Start Now to Avoid Calf Scours Next Spring

January 2010

Calf Scours, or neonatal calf diarrhea, is a problem experienced by most every cowman sooner or later. It is quite possibly the biggest health related financial loss to the cow calf industry. It is easy to recognize the impact that dead calves and increased cost of medical treatment has on the bottom line, but poor performance is an even greater though less noticeable loss. A Colorado study shows that calves that experienced calf scours and recovered had a 23 pound lower average weaning weight than their herd mates who did not experience difficulty. Other studies have shown that the loss of performance carries through the stocker and feedlot phases of production. When scours hits a herd at calving time it is too late to avoid the financial setback. Prevention consists of an all-year management plan to enable newborns to deal with the challenge when they have to face it.

It is important to understand that calf scours is not a specific disease, but a clinical sign that can be caused by many different infectious agents and several predisposing factors. Scours results in dehydration, often severe and non-reversible, due to the failure of absorption of water and electrolytes from the gut and increased secretion of water into the gut. The bacterium E. coli causes scours during the first few days of life, while Roto virus, Corona virus and Cryptosporidium cause problems between 7 and 21 days of age. Other organisms can cause infections also but the mechanism is about the same no matter what agent or agents are involved.

Three things determine the eruption of clinical disease

Three things determine the eruption of clinical disease: 1) Exposure rate or the number of organisms impacting the calf, 2) calf immunity levels, and 3) stress on the calf. These are all variables that can be influenced by management. Disease will occur any time the exposure rate exceeds the calf's immunity level. Exposure rate is basically a summary of each herd's sanitation conditions. Too often we actually "kill 'em with kindness" when we bring cows into confinement or small calving pastures to calve. The cleaner the area where the calf is born, the less exposure there will be. Calves are exposed with organisms primarily by fecal – oral transfer but in the case of E. coli, exposure can also be through the navel at birth. Since the organisms live for several months in the guts of calves that survive a slight infection, older calves play a role by passing the organisms to their younger siblings. Move older calves and their dams to other areas and do not allow calves of various ages to share the same environment.

Calf immunity is from passive transfer of antibodies from the dam. Since calves are unable to receive antibodies in the uterus, they must rely solely on colostrum and they need to receive sufficient quantities in the first few hours of life. Graph 1 shows how the calf's ability to absorb these complex immunoglobulins starts to decrease soon after birth. (Source: Besser and Gay, 1994. Vet. Clinics of North Amer.)

[chart not available, 5/1/14]

In another experiment, calves that received 2 liters of colostrum within 4 hours of birth had 3 to 4 times greater serum levels (15 mg/ml) of immunoglobulin G (IgG) than calves that only received a ½ liter of colostrum (5 mg/ml) and nearly twice as much IgG in the serum as calves that received 1 liter of colostrum. Again in this experiment, the amounts of serum IgG decreased linearly as first feeding of colostrum was delayed from birth to twenty four hours of age.

Table 1 shows the delay in first nursing when cows have pendulous udders, and as we have seen above, time to first nursing is of the essence.

Culling cows with bad bags is a management tool that can go a long way towards preventing calf scour cases. Not only are their calves more at risk, but more affected calves means more calves shedding organisms that contribute to the exposure rate and affect all of their siblings. In herds with a history of problems cow vaccination programs may be helpful by elevating the amount of immunity transferred in colostrum. Cows should be vaccinated with a scour vaccine product 6 to 8 weeks before calving and then given a booster 3 weeks prior to calving. In cows that have previously received scour vaccine, the circulating antibody level and thus the colostrum antibody levels reaches it's maximum elevation about 3 weeks after vaccination. Antibody preparations are available for oral administration to newborn calves but they are expensive and of questionable value in that they do not offer protection against all possible causative organisms.

The third consideration is stress. Anything that stresses the calf increases the likelihood of scours by decreasing the tissue's ability to resist invasion. Stress factors can be classified as nutritional, environmental, or social. Poor cow nutrition results in poor milking and subsequently nutritional stress in the calf due to low energy level and metabolic rate. Nutritional deficiency in the dam, especially mineral or protein deficiency, also results in problems by depressing their immunity and the immunity they pass to the calf. Newborn calves are stressed more by inclement weather than older animals because for the first hours of life they cannot regulate their body temperature effectively. Colostrum deprivation is a triple threat because colostrum not only provides the total available immunity but also provides easily absorbed nutrients and helps to warm the newborn. Social stress is often due to overcrowding, which also raises the exposure rate, or separation of the newborn from his mother.

Treatment of scours consists of rehydrating the calf with electrolyte solution and treating with antibiotics to prevent the infection in the gut from entering the bloodstream. It is important to use a drug that is labeled for calf scours to ensure that it is effective in the gut and to prevent liability due to drug residues. Calves that have loose stools but are zipping around the pasture with their tails up do not need treatment. The decision to treat should be based on the degree of depression, loss of appetite, dehydration and elevated body temperature. Perhaps the most important decision is determining when to seek help. If over 5% of the calves are needing treatment, or death loss due to scours is running over 2%, it is time to get help from your veterinarian.

Like many health challenges, calf scours is better prevented with a comprehensive management program than treated. Treatment may help with recovery of individual cases but it is a lot like "shutting the gate after the cows are out" when it comes to avoiding economic losses.

Dr. Glenn Selk, Professor-Animal Reproduction Specialist
Animal Science - Oklahoma State University, Stillwater, OK