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Environmental Factors and Calving Management Practices that Affect Neonatal Mortality in the Beef Calf
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PERINATAL MORTALITY IN BEEF HERDS
ENVIRONMENTAL FACTORS AND CALVING MANAGEMENT PRACTICES THAT AFFECT NEONATAL MORTALITY IN THE BEEF CALF Hugh C.C. Townsend, DVM, MSc
RATES AND CAUSES OF MORTALITY OF NEONATAL CALVES
Depending on the study and the definitions used, reported rates of neonatal mortality in beef calves range from about 4% to 60/0. 1,2,8,10,15,18 The most common causes are dystocia, diarrhea, pneumonia, and the effects of exposure during inclement weather. 1,4 Neonatal mortality tends to cluster in individual herds,l' 15, 17 often with serious financial consequences for the owners. Diarrhea is the most important infectious disease causing these losses1 and, from an epidemiologic point of view, is the one studied most extensively. Outbreaks of diarrhea affecting 30% to 50% of newborn calves and caused by enterotoxigenic Escherichia coli, rotavirus, coronavirus, Cryptosporidium, or combinations of these agents are relatively common. 1 The case fatality rates are often in the range of 1.5% to 3%, but may be as high as 30% or more. Acres l estimated that, in any given year, about 10% of herds experience outbreaks of diarrhea in which 4% or more of the calves in the herd die. Based on a more recent but smaller study, Schumann17 found that 4% of beef herds in Alberta
From the Department of Veterinary Internal Medicine, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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experienced a death loss of greater than 4% due to scours during a single calving season. In a study of beef herds in Ontario, death losses among calves exceeded 5% in 14% to 16% of the herds. 9 Based on the results of these studies, an individual practice should expect that between 4% and 16% of cow/calf clients will experience unacceptable calf mortality in any given year. Although some herds may experience problems for several years, different herds tend to be involved from year to year. 1 To prevent outbreaks of infectious diseases in newborn calves, efforts must be made to limit their exposure to the causative agents, to increase nonspecific and specific immunity, and to decrease stress. To meet these objectives, it is necessary to provide the newborn calf with a suitable environment and adequate nutrition. Other methods aimed at increasing nonspecific and specific immunity are unlikely to yield the desired results in stressed, poorly nourished, poorly sheltered calves exposed to high concentrations of virulent organisms. Several detailed discussions of the importance of these factors and their relationship with neonatal morbidity and mortality have been published1, 12-14 and are based on research conducted in western Canada during the 1970s. More recently, epidemiologic studies have been conducted in Montana,4, 10 Colorado,I6 Alberta,17 and Ontari02,9 in an attempt to further characterize and measure the effect of some of these factors.
THE IMPORTANCE OF TIMING OF THE CALVING SEASON
The majority of calving occurs in the spring of the year, with the peak in April or May. Because of the demand for feeder calves in October and November, there has been a tendency for cow / calf operators to push calving dates back toward the first of January in an attempt to deliver well grown calves to this market. The results of three independent studies suggest that increased calf mortality is associated with calving early in the year,3, 17, 18 and McDermot~ reports that calving heifers earlier in the season results in increased rates of dystocia. Calves born prior to the first of April are frequently exposed to extremely adverse climatic conditions. An increased incidence of neonatal diarrhea is reported following inclement weather conditions1 and exposure-related chilling is an important cause of neonatal mortality.4, 10 This is particularly true in regions where the calving grounds become covered with snow. Calving in very cold weather leads to the use of sheds, barns, or other confined and covered areas that tend to become contaminated with infectious agents, particularly when overcrowding occurs. As the calving season progresses and the snow melts, the calving grounds tend to become wet and muddy. This forces the concentration of calvings onto limited areas of the calving ground where shelter, drainage, and exposure to the sun are suitable to the dam. Newborn calves also may not have adequate access to clean, dry, sheltered areas in which to get the long periods of rest and sleep they require. The end results of calving under these conditions are a
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tendency to maximize the influence of environmental factors that contribute to outbreaks of infectious diseases, particularly calf diarrhea, and, as a result, an increase in the number of mortalities.
HERD STRUCTURE (AGE OF DAMS AND HERD GROUPINGS)
Calves born to heifers are more likely to die by 1 month of age than calves born to cows. As a result, the higher the percentage of heifers in the herd, the greater the risk of high neonatal mortality.17 This increased risk among calves born to heifers appears to be true for all causes of mortality,I, 15 with the most important being dystocia and neonatal diarrhea.I, 4,5,8-10 The case fatality rate due to scours for calves born to heifers is at least three times greater than that in calves born to cows. I, 17 The mortality rate due to scours for calves born to heifers on farms with a high incidence of diarrhea was 14.8%, compared with 4.3% for calves born to cows. On farms with a low incidence of diarrhea, the mortality rate due to scours in calves born to heifers was 0.44%, compared with 0.07% for those born to COWS. 17 The reasons for these findings are related to the fact that calves born to heifers are more likely to experience both inadequate passive transfer immunity and exposure to high concentrations of infectious agents. Heifers tend to be poorer mothersl and to produce less colostrum, with lower antibody concentration, than cowsY There also is a higher rate of dystocia among heifers, with an increase in the incidence of exhaustion, weakness, and swollen tongues in their calves. These conditions limit the ability of the calf to nurse normally during the first hours of life. Because of the risks associated with calving, heifers tend to be kept nearer the calving facility and more closely confined than cows. These circumstances contribute to increased contact between animals, increased contamination of the environment, and an increase in the rate of mismothering. Maintaining both heifers and cows in a single group increases the risk of mortality among their calves. The odds of high mortality due to calf scours was 3.6 times greater in herds in which the cows and heifers were wintered together, versus those where they are wintered separately.17 This may be related to the facts that (1) the production of colostrum depends on prepartum nutritional intake and (2) a higher rate of dystocia has been reported among heifers that are kept together with the cows. 8 Heifers are less likely to experience difficulty competing for feed and therefore are more likely to reach growth potential and produce adequate amounts of colostrum if they are wintered separately from the cows. There also is a tendency for mortality to increase in herds in which heifers and cows are calved in the same group.17 This may be due to the higher incidence of diarrhea that occurs in calves born to heifers, resulting in increased environmental contamination and a greater risk of disease in all calves born in that same area.
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The odds of high mortality were increased by a factor of 4.3 in herds where dead calves were replaced by purchased calves less than a month of age. 17 Because of the design of the study, however, it was not possible to determine whether this was a true risk factor or simply that replacements were more likely to be purchased in reaction to high rates of mortality. Schumann17 also reported an increase in the risk of high mortality as the duration of the calving season increased. This may have been because of an increase in the level of contamination over a prolonged calving season. The possibility that herds with short calving seasons were subject to better overall management than those with long calving seasons also must be considered. For these reasons, the influence of purchasing replacement calves and the duration of calving season upon mortality both deserve further study. PHYSICAL FACILITIES (PASTURES, PENS, SHELTERS)
Increased contamination of the environment with viral and bacterial agents or increased contact among susceptible animals results in increased morbidity and mortality among neonatal calves. Close confinement of cows and heifers during the wintering period, the calving period, or the nursing period; calving on the wintering ground; nursing on the calving ground; calving and nursing in poorly drained areas; and calving in sheds or barns all have been reported to increase neonatal calf morbidity due to infectious diseases. 1,2, 13,14,17 The odds of experiencing high neonatal mortality were three times greater in herds that calved on the wintering ground than in those in which separate wintering and calving grounds were maintained. 17 According to some unpublished re:" sults,13 high rates of neonatal diarrhea were not observed when each cow was allowed 1000 square feet of calving area but did occur when this area was limited to 250 square feet. McDermottB reports higher rates of dystocia in herds calved in barns and progressively decreasing rates of dystocia as the site of calving becomes less confined. PREVENTION
There are three basic principles involved in limiting mortality caused by infectious disease in newborn beef calves: (1) limit exposure to the causative organisms, (2) maximize the nonspecific resistance of the calf, and (3) maximize the specific resistance of the calf. Exposure to infectious agents and low levels of nonspecific immunity are probably the two most important factors contributing to outbreaks of infectious disease. Unless these two points are addressed, increasing the specific immunity of the calf through vaccination is unlikely to lead to decreased morbidity or mortality. Attempts to limit the risk of mortality in newborn calves due to infectious diseases usually require careful, long-term planning and ade-
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quate preparations for the calving season. This is particularly true for producers who elect to calve early in the season and under relatively confined conditions. Detailed outlines for procedures to be taken in the prevention and control of epidemics of acute diarrhea in beef calves have been published. 12- 14 A list of recommendations that should be considered when addressing the problem of high levels of neonatal mortality follows. Not all of these recommendations have been shown to be effective in decreasing mortality but they serve as useful guidelines until more information becomes available. 1. A herd visit should be conducted well in advance of the calving season to identify the presence of risk factors associated with outbreaks of infectious disease. This visit may occur as part of a routine herd health program or may be decided upon as a result of unacceptable losses during the previ()us calving season. 2. Unless demanded by other considerations, calving in the winter months, when adverse weather conditions are certain, should be avoided. 3. Maintain separate cow and heifer herds throughout the wintering, calving, and nursing periods. 4. Ensure adequate nutrition and weight gains in both the heifers and the cows. 5. Prepare the calving and nursing areas well in advance. Ensure that there is sufficient drainage and bedding and that snow removal and other equipment necessary to prepare the ground is readily available. 6. Adequate shelter must be available in both the calving and nursing grounds. Depending on the time of year and local conditions, this may be provided through the use of shelter belts, porosity fences, large open-faced overhead shelters, and moveable calf hutches. 7. To limit contamination of the calving areas, do not use them until about 2 weeks before calving begins. Retain late calvers in the wintering area as long as possible. Keep the bedding clean and dry, provide multiple feeding and bedding areas in the calving grounds, and rotate these areas regularly. Infectious agents are capable of prolonged survival in contaminated buildings, bedding, soils, and surface water. Avoid calving in barns or sheds. Such facilities are easily contaminated and, once this occurs, it is very difficult to correct the situation. When calving is completed, the ground should be cleaned, harrowed, and, if possible, left vacant until the next calving season. If possible, calving and nursing areas should be rotated to new ground each year to prevent the build-up of infectious organisms. 8. Prevent crowding in the calving area. Provide a minimum of 1000 square feet of well-drained ground per cow/calf pair. Calve in small groups and move cow/calf pairs to a nursing area of adequate size as soon as the cow/calf bond has been well established, usually within the first 24 hours.
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9. Limit contamination in the nursing grounds. Choose welldrained areas with plenty of exposure to the sun and provide multiple feeding and bedding areas within the nursing area. Disinfect and move any calf hutches or shelters frequently. Move cow / calf pairs out of the nursing ground by the time the calf reaches 3 weeks of age. 10. Consider a vaccination program for cows and heifers against E. coli, rotavirus, and coronavirus.
MANAGEMENT OF OUTBREAKS OF DISEASE ASSOCIATED WITH HIGH MORTALITY
High rates of neonatal mortality should not occur in circumstances in which the aforementioned recommendations for prevention of infectious disease have been followed adequately. When outbreaks do occur, a herd visit is required because recommendations for prevention or management of disease cannot be made based on an office visit. Herd visits usually reveal the presence of a combination of risk factors. In the face of a disease outbreak, owners and managers may become overwhelmed by the situation and experience difficulty developing an effective management plan. For this reason the consulting veterinarian should conduct a herd visit and become directly involved in the process of planning and implementing corrective procedures. The objective of this process should be the development of a list of recommendations that are clear, simple, and efficient in terms of both cost and time.
Recommendations for Control of Outbreaks
1. After obtaining a detailed history of the problem, both the animals and the facilities should be inspected. The purpose of this inspection is to establish the diagnosis and the extent of the problem, to identify known risk factors for the disease, and to identify the range of options available for treatment and control. Detailed protocols for conducting investigations of outbreaks have been published elsewhere.6,7 As a reminder, inspection of the animals should include examination and sampling of both affected and unaffected calves and necropsy of all those that have died recently. 2. Recommendations should address all the important risk factors for the disease identified on the farm or ranch. These recommendations should include the removal of all calves from contaminated areas, dispersion of cows and calves over as wide an area of new ground as possible, and separation of affected and unaffected cow/calf pairs. In the short term, serious consideration should be given to hiring temporary help to assist with the extra work load associated with management of an outbreak. Existing
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4.
5. 6.
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personnel may be exhausted and demoralized by the time they call for help. Specific individuals, equipment, clothing, and facilities should be dedicated to the treatment of affected calves. If at all possible, these people and their equipment should not come into contact with healthy cow / calf pairs. Design a simple protocol for identifying sick calves and a decision tree for determining which calves should be isolated and treated on the farm and which should be transported to a veterinary clinic for more intensive therapy. Design protocols for the isolation and treatment of affected calves and the disinfection of equipment and facilities. These protocols should be simple, rapid, and efficient to carry out. Examples would include some training of personnel in the necessary techniques, developing a treatment kit, and recommending a simple system for identifying treated calves and recording treatments administered. Put all recommendations in writing and follow up with phone calls and visits to see that they are being followed. It may not be wise to spend time making detailed recommendations for disease prevention in subsequent years to an exhausted, worried client in the middle of a disease outbreak. The consulting veterinarian should consider conducting a follow-up visit in the late spring or early summer for this purpose. At that time, both parties should have more time to design a program for preventing neonatal mortality.
SUMMARY
This article reviews the relationship of environmental and calving management factors and the occurrence of neonatal mortality. The importance of these factors, considered individually or in combinations, has been the subject of a limited number of scientific investigations. As a consequence, some recommendations are based on clinical impression and reasoning rather than the results of carefully controlled field studies. Significant costs are incurred by cow / calf operators in the implementation of many of these ideas. Hopefully, they are all appropriate and useful, but more research should be conducted in this area. There is a need to learn more about environmental causes of neonatal mortality, including individual effects, the effect of various combinations of these factors, and the relative magnitude of the effect of both individual factors and various combinations of them.
References 1. Acres SD: The epidemiology of acute undifferentiated neonatal diarrhea of beef calves in western Canada [PhD thesis]. Saskatoon, University of Saskatchewan, 1976
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2. Alves DM, McDermott H, Anderson NG, et al: Health, productivity, and management of calves on Ontario beef cow-calf herds. The Bovine Practitioner 21:135, 1989 3. Bagley CP, Carpenter JC, Feazel JI, et al: Influence of calving season and stocking rate on beef cow-calf productivity. J Anim Sci 64:687, 1987 4. Bellows RA, Patterson DJ, Burfening PJ, et al: Occurrence of neonatal and postnatal mortality in range beef cattle. II. Factors contributing to calf death. Theriogenology 28:573, 1987 5. Gregory KE, Cundiff LV, Koch RM: Breed effects and heterosis in advanced generations of composite populations for birth weight, birth date, dystocia, and survival as traits of dam in beef cattle. J Anim Sci 69:3574, 1991 6. Lessard PR, Perry BD (eds): Investigation of disease outbreaks and impaired productivity. Vet Clin North Am Food Anim Pract 4(1), 1988 7. Martin SW, Meek AH, Willeberg P: Veterinary Epidemiology, Principles and Methods. Ames, Iowa State University Press, 1987, p 283 8. McDermott H, Allen OB, Martin SW, et al: Patterns of stillbirth and dystocia in Ontario cow-calf herds. Can J Vet Res 56:47, 1992 9. McDermott H, Alves DM, Anderson NG, et al: Measures of herd health and productivity in Ontario cow-calf herds. Can Vet J 32:413, 1991 10. Patterson DJ, Bellows RA, Burfening PJ, et al: Occurrence of neonatal and postnatal mortality in range beef cattle. I. Calf loss incidence from birth to weaning, backward and breed presentations and effects of calf loss on subsequent pregnancy rate of dams. Theriogenology 28:557, 1987 11. Petrie L, Acres SD, McCartney DH: The yield of colostrum and colostral gammaglobulin in beef cows and the absorption of colostral gammaglobulins by beef calves. Can Vet J 25:273, 1984 12. Radostits OM: The role of management and the use of vaccines in the control of acute undifferentiated diarrhea of newborn calves. Can Vet J 32:155, 1991 13. Radostits OM, Acres SD: The control of acute undifferentiated diarrhea of newborn beef calves. Vet Clin North Am Food Anim Pract 5(1):143, 1983 14. Radostits OM, Acres SD: The prevention and control of epidemics of acute undifferentiated diarrhea of beef calves in western Canada. Can Vet J 21:243, 1980 15. Rogers RW, Martin SW, Meek AH: Reproductive efficiency and calf survival in Ontario beef cow-calf herds: A cross-sectional mail survey. Can J Comp Med 49:27, 1985 16. Salman MD, King ME, Odde KE, et al: Annual disease incidence in Colorado cow-calf herds participating in rounds 2 and 3 of the National Animal Health Monitoring System from 1986 to 1988. J Am Vet Med Assoc 198:962, 1991 17. Schumann FJ, Townsend HGG, Naylor JM: Risk factors for mortality from diarrhea in beef calves in Alberta. Can J Vet Res 54:366, 1990 18. Whittum TE, Salman MD, Curtis CR, et al: The national animal health monitoring system of Colorado beef herds: Management practices and their association with disease rates. Prev Vet Med 8:215, 1990
Address reprint requests to Hugh G. G. Townsend, DVM, MSc Department of Veterinary Internal Medicine Western College of Veterinary Medicine University of Saskatchewan Saskatoon, Saskatchewan S7N OWO Canada
PERINATAL MORTALITY IN BEEF HERDS
ENVIRONMENTAL FACTORS AND CALVING MANAGEMENT PRACTICES THAT AFFECT NEONATAL MORTALITY IN THE BEEF CALF Hugh C.C. Townsend, DVM, MSc
RATES AND CAUSES OF MORTALITY OF NEONATAL CALVES
Depending on the study and the definitions used, reported rates of neonatal mortality in beef calves range from about 4% to 60/0. 1,2,8,10,15,18 The most common causes are dystocia, diarrhea, pneumonia, and the effects of exposure during inclement weather. 1,4 Neonatal mortality tends to cluster in individual herds,l' 15, 17 often with serious financial consequences for the owners. Diarrhea is the most important infectious disease causing these losses1 and, from an epidemiologic point of view, is the one studied most extensively. Outbreaks of diarrhea affecting 30% to 50% of newborn calves and caused by enterotoxigenic Escherichia coli, rotavirus, coronavirus, Cryptosporidium, or combinations of these agents are relatively common. 1 The case fatality rates are often in the range of 1.5% to 3%, but may be as high as 30% or more. Acres l estimated that, in any given year, about 10% of herds experience outbreaks of diarrhea in which 4% or more of the calves in the herd die. Based on a more recent but smaller study, Schumann17 found that 4% of beef herds in Alberta
From the Department of Veterinary Internal Medicine, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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experienced a death loss of greater than 4% due to scours during a single calving season. In a study of beef herds in Ontario, death losses among calves exceeded 5% in 14% to 16% of the herds. 9 Based on the results of these studies, an individual practice should expect that between 4% and 16% of cow/calf clients will experience unacceptable calf mortality in any given year. Although some herds may experience problems for several years, different herds tend to be involved from year to year. 1 To prevent outbreaks of infectious diseases in newborn calves, efforts must be made to limit their exposure to the causative agents, to increase nonspecific and specific immunity, and to decrease stress. To meet these objectives, it is necessary to provide the newborn calf with a suitable environment and adequate nutrition. Other methods aimed at increasing nonspecific and specific immunity are unlikely to yield the desired results in stressed, poorly nourished, poorly sheltered calves exposed to high concentrations of virulent organisms. Several detailed discussions of the importance of these factors and their relationship with neonatal morbidity and mortality have been published1, 12-14 and are based on research conducted in western Canada during the 1970s. More recently, epidemiologic studies have been conducted in Montana,4, 10 Colorado,I6 Alberta,17 and Ontari02,9 in an attempt to further characterize and measure the effect of some of these factors.
THE IMPORTANCE OF TIMING OF THE CALVING SEASON
The majority of calving occurs in the spring of the year, with the peak in April or May. Because of the demand for feeder calves in October and November, there has been a tendency for cow / calf operators to push calving dates back toward the first of January in an attempt to deliver well grown calves to this market. The results of three independent studies suggest that increased calf mortality is associated with calving early in the year,3, 17, 18 and McDermot~ reports that calving heifers earlier in the season results in increased rates of dystocia. Calves born prior to the first of April are frequently exposed to extremely adverse climatic conditions. An increased incidence of neonatal diarrhea is reported following inclement weather conditions1 and exposure-related chilling is an important cause of neonatal mortality.4, 10 This is particularly true in regions where the calving grounds become covered with snow. Calving in very cold weather leads to the use of sheds, barns, or other confined and covered areas that tend to become contaminated with infectious agents, particularly when overcrowding occurs. As the calving season progresses and the snow melts, the calving grounds tend to become wet and muddy. This forces the concentration of calvings onto limited areas of the calving ground where shelter, drainage, and exposure to the sun are suitable to the dam. Newborn calves also may not have adequate access to clean, dry, sheltered areas in which to get the long periods of rest and sleep they require. The end results of calving under these conditions are a
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tendency to maximize the influence of environmental factors that contribute to outbreaks of infectious diseases, particularly calf diarrhea, and, as a result, an increase in the number of mortalities.
HERD STRUCTURE (AGE OF DAMS AND HERD GROUPINGS)
Calves born to heifers are more likely to die by 1 month of age than calves born to cows. As a result, the higher the percentage of heifers in the herd, the greater the risk of high neonatal mortality.17 This increased risk among calves born to heifers appears to be true for all causes of mortality,I, 15 with the most important being dystocia and neonatal diarrhea.I, 4,5,8-10 The case fatality rate due to scours for calves born to heifers is at least three times greater than that in calves born to cows. I, 17 The mortality rate due to scours for calves born to heifers on farms with a high incidence of diarrhea was 14.8%, compared with 4.3% for calves born to cows. On farms with a low incidence of diarrhea, the mortality rate due to scours in calves born to heifers was 0.44%, compared with 0.07% for those born to COWS. 17 The reasons for these findings are related to the fact that calves born to heifers are more likely to experience both inadequate passive transfer immunity and exposure to high concentrations of infectious agents. Heifers tend to be poorer mothersl and to produce less colostrum, with lower antibody concentration, than cowsY There also is a higher rate of dystocia among heifers, with an increase in the incidence of exhaustion, weakness, and swollen tongues in their calves. These conditions limit the ability of the calf to nurse normally during the first hours of life. Because of the risks associated with calving, heifers tend to be kept nearer the calving facility and more closely confined than cows. These circumstances contribute to increased contact between animals, increased contamination of the environment, and an increase in the rate of mismothering. Maintaining both heifers and cows in a single group increases the risk of mortality among their calves. The odds of high mortality due to calf scours was 3.6 times greater in herds in which the cows and heifers were wintered together, versus those where they are wintered separately.17 This may be related to the facts that (1) the production of colostrum depends on prepartum nutritional intake and (2) a higher rate of dystocia has been reported among heifers that are kept together with the cows. 8 Heifers are less likely to experience difficulty competing for feed and therefore are more likely to reach growth potential and produce adequate amounts of colostrum if they are wintered separately from the cows. There also is a tendency for mortality to increase in herds in which heifers and cows are calved in the same group.17 This may be due to the higher incidence of diarrhea that occurs in calves born to heifers, resulting in increased environmental contamination and a greater risk of disease in all calves born in that same area.
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The odds of high mortality were increased by a factor of 4.3 in herds where dead calves were replaced by purchased calves less than a month of age. 17 Because of the design of the study, however, it was not possible to determine whether this was a true risk factor or simply that replacements were more likely to be purchased in reaction to high rates of mortality. Schumann17 also reported an increase in the risk of high mortality as the duration of the calving season increased. This may have been because of an increase in the level of contamination over a prolonged calving season. The possibility that herds with short calving seasons were subject to better overall management than those with long calving seasons also must be considered. For these reasons, the influence of purchasing replacement calves and the duration of calving season upon mortality both deserve further study. PHYSICAL FACILITIES (PASTURES, PENS, SHELTERS)
Increased contamination of the environment with viral and bacterial agents or increased contact among susceptible animals results in increased morbidity and mortality among neonatal calves. Close confinement of cows and heifers during the wintering period, the calving period, or the nursing period; calving on the wintering ground; nursing on the calving ground; calving and nursing in poorly drained areas; and calving in sheds or barns all have been reported to increase neonatal calf morbidity due to infectious diseases. 1,2, 13,14,17 The odds of experiencing high neonatal mortality were three times greater in herds that calved on the wintering ground than in those in which separate wintering and calving grounds were maintained. 17 According to some unpublished re:" sults,13 high rates of neonatal diarrhea were not observed when each cow was allowed 1000 square feet of calving area but did occur when this area was limited to 250 square feet. McDermottB reports higher rates of dystocia in herds calved in barns and progressively decreasing rates of dystocia as the site of calving becomes less confined. PREVENTION
There are three basic principles involved in limiting mortality caused by infectious disease in newborn beef calves: (1) limit exposure to the causative organisms, (2) maximize the nonspecific resistance of the calf, and (3) maximize the specific resistance of the calf. Exposure to infectious agents and low levels of nonspecific immunity are probably the two most important factors contributing to outbreaks of infectious disease. Unless these two points are addressed, increasing the specific immunity of the calf through vaccination is unlikely to lead to decreased morbidity or mortality. Attempts to limit the risk of mortality in newborn calves due to infectious diseases usually require careful, long-term planning and ade-
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quate preparations for the calving season. This is particularly true for producers who elect to calve early in the season and under relatively confined conditions. Detailed outlines for procedures to be taken in the prevention and control of epidemics of acute diarrhea in beef calves have been published. 12- 14 A list of recommendations that should be considered when addressing the problem of high levels of neonatal mortality follows. Not all of these recommendations have been shown to be effective in decreasing mortality but they serve as useful guidelines until more information becomes available. 1. A herd visit should be conducted well in advance of the calving season to identify the presence of risk factors associated with outbreaks of infectious disease. This visit may occur as part of a routine herd health program or may be decided upon as a result of unacceptable losses during the previ()us calving season. 2. Unless demanded by other considerations, calving in the winter months, when adverse weather conditions are certain, should be avoided. 3. Maintain separate cow and heifer herds throughout the wintering, calving, and nursing periods. 4. Ensure adequate nutrition and weight gains in both the heifers and the cows. 5. Prepare the calving and nursing areas well in advance. Ensure that there is sufficient drainage and bedding and that snow removal and other equipment necessary to prepare the ground is readily available. 6. Adequate shelter must be available in both the calving and nursing grounds. Depending on the time of year and local conditions, this may be provided through the use of shelter belts, porosity fences, large open-faced overhead shelters, and moveable calf hutches. 7. To limit contamination of the calving areas, do not use them until about 2 weeks before calving begins. Retain late calvers in the wintering area as long as possible. Keep the bedding clean and dry, provide multiple feeding and bedding areas in the calving grounds, and rotate these areas regularly. Infectious agents are capable of prolonged survival in contaminated buildings, bedding, soils, and surface water. Avoid calving in barns or sheds. Such facilities are easily contaminated and, once this occurs, it is very difficult to correct the situation. When calving is completed, the ground should be cleaned, harrowed, and, if possible, left vacant until the next calving season. If possible, calving and nursing areas should be rotated to new ground each year to prevent the build-up of infectious organisms. 8. Prevent crowding in the calving area. Provide a minimum of 1000 square feet of well-drained ground per cow/calf pair. Calve in small groups and move cow/calf pairs to a nursing area of adequate size as soon as the cow/calf bond has been well established, usually within the first 24 hours.
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9. Limit contamination in the nursing grounds. Choose welldrained areas with plenty of exposure to the sun and provide multiple feeding and bedding areas within the nursing area. Disinfect and move any calf hutches or shelters frequently. Move cow / calf pairs out of the nursing ground by the time the calf reaches 3 weeks of age. 10. Consider a vaccination program for cows and heifers against E. coli, rotavirus, and coronavirus.
MANAGEMENT OF OUTBREAKS OF DISEASE ASSOCIATED WITH HIGH MORTALITY
High rates of neonatal mortality should not occur in circumstances in which the aforementioned recommendations for prevention of infectious disease have been followed adequately. When outbreaks do occur, a herd visit is required because recommendations for prevention or management of disease cannot be made based on an office visit. Herd visits usually reveal the presence of a combination of risk factors. In the face of a disease outbreak, owners and managers may become overwhelmed by the situation and experience difficulty developing an effective management plan. For this reason the consulting veterinarian should conduct a herd visit and become directly involved in the process of planning and implementing corrective procedures. The objective of this process should be the development of a list of recommendations that are clear, simple, and efficient in terms of both cost and time.
Recommendations for Control of Outbreaks
1. After obtaining a detailed history of the problem, both the animals and the facilities should be inspected. The purpose of this inspection is to establish the diagnosis and the extent of the problem, to identify known risk factors for the disease, and to identify the range of options available for treatment and control. Detailed protocols for conducting investigations of outbreaks have been published elsewhere.6,7 As a reminder, inspection of the animals should include examination and sampling of both affected and unaffected calves and necropsy of all those that have died recently. 2. Recommendations should address all the important risk factors for the disease identified on the farm or ranch. These recommendations should include the removal of all calves from contaminated areas, dispersion of cows and calves over as wide an area of new ground as possible, and separation of affected and unaffected cow/calf pairs. In the short term, serious consideration should be given to hiring temporary help to assist with the extra work load associated with management of an outbreak. Existing
PRACTICES THAT AFFECT NEONATAL MORTALITY IN THE BEEF CALF
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4.
5. 6.
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personnel may be exhausted and demoralized by the time they call for help. Specific individuals, equipment, clothing, and facilities should be dedicated to the treatment of affected calves. If at all possible, these people and their equipment should not come into contact with healthy cow / calf pairs. Design a simple protocol for identifying sick calves and a decision tree for determining which calves should be isolated and treated on the farm and which should be transported to a veterinary clinic for more intensive therapy. Design protocols for the isolation and treatment of affected calves and the disinfection of equipment and facilities. These protocols should be simple, rapid, and efficient to carry out. Examples would include some training of personnel in the necessary techniques, developing a treatment kit, and recommending a simple system for identifying treated calves and recording treatments administered. Put all recommendations in writing and follow up with phone calls and visits to see that they are being followed. It may not be wise to spend time making detailed recommendations for disease prevention in subsequent years to an exhausted, worried client in the middle of a disease outbreak. The consulting veterinarian should consider conducting a follow-up visit in the late spring or early summer for this purpose. At that time, both parties should have more time to design a program for preventing neonatal mortality.
SUMMARY
This article reviews the relationship of environmental and calving management factors and the occurrence of neonatal mortality. The importance of these factors, considered individually or in combinations, has been the subject of a limited number of scientific investigations. As a consequence, some recommendations are based on clinical impression and reasoning rather than the results of carefully controlled field studies. Significant costs are incurred by cow / calf operators in the implementation of many of these ideas. Hopefully, they are all appropriate and useful, but more research should be conducted in this area. There is a need to learn more about environmental causes of neonatal mortality, including individual effects, the effect of various combinations of these factors, and the relative magnitude of the effect of both individual factors and various combinations of them.
References 1. Acres SD: The epidemiology of acute undifferentiated neonatal diarrhea of beef calves in western Canada [PhD thesis]. Saskatoon, University of Saskatchewan, 1976
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2. Alves DM, McDermott H, Anderson NG, et al: Health, productivity, and management of calves on Ontario beef cow-calf herds. The Bovine Practitioner 21:135, 1989 3. Bagley CP, Carpenter JC, Feazel JI, et al: Influence of calving season and stocking rate on beef cow-calf productivity. J Anim Sci 64:687, 1987 4. Bellows RA, Patterson DJ, Burfening PJ, et al: Occurrence of neonatal and postnatal mortality in range beef cattle. II. Factors contributing to calf death. Theriogenology 28:573, 1987 5. Gregory KE, Cundiff LV, Koch RM: Breed effects and heterosis in advanced generations of composite populations for birth weight, birth date, dystocia, and survival as traits of dam in beef cattle. J Anim Sci 69:3574, 1991 6. Lessard PR, Perry BD (eds): Investigation of disease outbreaks and impaired productivity. Vet Clin North Am Food Anim Pract 4(1), 1988 7. Martin SW, Meek AH, Willeberg P: Veterinary Epidemiology, Principles and Methods. Ames, Iowa State University Press, 1987, p 283 8. McDermott H, Allen OB, Martin SW, et al: Patterns of stillbirth and dystocia in Ontario cow-calf herds. Can J Vet Res 56:47, 1992 9. McDermott H, Alves DM, Anderson NG, et al: Measures of herd health and productivity in Ontario cow-calf herds. Can Vet J 32:413, 1991 10. Patterson DJ, Bellows RA, Burfening PJ, et al: Occurrence of neonatal and postnatal mortality in range beef cattle. I. Calf loss incidence from birth to weaning, backward and breed presentations and effects of calf loss on subsequent pregnancy rate of dams. Theriogenology 28:557, 1987 11. Petrie L, Acres SD, McCartney DH: The yield of colostrum and colostral gammaglobulin in beef cows and the absorption of colostral gammaglobulins by beef calves. Can Vet J 25:273, 1984 12. Radostits OM: The role of management and the use of vaccines in the control of acute undifferentiated diarrhea of newborn calves. Can Vet J 32:155, 1991 13. Radostits OM, Acres SD: The control of acute undifferentiated diarrhea of newborn beef calves. Vet Clin North Am Food Anim Pract 5(1):143, 1983 14. Radostits OM, Acres SD: The prevention and control of epidemics of acute undifferentiated diarrhea of beef calves in western Canada. Can Vet J 21:243, 1980 15. Rogers RW, Martin SW, Meek AH: Reproductive efficiency and calf survival in Ontario beef cow-calf herds: A cross-sectional mail survey. Can J Comp Med 49:27, 1985 16. Salman MD, King ME, Odde KE, et al: Annual disease incidence in Colorado cow-calf herds participating in rounds 2 and 3 of the National Animal Health Monitoring System from 1986 to 1988. J Am Vet Med Assoc 198:962, 1991 17. Schumann FJ, Townsend HGG, Naylor JM: Risk factors for mortality from diarrhea in beef calves in Alberta. Can J Vet Res 54:366, 1990 18. Whittum TE, Salman MD, Curtis CR, et al: The national animal health monitoring system of Colorado beef herds: Management practices and their association with disease rates. Prev Vet Med 8:215, 1990
Address reprint requests to Hugh G. G. Townsend, DVM, MSc Department of Veterinary Internal Medicine Western College of Veterinary Medicine University of Saskatchewan Saskatoon, Saskatchewan S7N OWO Canada