Tarleton State University, Department of Animal Sciences, Box 0070, Stephenville, TX, 76402 U.S.A.

There are various ways to dehorn calves, and probably the most widely used are the Barnes dehorner and electrical dehorners. Dehorning with these tools is usually performed when the calves are a few weeks or months old, and these methods cause temporary setbacks in growth due to the trauma associated with them. This trauma can be avoided by dehorning the newborn calf with caustic paste. Caustic pastes cause a chemical burn when applied to the skin, and when applied at a very young age to the cells that will develop into horn tissue, the paste will prevent development of horns. Those who properly use caustic pastes boast of its ease of application and the beautiful polls that develop on their animals. Those who have improperly used caustic pastes can tell tales of disfigured calves and sloppy dehorning jobs. There is a right way and a wrong way to use these products. Following are some suggestions for success when dehorning with caustic pastes.

• Only use caustic pastes to dehorn calves that are less than 2 days old. If they are much older than this, they will be coordinated enough to rub the paste off, resulting in incomplete dehorning or spreading of the pastes to body parts where it is not wanted.
• Do not use the pastes if calves will be in rain (snow) in the next couple of days.
• Use only on calves that are isolated from other animals, so they don't rub it on others.
• Use clippers to remove hair around the horn button. This will help ensure that the paste is applied to the skin, and actually, it is often hard to find the horn button on baby calves without clipping the area.
• Apply only enough paste to make a thin layer the size of a nickel (about 20 mm diameter). Excessive application of paste is the most frequent cause of dislike of these products.
• Use caution not to get the paste in the calf's eyes, or on your own skin.

Regularity in the feeding of the baby calf is important. Several factors need to be controlled for optimum calf performance during the milk-feeding phase. These factors include:

• Type of product fed (milk or milk replacer)
• Time of feeding and feeding interval.
• Amount fed each feeding.
• Temperature of milk.

Milk is the food for mammalian babies, and nothing has ever been invented or synthesized that is superior. Some products can take its place if they closely mimic the chemical and physical properties of milk. For dairy calves, we basically have two sources of liquid "milk" - whole milk from a cow or powdered milk replacer that we reconstitute to the consistency of milk. There are health, performance, and economic considerations to be made when choosing which of these will be fed.

Many dairies feed "dump" or "waste" milk to calves. This often is milk from cows that are too fresh to put into the milk tank, or from cows that have been treated for mastitis. "Fresh cow" milk is excellent for young calves. Fresh cow milk may still contain a small amount of colostral immunoglobulins for a couple of days, and even though the calf can't absorb them after the first day of life, these antibodies may provide some health benefits by combating pathogenic organisms in the lumen of the intestine. Milk from cows with mastitis may contain infectious bacteria, as well as antibiotics from the treatment of that infection. Both of these may have detrimental effects on the calf. It has been suggested that calves fed mastitic milk may harbor the mastitis bacteria on their mouth and in their saliva, possibly spreading these mastitis pathogens to the udders of other calves by sucking them. Some of these bacteria can live for a couple of years in the udder of a heifer, causing her to freshen with a case of infectious mastitis. Housing calves individually can prevent this problem. Feeding of milk that contains antibiotics is considered as one possible means by which certain bacteria may develop resistance to antibiotics. Once bacteria develop resistance to the antibiotic, that drug may no longer be effective in treating clinical infections caused by the same bacteria, and we may have a harder time combatting diseases in that calf. Indiscriminate feeding of antibiotics may also inhibit establishment of beneficial bacteria in the digestive tract of the calf.

The alternative to feeding real milk is powdered milk replacer. There are many on the market, and some are better than others. Some characteristics of a high quality milk replacer are:

• All or most of the protein is from a milk source.
• Contains minimum of 20% protein.
• Contains minimum of 20% fat.
• All or most of the fat is from an animal source (tallow).

There is considerable variation among milk replacers regarding sources of nutrients and nutrient content. Protein source is perhaps the greatest variable, and some protein sources are superior to others (4, 5, 10). However, no sources of protein have been found to be superior to milk proteins. A summary of protein sources used in milk replacer, and their relative suitability for young calves is presented in table 2. Most of the milk protein in today's milk replacers is whey protein, a by- product of the cheese industry. When whey proteins first started being economically available for use in milk replacers, there were concerns over its digestibility, due to the fact that it doesn't coagulate or clot in the calf's abomasum like casein proteins do. However, we now know that the digestibility of whey protein is similar to that of casein, and that there is little difference in the performance of calves fed either of them. A newer protein source is animal plasma. Performance of calves fed milk replacer in which animal plasma replaced a portion of the milk protein was reported to be similar to performance of calves fed an all-milk protein liquid feed (12, 14).

Scours is one of the major health concerns of young calves. Scours is characterized by loose, watery feces, and can kill a calf fairly rapidly, depending on its severity. Scours kills the calf by a combination of dehydration, loss of electrolytes, and metabolic acidosis. Causes of scours can be classified as non-infectious and infectious. Non-infectious scours are usually caused by overfeeding of milk or a lack of consistency in our feeding program. While usually not severe enough to cause death, non-infectious scours can weaken the calf and make it more susceptible to infectious scours. Scours caused by infectious organisms are our biggest problem. The three basic categories of organisms that cause infectious scours are bacteria, viruses, and protozoa. As with most diseases, it is usually cheaper and easier to manage the problem by prevention rather than by treatment. Some measures for preventing infectious scours are:

When preventive measures fail and infectious scours occurs, finding the appropriate treatment is the key to success. The appropriate treatment depends on the causative organism. Of the bacterial scours, E. coli and Salmonella spp. are the two organisms most frequently involved in severe cases, with several other bacteria possibly involved. While bacterial scours can be treated with antibiotics, different antibiotics are effective against different organisms. This necessitates a diagnosis of the causative organism in order to select the most appropriate antibiotic therapy. Populations of scours-causing bacteria can change over time, and if the scours treatment that was successful for you in the past seems to have become ineffective, it is possible that you are now dealing with a different organism. The small amount of time, effort, and money required to collect a fecal sample from a sick calf and send it to a veterinary diagnostic laboratory is well spent when one considers that treating calves with the wrong medication is sometimes completely useless and will not prevent death of the calf.

Scours caused by viral infections usually doesn't respond to antibiotic treatment because viruses are not affected by antibiotics. The best protection against viral scours is sanitation and good colostrum management, and the most suitable therapy for viral scours is to keep the calf alive with oral electrolyte therapy until the viral infection is over. Oral electrolyte therapy will be discussed shortly.

There are two categories of protozoa that commonly cause scours; coccidia and cryptosporidia. There are products available for treating coccidiosis, but no products are currently effective against cryptosporidia. Feeding of ionophores (monensin, lasalocid, marketed as "Rumensin" and "Bovatec" respectively) has proven effective in preventing coccidial infection. Feeding or drenching with decoquinate (marketed as "Deccox") or amprolium (marketed as "Corrid") is effective in controlling coccidial infections once they get started. Again, a correct diagnosis of the cause of the disorder is essential for selection of the appropriate treatment compound. Diagnosing cryptosporidia as a source of scours is often difficult. Since no currently available compounds are effective against this organism, it can be devastating to the calf crop unless its spread is controlled by other management strategies. There are additional concerns with cryptosporidia because it can infect humans, and severe dehydration and death have been attributed to its infection of persons working around dairy animals.

Oral electrolyte therapy is a means of keeping calves alive until they can overcome the infectious organisms that are causing the scours. There are dozens of commercial oral electrolyte products available, with a wide range of costs. There is tremendous variation in both the types and amounts of ingredients used in these products. These products are mostly designed to replace the water and electrolytes (sodium and potassium) lost during scours, and to correct the metabolic acidosis that results from loss of these electrolytes. Two types of products are used to correct the metabolic acidosis, bicarbonate compounds and metabolizable bases. Bicarbonate compounds (sodium and potassium bicarbonate) are frequently used to directly neutralize acids in the body. They also neutralize the acid in the calf's abomasum (the abomasum is supposed to be acidic all the time), which can negatively impact the calf's ability to digest protein. The protein digesting enzyme, pepsin, requires an acid condition in the abomasum to function properly, thus, oral electrolyte solutions containing the bicarbonate compounds should not be used in calves that are still being fed milk. Metabolizable bases are use to combat acidosis without affecting the pH of the stomach contents (9). Products containing metabolizable bases and no bicarbonates will not interfere with protein digestion.

Opinions among dairymen vary regarding how to use oral electrolytes, but research has clearly defined the most appropriate application. Corbett (2, 3) provided excellent discussions of the causes and treatment of scours. Perhaps the most common misconception about scours is that milk causes scours. This is not the case. While it is true that withholding milk from a scouring calf will result in less fecal material on the ground, that is by no means an indication that the calf is recovering. Many dairymen mistakenly believe that feeding of milk should be suspended while electrolyte solutions are fed to scouring calves. Garthwaite et al. (6) demonstrated that this practice does not improve the recovery rate. Additionally, continuing to feed milk along with fluids and electrolytes helps calves maintain acceptable rates of gain (6, 7).

In general, oral electrolyte solutions keep a calf alive by replacing the fluids and electrolytes (primarily sodium and potassium) it has lost, and by correcting the metabolic acidosis that develops during scours. Some guidelines for treating infectious scours and using oral electrolyte solutions are:

Sanitation is vitally important in the fight against infectious disease in young calves. Sanitation doesn't necessarily imply that everything around the calf needs to be spotlessly clean, but that everything with which the calf comes into contact is free of infectious organisms.

A few simple suggestions for practicing good sanitation around calves are:

Sanitation is one area of management where a small dose of common sense goes a long way. Try to think about whether or not you would mind sticking any of your calf equipment in your own mouth. If you would hesitate to do so because of its cleanliness, it is not clean enough for the calf.

One of our primary objectives in raising the calf during the milk-feeding phase should be to develop its ability and desire to consume dry starter feed, and to end the necessity of feeding milk as soon as possible. Unless suitable waste milk is available, the milk-feeding phase will cost more per day than any time up until the calf reaches close to 400 kg body weight (depending on forage and grain prices). Most of this expense is the milk or milk replacer, but a considerable amount of labor must also be considered. There are several management practices that can be employed to help enhance dry feed intake by the calf.

• Provide clean, fresh water continuously throughout the milk-feeding phase.
• Provide calves with a dry starter feed by about the third day of life. Don't give them more than a handful at first, clean up what they don't eat each day, and provide fresh feed each day.
• Make starter feeds from high quality ingredients. Use of textured and processed grains (flaked or rolled corn, oats, barley) and pelleted supplements will make the starter more attractive to the calf.
• Calf starters should contain monensin (Rumensin) or lasalocid (Bovatec) for prevention of coccidiosis and increased rate of gain.
• Do not provide hay to the calf until it is about 5 weeks old, and feed only top-quality hay.

Naturally, calves won't eat much dry feed in the first few days, but calves who are continuously exposed to dry feed from an early age will begin to consume significant amounts of it earlier than calves who do not have early exposure. Consumption of dry feed is important because it should be our primary criterion for determining if a calf is ready to be weaned. When calves are taking in significantly more sustenance (protein, energy, minerals) from dry feed than they would from 4 liters of milk or milk replacer, they no longer need the milk to grow at an acceptable rate. It will take about 0.68 kg of an 18% protein all grain starter to provide this nourishment. Calves that consume at least 0.68 kg for three or more consecutive days are indicating sufficient intake for weaning (11). If the above-mentioned management is followed, and if the calves have suffered no setbacks due to scours or other illness, calves can be successfully weaned from milk at 5 weeks of age without jeopardizing their subsequent growth rates (19). A feeding strategy that seems to encourage starter intake while minimizing the stress of abrupt cessation of milk feeding is to cut the calves back to one feeding of two liters of milk per day during the last week before weaning. Although the calves will want the extra milk, they will quickly learn that eating more starter feed will ease their hunger. Intake of starter feed will increase rapidly, and from this point onward, calves should be off to a good start as herd replacements.

Dry starter feeds need to be palatable as well as provide the nutrients that the calf needs for maintenance and growth. Recommended nutrient content of a dry calf starter is given in Table 3.

It was once believed that calves needed to eat hay (for its "scratch factor") in order to develop early rumen function. We now know that it is actually volatile fatty acids (VFA) from the fermentation of feeds that enhances development of rumen function, and the VFA produced from the fermentation of grains is more stimulatory to ruminal development . There is little fear of ruminal acidosis in calves on all grain diets up until weaning time. Occasionally a calf may bloat, but an oral drench of poloxaline ("Bloat Guard", "TheraBloat") will usually relieve the problem. Some calves are chronic bloaters, and should be watched carefully until they grow out of the problem.

There currently are several "direct fed microbial" or "probiotic" products that are marketed to promote better performance (feed intake, growth rate, etc.) in calves. While controlled research on many of these products is scarce, they may have some benefit. These products come in different forms (pastes, powders), and vary somewhat with regard to their composition. Most, however, will contain species of live bacteria from the Lactobacillus genus that are considered to be beneficial to the health and function of the gastrointestinal tract (8). Vazquez (17) evaluated the efficacy of one of these products, and reported that calves who were given an oral dose of seven grams of probiotic paste at five days of age and who also received two grams of powdered probiotic product daily in their milk consumed more starter feed and increased in heart girth measurement more than calves who did not receive this treatment. Of the calves treated with the probiotic, 53% met weaning criteria (0.68 kg starter intake for 3 consecutive days) at 29 days of age, compared to 22% of the untreated calves. Patterns of dry starter intake for these two groups of calves are depicted in Figure 1. The use of probiotic products for young calves needs further study to determine the most effective organisms and applications to use.

Success in raising the calf from birth to weaning does not happen by accident. By adequate preparation, observation, good husbandry, colostrum management, sanitation, disease prevention and control, and good nutrition, are the key to maximizing calf growth and keeping death losses below 5%.