be directed toward correction of the dehydration, acidosis, and electrolyte loss. The best treatment is prompt and complete and should be aimed at correcting the clinical signs. The most important treatment is to correct dehydration and metabolic acidosis. If they are not corrected, the calf will die. Both are treated simultaneously by administering electrolytes.

• Oral electrolytes can keep acidosis under control in a calf that is strong enough to stand and suckle.
• When the calf is down, oral electrolytes are not enough, and intravenous therapy is needed. Intravenous fluids are necessary to correct acidosis and dehydration in calves at this stage of the disease.
• Systemic (injectable) antimicrobials will help eliminate bacteria but do not work against viruses.
• Keep feeding the calf; milk is its only source of energy. If body cells don’t get energy, the calf will die. If you cannot feed milk, use a good milk replacer. If the calf does not suckle, you will need to feed milk via a tube or administer intravenous therapy.
• Provide supportive care: Protect sick calves from the cold (minimum 50°F), wind, and rain.

Prevention of Scours

Several steps can be taken to help prevent calf scours:

• Ensure that all newborn calves receive colostrum. If the delivery was difficult, the dam may be tired or painful, and the calf may be weakened as well; this may result in a failure of the calf to nurse colostrum. In such cases, it is prudent to milk the colostrum from the dam and feed it to the calf via an esophageal feeder. How much colostrum should a calf receive? The calf must nurse or be given 2 quarts of colostrum during the first 2-4 hours after being born and a total of 4 quarts in 12 hours.
• It is often a good plan to obtain fresh colostrum from a local dairy and freeze it or purchase a colostrum replacer for occasions when the dam does not have colostrum. If sourcing colostrum from a local dairy farm, beware of potential pathogens that can be transmitted through colostrum such as Johne’s disease and Bovine Leukosis Virus.
• Consider a vaccination program for your cow herd. Be sure to consult your local veterinarian about vaccine products and time of administration. Timing is critical as colostral antibodies need to be in adequate concentrations in colostrums to provide ample passive immunity to the calf.
• Maintain a clean calving area. Do not calve on pastures where cows have been kept in large numbers for long periods of time or sours has been recently diagnosed.
• Calve in dry areas and drain pastures or corrals to minimize accumulation of moisture.
• Segregate calves by age to prevent passage of infectious agents from apparently healthy older calves to newborns.
• Maintain adequate protein, energy, and micronutrient nutrition for the dam during gestation.

Supportive Care of Calves

Many products are sold for supportive care of calves with diarrhea. These include gut protectants such as kaolin and pectin, toxin adsorbents such as activated charcoal, and probiotics. Efficacy of these products is debated. They are beneficial only when the three main elements of treatment have been addressed: correcting dehydration and acidosis, treating infections, and providing energy. Not all products—whether electrolytes, antimicrobials, or milk replacers—work the same. Do not mix electrolytes with milk; they may interfere with curd formation and cause diarrhea due to digestive upset, worsening the problem. Ask your herd veterinarian which products are the best for your situation and administer all products according to manufacturer instructions (read the label).

This article also appeared in Mid-America Farmer Grower, February 9, 2018