Calf Management

Sandra Godden, DVM, DVSc and  Whitney Knauer, VMD, PhD

College of Veterinary Medicine, University of Minnesota

Summary

1. Understand health and growth targets for calf and heifer programs
2. Maternity pen management
3. Newborn care
4. Colostrum management
5. Nutrition of preweaned calves
6. Housing basics
7. Developing systems to detect, diagnose, treat and monitor disease
8. Review the pathophysiology, detection, treatment and prevention of calfhood respiratory disease and calfhood diarrheal disease.

Introduction

A thorough understanding and appreciation for good calf management practices and disease prevention and detection techniques is important for veterinarians, as a calf that grows well and maintains her health throughout the pre-weaning period benefits the producer in both the short and long term. Certainly, not every dairy veterinarian has a keen interest in calves, but knowing the basics, and knowing how to tackle disease/management failure investigations, will solidify your role as a valuable member of the dairy team.

Content

Calf and Heifer Program Goals

(For more details check out this link for Dr. Godden’s presentation on Kaltura)

The primary goal for the replacement program is to raise a replacement animal in an efficient and economical manner. This means an animal that’s going to cave in between 22 to 24 months of age, with the appropriate genetics, size, health, immune function, and body condition to be a productive member of the herd for a long time. To achieve this age at first calving of 22-24 months we need adequate growth, good health, and a good reproductive program. The pre weaning period is an important period in order to achieve adequate growth and health.

Calfhood disease has both short term and long term impact on welfare and economics, so prevention of these diseases is key. Some suggested goals for monitoring the replacement program are listed below.

To achieve these goals and promote calf health and growth we need to maximize immunity and minimize infectious disease challenge out of the environment. Strategies to achieve this will be discussed further below.

Maternity Pen Management

There are various options for maternity pen systems starting with a group maternity pen where cows are brought into the pen anywhere from 28-1 day pre calving and leave after calving. An alternative in larger herds where they may have labour present 24 hours a day is an individual pen or box stall that uses just-in-time calving. In this system cows that have initiated the calving process in the close up pen are moved into an individual box stall for calving and only spend 2-4 in this pen. Regardless of the system in use, the goals for management and for the environment are the same. It needs to be clean, dry, comfortable with good footing, good air quality (ventilation) and heat abatement systems in place. Additionally, it needs to be quiet to avoid interrupting the calving, because once the calving process is interrupted and prolonged there is an increased risk of stillbirth. Ideally the maternity pen is just a maternity area and does not do double duty as a sick pen as sick cows will contaminate the environment. To allow for the cow’s natural behaviour there needs to be room for that cow to remove herself from the group and calf in a quiet corner. The system also needs to allow for the ability to monitor and assist the calving process if needed using a gate, headlock or chute.

Newborn Calf Care

The goal in newborn care is to have a live calf born without injuring either the calf or the dam. This requires protocols and appropriate training of maternity staff to ensure they know the normal calving process and when to intervene. These protocols and training should be reviewed regularly, and particularly in herds with an elevated stillbirth rate.  Once the calf is born it needs to immediately assess the vigor of the calf and provide immediate resuscitation if need be. If the calf is in trouble and not breathing well the following things to can be used to initiate breathing:

1. Clear the fluid from the mouth and nostrils with clean hands or gloved hands
2. Use postural drainage to drop the head below the level of the chest to drain fluid out of that. Just do not hang the calf upside down as then the abdominal viscera ends up putting pressure on the diaphragm instead prop the calf into a sternal position upright position as then it has an easier time to expand both sides of the lungs.
3. Vigorously rub the calf with a towel to dry it off and to stimulate circulation and breathing.
4. Dumping cold water over the head or into the ear.

If the calf has appropriate vigor it should be removed from the maternity pen environment within 30 minutes of birth. This time allows the cow to lick the calf clean and dry and avoids leaving the calf in a dirty environment with increased risk of exposure to infectious pathogens. Once removed from the maternity pen, the calf’s navel should be dipped with a 7% tincture of iodine or some other validated and approved naval dip product in order to prevent umbilical infections. Additional management procedures may also occur at this time depending on the herd.

In cold months when the temperature is less than 52 oF or 10 oC the calf needs to be warm and dry that calf before it goes outside into a cold environment. This means that having a warm room, a heat lamp or a warming box is going to be critical in the cold months. Regular cleaning and sanitation of this ‘warming area’ is critical. Finally pain management for calves born via dystocias or with poor vigor. should be considered. Providing pain management like meloxicam (a non-steroidal anti-inflammatory) can improve pain control, improve suckling, improve vigor, and even improve health and growth. Note that meloxicam, while labeled in Canada, is not labelled for use in cattle in the U.S. Therefore careful attention to dosage and observing recommended withhold times is critical.

Colostrum Management

Newborn calves are born without any circulating antibodies because of the nature of the cow’s placenta. Therefore it is important that the calf absorbs protective antibodies from colostrum into its circulation very quickly after birth. This is called transfer of passive immunity (TPI). These antibodies will provide protection from infectious disease in the first days, weeks and months of life while giving that calf time to mount its own acquired immune response and produce its own protective antibodies. Colostrum is not just about the antibodies however. Other immune factors, growth factors, and hormones found in colostrum will stimulate not just immune responses, but also growth and development of that animal. Colostrum also is full of nutrients, containing higher levels of fat, protein, vitamins, etc. than regular milk,  to support the calf's growth and development. The total solids content of colostrum is approximately 24%, roughly double the total solids of tank milk (12.5% TS).

There are several short- and long-term benefits to successful transfer of passive immunity. Reduced morbidity, mortality rates, and improved rates of gain and feed efficiency, decreased age at first calving, and improved milk production. This may be a consequence of the calf not getting sick or it could be a consequence of all of the extra growth factors and nutrients.

To ensure calves do not have failure of transfer of passive immunity (FPTI) there are 5 keys of a successful colostrum management program: Quality, quantity, quickness, cleanliness, or Q for squeaky clean and quantify (monitor) passive transfer rates.

Quality

Our goal for high-quality colostrum is for it to have an IgG level greater than 50 g/L. Colostrum quality is impacted by some factors that we can’t control, with examples including the breed and age of the cow. However, there are several things that we can manage that can impact quality. These include vaccination during the dry period, feeding a balanced dry cow ration, avoiding dry cow stressors, avoiding short dry periods, and timing of collection after calving.

In particular, we encourage incorporating vaccines against common calf scours pathogens into the dry period vaccination program. If we vaccinate the dam well in advance of calving, then she manufactures those antibodies and moves them into the colostrum.

Feeding a balanced dry cow ration in the far off and close-up period is not just for the cows benefit and her future lactation, health and performance, but is also important to achieve sufficient volume and quality of colostrum.

Preventing stressors, such as heat-stress or overcrowding, are important because these stressors could interfere with the immune response that is part of manufacturing colostrum. We also want to avoid excessively short dry periods. Anything less than 21 days dry results in poor volume and quality, since she doesn’t have time to involute and regenerate that gland, or to move immune components into the gland. Furthermore, anything less than 40 days dry can result in impaired volume.  As such, we want to aim for dry periods between 50-60 days in length to ensure that the vast majority of our cows will have at least 40 days dry.

Collecting the colostrum within 1-2 hours post-calving will maximize quality. For farms that lack labor or systems to harvest colostrum shortly after calving, a reasonable goal would be to have 90% of cows milked within 6 hours of calving,

To monitor colostrum we use Brix refractometer, which measures total solids. This is an indirect test to estimate the IgG level in colostrum. A Brix measurement of >21% means that the colostrum is probably high-quality (>= 50 g/L). A reasonable goal would be to have 90% or more of your cows producing high-quality colostrum.

Quantity

Our goal with colostrum feeding is to feed enough volume in order to get at least 200 g, and ideally 300 g, of IgG into the calf. The standard recommendations are to feed 10% of the birth weight of the calf at the first feeding. For a typical Holstein calf this will be roughly 4 qts or L, and for a Jersey calf roughly 2.5-3 L at first feeding.  

Quickness

 In order to maximize absorption of IgG, we want to feed the calf as soon as possible after birth. A newborn calf is able to absorb these large antibody molecules intact across the ‘open’ gut into the circulation. However, over time, during the first 24 hours of life, the gut epithelium turns over and the calf loses its ability to absorb these antibodies, a process called ‘closure’. In order to maximize absorption of IgG, we want to feed this calf as soon as possible after birth. As shown in the diagram below even after birth, immediately after birth, absorption efficiency isn't 100%, it might only be 30 or 40%. Ideally we want to feed within one to two hours to capture maximum efficiency of absorption. However, for farms lacking labor or systems to always feed within 1-2 h, a reasonable goal would be to get at least 90% of calves fed within 6 h of birth.

There are three different options in order to get sufficient quantity into the calf, nursing from the dam, using a nipple bottle or an esophageal feeder. Of those three options, the one that we know works the poorest is letting the calf nurse the dam because we can not control the volume or the timing.  This means we need to hand feed the calf with either a nipple bottle or a tube feeder in order to control volume and timing. Between these 2 methods what is important is not the route or method of delivery, but the quantity delivered. If using a bottle not every calf will voluntarily consume 4 L and so the producer may have to either offer a 2nd bottle a couple of hours later or feed the remaining volume using an esophageal feeder. Using an esophageal feeder requires training clients on how to correctly and safely place that tube so that they don't traumatize the calf or cause aspiration.

If the farm can only manage a single feeding and is getting good results, that’s fine.  However, if it can be implemented by the farm there is value to offering a second feeding 12 hours after birth, or by offering transition milk (second or third milking colostrum) a day or two later, even after the gut has presumably closed. A second feeding can provide a bump in calf serum IgG levels. Third or fourth feedings of transition milk can help in other ways, as they have a high nutritional value plus lactogenic (local) immunity in the gut: Antibodies floating down the lumen of the intestine can still bind and neutralize pathogens in the digestive tract, even if not absorbed into the circulation.

There are several ways to achieve this lactogenic immunity: Farms could add a commercial colostrum supplement (costly) or frozen colostrum cubes to milk or milk replacer, or could add transition milk to the pool if feeding pasteurized milk. Not all farms need to feed transition milk to calves, but for farms experiencing endemic scours problems this could be beneficial.

Cleanliness (sQueaky Clean)

There are 2 reasons to consider colostrum cleanliness: First, we do not want to feed the pathogenic bacteria to a calf, particularly a calf that has an open gut and may be more inclined to absorb these bacteria into the circulation. Second, high bacterial levels in colostrum seem to block or interfere with IgG absorption, resulting in lower levels of PTI. Studies have repeatedly shown that the higher the bacterial level in the colostrum fed, the lower the serum IgG achieved.  

We can monitor colostrum cleanliness by doing periodic cultures. In fresh (not heat-treated) colostrum, the total plate count (TPC) should be <100,000 colony forming units (CFU)/ml) or the coliform count to be less than 10,000 CFU/ml. In dairies with problems, performing colostrum cultures can be a starting point. If the colostrum is contaminated, then either the cow, equipment, or storage are typical areas of concern to investigate as potential points for contamination. The cow could either be infected and shedding bacteria like Salmonella or Mycoplasma spp. in her colostrum, she could have fecal material on her udder that contaminates the colostrum if the teats are not properly cleaned and sanitized before milking. Equipment used to collect, store and feed colostrum could be contaminated. Finally, perhaps colostrum is stored inappropriately, allowing for bacterial growth or proliferation. As a veterinarian there are opportunities to become involved in developing protocols and training to limit bacterial contamination from each of these areas.

There are several ways to prevent growth or proliferation of bacteria in stored colostrum. One way is to feed it shortly after harvest, and simply not store colostrum. Or it could be frozen quickly after collection and bacteria won't multiply while frozen. Rapid refrigeration after collection is another option, but it should still be fed within 48 hours. Another option is the use of approved preservatives, like potassium sorbate, which can extend the shelf life by one or two additional days by slowing bacterial growth in refrigerated colostrum. Other tools or management strategies that are useful to reduce pathogen exposure on some farms include heat-treating colostrum or feeding colostrum replacement products.

Colostrum replacement products are basically powdered products containing antibodies that you can mix up in water and quickly administer. Unlike supplements, which contain a much lower dose of Ig, colostrum replacement products will provide between 100-175 g of Ig per packet, and cost $30-45 USD. There are a variety of products out in the marketplace and they are manufactured very differently. Some are colostrum derived, meaning they are sprayed right colostrum. Other products are serum or plasma derived where the antibodies are separated from plasma collected from blood at an abattoir. There are definitely different levels of quality among available products, with some being USDA licensed and others not. Studies have shown that colostrum derived products have better efficiency of absorption of IgG, thereby resulting in higher serum IgG levels, as compared to feeding an equal dose of serum/plasma derived products. Regardless of the source, it is crucial to provide doses of at least 150-200 grams of Ig if producers hope to achieve even close to the same level of PTI as is achieved when feeding 4 quarts of high quality maternal colostrum.

Heat treating colostrum is another relatively new technology. Heat treating colostrum starts with collecting and refrigerating fresh colostrum from all cows that calve that day. Once there is enough for a batch it is run through a batch pasteurizer or heat treated. Once heat treated, the colostrum will be put in clean bags or bottles, then refrigerated or frozen. It can later be warmed in a warm water bath (water bath temp 115 oF or 46 oC), and then fed to calves that are born over the next day or two. It is important to use a lower temperature - longer time approach to heat-treat colostrum than is used for pasteurizing milk, in order to protect the colostrum antibodies from heat damage. The recommended protocol to heat-treat colostrum is 140 oF (or 60 oC) for 60 minutes. There are various types of equipment that allow both large and small farms to utilize this technology.

Monitoring

Monitoring the transfer of passive immunity (TPI) rates is important to ensure the colostrum program is working. On farm or in the local clinic indirect tests like Serum total protein (TP) or serum Brix readings are options. Instead of using expensive lab based methods to measure serum IgG in calves, we can use simple, rapid indirect tests to estimate IgG. In the first week of life there is a positive correlation between the serum IgG (g/L) and serum total protein (g/dL) for calves. If our goal is a serum IgG level of 10 g/L or more, the corresponding serum total protein value would be roughly 5 or 5.2 g/dL. At the population level we can monitor the success or failure of the program by bleeding 12 or more clinically normal (not dehydrated) calves between 1-7 days of age. Then the serum would either be tested using a serum refractometer or a Brix refractometer. At a minimum, we want at least 90% of calves tested to have successful TPI (serum IgG >= 10 g/L). However higher levels do result in a further reduction in morbidity and mortality.  The table below shows new consensus goals for monitoring TPI in dairy herds (Lombard et al., J. Dairy Sci, 2020).

Pre-Weaning Nutrition

After colostrum, the next most important determinant of calf health and performance is nutrition. Nutrition has a huge impact on the calf’s ability to meet maintenance and growth requirements, immune function (health), and ability to deal with cold stress. Furthermore, growth rates in the preweaning period are strongly associated with enhanced milk production in the adult animal.  By having a basic understanding of preweaning nutrition, you can have a tremendous positive impact for your producers. And don’t be intimidated by this - The basic principles of feeding a monogastric calf are fairly simple. . The following section will review the importance of starter grain and water management to develop the rumen, as well as the importance of the milk feeding program.

Rumen Development.  The calf is born effectively a monogastric, with a small non-functional rumen. It is critical that we develop a healthy functioning rumen before weaning the calf onto an all-dry feed diet. Rumen development involves increasing the volume (capacity), muscularity (needed for contractions), papillae development (to absorb volatile fatty acids and other nutrients), and establishing the complex microbial populations (bacteria, protozoa, fungi) needed to ferment dry feed consumed by the animal.  There are three phases of rumen development:

1. Preruminant phase. Birth to approximately four weeks of age. The calf may begin consuming a small amount of starter pellet during this period but is capturing very little in nutritional value from the dry feed. The calf is almost entirely dependent upon the milk diet to support maintenance and growth requirements, as well as to support a functioning immune system and to deal with cold stress during colder months.
2. Transition phase.  Approximately 1 month of age to weaning. The rumen is slowly developing. Dry feed fermentation in the rumen is now contributing to the calf’s nutrient intake, in addition to the milk diet.  However, the rumen is not yet adequately developed to wean.  If we wean the calf before the rumen is adequately developed, it won’t be able to meet its nutrient needs from just the dry feed. This may result in post-weaning slumps, with associated negative energy balance, weight loss and increased disease risk.
3. Ruminant phase. The calf is weaned. Nutrients are entirely derived from dry feed.
   

Rumen development is stimulated by the volatile fatty acid, butyrate, which is produced after the consumption and fermentation of carbohydrates in grain (calf starter pellet). The importance of grain consumption to rumen development is evident in the image below. The availability of free choice, palatable water increases the rate of grain consumption and rumen development.  It is recommended that fresh starter pellets (22-24% CP) and fresh, palatable water be made available free choice starting by 3 days of age.  Calves should be consuming at least 3 lbs of starter pellet daily for at least 3 consecutive days before the rumen is likely to be adequately developed in preparation for weaning. It is generally not recommended to introduce forages (e.g. dry hay) until 2 or 3 weeks post weaning. If introduced preweaning, high quality forages may be top dressed in small amounts or chopped finely (1 cm lengths) and mixed into the grain mix, but should be done so at a low inclusion rate (< 15% of total DM).

Milk Feeding Program.  Until the calf is weaned (usually 8 weeks of age or later) and particularly in the preruminant phase, getting adequate nutrition from the milk diet is critical to meet maintenance requirements, support growth (ADG goal: 1.6-1.8 lbs/day), support a functioning immune system, and provide extra calories needed for thermoregulation during periods of cold stress.  Options for the milk diet include whole milk (preferably pasteurized) or commercial milk replacer (CMR).  When expressed on a dry matter basis, the crude protein:crude fat (CP:CF) levels in whole milk are 26%:31%. Meanwhile components in CMR are highly variable between different formulas, with CP ranging from 18-28% and CF ranging from 15-25%.  The quality and digestibility of ingredients in CMR are also variable, with milk protein sources (e.g. whey protein) being the most digestible for calves. More information on the evaluation of milk replacers can be found at this link (Link to BAMN publication A Guide to Milk Replacers).

Traditional feeding rates are restricted, offering calves only 4 or 5 quarts/day of milk or milk replacer, or approximately 1-1.2 lb (0.5 kg) of DM per day.  Even in a thermoneutral environment, this amount of milk will support less than 0.5 lb/day ADG.  Many producers still feed a restricted milk diet, believing that making the calf hungry will encourage it to consume calf starter earlier, thereby allowing for earlier weaning onto a cheaper dry feed diet.  However, if we are serious about wanting to achieve 1.6-1.8 lbs/day ADG, then we must provide calves with a more full potential milk diet. Specifically, this will require feeding 8+ quarts/day of whole milk or a high quality milk replacer (or 2.2 lbs/1 kg of DM per day). It is true that feeding these higher volumes of milk results in calves coming onto grain more slowly. However, rumens may still be adequately developed in preparation for weaning by adopting the following two management strategies:

1. Stepping down the daily milk allowance (e.g. 50% reduction) starting two weeks prior to the target weaning date  
2. Delaying weaning for an additional one or two weeks    

There are several benefits to feeding full potential milk programs year-round, including improved growth and health in the preweaning period, reduced age at first calving, and improved milk production in the adult.  As such, producers are encouraged to feed full potential milk feeding programs year round.  However, for producers still feeding smaller volumes during the summer months, it will still be important to increase the daily allowance in colder months (when ambient temperature falls below 52 oF or 11 oC ) to provide calves the extra calories needed for thermoregulation.  In addition to a high plane of nutrition from the milk diet, other strategies that can help calves deal with cold stress include fully drying the calf before putting it into a cold environment, blankets, the liberal use of deep, dry straw bedding (for nesting/insulation value), and protection from wind and precipitation.

Housing

The characteristics of a ideal housing system include:

• No contact between younger calves and older animals (or their environment)
• Avoid direct contact between baby calves
• Easy to clean and sanitize between use
• Good ventilation with clean, dry and comfortable bedding.
• Allows for socialization among calves, and between calves and people
• A good working and calf handling environment for the employees

Three commonly used calf housing systems include individual housing outside (e.g. hutch), individual housing inside a naturally or mechanically ventilated barn, or group housing.  With individual housing systems, calves are usually hand fed by a nipple bottle or bucket two or three times daily.  In group housed calves, calves may be hand fed (e.g. mob feeder), or milk may be delivered via a computerized (automated) feeder or an ad lib acidified milk feeding system. When considering the characteristics of an ideal housing system (listed above), it should be immediately apparent that no one system is perfect. Each has benefits and trade offs from both a calf and people welfare perspective. Specific advantages and disadvantages are discussed below. As veterinarians our goal is to guide producers in selecting a housing system that best aligns with their goals and priorities, and to help them manage existing systems to achieve the best results possible with respect to calf health and well being.

Outdoor hutches

Hutches have many advantages. There's no calf to calf contact, when spaced correctly
(four feet). It is an all-in-all-out system. There's usually good air quality. We can move it to new ground and disinfect.rest ground between calves. It is very easy to detect a sick calf because we're feeding them, working with them at least two or three times a day. We can easily monitor their appetites and attitudes to detect sick calves. And calves become socialized to humans. Taken as a whole, hutches probably come closest to meeting most of the characteristics o an ideal housing system.  However, one disadvantage is that they don’t allow for socialization between calves. Furthermore, people don’t always enjoy working out in the elements (e.g. rain/snow/cold), potentially resulting in less time taken to provide the necessary care for an individual calf that might require more attention.

Individual Indoor Housing

Moving calves into individual pens in an indoor housing improves working conditions for people.  Ventilation may be natural (e.g. curtain barns) or mechanical. However, from the perspective of preventing disease transmission, these systems may/may not introduce compromises, depending on the design and management of the facility. Concerns may include more opportunity for direct contact between calves, poor ventilation (especially in winter months), and pathogen buildup if sanitation of floors or partitions is less than ideal. Compromises could result in impaired health, depending on the system and management.

Some factors to reduce the prevalence of respiratory disease in these systems are shown in the image below (from Lago et al., 2006. JDSci. 89:4014). These include adequate space per calf, a solid panel side-to-side to prevent calf-to-calf contact, an open panel at front and back to allow for fresh air to enter the pen, and deep loose straw bedding in winter allows for the calf to ‘nest’ to conserve heat. can borough or nest in the betting and conserve heat loss.

Indoor group housing

There are several different ways to deliver milk to calves in a group housing system including an auto feeder/computer feeder system, mob feeders, or ad lib feeding of acidified milk. One potential benefit of group housing includes that it can be easy to deliver a full potential milk feeding program, especially if using a computer feeder or an ad lib feeding system.  Also, while these systems don’t in fact save labor, they allow for reallocation or increased flexibility of labor. And finally, group housing allows calves the freedom to socialize and exercise.  Socialization of calves before weaning results in differences in cognitive development, in that they are less reactive or scared of novel environments, objects or other calves. Also, most (though not all) studies show improved grain intake prior to, and during, the weaning process.  However, these benefits may not persist after weaning.

However, there are several disadvantages to group housing, with increased disease risk being a real concern. Just as ‘day care disease’ happens in preschool children, Increased disease risk can occur with group-housed calves due to sick calves having direct contact with other group members and/or contaminating the environment.  One of the biggest risk factors for increased disease in group housing appears to be large group sizes. Other potential disadvantages of group housing include the potential for aggression or competition for resources, especially in large groups, with younger/smaller or more timid calves potentially  having reduced access to the feeder. The potential for increased cross sucking also exists. Finally it may be harder to detect sick calves housed in groups, as it becomes harder to monitor individual intakes and behaviors. Best management practices for group housing include:

• Delay introduction to the group until 12 to 14 days of age
• Keep the group size as small as possible, ideally less than seven or eight calves
• Don't overcrowd: Offer at least 40 square foot per calf
• Managers and all-in-all-out system.
• Do not restrict milk allowance
• Pay attention to sanitation, calibration, monitoring of the feeding equipment,
• A trained person must observe calves for illness every day, as computer feeder algorithms are imperfect in their ability to detect sick calves (many false positive signals / many false negative signals).

Pair housing of preweaned calves has been put forward as a potential compromise to capture the best of both worlds between individual vs group housing systems: Having a buddy allows for the social benefits previously described, while the group size is kept as small as possible (n=2) to minimize disease risk. There are different ways that we can pair house calves. Calves can be paired from birth or individually housed for the first 2-4weeks before removing the panel/divider to create a pair..

Disease Detection, Diagnosis and Treatment

In most cases early detection and treatment will result in a better case outcome.  This means people need to be trained in order to be able to detect, diagnose accurately,and treat appropriately, followed by accurate and consistent record keeping, and regular monitoring of the results. Detecting disease should be done by daily observation by trained staff. In individually housed calves this is best done during other chores when you're feeding milk, water, or grain. Calves that are slow to get up to, slow to drink their milk or don’t finish their milk, or calves that are acting differently are laying down when other calves are standing, should be flagged for a full exam. In group housed calves disease detection becomes harder, given that computer algorithms that monitor milk intake or feeding behaviors to predict disease are far from perfect:  There are many false positives, where the algorithm might flag a calf that really isn't truly sick, and many false negatives as well, where a sick calf may not change its feeding behaviors, and therefore not be flagged by the algorithm. As such, staff still need to be trained to routinely observe and identify sick calves.

Once a calf is suspected of being sick, It needs a thorough physical exam with signs in the figure below indicating a problem and the need for to treat appropriately.

There are also screen protocols available such as the University of Wisconsin calf health scoring system (link to U of W scoring system here)

Once disease has been diagnosed and appropriate treatments administered they need to be recorded to allow for regular monitoring of disease, death and cure rates. The herd veterinarian can be involved in developing protocols for disease detection, diagnosis and treatment, training farm staff in proper protocol implementation, and routine monitoring of the results in order to quickly identify problems as they emerge. Providing regular feedback on program performance to management and staff is a must to motivate people to continue to want to do well.

Bovine Respiratory Disease: Calves and Heifers

What is it?

Bovine respiratory disease (BRD) is an economically important disease of both pre- and post-weaned dairy heifers. It is the second most common cause of morbidity and mortality in pre-weaned heifers, and the primary cause of morbidity and mortality in weaned heifers. BRD affects 12% of milk-fed calves, and accounts for 24% of pre-weaned calf mortality and most commonly affects calves after 30d of age. BRD affects only 6% of post weaned heifers but accounts for more than 50% of death in this age group.

How to recognize it?

Signs of BRD in calves include an increased respiratory rate and/or effort, ocular and/or nasal discharge which may be purulent, a fever ( > 103F), a head tilt, and generalized malaise (including anorexia) (see above for University of Wisconsin Calf Health Scoring Chart). It is typical for calves with BRD to stand in a hunched position, possibly indicating thoracic abdominal pain, or to lay in sternal recumbency with head and neck extended, in an effort to increase the ease of air exchange.

Diagnosis of BRD in the field is typically based on clinical signs and calves are treated empirically. However, many advanced diagnostic techniques are available for pathogen characterization as well as antimicrobial sensitivity testing. Swabs can be taken from the nose, nasopharynx, as well as the trachea. Trans-tracheal washes, as well as Bronchoalveolar lavage, are further techniques described to get a diagnostic sample in animals with BRD. A sterile sample taken directly from lung tissue at necropsy is also acceptable, assuming the sampled animals have not been treated with antimicrobials during the course of their disease.

Pathogenesis:

Viral and bacterial pathogens responsible for BRD are typically transmitted via aerosol or direct contact, but can also be spread through milk or colostrum (e.g. mycoplasma). BRD is typically preceded by a stressful event (e.g. social stress at grouping, nutritional stress at weaning) paired with adverse environmental conditions (e.g. poor ventilation, drafty conditions, high ammonia levels) . This leads to viral infection of the upper airway, damage to the respiratory mucosa and impairment of innate defense mechanisms such as the mucociliary escalator. This leads to secondary bacterial invasion which leads to bronchopneumonia, typically in the right cranial lung lobe due to the tracheal bronchus, which is unique to ruminants. If not treated, bronchopneumonia can lead to hypoxia, septicemia, and death. Calves that recover from BRD have impaired performance throughout their lifetime.

Treatment:

There are many antibiotics that are labeled and approved to treat BRD in dairy calves and heifers under 20 months of age. Factors to consider when choosing an antibiotic include susceptibility of the pathogen to the antibiotic chosen, drug pharmacokinetics, cost of the drug, and withdrawal time. Non-Steroidal Anti-inflammatories and Corticosteroids can be used in addition to antibiotic therapy, but their use also decreases body temperature, which is the best indication that the course of antibiotics is working.

Prevention:

The focus on prevention of BRD involves providing calves and weaned heifers with adequate ventilation, preventing overcrowding (calves need at least 3m2 of space), minimizing contact between young and older calves, and segregation of sick calves from the group when appropriate. The use of vaccines, both intra-nasal in neonates, as well as parenteral vaccination in older heifers is another important component to the control and prevention of BRD.

After ventilation and vaccination, the most important aspect of BRD control is early detection and treatment. This can be accomplished through health screening (e.g. Wisconsin Calf Health Scoring Chart; California BRD scoring system), which evaluates rectal temperature, nasal and ocular discharge, ear position (head tilt), and whether or not a cough can be elicited. Calves can be screened two or three times per week and any calf that scores a 5 or greater is treated. Early detection and treatment result in improved performance of antimicrobials, treatment success, and a decrease in progression to more advanced BRD.

Neonatal Calf Diarrhea

What is it?

Neonatal calf diarrhea (NCD), commonly called scours or calf scours, is one of the most common diseases affecting pre-weaned dairy calves. According to a recent USDA study, 23% of milk-fed dairy calves will be affected by diarrhea during the preweaned period (first 8 weeks of life), of those affected, more than half (56%) will die.

How to recognize it?

Feces in young calves can have a wide range of color and consistency. A fecal score, on a scale of 0-3, can be used to characterize the fecal consistency of each individual calf. Normal feces in calves can range from solid to semi-solid, depending on the diet (higher amounts of milk-fed can lead to softer feces). When feces becomes loose or watery, the calf is considered to be scouring.  

Other than loose to watery feces with or without blood, other signs of neonatal calf diarrhea can include lethargy, depression, weakness, generalized malaise, dehydration, anorexia, fever (over 103F), and death. Diagnosis is typically based on clinical signs, as diagnostic testing is often unrewarding (multiple pathogens are often present in one fecal sample). Situations in which diagnostic testing would be warranted include: high mortality rates or an increase in incidence or severity. Fecal samples and/or swabs can be sent in for a “calf diarrhea panel” which includes testing of the relevant viral, bacterial, and protozoal causes of diarrhea.

Pathogenesis:

Viral, bacterial, and protozoal pathogens are transmitted via the fecal-oral route. These pathogens all have different mechanisms of action, but all result in either malabsorptive, secretory, or inflammatory diarrhea due to damage to intestinal villi. Fluid and other losses eventually lead to dehydration and metabolic acidosis. Septicemia is also a possible sequela to NCD. An important consideration when investigating NCD is what population of calves is affected and when they are showing clinical signs of disease. For example, if diarrhea is observed in the first several days of life, it is more likely to be due to E. Coli or Salmonella, usually encountered soon after birth. Conversely, diarrhea observed later in the pre-weaning period could be due to any number of pathogens. Another important consideration is the lifecycle of the pathogen. For example, Coccidia (Eimeria species of protozoa) cannot cause diarrhea before 21d due to the long prepatent period of the protozoa.

How to treat:

Fluid therapy is the most important component of treatment for NCD, and is based on the correction of dehydration and metabolic acidosis. Route of fluid therapy (IV or Oral) is based on the clinical signs of the calf. If the calf appears strong and is standing, she is treated with oral electrolytes only. If the calf is weak, is more than 8% dehydrated, and is less than 1 week of age, 5L of saline with 250meq of bicarb is indicated Intravenously, followed by oral electrolytes. If that same calf is older than one week of age, or is unable to stand, she is treated intravenously with 5L of saline with 500meq of bicarb added, and then followed by oral electrolytes.

There are many oral electrolyte solutions available. The most important considerations when choosing an oral electrolyte is the sodium concentration (90-130mM/L), the presence of an alkalizing agent (acetate/citrate), and the total osmolality (400 – 600mOsmol/L) of the solution when mixed. If treatment successfully addresses calf dehydration and acidosis, the calf should be improved in 12 hours. Another important component of treatment is nutritional support. If the calf is able to suckle, milk should not be withheld during a scouring episode. However, tube feeding milk is contraindicated in calves that cannot suckle and can predispose calves to abomasal bloat and death.

Antibiotics for the treatment of NCD are indicated in cases where bacteremia or septicemia are present but are not part of the mainstay of clinical treatment for scours. Non-steroidal anti-inflammatory drugs  (e.g. Meloxicam) can also be administered, as NCD is a painful disease.

Prevention:

Prevention of NCD is achieved through excellent calf management and attention to cleanliness, boosting immunity in the dam, and reducing stress in the calf. The dam should be vaccinated in late gestation with a product that confers protection against K99 E. Coli as well as Rota and Coronavirus. This will ensure adequate passive immunity to these organisms in the colostrum. Shortly after birth (<12hr of life), the calf should be administered 4 quarts of high quality, clean colostrum. The calf should then be placed in a clean environment and fed clean milk with clean utensils (buckets, bottles, etc). Sick calves should always be handled last, and isolated from healthy calves when appropriate.

Guided Learning Activities

Virtual Calf Barn Review

1. Watch this link to a video of a calf barn in Finland observe how they are addressing management areas including:

1. Newborn Care
2. Colostrum Management
3. Housing and Ventilation
4. Nutrition
5. Biosecurity
6. Calf Socialization

2. Answer the following questions about this system

1. Would you want to be a calf in this barn (why/why not)?
2. Do you have any concerns that you’d like to investigate?

1. Link to a calf investigation guide

3. Do you have immediate specific recommendations for improvement?
4. What additional information would you collect to do a more thorough investigation of the facility and management?

1. What questions do you have for management?
2. What records do you want to examine

1. What metrics and what are appropriate goals?

3. What tests or biological measures would you do/collect?

Self Guided Learning Activity

• Create a treatment protocol of calf diarrhea and pneumonia
• Create an SOP for tubing a calf with an esophageal feeder and the process to screen calves for disease.

Additional Resources

Key Resources for NCD and BRD:

1. Smith G.W., J. Berchtold. 2014. Fluid Therapy in Calves. Vet Clin NA Food Animal Practice. 30 (2): 409 - 427. https://doi.org/10.1016/j.cvfa.2014.04.002
2. McGuirk S.M. 2008. Disease Management of Dairy Calves and Heifers. Vet Clin NA Food Animal Practice. 24 (1): 139 - 153. https://doi.org/10.1016/j.cvfa.2007.10.003
3. Dr. Sam Ledley’s Calf Notes: Calf Health Section
4. University of Wisconsin Dairy Calf and Heifer Management - Extension: Calf Management

Acknowledgments