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Treatment of the Calf with Diarrhea
Abstract
from the colostrum as well as that actively produced by the calf itself; irregular feeding or overfeeding; the degree of confinement and crowding, which determines the pathogenic challenge to which the calf is exposed; and a multitude of stress factors such as inclement weather and difficult birth.
Calf scours may affect calves up to two months of age, but it is generally the greatest problem in calves less than two weeks of age, and frequently occurs in those less than one week old. In contrast, coccidiosis is more common in older calves and is generally hemorrhagic. Clostridial enterotoxemia causes sudden death more commonly than it causes diarrhea. Although large numbers of clostridia are present in the small intestine of some calves with diarrhea, they may not be the primary pathogen; therefore, their presence does not confirm clostridial enterotoxemia as the cause of the diarrhea. Salmonellosis occurs most often in calves two weeks to four months of age that are debilitated, stressed, and under close confinement. In some areas it may be endemic and therefore may be the most common cause of diarrhea in those calves. However, in most areas, calf scours is by far the most common cause of diarrhea in the calf. Frequently, the primary etiologic agent is not identified.
The two clinical forms of enteritis in the calf are septicemia endotoxemia and diarrheal dehydration. The septicemic-endotoxemic form is most common in calves that have been deprived of colostrum and occurs most commonly in the first few days oflife. This form of the disease has an acute, fatal course. Afflicted calves are often found dead without ever having been observed to be sick, and even before diarrhea has occurred. They account for less than 10 per cent of the cases reported, although in some herds, this form of the disease may be more prevalent.
The most common clinical manifestation of enteritis is diarrhea which results in extensive losses of fluids and electrolytes. These losses and their effects have been described in detail elsewhere 6 and are quite similar regardless of the causative agent. Therefore, the treatment of the calf with diarrhea is also quite uniform regardless of the etiology of the disease.
The most important aspect in the treatment of the diarrheic calfis the administration of fluids to replace the extensive losses of water and electrolytes that occur and which are responsible for the clinical signs and potential death of the calf. These fluids should also supply energy, particularly in patients requiring more than one or two days of treatment, since anorexia often accompanies the disease. Optimal administration of fluids requires familiarity with several general principles of fluid therapy. In addition, the selection of the route and rate of administration of fluids and the type of fluid used is based upon the acuteness of the illness and the degree of dehydration.
The degree of dehydration is best estimated from the clinical signs described in Table 1 . The amount of fluid needed as well as the condition of the animal can be determined from the degree of dehydration. For example, if a 30 kg calf is 10 per cent dehydrated, the amount of fluid needed to correct this dehydration is 30 kg times 10 per cent, or 3 liters.
Although the hematocrit and plasma protein concentrations increase linearly as diarrheal dehydration in the calf progresses,6 they are poor indicators of the degree of dehydration. Both parameters may vary widely in normal calves;6 therefore changes from an average value may be meaningless in any individual animal. However, changes in hematocrit and plasma protein concentration as well as in body weight are quite useful in determining whether fluid therapy is correcting the dehydration and compensating for the continuing loss of fluid. Weighing the patient periodically is one of the simplest and most reliable modes of assessment; it is also the most frequently overlooked method.
All fluids, regardless of the route of administration, should always be administered at body temperature. Warming cold blood to body temperature prior to massive blood transfusion decreased the incidence of cardiac arrest from 58 per cent to 7 per cent in one study in humans. 2 Ringer's lactate solution given intravenously at 5°C to five dogs in hemorrhagic shock resulted in three deaths. However, when five dogs with a similar blood loss were given the same amount of fluid warmed to body tempera- ture prior to administration, no deaths occurred. 2 Cold fluids given intravenously have a direct effect on the sino-atrial node, decreasing heart rate, cardiac output, blood pressure, and coronary artery flow, and causing death from arrhythmia and diminished contractility.2 Cold fluids given by nonintravenous routes are absorbed more slowly than are warm fluids.
Oral. Oral administration of fluids is always the route of choice in the treatment of the diarrheic calf, unless the condition is so acute that intestinal absorption is not rapid enough to keep up with losses of fluid or unless the animal is too severely dehydrated. If the animal is more than 6 per cent dehydrated or if the disease is fulminating, fluids must be given parenterally (Table 1 ). In these cases, however, giving fluids by both routes is beneficial and lessens the amount of fluids that must be given parenterally.
Oral fluid therapy has several advantages over the parenteral administration of fluids: the ability to give large volumes rapidly; a sustained input as fluids are absorbed; a lesser expense since the fluids need not be sterile and may be given by the owner; a less critical composition of the fluid compared with fluids given parenterally; and the relative safety of this route.
For best results, fluids administered orally should be formulated to afford the maximal rate of intestinal absorption. This is accomplished by using fluids which contain proteins or amino acids, glucose, sodium, and bicarbonate. These solutes have a synergistic effect on the rate of intestinal absorption of each other and, therefore, of water. 7 For example, the rate of intestinal absorption of sodium is greatly increased if glucose is present; conversely, the rate of intestinal absorption of glucose is more than doubled if sodi)1m is present. Of course, through salivary, pancreatic, and hepatic secretion, some sodium is always present in the intestine, but the quantity may not always be sufficient for maximal rates of absorption to occur. Absorption of water is passive; as solutes are absorbed, it is absorbed. Thus, to obtain the maximal rate of water absorption a fluid designed to attain the maximal rate of solute absorption is required. A number of fluids designed for this purpose are available commercially* or can be formulated as shown in Table 2 . Oral fluids constitute excellent media for microbial growth and are nonsterile; therefore, after use, the remainder should be refrigerated and, if not used within one to two days, it should be discarded.
The energy, amino acids, and proteins derived from oral fluids have a dual purpose. They not only enhance intestinal absorption but they also *Life Guard Oral-Norden Labs, Lincoln, Nebraska; Resorb-Beecham-Massengil, Bristol, Tennessee. assist in the nutritional maintenance of the animal. Although the energy and protein that most oral fluids provide are certainly of benefit, they are not sufficient to meet the animal's requirements. Therefore, additional energy must be provided if more than two days of therapy are required. Although the administration of oral fluids may increase the loss of fecal fluid, this does not negate their benefit. Their use will either reduce the net loss of water from the body or will result in a net gain of water. This is demonstrated in the example shown in Table 3 , in which, prior to receiving oral fluids, the calf had a net water loss and a decrease in body weight of I kg per day. When oral fluids were given, fecal losses doubled, but the calf then had a net water gain and an increase in body weight of I kg per day. Weighing the patient eight hours or so after administration of oral fluids will confirm whether or not the fluids given orally or by any other In preruminant calves and lambs, suckled fluids will bypass the rumen and reticulum and go directly into the omasum and abomasum. Nursed fluids, therefore, reach the intestine more rapidly than those given by stomach tube and are absorbed.more quickly. Thus, the calf should first be encouraged to nurse as much fluid as possible. The remainder of the fluids needed may be given by stomach tube. Most of the fluid administered by stomach tube is deposited in the rumen and takes longer to reach the intestine where absorption occurs. In some cases, this may be of benefit in providing a more prolonged therapeutic delivery.
The subcutaneous route of fluid therapy is quite useful in animals other than the horse and pig which lack sufficient subcutaneous space for the administration of significant volumes by this route. Fluids given subcutaneously are absorbed in four to six hours following administration. They provide a slow but sustained delivery of fluid during this period, which may be adequate iflosses of fluid from the body are not occurring faster than the rate of absorption. In more severe cases, the subcutaneous administration of fluids in conjunction with intravenous fluids may be quite beneficial and may lessen the amount of fluids that must be given intravenously. If the degree of dehydration is greater than 8 per cent, peripheral circulation is decreased to the extent that fluids given subcutaneously will not be absorbed or will be absorbed more slowly. After correcting dehydration, the continued absorption of additional fluids given subcutaneously can help in replacing continuing losses.
Fluids given subcutaneously should be sterile and warmed to body temperature. They should be from 1 to 1 Y2 times isosmotic. Electrolytes should be Y2 to 1 times isosmolality; they may contain from 0 to 2Y2 per cent glucose and generally contain at least 70 mEq per liter of sodium (Table 4 ). If their content varies from this formula, they will draw fluids or electrolytes out of the blood and may worsen the condition, at least initially. Addition of Ringer's lactate solution is often used to treat acidosis; the lactate must be metabolized to be effective, however. In the diarrheic calf, more lactate is present than can be metabolized as indicated by an increase in plasma lactate levels. 6 In addition, half of the lactate in lactated solutions is the D-isomer. Only the L-isomer is normally metabolized in the body. The D-isomer is poorly metabolized even by healthy animals. Thus, it is better if a lactate solution is not used for the treatment of the diarrheic calf. Based on existing data and clinical results, Ringer's bicarbonate is recommended instead. However, if Ringer's bicarbonate is not available, Ringer's lactate, acetate, or gluconate may be used. The following should be added to any of these fluids used:
For the calf that is dehydrated 8 per cent or more (Table 1) , 20 mEq of potassium chloride, 50 mEq of sodium bicarbonate, and 120 ml of 50 per cent glucose or dextrose solution should be added to the first liter of fluids given intravenously.
To any additional fluids given intravenously, to all fluids given subcutaneously, and for the calf that is less than 8 per cent dehydrated, 10 mEq of potassium chloride, 25 mEq of sodium bicarbonate, and 50 ml of 50 per cent glucose or dextrose solution should be added to each liter.
If Ringer's bicarbonate, acetate, gluconate, or lactate are not available, mix equal parts of a 5 per cent glucose solution either with isotonic saline or Ringer's . solution. Then add the same amount of potassium chloride, 25 mEq per liter more sodium bicarbonate than that given in either case mentioned above, and omit the glucose.
The easiest way to add the potassium chloride and sodium bicarbonate is to inject the correct number of milliliters of a concentrated solution of these substances into the fluid used. Ringer's lactate solutions often contain calcium, and therefore should be administered immediately after adding sodium bicarbonate. If this is not done, the calcium will combine with the bicarbonate to form a precipitate. It takes two to three hours for the precipitate to be seen.
In the treatment of severe, acute diarrhea, orally administered antimicrobial drugs are often of questionable value. Controlled studies have failed to show benefit or harm from the oral administration of a number of different antimicrobial drugs in the treatment of acute undifferentiated diarrhea in the calf.8 In some bacterial cases of diarrhea, normal intestinal flora have been shown to be instrumental in clearing enteropathogenic organisms from the intestinal tract. Therefore, antibacterial suppression of the normal flora may succeed only in prolonging the disease without affecting the signs.
It is also difficult to determine to which antibacterial drug the actual enteropathogenic agent is sensitive. If the diarrhea is vir ally induced, as many are, none of the antibacterial agents is effective, but they may be effective against secondary opportunistic bacteria such asE. coli. In vitro determinations of antibacterial sensitivities to fecal swabs may show little or no correlation to the actual sensitivity in the calf. If the calf is still getting milk, tetracyclines will be bound to calcium, decreasing their effectiveness despite the fact that the causative agent may be sensitive to tetracycline. If given in conjunction with intestinal adsorbents, antimicrobial drugs may be bound to the adsorbent with subsequent decreased effectiveness.
However, the clinical impressions of many have indicated that oral antibacterial drugs are of benefit in the treatment of acute, severe diarrhea in the calf. If used at all, they should be restricted to acute, severe cases, and they should be given only at the proper dosage for an interval of two to three days. The antibacterials generally thought to be the most clinically beneficial in these cases in our area are the nitrofurans, gentami- cin, chloramphenicol, and polymyxin B (Fig. 1) . The dosages used are: nitrofurans (Enterfur*), two boluses initially, followed by one twice a day per calf; chloramphenicol, 100 mg per kg initially, followed by 50 mg per kg two to three times a day; gentamicin, 2 to 3 mg per kg twice a day; and polymyxin B, 4 to 6 mg per kg twice a day. These drugs were the only ones found by the Kirby-Bauer technique to effectively inhibit in vitro the majority of E. coli isolated from 75 diarrheic calves over a two year period.
It must be remembered, however, that chloramphenicol is not approved for use in food-producing animals. The nitrofurans are currently being carefully scrutinized by the Food and Drug Administration; they are suspected to be potential carcinogens and may be removed from the market in the near future. In addition, because of manufacturing problems, Enterfur is not presently available. Gentamicin is approved for use . in food-producing animals, but is extremely expensive.
Regardless of whether antimicrobial drugs are given orally, for severe cases of diarrhea in the calf they are indicated systemically to prevent or treat respiratory disease. Pneumonia commonly occurs in conjunction with or secondary to diarrhea in the calf. I n one study imohing 19 field cases of acute, severe diarrhea in which the calves were given extensive fluid therapy intravenously but were given no antibacterial drugs systemic-*Norden Labs, Lincoln , Nebraska. ally, 10 died. All deaths occurred after the diarrhea had resolved and when the calves were well hydrated with normal blood electrolytes, glucose, and acid-base values. Based upon evaluation at necropsy, the death of each of these calves was a result of pneumonia.
Systemic antimicrobial drugs may be given parenterally or, in the case of those such as chloramphenicol which are readily absorbed from the intestinal tract, they may be given orally. Nitrofurans and polymyxin B are poorly absorbed following oral administration. Systemic administration of nitrofuran is not recommended.
The best method of treatment for any disease for which prevention has failed is to correct the primary alteration which has caused the disease. For diarrhea, this means the correction of the intestinal dysfunction. Currently, knowledge of the intestinal defects responsible for diarrhea is minimal, which makes rational treatment difficult or impossible. In addition, there have been few controlled trials of therapy to correct intestinal dysfunctions responsible for diarrhea in the calf. This includes the treatments given below.
Intestinal protectants, such as kaolin and pectin products, are of doubtful value in severe diarrhea. They have not been shown to alter losses of fluids and electrolytes. Although they may bind toxins and protect the mucosal wall, they have not been shown to be of any definitive benefit or harm.
It is not known whether the drugs that alter intestinal motility are beneficial or detrimental. Anticholinergic agents decrease intestinal peristalsis, segmentation, and sphincter tone. A decrease in all of these parameters may allow an increase in bacterial migration or multiplication of bacteria in the more cranial aspects of the small intestine. Although some of these organisms may not be pathogenic when restricted to the large intestine, in the small intestine they may produce a number of detrimental effects which will cause diarrhea.!' 3 In addition, a decrease in segmentation and sphincter tone allows a more rapid passage of fluid down the intestinal tract, particularly the colon, which could worsen diarrheal fluid losses. For these reasons, anticholinergics are not recommended in the treatment of the diarrheic calf.
Narcotic analgesics such as paragoric may, in contrast, be beneficial. These drugs decrease peristalsis and stimulate segmentation and sphincter tone which increase resistance to the flow of ingesta down the tract. These effects may decrease diarrheal fluid losses and aboral bacterial migration. However, these beneficial effects from narcotic analgesics have not been documented in the diarrheic calf.
Anticholinergics decrease intestinal secretion, an action that would be expected to be of benefit in the treatment of diarrhea. Howev.er, because of their effect on intestinal motility, their use is not recommended. Salicylates, such as are contained in Pepto Bismol and aspirin, may be beneficial in diarrheal diseases associated withE. coli or Clostridium perfringens, whether these organisms are primary or secondary factors. These organisms induce diarrhea by secreting an enterotoxin which stimulates secretion from the intestinal epithelial cells. Salicylates inhibit prostaglandin synthesis which decreases enterotoxin-induced intestinal secretion of water and electrolytes. However, the role of prostaglandins, if any, in bacterial or virus-induced diarrhea is not known at this time. In the rabbit, Pepto Bismol has been shown to bind Vibrio cholerae and E. coli enterotoxins which were not previously bound to the intestinal wall, and to decrease intestinal secretion stimulated by these toxins by 91 and 78 per cent, respectively.4
There is no indication for the use of either corticosteroids or anti histamines in the treatment of diarrhea. The diarrheic calf already has an increased circulating level of endogenously produced corticosteroids. 6 Supplementation of this natural level of corticosteroids has not been shown to be of benefit. Massive doses of corticosteroids (5 mg per kg of dexamethasone) have been shown to be beneficial when given early in the treatment of hemorrhagic shock in the dog. 5 In addition, prolonged glucocorticoid therapy is beneficial in endotoxic shock, which can be a sequela of diarrhea. However, a more beneficial response may be obtained from the diarrheic calf in h ypovolemic shock by correcting the hypovolemia with proper fluid therapy. Therefore, corticosteroids, as well as drugs such as antihistamines and stimulants, are of doubtful value and are not recommended in the general treatment of the diarrheic calf.
Regardless of all other treatments given the diarrheic calf, the most important aspects are fluid therapy, care, and timing. The earlier in the course of the disease that treatment is initiated, the less therapy required and the greater the chance of recovery. Treatment is not usually indicated in the lively, nursing calf with a loose, pasty stool unless prior experience in that herd indicates that this may lead to a more severe diarrhea. Watery, voluminous feces, however, indicate the need for immediate therapy, even if the calf is not dehydrated, appears alert, and is nursing. The calf generally will not become depressed or decrease its food intake until the state of dehydration is greater than 8 per cent (Table 1) . Do not allow this to occur, since treatment becomes much more extensive with progressive disease. The owner should begin giving oral fluids as soon as diarrhea occurs. However, it should be emphasized that if the rate of absorption of oral fluids does not compensate for the rate ofloss of fluids from diarrhea, fluids must be given either subcutaneously, intravenously, or both. The calf should not be allowed to become severely dehydrated before fluids are given parenterally.
In addition to fluid therapy, tender loving care is indicated. Make sure that the calf is dry and warm. A heat lamp or electric blanket works nicely. Also, do remember to consider the recumbent side of the calf. Extensive loss of heat may occur as a result of an uninsulated cold floor or ground. Bare concrete is particularly detrimental. Plenty of bedding should be placed underneath the calf or, preferably, something such as an electrically warmed pad similar to that used for baby pigs.* Following recovery, care must be taken to ensure that the calf does not overeat. If the calf is with the cow or will be returned to her, the cow should be milked out first. If this is not possible, the calf should be given several liters of the oral replacement fluid just prior to returning the calf to the cow. If this is not done, frequently the calf will ingest a large quantity of milk which may result either in a relapse or in sudden death from septicemia or endotoxemia. If the calfis to be fed by hand, dilute the milk by half with water or oral replacement fluid for the first one to two days.
Many calves are lost as a result of diarrhea during the first few weeks of life. Prevention is the most important goal. When prevention fails, proper therapy will save many affected calves. The most important aspects of therapy are the administration of fluids to replace the extensive losses of water and electrolytes which have occurred, and tender loving care. If treatment is begun early, fluids may be given orally. This reduces the need for more intensive therapy that must be administered either subcutaneously or intravenously. Although oral antimicrobial drugs are *Protein Plus Labs, Box 190, Colfax, Illinois; or Osborne Industry Inc. , Box 294, Osborne, Kansas. often given, there is little evidence to indicate that they are of benefit. However, systemic antimicrobial drugs are recommended in all severe cases of diarrhea to treat or prevent respiratory diseases. Corticosteroids, antihistamines, stimulants, and anticholinergic drugs are not recommended.
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