Chapter 69 Ricardo Stockler Veterinary Medicine Teaching and Research Center (VMTRC), University of California Davis, Tulare, California, USA Raising healthy and productive replacement dairy heifers is well known to be challenging to dairy farmers. This chapter emphasizes practical approaches for decreasing morbidity and mortality of dairy heifers from birth to weaning, focusing on topics such as the pregnant dam, the calving period, neonatal dietary requirements, and husbandry and health maintenance of the newborn heifer calf. Perinatal mortality is directly associated with both genetic and nongenetic causes.1 Calf sire and breed,2 dam breed,3 trait heritability,4,5 and gestation length3 are some examples of genetic variabilities that will in some degree influence neonatal death.1 Nongenetic factors would include season,6 calving environment, dry cow nutrition, dam vaccination history, and other specific risk factors associated with dystocia such as age at first calving,2 gender and birthweight,3,6 stress and uterine inertia as well as infectious and noninfectious causes following eutocia such as congenital defects,7 twinning,6,8 prematurity or dysmaturity, and abnormal placentation or premature placenta separation9 leading to the demise of the calf during or shortly after calving. Thus, knowing the risk factors, farmers must then focus on identifying cows that are in labor (close up) and move them promptly to a designated area separate from the rest of the herd. This can be determined based on the dam’s due date and/or clinical signs of labor. Maternity area or pen should have good lighting, minimum human and farm equipment traffic, and be separate from the rest of the herd to prevent transfer of diseases between newborns and adults. A well-designed facility does not replace good management, and thus close observation is essential so that cows spend the minimum necessary amount of time in the calving area. It is imperative to note that if cows are to be calved in a designated pen or stall, providing a well-bedded dry enclosure with good air quality is essential. Larger dairies may opt to use calving paddocks or pastures, close observation of cows, and the prompt movement of close up and fresh cows. The first hours of life to 3 months of age are crucial for the replacement heifer calf. Several variables will directly affect the health of the newborn calf and therefore its growth and potential productivity. The costs associated with raising a dairy heifer are positively related to price of feed (milk, milk replacer, waste milk and pasteurization, concentrate), type of housing, death losses, culling rate, and other fixable variable costs.10 In an article published in 2007, Zwald et al.11 reported that the average cost of raising a replacement heifer in northern United States was about $4.28 per day from birth to moving the heifers out of hutches into group pens. Colostrum management is critical: for neonates to achieve successful transfer of maternal immunoglobulin, a sufficient amount of immunoglobulin must be present in the colostrum, combined with a low bacterial count (measured in colony-forming units or cfu), and be consumed by the calf shortly after birth while the large immunoglobulin molecules are still able to be absorbed through the intestinal mucosa. High-quality colostrum contains immunoglobulin at a concentration in excess of 50 g/L with a bacterial count of less than 100 000 cfu/mL.12 Every neonate should be ingesting a minimum of 150–200 g of immunoglobulin within the first 4 hours of life.13 As far as the volume to be offered, the rule of thumb is 3–4 L of good-quality colostrum; however, one must also consider the 10–12% of body weight rule14 such that overfeeding should be avoided in some lighter calves, such as Jerseys and low-birthweight Holsteins. For optimum health, calves less than 1 week old that received sufficient good-quality colostrum should manifest minimum serum IgG1 concentrations of 1 g/dL.15 Recent work by Elizondo-Salazar and Heinrichs16 showed that the best method to reduce bacterial counts in colostrum is to batch pasteurize at 60 °C for 60 min, known as the 60/60 rule. This treatment has been proven to reduce the concentration of pathogenic bacteria while preserving the nutrient values, and provides a superior-quality immunoglobulin to the neonate. The shelf-life with refrigeration is 8–10 days.14 Drackley17 published a comprehensive report on calf nutrition in 2008. To summarize, a 45-kg calf requires 1.75 Mcal/day for maintenance in a thermoneutral environment. This is equivalent to 325 g of milk solids or 2.5 L of whole milk or 3 L of milk replacer, as the latter is lower in fat content compared with whole milk. As a guideline, producers should be feeding calves a milk diet from birth to weaning at a measured quantity of 8–10% of body weight per day, divided into two feedings; this amount may be adjusted up to 12% during the winter months.18 With regard to solid diet, 1.5% of body weight for the first week after birth increasing to 2% until weaning is recommended. It is also important to note that a calf should not be weaned off milk completely until it is regularly consuming 1 kg of starter feed daily.17 Housing is also particularly important and it is commonly understood that all calves must be kept dry, free from drafts, and separate from each other (no nose-to-nose contact) until weaning. The reasoning behind each is well described in the literature.18–20 Calf hutches or individual pens have been standard in the dairy industry;21 a minimum of 3 m2 is recommended and about an extra 10–15% open area between calves must be available to allow for cleaning and disinfection.20 Different calf hutches/pens are available in the market and their use will vary depending on region of the United States. Calf barns are very popular in the northern region, whereas outdoor hutches are commonly found in other areas of the United Statres. Hutches are usually not bedded (slatted wood floors, California style hutches), or bedded with sand, straw, shavings, or other suitable material. The calf hutch should face south in the winter and north in the summer,18 and be located in a prepared sloped area to allow water drainage away from the hutch. Dirt, gravel, concrete, or slatted wood may be used as flooring material. A rack to hold water and feed buckets and or nipple bottle should be placed outside the hutch, as this significantly reduces bedding maintenance. Common biosecurity practices should be practiced daily. Nipple bottles, water and feed bucks must be properly disinfected and rinsed, and must not be swapped between calves. Although age (12 weeks), weight (90–100 kg), and health condition must be considered, a calf should be weaned off milk and moved into a group pen only when consuming at least 1 kg of solids for three consecutive days.17,18 It is advisable to keep the calf in the hutch up to 10 days with starter feed ad libitum, after complete removal of milk diet; this practice allows the calf to lose its urge to nurse, as well as encourage the consumption of dry feed on a regular basis, adapting and promoting rumen growth. As discussed previously, good-quality colostrum delivered to the neonate within the first 4–6 hours after birth is essential for successful passive transfer of maternal immunoglobulins. It is recommended practice to remove the calf to a clean and dry area, protected from severe weather conditions where basic calf care can be done. Close examination for any obvious gross abnormalities, such as cleft palate or other birth defects, followed by inspection and disinfection of the umbilicus is critical. Proper identification and maintenance of accurate records is also important. The use of a “calf card” with information such as date of birth, sex, dam number, colostrum feeding (amount and quality), calving ease and general comments is recommended. This information can be easily transferred to the dairy management software for easy access at a later date. Chase et al.22 recently published a review that summarized the role of vaccines and of the neonatal immune system, as well as its impact on vaccine response. They concluded that, first and foremost, one must assess the disease risks at the production site, consider the dam’s immunity (i.e., colostrum quality), and age of the calf in order to determine the vaccination protocol. Despite new research being done to avoid vaccine interference with maternal antibodies, one must never undervalue the importance of delivering good-quality colostrum, nor support the extra-label drug use of vaccines.20 Vaccination schedules are farm specific and vary according to dairy practices; however, an example of a classic timetable is summarized in Table 69.1. Table 69.1 Typical vaccination protocol. Variation and inclusion of other pathogens may vary among farms.
Management to Decrease Neonatal Loss of Dairy Heifers
Introduction
From birth to weaning
Colostrum
Calf nutrition
Calf housing
Weaning
Health maintenance
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