Raising healthy calves is crucial to the success of a dairy operation as heifers are the future of the milking herd. There are several important aspects related to pre-weaned calf management including maternity pen management, colostrum management, nutrition, housing, and proper hygiene is a key to all of these factors. Timely diagnosis of disease and treatment is also an important component of calf rearing. Although calves are not actively contributing to milk sales, it is in the farm’s best interest to closely monitor calf health in an effort to produce high quality replacement heifers.
Despite all of the advances in management and technology on farms, preliminary estimates from the National Animal Health Monitoring System (NAHMS) Health and Management Practices on U.S. Dairy Operations 20141 study report the average mortality rate at 6.5% during the pre-weaning phase. Diarrhea or digestive problems accounted for 56.4% of the deaths and respiratory problems were attributed to another 24.0% of deaths in pre-weaned calves. Death due to diarrhea is mainly related to dehydration and also septicemia (infection of the blood). When looking at pre-weaned calf morbidity, 21.3% had diarrhea (75.7% of calves with diarrhea or digestive problems were treated with antimicrobials) and 12.2% of calves had respiratory disease (94.5% of calves with respiratory issues were treated with antimicrobials). Additionally, 1.7% of pre-weaned heifer calves affected with navel infections (90.7% of calves with navel infections were treated with antimicrobials). Regular monitoring and good record keeping may hasten diagnosis of sick calves. Supportive therapy during early stages of illness may help reduce calf loss.
Proper hygiene is necessary in all aspects of calf management. This begins in the maternity pen. Maternity pens should be well-bedded with clean and dry bedding and are ideally separated from pens housing sick animals. Regular bedding changes and disinfection in between uses can help to reduce pathogen loads. Calves are born with little to no immunity, so reducing exposure to pathogens is important. Additionally, calves have very little fat reserves at birth, so the maternity pen should be draft-free, especially in colder climates and seasons. Maternity pens should be well-supervised so that calves can be removed from the dam in a timely manner. This will help reduce pathogen exposure as well as reduce potential injuries which may occur especially in group pens. The cleanliness of the maternity pen can also contribute to navel infections. The use of a 7% tincture of iodine dip shortly after calving can help reduce navel infections.
There are many important aspects of pre-weaning calf management, but the quality, amount, and timing of colostrum fed to calves is a main focus on most farms. Feeding four liters of high quality colostrum (> 50 mg/mL of immunoglobulins) within 6 to 12 hours of birth has been a common recommendation. Absorption of immunoglobulins (Ig) in the intestinal tract decreases over time, therefore, it is important to deliver these nutrients to the calf in a timely manner. Immunoglobulins help provide protection during the first couple weeks of life while the calf develops its own active immunity.
In addition to timing, colostrum quality is key. Colostrum quality can be estimated easily on-farm via use of a colostrometer or hydrometer. This tool is reliably used to distinguish good quality colostrum from poor quality colostrum. A Brix Refractometer is another tool which can be used on-farm to determine colostrum quality. It is best to measure colostrum quality, no matter which tool is used, using room temperature (72 °F) samples as lower or higher temperature can provide false quality readings.
Another indicator of colostrum quality is bacterial content. Bacterial counts can be limited with sanitary collection and handling. Colostrum should be fed to the calf or refrigerated/frozen within one to two hours to prevent excessive bacterial growth. Additionally, colostrum (or milk) can be pasteurized to reduce bacterial loads. Studies have shown that batch pasteurization for 60 minutes at 60 °C significantly reduce bacterial counts with minimal destruction of immunoglobulins. Pasteurizers require proper cleaning and regular maintenance to help ensure they are effectively reducing bacterial counts. One good way to monitor pasteurizer efficiency is to test the bacterial counts of milk samples both before and after pasteurization to know if bacterial content is being reduced. Again, hygienic handling of the pasteurized milk is important to prevent re-contamination prior to feeding.
Dairy calves have traditionally been limit-fed liquid feed (at approximately 10% of bodyweight which is estimated to be half of normal consumption) in an effort to accelerate weaning and reduce input costs. Multiple studies conducted during the past decade have investigated the potential benefits of increasing the amount of milk or milk replacer offered to calves. Data suggests that more intensive feeding programs promote growth, improve feed efficiency, improve health and animal welfare, and potentially improve future milk production. These improvements may be due to increased availability of nutrients for growth, improved immune function, and improved ability to deal with climate-induced stress.
Limit feeding may only provide enough nutrients and energy for maintenance requirements. During cold weather (and also hot weather) more energy is required to maintain body temperature. Additionally, energy requirements are increased when a calf is ill in order to mount an immune response, but dietary intakes typically decline during this increased need, putting the calf at an even greater disadvantage. Calves which received greater amounts of milk or milk replacer experienced lower mortality and morbidity than those which had restricted intakes most likely due to their improved ability to cope with challenges.
In addition to reconsidering the sheer volume of milk or milk replacer fed, the fat and protein formulation of traditional milk replacers have also been investigated. A 20% protein: 20% fat powder is commonly fed. Higher nutrient dense formulations have been created which have nutrient profiles more similar to whole milk. These are especially beneficial during cold weather and for small breeds, such as Jerseys, which are at a greater risk of heat loss.
Feed additives are available for use in milk replacers and also calf starters. Prebiotics and probiotics can help establish beneficial gut flora which may improve resistance to gastrointestinal disease. Phytogenic feed additives can help increase intake as well as having biological effects including antimicrobial, anti-inflammatory, and antioxidative, all of which can help improve gut health. Yeast and yeast cell wall products have been shown to bind Gram negative bacteria and support digestive health. Acidifiers can improve liquid feed hygiene and improve digestibility. There are many products on the market which may be beneficial, but none of these can overcome excessively poor hygiene or extremely poor quality feeds.
Housing is also important to raising healthy calves. Proper hygiene is key and calves should be provided with plenty of clean, dry bedding. Ventilation is also important to maintain good air quality and reduce respiratory issues. Most calves are housed individually prior to weaning, but recent research has seen benefits in performance parameters and social interactions for calves housed in pairs. Cross-suckling is a concern when calves are housed together, but non-nutritive suckling can also be detrimental to the health of individually housed calves due to potential pathogen ingestion. Further research is needed in regard to group housing and reduction of all types of suckling.
Many factors influence pre-weaning calf health and can have carry-over effects later in life. During times when milk prices are low it may be tempting to cut input costs, especially at a stage of production where earnings are not apparent, but poor calf rearing can eventually affect profits when those heifers enter the milking herd. Spending time and money to raise healthy calves will pay off in the future.
USDA. 2017. Preliminary estimates. Dairy 2014, Health and Management Practices on U.S. Dairy Operations, 2014 USDA–APHIS–VS–CEAH–NAHMS. Fort Collins, CO #696.0317
23 January 2023
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