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Managing newborn calf health – Part 1 - Assessment (Proceedings)
In the overwhelming majority of cases (except when a veterinarian delivers a calf in dystocia), the owner/herd manager will be the person best positioned to combat newborn calf health problems.
In the overwhelming majority of cases (except when a veterinarian delivers a calf in dystocia), the owner/herd manager will be the person best positioned to combat newborn calf health problems. Veterinary intervention will generally involve helping to establish and guide a system of newborn calf assessment and monitoring. This system should include specific guidelines on what parameters to evaluate and how to respond when abnormalities are seen.
A description of the normal newborn calf provides the measure against which problems can be compared. Normal calves should be born from an uncomplicated vaginal delivery, should breathe spontaneously, and should show strong activity almost immediately after birth. Any calf born in dystocia should be considered abnormal. Normal newborn calves may reasonably be expected to stand within one hour of birth. The calf's body temperature should not decrease below 101o F. An active suckling reflex should be present, even before the calf has stood, and the calf should have sought after feeding within two hours of birth. The calf should remain attentive, responsive, and strongly active throughout the first two hours of life.
A simple but effective monitoring program would include assessment of the dam's health, the type of delivery, the maturity of the newborn, and the physical and behavioral characteristics of the newborn. Specific monitoring points on all (but especially dystocia) calves should include: Calf vigor, Time to stand, Body temperature maintenance within the first hour, Active suckling. Calves born from an ill dam or with any degree of dystocia, or that appear premature at birth, will have an increased likelihood of encountering adaptive problems. If these problems are anticipated and treated before they manifest overtly, the likelihood of survival and reasonably good health can be increased dramatically. Such calves can be promptly dried and warmed, provided adequate shelter, stimulated to move about and suckle, and provided colostrum early and for a prolonged duration. Additional treatments to circumvent hypoxemia and acidosis would include nasal insufflation of oxygen and intravenous fluid therapy. Hypoglycemia can be easily monitored and managed with intravenous supplementation.
Calves that encounter adaptive problems without apparent predisposing risk factors can be detected by observation of their behavioral and physical characteristics. Calves that do not follow the normal pattern described above should be carefully monitored for changes in body temperature, physical strength, suckling ability, activity level, and blood glucose concentration. Such observations can be easily made by dairy personnel if they are instructed properly. Prompt attention to the frequently encountered problems of the newborn can dramatically enhance the newborn's chances of survival. Although compromised newborns will occasionally be found without apparent predisposing causes, the repeated appearance of such cases should prompt a thorough investigation of prepartum health and nutrition of the dams. Deficiencies and imbalances of protein, energy, and certain micronutrients may manifest with neonatal weakness and physiological derangement without readily apparent compromise of the dam.
Inactivity or lethargy: A dam with good mothering instincts can frequently stimulate the calf and thus is responsible for increased survival of her calves. Decreased activity is usually characterized by delayed standing and suckling behavior. These two critical activities generate heat and allow the calf to obtain nutrition and immunological support against disease. One of the most basic supportive care procedures for beef calves is to encourage good mothering behavior on the part of the dam. In the dairy industry, management systems mandate that calves be orphaned, so the calf manager must replace the role the dam would play in a more natural setting, so this person must directly intervene and provide that same mothering activity. These are the typical duties of any good calf manager and include rubbing the calf, lifting it to stand, encouraging it to walk about, providing colostrum via nipple feeder, or, if no suckle is elicited after a couple of hours, providing colostrum via esophageal intubation.
Hypothermia: The calf's body temperature is usually 1 to 2o F above the rectal temperature of the dam immediately after birth. The calf's temperature will usually drop to about 102o F within 15 to 30 minutes after delivery. A typical sign of neonatal adaptive problems is a body temperature that continues to drop below this level. As discussed above, there are numerous likely causes of hypothermia that can occur even in very warm surroundings, including hypoxemia, poor circulation, acid base disturbances, and calf lethargy and inactivity. Prompt drying with towels or warm hair dryers, application of heat lamps and heating blankets, as well as shelter from the elements are warranted from any calf suffering from dystocia or that fails to show normal efforts to rise within the first half to one hour after birth.
Hypoxemia: There are numerous pathogeneses for this abnormality, including atelectasis, weak ventilatory efforts, abnormal lung circulation, and maintenance of fetal cardiovascular shunts, as well as gas diffusion barriers in the alveoli. It is likely that one or more of these mechanisms is operative with any of a wide variety of adaptive problems. Fortunately, this problem is usually responsive to oxygen supplementation via nasal insufflation. Contrary to popular belief, arterial blood samples are easily obtainable even in the newborn calf via the brachial artery. Further, while many practitioners have found limited access to blood gas measuring devices, recent technological advances have made this measurement readily adaptable to the field situation. Even in the absence of a direct oxygen measurement, nasal oxygen supplementation is an easy procedure and could be practiced on the presumption of hypoxemia. We have seen no detrimental effects of providing supplemental oxygen.
Acidosis: Metabolically compromised or dystocia-asphyxiated calves will likely demonstrate metabolic acidosis due to lactic acid accumulation. While some have advocated the use of bolus sodium bicarbonate injection in the past, this problem is correctable by the calf's own energy metabolism if the cardiovascular and metabolic systems are functioning normally. Calves are typically born with a relative volume contraction that corrects after the first feeding and absorption of colostrum. This normal process is better mimicked by large volume fluid expansion than by small volume sodium bicarbonate bolus injection. Respiratory acidosis is also common in the neonate. This problem is responsive to improved ventilation. In extreme cases, mechanical ventilation could be provided, but this is impractical to maintain on an ongoing basis in a field practice. Usually the respiratory acidosis is self correcting as the calf's vigor and ventilation improve with other supportive measures.
Poor Colostral Transfer: An additional note is probably warranted concerning colostrum consumption. Calves born in dystocia or with physiological disturbances from some other cause are more prone than their normal counterparts to poor colostral immunoglobulin protection. This tendency is attributable to numerous factors including delayed or decreased consumption of colostrum, decreased colostrum availability due to problems with the dam, and decreased intestinal absorption due to poor gastrointestinal activity or poor mucosal absorptive capacity. A calf's disease susceptibility is also increased by some of the physiological disturbances mentioned in the paragraphs above. This combination of factors is in part responsible for the increased infectious disease occurrence seen in dystocia-affected calves. Even when the problems discussed above have been properly addressed, special attention should be given to increasing colostral administration to these calves. It has been demonstrated that hypoxemic and acidotic calves display decreased immunoglobulin absorption but also delayed closure of the absorptive process. For this reason, it is worthwhile to supplement colostrum both at increased volumes and for a prolonged time period. It is advisable to measure plasma immunoglobulin or total protein concentration in valuable calves from dystocia since colostral absorption is unpredictable.
Infectious calf diseases For calves beyond a couple days old, infectious conditions become the predominant health problem. For these conditions, the assessment of calf health should include all of the parameters discussed above, but include specific observations that help distinguish between the most common disease problems of viral enteritis, bacterial infections, and septicemia. These include dehydration, diarrhea, perfusion of mucous membranes, body temperature. Simple scours produces substantial fluid and electrolyte loss as the primary problem, leading to dehydration and acid-base imbalance, which are life-threatening when severe. Affected calves show varying degrees of diarrhea and a consistent feature of the clinical picture is metabolic acidosis, commensurate with the degree of fluid loss and dehydration. Affected calves can show mild to profound metabolic acidosis, usually with compensating respiratory alkalosis. The metabolic changes are more closely associated with bicarbonate loss than with lactate accumulation and are very responsive to supplementation of bicarbonate in the fluid therapy protocol. It is common for severely affected calves to show serum bicarbonate concentrations as low as 4 to 6 mEq/L. Responsiveness to treatment is remarkable, however, and affected calves may be standing and nursing as little as several hours after initiation of corrective intravenous fluid treatment.
A good diagnostic workup can and should distinguish between viral/protozoal enteritis and other causes of diarrhea in calves. Making this distinction is important because successful treatment and prevention measures will depend on being appropriately directed at the right disease. No single physical or laboratory parameter is capable of accurately identifying the septicemic calf, except the positive identification of an invading microorganism in the blood or multiple body sites. There are, however, some physical findings and laboratory parameters highly suggestive of septicemia. These findings included hyperemic mucous membranes, injected scleral vasculature, depression that exceeded the degree of dehydration or apparent fluid loss, and profound depression in the absence of signs of severe diarrhea. Laboratory findings that suggest septicemia include minimal acid base disturbance associated with severe systemic weakness or depression, moderate to severe hyperfibrinogenemia, prominent neutrophilia or neutropenia, and the presence of metamyelocytes or myelocytes on a peripheral blood smear.