Although generally easy to treat, neonatal calf diarrhea is still a major cause of death and economic loss in the dairy industry. The use of oral rehydration for treatment is limited when farm protocol is lacking. Farms should have a standard operating procedure for treatment of scouring calves that includes when to use oral rehydration solutions, how much to give and other care issues.
Oral rehydration solutions, or electrolytes, replenish fluids and electrolytes lost during episodes of diarrhea. Oral rehydration therapies are used to improve acid-base balance by providing electrolytes and water. Many brands of electrolytes are commercially available; however, products are variable and the right one needs to be chosen for each individual dairy.
A recent survey of US calf mortality found an average of 8.7% annually, 62.1% of that due to scours (NAHMS, 2002). In past surveys, mortality due to scours averaged 60.5% in 1996 and 52.5% in 1991, indicating an expanding problem in the US dairy industry.
Causes of scouring
Scouring in neonatal calves has two causes: nutritional and pathogenic. Causes of nutritional scours can include changing milk replacer brand, changing from waste milk to milk replacer, transport, weather, vaccinations, dehorning, etc.
Nutritional scours are caused by stress and are usually temporary. Because there is minimal damage to the intestinal villi, the calves’ condition can improve even without treatment by removing the source of stress. However, nutritional scours can cause as much water loss and dehydration as pathogenic scours; these calves should be monitored closely and possibly treated, especially if young.
Virtually any bacteria or virus found on a farm can cause pathogenic scours. Calves begin showing clinical symptoms between one and three weeks of age. Infection can occur from contact with other calves, farm workers, or environment. Common causes for pathogenic scours include rotavirus, coronavirus, E. coli, salmonella and cryptosporidia. After birth, passive immunity is provided by colostrum; however this immunity decreases while the calf’s immune system develops. Calves become vulnerable to infection when passive immunity has decreased but their own immune system has not yet fully strengthened.
When should you treat with electrolytes?
Calves can lose 5 to 10% of their bodyweight as water within 1 day of scouring. Fluid loss in excess of 8% requires IV treatment, and over 14% loss can result in death. This makes daily calf monitoring and quick treatment essential. The amount of water lost by scouring calves can estimated by skin tenting, gum condition, attitude, and ability to stand or suckle (Table 1).
Clinical symptoms that help evaluate amount of dehydration in calves.
|Degree of dehydration
||Diarrhea, no clinical signs, strong suckling reflex
||Mild depression, skin tenting 2-6 seconds, calf still suckling, sunken eyes, weak
||Calf depressed, laying down, eyes very sunken, dry gums, skin tenting >6 seconds
||Calf will not stand, cool extremities, skin won’t flatten when tented, comatose
Adapted from J. M. Naylor, Can. Vet. J. (1989).
To evaluate hydration using skin tenting, pinch a fold of skin (best done on the neck) and count the seconds it takes to flatten. Flattening of skin in less than 2 seconds indicates normal hydration. If skin takes 2 to 6 seconds to flatten, the calf is about 8% dehydrated. Over 6 seconds indicates severe dehydration above 10%. Gums are evaluated by color and moisture. Normal gums should be pink and damp; gums that are white and dry indicate 8 to 10% dehydration. One of the best estimates of dehydration and illness in calves is their attitude during milk feeding. Calves may show no symptoms of dehydration but if they need encouragement to drink, they should be monitored closely for scouring or other illnesses.
Protocols for managing sick calves are critical to consistency. Because water loss in calves occurs rapidly, all employees must be able to diagnose and treat calves quickly and efficiently to prevent mortality. Evaluation of calves should include scores given for scours, respiration and appearance.
Scoring of scours can be based on a 1 to 4 or 5 scale.
- The lowest number is better, so a 1 should be normal feces, with the consistency of pudding.
- A 2 should be slightly less firm, such as yogurt.
- A 3 should be considered scours and have the consistency of syrup, loose to watery with a strong odor.
- With a 1-4 scale, a 4 can then be anything more fluid than syrup, such as water. For a 1-5 scale, a 4 should have the consistency of fruit juice, with fecal matter still visible.
- A 5 should be the consistency of water with no fecal matter or with mucous and/or blood.
Respiration should be scored on a 1 to 5 basis.
- A 1 is normal breathing, no problems.
- A slight cough, runny nose but regular breathing is Score 2.
- A 3 should have a moderate cough and rapid breathing.
- A 4 should have a severe cough that is frequent with rapid breathing.
- A 5 should have a severe cough that is chronic with irregular breathing.
Appearance scores should range 1 to 5
- with a 1 being alert and active.
- A 2 should have droopy ears and be slightly unresponsive.
- A moderately depressed calf with head and ears drooping is score 3.
- A 4 should be depressed with drooping ears and head and no interest in getting up.
- And a 5 should be flat on its side.
A calf’s scores should be totaled daily. When scores reach a threshold value, the protocol should consist of taking a temperature reading, treating with oral rehydration solution and/or giving antibiotics. This will ensure proper, consistent treatment for all calves and should decrease mortality.
Calculating the amount to feed
Although there is little detriment in feeding excess oral rehydration solution, feeding too little may not alleviate dehydration and can prolong scouring. Although individual calf weights may not be available, approximate amounts to feed should be established. For example, small calves (or breeds other than Holstein) can be estimated at 60 lbs and fed less than high birth weight calves (110 lbs) or even medium size calves (80 lbs). To estimate how much to feed a calf:
- Multiply weight of calf by (dehydration percent/100). This will give you the pounds the calf needs to drink IN ADDITION TO ITS MILK OR MILK REPLACER FEEDING.
Then divide by 2 to get quarts of liquid needed.
- Example: A 100-lb calf is dehydrated 6%.
100 × 0.06 = 6 lb. 6 lb/2 = 3 quarts to be fed per day in addition to her usual milk
Should milk be fed while calves are scouring?
Different methods are used in feeding milk or milk replacer while feeding oral rehydration solution to scouring calves. Some cease milk feeding completely and only feed oral rehydration solution for the entire treatment period. Another method is to feed only oral rehydration solution for 2 days then feed half and half with milk the last day. And the third way is to feed the rehydration solution and milk as well in separate feedings.
Calves need enough energy to maintain their weight as well as their immune system, especially when they are sick. Oral rehydration solutions cannot provide enough energy because they are limited in the amount of glucose that can be added in order to keep the osmolarity of the solution low.
Therefore, feeding milk or milk replacer increases energy and protein intake, allowing calves to maintain weight. The benefit of milk feeding while treating with rehydration solution was shown (Garthwaite et al., 1994). Once scouring occurred, calves received one of three treatments. Treatment 1 was rehydration solution alone for 2 days, after which milk was slowly incorporated back into the diet for 7 days. Treatment 2 consisted of a partial removal of milk during therapy, and treatment 3 was a full feeding of milk as well as rehydration solution for 7 days. Fecal scores did not differ between treatments and bodyweights were higher for treatments that included milk and oral rehydration solution, especially the treatment with a full feeding of milk for the entire treatment period.
Should antibiotics be given?
If scouring becomes a regular occurrence a veterinarian should be consulted to determine the source and whether antibiotics are appropriate. Also, a few fecal samples should be taken and sent to a diagnostic lab to evaluate the cause of enteric infection. This may help establish a preventative program and save time and labor in treatment of scouring calves
What should the oral rehydration solution contain?
Oral rehydration solutions used for treatment of scouring calves are different from those used for electrolyte supplementation. The latter provide supplemental electrolytes to older, usually weaned, calves or cattle during times of stress from transport, weather or other situations likely to cause loss of fluids and electrolytes. It is easy to confuse the 2 types of product; however, if the directions require small amounts of powder being mixed into gallons of water, this indicates that the solution is only supplemental and should not be used for treatment of scours.
One of the most important components of oral rehydration solutions is water. Water is the essential ingredient in any rehydration solution.
Sodium should be included in the solution at 70 to 145 mmol/L. Sodium is tightly regulated by the body; both low (from diarrhea, for example) and high levels of sodium in the body can cause problems. Excess sodium means calves will need to drink more water to dilute the sodium; extra water may not be available or the calf may be too weak to reach it. Sodium should be at an average ratio of one to one with glucose to be absorbed efficiently.
Glucose serves as an energy source (dextrose may be listed this is just anonther name for glucose). Glucose is transported into the intestine on a one to one ratio with sodium, helping sodium absorption. However, no more than 200 mmol/L should be included because this may change the osmolarity of the solution. A solution with high osmolarity will draw water out of the intestine instead of into it in order to equalize osmolarity on both sides of the intestine.
Glycine is a non-essential amino acid that is commonly added to oral rehydration solutions to enhance absorption of glucose. To calculate the amount that should be included, the levels of glycine and sodium should be added and the total should not exceed 145 mmol/L. The total of glycine and sodium should also equal the glucose level.
Alkalinizing agents are added to decrease metabolic acidosis and may also provide some energy. They are usually attached to sodium and include bicarbonate, citrate, lactate, acetate or propionate. One of the most common alkalinizing additions is bicarbonate, which should be fed about 4 hours after milk feeding. Bicarbonate and citrate inhibit casein curd formation in the abomasum. Acetate is the most easily metabolized. Alkalinizing agents should be included at 50 to 80 mmol/L.
Oral rehydration solutions will also contain other electrolytes, especially potassium and chloride, as well as many minerals. Potassium and chloride are needed to maintain pH of the blood and for muscle contractions, especially in the heart. Although little research has concentrated on evaluating amounts of potassium and chloride needed to replenish electrolytes in scouring calves, the range of potassium found in most solutions is 20 to 30 mmol/L and chloride is 50 to 100 mmol/L.
Other additions can include gelling agents such as guar gum, pectin and others. These have not been shown to be largely beneficial nor detrimental. Oral rehydration solutions containing gelling agents reduce diarrhea within hours of feeding and may coat inflamed intestinal mucosa. Slowing down the passage rate of the rehydration solution also may allow the intestine to absorb more nutrients. However, this may also reduce the body’s ability to flush toxins out.
Many rehydration solutions add direct-fed microbials. These bacteria are meant to re-establish the correct ratios of gut microflora. Usually these probiotics consist of lactobacillus and bifidobacterium species, both of which work against E. coli and benefit the intestinal environment. No published research has yet evaluated direct-fed microbials in rehydration solutions. An oral rehydration solution should be chosen based on its ability to provide correct levels of electrolytes and to rehydrate rather than whether it contains microbials.
Making your own oral rehydration solution
Although making your own oral rehydration solution can be relatively simple if all the ingredients are available, it is easier to buy one that is already made up correctly.
If you are in a bind and need to make your own, remember not to use table sugar for the glucose portion of it. Table sugar, or sucrose, is a carbohydrate that cannot be metabolized by cattle because they do not have the enzyme to break it down. Adding sucrose may actually increase scouring and worsen dehydration.
Feeding calves plain water does not work either when the calf is infected with a virus or bacteria that have affected absorption in the intestine. Water “follows” sodium into the intestine and therefore, both sodium and glucose need to be present for maximal water absorption. It is always best to have an oral rehydration solution on hand to treat scouring calves.
Homemade example for an oral rehydration solution from Feeding the Newborn Dairy Calf (1984):
1 tsp. low sodium salt
2 tsp. baking soda
1 ¾ oz. (1 packet) fruit pectin
1 can beef consommé
Add water to make 2 quarts. Feed at the rate of 1 pint per 10 pounds of bodyweight 3 to 4 times a day. Feed milk 2 to 3 hours before or after due to bicarbonate content.
It can be difficult to compare oral rehydration solutions because of differing units. Most solutions are expressed in percents; however others are expressed in mmol/L, mg/ml or µEq. For ease of determining the quality of oral rehydration solutions, a conversion table is provided (Table 2).
To calculate from g/L to mmol/L, the molecular weight of each ingredient needs to be known. Take the amount given and then divide by the respective molecular weight and multiply by 1000 (which will convert from mol to mmol). For example, if there is 3 g/L of sodium divide by 23 and then multiply by 1000. This equals 130 mmol/L.
Other molecular weights are given below. Converting grams or percent to mmol/L is the best way to compare whether ratios of sodium to glucose are approximately one to one.
Requirements of ingredient concentrations included in oral rehydration solutions in different units.
||50 - 80
||4.2 - 6.7
||50 - 80
||14.7 - 23.5
||50 - 80
||6.8 - 10.9
||20 - 30
||0.8 - 1.2
||50 - 100
||1.8 - 3.5
* Molecular weight in grams per mole.
Useful conversion: 1 quart is approximately 1 liter (0.95 L).
Garthwaite, B. D., J. K. Drackley, G. C. McCoy, and E. H. Jaster. 1994. whole milk and oral rehydration solution for calves with diarrhea of spontaneous origin. J. Dairy Sci. 77:835–843.
Naylor, J. M. 1989. A retrospective study of the relationship between clinical signs and severity of acidosis in diarrheic calves. Can. Vet. J. 30:577–580.
USDA. 2002. Part I: Reference of dairy health and management in the United States, 2002.
Wattiaux, M. A. Heifer raising - birth to weaning. Neonatal diarrhea. Babcock Institute for International Dairy Research and Development. 2005. University of Wisconsin- Madison.
Condensed by Milkproduction.com staff from DAS 05-104 by Sylvia Kehoe and Jud Heinrichs, The Pennsylvania State University, USA