Assess and treat calf diarrhea

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Dehydration and acidosis are the keys when treating diarrheic calves.Geni WrenDehydration and acidosis are the keys when treating diarrheic calves. Diarrhea increases the loss of electrolytes and water in the feces of calves and decreases milk intake. This results in dehydration, strong ion acidosis, electrolyte abnormalities (usually decreased sodium and increased or decreased potassium), increased D-lactate concentrations, and a negative energy balance (from anorexia and malabsorption of nutrients). Therefore diarrhea is by far the most common indication for fluid therapy in neonatal calves.

Geof Smith, DVM, MS, PhD, Dipl. ACVIM, North Carolina State University, says we see some diarrhea in young calves (around 5 days of age) but it seems like the majority of cases are 7–14 days of age. “There’s a magic window for diarrhea on many dairy farms right around day 8–10,” he says. “You can have diarrhea in older calves — but once we make it past 2 weeks — most farms seem to do okay.” (see “Treatment decision tree,” under Practice tips.)

Best methods for assessment

The most accurate methods for assessment of dehydration in calves are eyeball recession into the orbit and skin tent duration in the neck region. Smith says to gently evert the lower eyelid and estimate the recession of the globe into the orbit. Skin elasticity is best measured on the lateral side of the midcervical area by pinching a fold of skin, rotating it 90°, and measuring the time for the skinfold to disappear.

Geof Smith, DVM, PhD, Dipl. ACVIMWendy Savage, NCSUGeof Smith, DVM, PhD, Dipl. ACVIM Smith adds all other methods of assessment are inferior to these two methods. Those methods include things like mucous membrane color or dryness (how they feel), capillary refill time and packed cell volume (PCV). “These are things commonly used in horses and small animals but don’t seem to work well in calves,” he explains. The best laboratory test is change in plasma protein concentration, which he says is better than hematocrit.

Based on physical exam (eyeball position, depression score) most of the time Smith will go ahead and give oral fluids. “To do lab work you’re going to have to draw blood, drive back to the clinic, run the lab test and then head back out to the farm,” he says. “The main exception is folks that do a lot of haul-in work at their clinic; then lab work is fairly easy to do quickly.” He says a total protein value at a practice is pretty easy to get by spinning down blood and using a refractometer. “But not too many ambulatory vets have a centrifuge in the back of their trucks.”

click image to zoomCalf Dehydration Assessment Chart

Treatment and fluids

Treatment success for diarrheic calves has a lot to do with timing. “Very young calves seem quite fragile and may not respond as well to treatment in general as older calves,” Smith says. “Calves aren’t born with significant energy reserves, so when very young calves get diarrhea, the mortality rates seems to be higher.”

Dehydration and acidosis are the keys when treating diarrheic calves. “In general we will correct electrolyte imbalances most of the time with our standard fluid therapy,” he says. “However, if the acidosis is severe, it will not be corrected by standard oral fluid therapy. Therefore practitioners need to learn to use depression scores or run lab tests.” Smith says there are portable blood gas machines that can be used in the field to determine whether or not a calf has an acidosis. “If a calf has a severe acidosis, it probably needs IV fluids.”

Smith says to determine the most appropriate type of fluid therapy for a calf with diarrhea, we need to know 1) is the calf dehydrated and how severe the problem is and 2) how severe is the acidemia. “If the calf is still standing and has a suckle reflex, I usually only give oral fluids unless the eyes are severely sunken,” he says. “If they are really sunken, I recommend hypertonic saline together with the oral fluids. That will dramatically improve your ability to rehydrate the calf as compared to oral fluids alone.” If the calf won’t stand, then it likely has a moderate to severe acidosis and needs intravenous (IV) sodium bicarbonate to correct this.

Smith will commonly give both oral and IV fluids together to a calf that still has a suckle reflex, particularly if he is using hypertonic saline which corrects dehydration but not acidosis. “It works much better if oral fluids are given at the same time,” he says. Or some farms will use subcutaneous fluids and Smith recommends they use oral fluids at the same time. “The problem becomes when the calf is too sick to absorb the oral fluids,” he says. “This is usually a calf with a severe acidosis that has lost its suckle reflex. It also doesn’t have much gastrointestinal motility and therefore oral fluids aren’t of much benefit.”

Smith usually continues oral fluids after IV fluids based on the calf. “As long as they continue to have diarrhea, they will benefit from oral fluids,” he explains. When the diarrhea stops, the fluid therapy can stop. Be sure to examine these calves at least twice a day to make sure they can still stand and are drinking their milk each day. “Check their hydration status and depression score as well,” he advises. “Sometimes calves will relapse and require further IV fluids.”

The goals of fluid therapy are to replace fluid, acid-base, and electrolyte deficits; and to provide nutritional support. They are indicated in any diarrheic calf that has at least a partially functional gastrointestinal tract. If oral electrolytes are administered to a calf with ileus, the fluid pools in the rumen resulting in bloat and rumen acidosis. In general, a calf with any sort of suckle reflex or that demonstrates any “chewing” action should safely tolerate oral fluids.

Smith says generally oral electrolytes should be fed as an “extra” meal to calves with diarrhea. For example, if calves are normally being fed twice a day (morning and evening), then oral electrolytes can be fed in the middle of the day. If the additional labor required for the extra feeding is not available, then electrolytes can be fed along with milk (particularly those products that contain acetate or very low concentrations of bicarbonate).

The recommendation to temporarily discontinue milk feeding in calves with diarrhea is inappropriate, Smith adds. “Calves should be maintained on their full milk diet plus oral electrolytes when possible. If calves are depressed and refuse to suckle, milk can be withheld for one feeding (12 hours) and a hypertonic oral electrolyte product substituted. However milk feeding should always be resumed within 12 hours.”


Calves with diarrhea have a significantly higher serum concentration of D-lactic acid. Unfortunately the degree of metabolic acidosis is not highly correlated with the degree of dehydration, and cannot be assessed by evaluating eyeball recession or skin tent duration. Methods to assess the acid-base status of calves include blood gas analysis (considered the most accurate and effective method for assessing acid-base status in calves), serum biochemistry and depression scores.

If no laboratory data is available, veterinarians can use clinical signs and age to calculate a depression or demeanor score which can be used clinically to predict the degree of acidosis. In general, metabolic acidosis is more severe in calves less more 7 days of age than in calves less than 7 days of age with same degree of dehydration. Smith stresses that these are only guidelines and are limited to calves with uncomplicated diarrhea. Because of the percentage of calves that have complicating problems (ie. septicemia, hyperkalemia, hypothermia, hypoglycemia, etc), the use of demeanor scores alone can often be wrong. click image to zoomacid-base status of diarrheic calves chart

Oral electrolytes

An oral electrolyte solution must satisfy the following four requirements: supply sufficient sodium to normalize the extracellular fluid volume; provide agents (glucose, acetate, propionate or glycine) that facilitate absorption of sodium and water from the intestine; provide an alkalinizing agent (acetate, propionate, or bicarbonate) to correct metabolic acidosis, and provide energy.

Factors to consider when choosing an oral electrolyte solution include:

Sodium concentration. The ideal sodium concentration is 90 to 130 mM/L. Low sodium oral electrolyte solutions (<90 mM/L) are not recommended because they cannot adequately resuscitate dehydrated calves.

Amino acids. Neutral amino acids such as glycine, alanine or glutamine are necessary to facilitate sodium absorption and provide energy.

Osmolality. A study by Constable (2001) recommended a hyperosmotic oral electrolyte solution (500–600 mOsm/L) if milk is to be withheld or as a supplement to milk given at a different time than the normal feeding (ie. milk in the morning, hyperosmotic oral electrolyte solution at noon, and milk again in the evening). However, if oral electrolyte solutions are to be fed to suckling beef calves or in conjunction with milk replacer in dairy calves, an isotonic solution that does not contain bicarbonate or citrate can be used instead.

Alkalinizing agent. Acetate and propionate are also alkalinizing agents, and are preferred over bicarbonate because they stimulate sodium and water absorption in the calf small intestine whereas bicarbonate does not. Acetate and propionate do not alkalinize the abomasum whereas bicarbonate does — low abomasal pH is a natural defense mechanism against bacterial proliferation. Acetate and propionate inhibit the growth of Salmonella species and produce energy when metabolized; bicarbonate does not.

Psyllium. The addition of psyllium to oral electrolyte solutions actually produces a transient decrease in glucose absorption and is
not recommended as an additive to oral electrolyte solutions.

Strong ion difference. To correct strong ion acadosis, the goal should be to administer an oral electrolyte product with an excess of strong cations (Na+) relative to the concentration of strong anions (Cl-). Some clinicians some have advocated looking at the strong ion difference (SID) of an oral electrolyte solution which can be calculated using:  [Na+] + [K+] – [Cl-] = SID. An oral electrolyte product should contain a minimum SID of 60-80 mEq/L for a dehydrated or depressed calf, though there is no definitive research on optimal/minimum SID.

IV fluid therapy

The major indications for IV fluid therapy in neonatal calves are 1) dehydration, (2) severe depression, weakness, or inability to stand, (3) anorexia for more than 24 hours, and (4) hypothermia <38.0° C in newborn calves. Calves that are recumbent, severely depressed or comatose, and calves without a suckle reflex also need IV fluid therapy. Calves with rapidly progressing dehydration and consistent profuse watery diarrhea should be treated intravenously rather than rehydrated by continuous administration of oral fluids. Geof Smith, DVM, PhD, Dipl. ACVIMCalf on the left (A) has a normal hydration status -- there is no space between the eyelid and the eyeball. However, the calf on the right (B) is severely dehydrated. The eye is sunken at least 7 to 8 mm into the orbit.

Lactated ringers (LRS). LRS can be successfully used to treat dehydration and electrolyte abnormalities in neonates, but it is difficult and expensive to administer in the field.

Isotonic sodium bicarbonate. This is the alkalinizing fluid of choice in calves with severe metabolic acidosis (pH <7.2) and has been proven more effective than other metabolizable bases (such as lactate), bicarbonate precursors, or synthetic bases (i.e. Tris buffer). It can be easily prepared by adding
baking soda (NaHCO3-) to sterile water at 13 g/l (155 mEq/L HCO3-) and administered via an intravenous catheter.

Hypertonic saline (2400 mOsm/L). This can be used to rapidly expand plasma volume in a severely dehydrated calf. When combined with oral electrolyte solutions, it is as effective in resuscitating severely dehydrated calves as large volume LRS administration, is less expensive and easier to administer. Hypertonic saline does not correct acidemia. Hypertonic saline is also indicated for the treatment of hyperkalemia in calves.

Hypertonic sodium bicarbonate. Rapid administration of hypertonic sodium bicarbonate has been shown to be safe when administered to calves at doses of 5-10 ml/kg over 5–10 minutes. It is effective in reversing acidemia and does not cause cerebrospinal fluid pH to decrease (cerebral acidosis) as has long been hypothesized. More studies are needed to determine the effectiveness of this fluid type but it represents a good alternative to isotonic sodium bicarbonate when inserting an intravenous catheter is not an option.

Dextrose. In dehydrated calves a plain 5% dextrose solution is not sufficient to correct extracellular fluid deficits because the solution contains no sodium. To provide energy and rehydrate the neonate, 25 to 50 grams of dextrose or 50 to 100 ml of 50% dextrose solution can be added per liter of LRS or isotonic sodium bicarbonate to make a mildly hypertonic solution.

Smith says the perception may be that older calves respond to treatment better sometimes than younger calves. But, he says, “Both age groups will respond to therapy as long as we catch the diarrhea early and get treatment started in time.”


Common fluid therapy mistakes

Fluid therapy can be critical to saving diarrheic/dehydrated calves, but common mistakes can be made when administering it.

Geof Smith, DVM, MS, PhD, Dipl. ACVIM, says one mistake is that diagnosis of diarrhea is not made fast enough and/or fluid therapy is not started in time. “Calves are dead or severely dehydrated/recumbent before fluids are started,” he says. “These calves become much more difficult to treat and are less likely to respond.”

Train calf feeders to look for diarrhea as well as other abnormal clinical signs (sunken eyes, calf that won’t drink milk, calf that doesn’t get up, etc).

“Catch sick calves quickly and treat promptly to increase success rates,” Smith says.

Another major problem is not being aggressive enough with fluid therapy and not giving enough fluids (volume) or not giving the right kind of fluids. Smith says an example is a calf with a severe metabolic acidosis that needs sodium bicarbonate. “Some veterinarians will give hypertonic saline because it’s easy to administer, but it won’t correct acidosis,” he says. “Or some producers will give 1–2 liters of IV fluids to a calf that needs 3–4. Oral treatment when IV is needed also falls into this category.”

Producers who stop feeding milk for more than 24 hours to a calf with diarrhea are also at an increased risk for treatment failures (calves not responding to therapy). “Glucose concentrations drop in these calves and they just get too weak,” Smith says.

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