Welfare of young dairy calves--myths and realities (Proceedings)

Animal welfare is the state of an animal as it attempts to cope with its environment.  Humans interact or affect the animals through their activities and husbandry practices.  Veterinarians have been advocates for animal welfare for years, long before it was ever defined as “animal welfare.”  Just a few years ago, many of us confused the term with being in line with radical animal rights groups.  Today, one of the biggest areas of research interest in universities is related to animal welfare.  

Over the last several years, there have been many video segments aired on the media outlets that have presented deficiencies in animal welfare on production animal facilities.  The animal production industry has many animal production methods that are not particularly pleasing to the everyday consumer, i.e. gestation stalls for sows and veal crates for young calves to name a couple.  Whenever one of these videos surface and consumers see how animals “are raised in the real world” (according to the anti-agriculture activists), there is a renewed effort calling for improved animal welfare on animal production farms. 

The dairy industry is not immune to these challenges and we need to work together and tell our story about how well dairy animals are raised.  This has resulted in the creation of programs such as the National Dairy FARM Program: Farmers Assuring Responsible Management Animal Care Guidelines being adopted by many dairy processors.  This has been done to assure consumers that their dairy producers use best management practices in the production of dairy products.

Despite the many advances in research affecting dairy calf management, calf rearing continues to be an area that challenges management.  According to the last NAHMS Dairy report, death loss in pre-weaned and weaned calves has changed very little over the last twenty years.  These surveys have shown that pre-weaned mortality has ranged from a low of 7.8% in the 2007 survey to a high of 10.8 in the 1996 survey. 

Weaned calf mortality has ranged from 1.8 – 2.8% in the last four NAHMS Dairy surveys (USDA, 2009).  These numbers represent a huge loss to the dairy industry and challenges producers and their consultants to create strategies to improve the health of these animals.  As a result, these changes should provide dairy farmers with more replacements allowing for genetics progress and potentially eliminating the need to purchase outside replacements.

Facilities

Facilities used to raise calves have made an about-face over the last twenty years.  Individual hutches or pens for calves that are placed outdoors, providing increased bio-security for the individual animal, have become common place.  These often have replaced poorly ventilated barns where calves were often group raised.  Now, many dairy farms are again raising calves in buildings to improve the working conditions for the people that manage the calves.  

The advent of computer feeders is also renewing interest in raising calves in groups.  Group feeding strategies appear to stress calves less through the weaning period, however, they do increase the risk for increased morbidity and mortality over calves raised in individual hutches.  No matter whether producers use hutches or group housing, raise the calves indoors or outdoors, there are a few basic tenants that must be in place in order for these operations to be successful. 

Calves should be removed from their dams immediately following birth to reduce the potential for contracting an infectious agent in the calving pen.  Calves should be transported in clean carts to a receiving area to allow the calf time to dry and acclimate to its new environment.  The use of towels to help dry the calf and/or the use of a heat box assures that the calf does not become hypothermic.  Drying of the head, ears, nose and mouth stimulates the calf to breath.  As soon as a suckle reflex is present, the calf can be fed colostrum.

The calf should be placed in a hutch or pen that provides a minimum of 28-32 ft2 of space per animal.  If calves are group housed, they still appear to get a better start if they are housed individually for a few days.  Solid plastic partitions between adjacent calves provide for the most protection against calf to calf spread of disease.  However, they also require special considerations to properly ventilate.  When ambient temperatures are below 58 F, sufficient bedding should be provided to allow the calf to nest into the bedding and conserve heat.  Additionally, consideration must be given to minimize heat stress during the warmer months of the year. 

Calves spend more than 75% of their time lying down between birth and weaning, so there is tremendous opportunity to expose calves to infectious agents via the bedding material.  Deep bedded straw provides the best ability to nest and should be sufficiently deep to allow the calves legs to be hidden while lying down.  Other bedding materials such as corn stalks, bean stubble, and wood shavings can be suitable bedding materials during warmer weather.  Materials with smaller surface areas are more prone to retaining moisture and manure and, therefore, can give rise to higher bedding bacteria counts.

In both individual and group housed barns, positive pressure ventilation systems have been shown to be effective at reducing airborne bacteria levels, thus reducing the risk for respiratory disease.  Building and pen design play a large role in determining the ventilation system requirements and design.  Buildings with individual pens that have solid partitions between calves produce individual pen microenvironments that need to be individually ventilated. 

In group housed barns, natural or negative ventilation systems do not provide sufficient air movement at the level where the calf is housed to properly replenish fresh air.  Positive pressure ventilation systems that provide at least 15 cubic feet per minute of additional air flow improve air quality at the calf level and reduce respiratory disease morbidity and mortality (Nordlund, 2007). 

When calves are housed in group pens, limiting group size to 7-10 animals per group has a positive effect on reducing calf morbidity and mortality from respiratory disease.  It is unclear whether this effect is due to improved social welfare of the calves or the effect of stocking density per unit of area of the barn (Gorden, 2010).  During design and construction of calf barns, sufficient space must be included to allow for small pens even during the periods with the highest calving rates.  In order to achieve these recommendations, space should be sufficient to accommodate up to 140% of the weekly calving rate.  Additionally, accommodations should be made to allow for a calf pen to be managed in an “all in-all out” format with sufficient time between groups to allow for proper cleaning and sanitation.

Nutrition

Once the calf has developed a suckle reflex after birth, three to four quarts (10-12% of the calf's body mass) of clean, good quality colostrum should be delivered to the calf within 4-6 hours.  Jersey calves should be limited to three quarts of colostrum.  While this recommendation has been common place for years in the literature, the evidence of successful implementation of this practice is lacking.  According to the NAHMS Dairy 2007 survey which reported 19.2% of dairy calves experience failure of passive transfer (USDA, 2010).  The desired goal of colostrum administration is to deliver enough colostrum to achieve a serum immunoglobulin 1 (IgG1) concentration of at least 1000 mg/dL. 

In order to achieve this goal, the calf must ingest 150-200 g of immunoglobulin through the delivery of good quality colostrum or a colostrum replacement product.  Good quality colostrum has a minimum concentration of 50 g/L, thus the recommendation of 3-4 quarts.  Colostrum quality is extremely variable and can be measured in the field but, this procedure has limited use.  At a minimum, colostrum should be collected within 4-6 hours of birth as lactogenesis will dilute the colostrum and reduce the quality.

Bacterial contamination of colostrum interferes with intestinal absorption, so it is essential that excellent udder preparation practices are in place prior to collection of colostrum.  In addition, the equipment used to collect, feed, and store the colostrum should be maintained in a sanitary manner in order to reduce bacterial contamination.  Unused colostrum can be stored in a good quality refrigerator for a period of 3 days and can be frozen for a period of 1-2 years without sufficient loss of quality.  Storage vessels should be thin walled and small in order to minimize insulation effects and allow for rapid cooling.  Slow cooling allows for bacteria in the colostrum to incubate during storage.  In addition, these types of storage vessels will make re-heating the colostrum more rapid. 

Reduction of bacterial numbers can be achieved through pasteurization or acidification of colostrum with the use of products like formic acid.  Colostrum should be pasteurized at 140 F for one hour.   Bacterial contamination can be monitored by completing total bacteria counts (TBC) and coliform counts.  As a goal, TBC of colostrum should be less than 1 million colony forming units (cfu)/mL and a coliform count of less than 10,000 cfu/mL (McGuirk, 2004).

Calves will typically not ingest 3-4 quarts of colostrum in one feeding on their own, so the use of an esophageal feeder is essential to assure adequate colostrum delivery.  The use of a four quart esophageal feed will assure employee compliance of this recommendation.  It should be noted that calves will typically not be very hungery at the next feeding but this should not deter farms from utilizing the recommendation of feeding 3-4 quarts of colostrum.  

Over the past 10-15 years, we have gained tremendous intellect in the area of calf nutrition.  Traditional feeding programs limit fed calves in an attempt to get the calves eating starter early in their life and lead to early weaning.  These feeding programs have not been overly successful in promoting good calf health.  Experience has repeatedly shown that increasing the plane of nutrition of calves during the milk feeding period has reduced morbidity and mortality rates. 

When looking at nutritional needs of calves, it is important to understand the nutritional needs of the immune system.  Studies have shown that nutrient consumption increases dramatically during bacterial challenge.  Moderate infections have been shown to increase gluconeogenesis rate 150-200%.  Sepsis in humans has been demonstrated to increase basal metabolic rate 25-55% while sepsis in laboratory rodents has resulted in loss of 40% of total body protein and a reduction in the rate of protein synthesis (Lochmiller, 2000).  If calves do not have sufficient body reserves when challenged, they are at an increased risk to show clinical disease.

According to the Dairy Calf and Heifer Association's Gold Standards, calves should double their birth weight through the milk feeding period.  Therefore, a calf with an 85 lb. birth weight will need to gain 1.30 lbs./day assuming a 60 day milk feeding period.  Utilizing the NRC software program, expected growth rates can be predicted for different feeding programs.  In addition, estimates of the impact of cold stress can be demonstrated.  The program does not do a good job of predicting growth during periods of heat stress. 

As an example, if a producer feeds one pound of a 20% protein:20% fat milk replacer to an 85 lb. calf during thermoneutral periods along with 0.25 lbs./day of starter, calves will only gain 0.67 lbs./day with protein being the growth limiting nutrient.  If the ambient temperature drops to 32 F, the expected growth rate drops to 0.12 lbs. /day with energy now becoming the growth limiting nutrient.  By comparison, feeding 4 quarts of whole milk per day would only result in a gain of 0.57 lbs. /day at 32 F and just over one pound of gain per day during thermoneutral periods. 

Increasing caloric intakes in calves during the milk feeding period is best accomplished by adding an additional feeding per day.  In many operations, the extra labor requirement to provide an extra feeding is not available so extra calories are delivered by increasing the volume of milk per feeding and/or increasing the concentration of milk replacer powder per volume of water, up to a maximum of 18% solids.  Feeding consistency is important for maintenance of calf health.  In order to minimize digestive disorders, changes in feeding should be made slowly with a minimum of 3-5 days between changes.

Assuring that plenty of fresh water is always available is essential for minimizing digestive upsets and for the consumption of calf starter.  Calves will not eat starter if they do not have water available. Starter consumption, not hay, is the driving force behind the development of the rumen.  Weaning of calves should occur once calves are consuming 2-2.5 lbs. of starter per day for at least three consecutive days.  Depending upon the plane of nutrition offered through milk feeding, the amount of milk offered per day may need to be decreased in order to encourage the consumption of starter.

Castration and dehorning

Castration of dairy calves should be completed at as young an age as practical.  There are many techniques available but, surgical castration is the recommended method in young calves.  The use of elastrator bands is an inexpensive method of castration but, has been associated with chronic pain and is not recommended.  The Animal Care Manual for the National Dairy Farm Program recommends that a licensed veterinarian perform castration on calves four months of age and older with the use of local anesthetic. 

Dehorning should also be done as early as possible.  The use of local anesthetic is becoming more common in the dairy industry.  Research workers at ISU recently completed a trial in which they evaluated a pressure algometer as an objective measure of pain tolerance following cautery disbudding.  Groups of calves were assigned to the treatment group which was disbudded following lidocaine administration or the control group that were sham disbudded following lidocaine administration. 

The project demonstrated that calves experienced pain for at least 59 hours after disbudding and that lidocaine eliminated the calf's perception of pain.  However, this pain relief was only effective for one hour after disbudding (Van Donselaar, 2009).  This project clearly shows that even though lidocaine prevents pain at the time of the surgical procedure, the effect is short-lived and far short of the time frame for which pain was present.  More research is needed to determine whether the use of certain analgesics would improve calf welfare during the time following surgical procedures.  

Conclusion

Dairy producers and their veterinarians are involved in animal welfare on a daily basis.  As veterinarians trained in production animal medicine, we are uniquely qualified to guide animal owners about best management practices that improve animal welfare.  The use of these practices in calf rearing operations will result in larger pools of calves available as replacements.  This will allow herds to make genetic progress and improve bio-security by not having to purchase heifers with unknown backgrounds. 

Programs like the National Dairy FARM Program help the dairy industry provide quality assurance to consumers that animals are being raised with the use of best management practices.  We must assure that this effort is not just cursory window dressing by demonstrating success stories to the consumer.