INTRODUCTION
Diarrhea is a disease that could be avoided by good management practices, yet it is the most common cause of death in young calves. Most fatal diarrhea occurs the first two weeks after birth. As calves grow older, their susceptibility to infections decreases rapidly but remains significant until three to four weeks of age.
Types of Diarrhea
Diarrhea is often classified as nutritional (overfeeding milk, milk replacer of poor quality, or sudden change in milk composition) or infectious (Table 1).
However, this distinction is somewhat arbitrary because nutritional imbalance can predispose the calf to infections. E. coli is the primary organism involved in diarrhea that occurs the during the first few days following birth (neonatal diarrhea).
Clinical Signs
Diarrhea is the excretion of feces containing excessive amounts of water. The feces of calves with diarrhea may contain five to 10 times more water than normal. In addition tobeing thin and watery, various types of diarrhea may result in the production of feces that have a fetid smell, are discolored (yellow, white), or that contain mucus and blood. As the disease progresses, other signs become evident (Figure 1).
The following clinical signs are listed in order of severity.
The calf:
- Shows loss of interest in feeding (poor appetite);
- Produces thin, watery feces;
- Shows signs of dehydration (sunken eyes, roughened hair, inelastic skin, etc.);
- Has cold extremities (hypothermia);
- Gets up slowly and with difficulty;
- Is unable to rise at all (prostration).
Predisposing Factors
The occurrence of diarrhea the first few weeks after birth increases when one or more of the following occurs:
Poor immune status of the calf:
(a) too little colostrum fed too late;
(b)poor quality colostrum;
High burden (build up) of infectious agents in the environment:
(a) no housing vacancy between calves;
(b) poor overall hygiene;
(c) poor ventilation;
Nutritional factors:
(a) overfeeding milk or milk replacer of poor quality
(b) abrupt change in milk composition;
Stress:
(a) difficult birth;
(b) long distance transportation.
Early Detection
Awareness of risk factors helps in early detection of diarrhea. Chances of clinical disease and death decrease sharply when early detection is followed by adequate measures to minimize the impact of the disease.
Normally, young animals and, in particular, young calves have good appetites. The first sign that a calf is becoming sick can be detected at feeding time. A young calf that does not seem hungry is telling you that something may be wrong. Careful observation of certain signs allows the producer to anticipate the onset of diarrhea the day before it occurs. The following signs indicate impending diarrhea:
- Dry muzzle;
- Thick mucus excreted from the nostrils;
- Very firm feces;
- Lack of appetite (refusal of milk);
- Prostration and a high rectal temperature (>39.3°C).
When a calf shows any of these signs, part of the calf’s milk can be withheld as a preventive measure. The diarrhea may not be entirely avoided, but the calf may recover more quickly.
PREVENTION
Management Practices
As with many calfhood diseases, adequate passive immunity and removal of the predisposing factors are the two primary measures that prevent diarrhea. Sound management practices and attention to details eliminate risk factors and considerably reduce the incidence of diarrhea and death (see gray box).
Vaccine
Vaccines for specific strains of E. coli are available.
The most effective way to use these vaccines is by inoculating the dams so that resistance can be transferred by colostral immunity. The immune system of a calf usually does not respond well to vaccination until six to eight weeks of age. The use of vaccines in the lactating cow is now widely used. There are numerous strains of E. coli that cause diarrhea. Introduction of new or different strains of E. coli (for example, with the purchase of an infected calf) may start new episodes of infection.
TREATMENT OF DIARRHEA
Oral Rehydration Solution
As soon as diarrhea is detected (the earlier, the better), the calf should be housed in a warm, dry place and therapy should focus on oral rehydration (Figure 1).
The general principle of oral rehydration is as follows: if salt and water are presented slowly enough to the intestine, then absorption should be complete. The various salt solutions presented in Table 2 can be prepared and fed at body temperature.
The presence of glucose in the electrolyte solution is optional. Glucose may enhance intestinal fermentation, but it may help in the absorption of electrolytes and, upon absorption, provides energy to the calf. Commercial oral rehydration solutions are also available. These products contain a mixture of electrolytes, glucose and other salts (as indicated in Table 2) as well as micro-minerals, vitamins and gelling agents (guar gum, xanthum agar, pectin, etc.). Pectin and gums are not essential in an oral rehydration solution; however, these ingredients may help slow down the passage of milk through the intestine andimprove digestion. They may also provide some protection and relief by coating inflamed, damaged intestinal cells.
Should Milk Still be Fed?
Calves with diarrhea partially lose the ability to digest milk. Diarrhea may be worsened by undigested milk passing through the intestine because it can encourage the growth of bacteria. Thus a common recommendation has been to replace milk, partially or completely, with an oral rehydration solution (ORS). However, recent research indicates that calves receiving ORS only for two days remain dehydrated and lose weight rapidly. In contrast, calves receiving their daily allotment of milk (10% of body weight) plus an acidic ORS do not exhibit a worsening of their diarrhea and actually gain body weight throughout the rehydration treatment period (seven days).
Treatment Method
At the onset of diarrhea, the calf should be fed its normal daily milk allotment; then ORS should be fed.
The acidity or alkalinity of the ORS may influence its effectiveness. Alkaline ORS may interfere with normal milk digestion in the abomasum and should not be fed until three to four hours after a meal. In contrast, acidic ORS may help protein digestion and may be fed immediately (15 - 20 min.) after a full meal of milk. Limiting the amount of milk offered keeps the calf hungry and more willing to accept the ORS.
Milk may be limited to the amount needed for maintenance: 1.8 kg/d for a 25 kg calf, 2.7 kg for a 35 kg calf, and 3.4 kg/d for a 45 kg calf. Also, the number of meals may be increased to three or four per day (and the amount offered per meal decreased correspondingly) to encourage the calf to drink more liquids. When calves refuse to take the ORS despite a reduction in milk and an increase in meal frequency, it may be necessary to use an esophageal tube to force-feed the animal
Antibiotics and Intravenous Rehydration
If diarrhea persists and signs of dehydration worsen, a veterinarian should be called. When the calf shows severe signs of dehydration (Figure 1—water loss from the body > 8%), the veterinarian is likely to administer electrolytes and antibiotics intravenously. Dehydrated calves, even those near death, usually respond very well to electrolytes administered intravenously.
