THE NEWBORN FOAL

Chapter 11


THE NEWBORN FOAL




NEONATAL PHYSIOLOGY


The changes that the newborn foal must make at birth are very profound, involving to a lesser or greater degree almost all the body systems.



CARDIORESPIRATORY ADAPTATION


The transition from a fetus that is protected and nourished within the uterus to the free-living neonatal foal is probably the most profound change the foal will have to face. Airway clearance and the establishment of a normal respiratory function are vital. This is integrally coordinated with the cardiovascular adaptations that need to occur. Passage of the foal through the birth canal provides significant beneficial thoracic compression to drive excess fluid from the airway. Foals delivered by cesarean section do not have this mechanism and so need extra care for a clear airway to be established.


At the moment of birth the lungs must expand and the pulmonary circulation ‘switched-on’ to ensure a perfect ventilation–perfusion match between the two sides of the circulatory system. The change to pulmonary breathing and the circulatory adjustments that must accompany such a change within minutes of birth must be perfect if the foal is to survive and be able to move quickly to ensure safety.1 Up to this point the blood from the pulmonary artery is shunted via the ductus arteriosus into the aortic circulation as a result of the high resistance afforded by the collapsed lungs and the relatively low aortic pressure. Oxygen-saturated blood arriving in the caudal vena cava from the placental vessels passes through the foramen ovale to the left atrium so that the brain receives freshly oxygenated blood. This pathway is obliterated within the first few weeks of life.2


At the moment of birth the lungs expand in response to a dramatic rise in PCO2. This reduces the pressure in the pulmonary artery to below that in the aorta and so blood is directed into the lungs, with some being shunted by the relatively high aortic pressure into the pulmonary artery. At the same time there is no further need for the foramen ovale. The highly elastic nature of the ductus arteriosus means that some shunting one way or the other is present for up to 48–72 hours, but thereafter the ductus closes and becomes a fibrous band.


In the newborn foal respiration is often gasping in character and necessarily rapid as the foal attempts first to ensure full insufflation of the lungs and then to correct the acid–base imbalances that have arisen during the birth process. The efficiency of oxygenation of the blood is profoundly affected by the breathing pattern and any decrease in ventilation can alter the blood oxygen severely (and possibly dangerously).


The position the foal adopts also influences the oxygenation of blood. A foal in lateral recumbency may have a markedly lower partial pressure of arterial oxygen than one in sternal recumbency. This forms one of the most important principles of the management of neonatal foals. Also, the chest wall of the newborn foal is very compliant and so any respiratory disorder may have a disproportionate adverse influence on lung efficiency.3



Cardiac murmurs in foals


Although congenital defects of the heart and great vessels are rare, up to 90% of newborn foals have obvious continuous murmurs associated with a patent ductus arteriosus that are audible over the left base of the heart for the first 15–30 minutes of life.4 In most cases the murmurs will not be audible by 72 hours, but some may persist for some weeks.5 Murmurs are also commonly associated with sepsis, fever, anemia, etc.; these may vary from day to day.



Note:




If cyanosis is present with a murmur it may indicate:



Arrhythmia, including atrial fibrillation, atrial tachycardia and ventricular depolarization, is also common in newborn foals within the first 15–30 minutes of life. However, although such events could be alarming they are almost invariably due to high vagal tone and will resolve spontaneously over a short period.6 It may be unwise to perform an electrocardiographic examination on a very new foal because the results may be misleadingly alarming. Differentiation of the abnormal is the challenge for the clinician.



LOCOMOTION


The foal needs to rise quickly to its feet and to move with certainty. This means that the muscles and skeleton also need to adapt quickly to new forces and functions. This also involves the nervous system, which has to perform a vast range of functions that have been only ‘tested’ in utero. It would be a major disadvantage if a full-term foal were to practice and develop the full range of muscular activity in utero. There is some evidence that in utero movement of the foal becomes progressively more limited in the last months of pregnancy. Owners might therefore report that the foal’s movements have reduced or may even have apparently stopped altogether, suggesting that there may be a problem with the pregnancy. The limited movement in the later stages of pregnancy may predispose the relatively long-legged foal to abnormalities of growth and discrepancies between bony growth (over which there is almost no control) and tendon/ligament growth (which is probably coordinated by movement, posture and forces applied during their development).



ALIMENTATION


The next obvious major adaptation is the change from placental nutrition to alimentation. In order for the foal to feed effectively it must first have a perception/instinct to rise and then to seek the teat. Sight may be less important than would be expected but it obviously helps. Having once located the teat it must be in a position to suckle effectively and to swallow. Once swallowed, the milk must be delivered to the gastrointestinal tract and then digested efficiently. The gut must be fully patent to the anus and there should be no physical, neurological or other obstruction. The waste material from the digestive processes, which have also been going on during gestation (the meconium), have to be passed shortly after birth. The residues from digestion of colostrum support this by a laxative effect.


Milk is the source of nutrients for the neonatal mammal and the composition of the mammary secretion changes considerably with time.7 In the first hours after birth the milk is rich in immunoglobulins (colostrum). It is tempting to assume that milk provides all the nutritional requirements for the foal. However, in the longer term this is not necessarily so; foals need to supplement the milk feed with other ingesta within weeks of birth and will often be seen to take grass or hay within days of birth. Although natural mare’s milk is used to provide the formula for the preparation of artificial milk supplements, it does contain a delicately balanced variety of essential nutrients, including vitamins, minerals and enzymes, and artificial milk replacers are unlikely ever to match the gold standard of normal milk for any particular species.


The normal foal has a defined demand for food materials, but the abnormal or sick foal will inevitably have an increased demand for all the components. The demand for energy is often at least 50% above normal and can be much higher. The same applies to protein and fats as well as minerals and vitamins. Premature foals require extra food to complete organ maturation, but infection, fever, etc. place extreme demands on the foal’s ability to ingest enough raw materials. In reality, a sick foal often has a reduced appetite and so can easily fall into a downward spiral.


The specific requirements of the normal newborn foal are:



Normal feeding should result in a normal growth rate (weight gain) of around 1.25–1.5 kg/day in a Thoroughbred foal.








RENAL FUNCTION


Urinary excretion begins during gestation, with passage of urine into the bladder and then into the allantoic space. A smaller volume of urine will pass into the amniotic fluid via the urethra. The mean urine production in a neonatal foal is around 145–155 ml/kg bodyweight per day.8 This figure is far higher than in mature horses. These factors can be explained simply by the fact that the neonatal kidney is not functionally mature at birth and so renal concentration of urine is much less efficient than in adult horses. Foal urine is frequently more dilute than that of adult horses. The naturally high fluid intake and the lack of concentrating ability means that a foal’s urine has a naturally low specific gravity. The inability to concentrate urine means that it may remain relatively dilute in the face of dehydrating conditions that might otherwise be expected to cause urinary concentration. Foals also often have a relatively high urinary protein concentration9 and this can be significant, even in the normal foal. Furthermore the ability of the kidney to withstand toxic insult and to excrete some drugs etc. efficiently may be very immature. Therefore, drugs and chemicals that damage renal tissue might be expected to have an enhanced toxicity in foals.


The first passage of urine is an important event with respect to neonatal assessment (see p. 371). Colt foals usually pass their first urine at around 5–6 hours of age. By contrast, filly foals may delay their first micturition up to 10–11 hours. Observation of the first and subsequent micturition is an important stud procedure and the timing of the first natural urination has implications for those foals that have urinary tract defects such as patent bladder or ruptured ureters.





ASSESSMENT OF A FOAL’S RISK CATEGORY


The concept of a risk category for foals11 has been used for many years and has been instrumental in saving many lives. A system involving three broad categories, in which the foal is classed as high-risk, moderate-risk or low-risk, is most widely used.12 This is simple and serves the purpose well. A two-category classification is a simpler method that avoids the equivocal moderate category and has the advantage that more foals will be classified as high-risk and are therefore likely to be monitored more closely. The recognition that a problem might be present will enable the clinician to take pre-emptive measures to minimize any clinical consequences. On the basis that prevention is better than cure, the system has much to commend it. The concept should be used to guide the level of supervision and interference for a newborn foal. All management strategies for pregnant mares should be directed towards detection of potential or actual problems before they are so advanced that therapy may not be effective.




Why is risk categorization useful?


An assessment of the likely risk category of the foal will be of considerable benefit to its survival. A predesignated high-risk foaling provides a good chance of improving the survival rate by taking suitable planned measures in advance. Some factors can be predicted (particularly those relating to the mare and her breeding history) but others become significant as the pregnancy and parturition advance. In considering these factors the reproductive and general history of the mare and the pregnancy is paramount. Furthermore, it is important to regularly assess both mare and the unborn foal during gestation so that potential problems can be identified early.


It is virtually impossible to categorize mares without any historical information and in this case they should probably be classified as high-risk immediately. The major problem here is that those with no history are probably those that are of less importance to their owners and their classification may be less significant.


High-risk mares are therefore those in which possible complications can be expected. This means that parturition can be monitored closely and completely. In this way a higher foal survival rate can be expected. An additional benefit is that the survival rate of mares can also be improved and in most such cases their future fertility can be supported.








High-risk foals


These are cases in which there is a significant danger to the life of the foal as a result of:




Maternal conditions

Factors that are present at any stage before birth may have a profound effect on the prognosis for the pregnancy (see Table 11.1). In particular, any factors that influence placental nourishment of the foal or subsequent colostrum production are of major importance.




• Prolonged or shortened pregnancy.


• Discrepancy between size of foal and size of mare and her birth canal.


• History of problem foals (e.g. dysmature/premature, neonatal isoerythrolysis, neonatal maladjustment/asphyxia syndrome, congenital defects).


• History of previous uterine torsion in present or previous pregnancy.


• History of colostral leakage or premature lactation prior to delivery.


• Purulent vaginal discharge or vaginal bleeding.


• Disease/injury with or without drug administration.


• Pelvic injuries (fresh or long-standing), or space-occupying lesions that might alter the dimensions and congruity of the birth canal.


• Lameness or neurological disorders that prevent normal behavior and posture prior to and during delivery.


• Pyrexia/toxemia/septicemia/endotoxemia.


• Poor bodily condition/poor nutritional status (primary or secondary).


• Hydrops amni (very rare).


• Colic/colic surgery/other surgery (cesarean section or uterine torsion)/anesthesia.


• Primiparous delivery (especially if suspect behavior) or history of aggression.


• Twin pregnancy.


• Transport prior to delivery (last 4 weeks of gestation).



Parturition conditions

Factors affecting the process of parturition would necessarily have a profound effect on the viability of the foal (see Table 11.2). Any factor that affects the ability of the foal to adapt (e.g. loss of blood from early cord separation may cause a slow adaptive period and inability to rise) will have significance:






Low-risk foals


A foal can be classified as low risk if:



• There are no maternal factors that might adversely affect survival of the foal.


• Gestation is of normal duration and there have been no complications with the health of the mare during pregnancy (or any previous pregnancy).



Note:




• Delivery of the foal is normal and without complication or delays.



Note:




• The adaptive period should be normal with the foal standing within 2 hours and suckling by 3 hours.


• Colostral intake is effective and raises the foal’s IgG concentration to over 8–10 g/l.


• The placenta is normal and is passed freely.


• There are no external dangers (such as infections in other horses, inclement weather, predators, etc.).




EVENTS FOLLOWING DELIVERY IN THE NORMAL FOAL (THE ADAPTIVE PERIOD)


The adaptive period is the time during which the foal must adjust from the uterine environment to the ‘independent dependence’ of extrauterine life.


It is important to recognize the normal events that take place (see Table 11.3) so that any abnormal events can be quickly recognized and appropriate corrective action taken. Unfortunately, there are wide variations in the normal pattern of delivery and neonatal adaptation, thus making the decision to interfere difficult. The extent of veterinary intervention will often depend heavily on the experience of the owner/handler or groom. More experienced grooms may not need anything like as much support and will also often recognize problems earlier than less experienced grooms. Furthermore, the value of the foal and any complications during pregnancy will often dictate the role of the veterinary surgeon. Probably the majority of foalings attended by veterinarians are recognizably abnormal in some respect.



The recognition of abnormalities can be more difficult than would appear. Intervention needs to be limited but sensible. There is little point in leaving an obviously abnormal situation to sort itself out; conversely, interfering when there is no need to do so can do harm.



• The foal is delivered during second-stage labor. Usually the foal is within the amnion, which usually breaks spontaneously as a result of opposing movements of the forelimbs and head.


• The foal takes its first breaths with chest and abdominal movements (usually within 30 seconds of delivery of the chest). There may be a series of initial gasps with neck arching.



• The normal respiratory pattern is rapidly established. The newborn foal will show fast and deep breathing; this is accompanied by a dramatic rise in arterial blood oxygen (PaO2) which progressively increases with increasing muscular effort. There are significant other signs for a similar increase in respiration rate (see below).


• The mare will usually undergo a period of tranquility (lasting up to 40 minutes), during which time the foal shakes its head and gains sternal recumbency with ‘righting reflex’. Throughout this the mare remains quiet (usually in sternal recumbency) and will often vocalize to the foal.



• The foal may show strong blinking reflexes as hearing and vision are established. It may whinny on its own or in response to the mare. The foal’s head bobs up and down markedly, and suckling responses with lips and mouth are present with increasing strength.


• The foal struggles and moves to the side of the mare. Usually the cord ruptures at this time, either because the foal moves or because the mare stands up. The cord usually ruptures about 6–8 minutes after delivery at a predetermined site (3–5 cm from the umbilicus). Shorter ruptures may have serious consequences, including internal hemorrhage. Severe tension on the cord at the umbilicus may also cause serious internal bleeding (although this is very rare). Premature rupture of the cord may compromise the foal (up to 25–30% of the foal blood volume can be lost).


• The mare nuzzles, licks and encourages the foal. In response, the foal makes its first attempts to stand, usually within 30 minutes of delivery.


• Normal foals will stand by around 45–90 minutes after delivery (often with apparent incoordination); they may fall several times before establishing a steady stance and the ability to move. A normal foal may take up to 2 hours before standing, but the longer it takes the greater the likelihood of a problem being present.


• The foal then seeks the mare’s udder (Fig. 11.1). This is often aimless at first but increases in accuracy. Once the teat is located a strong suckling reflex is established. The first effective suckling takes place within 60–90 minutes of delivery. In response, the mare will ‘let down her milk’ and the colostrum will be seen to stream from the teats.



• After about 30–60 minutes (especially if a feed has been successfully obtained) the foal will lie down again. The foal may make its first energetic steps on rising again, may jump up and down, and may then fall again. All foals have an inherent incoordination and may seem to be ataxic for the first 24 hours.



Note:



• The amnion must be distinguished from the chorioallantois and bladder.


• The correct time of interference needs to be recognized; minimal interference is desirable.


• Cutting the amnion is sometimes a desirable safety precaution; the foal’s nose can be uncovered and there is then less risk of asphyxia. However, it is important not to disturb the mare if at all possible while this is done.


• Cord rupture usually causes slight blood flow, most often from the placental end (venous flow at low pressure). Severe arterial blood loss from the umbilical end of a ruptured cord requires immediate attention: clamp with sterile artery forceps or umbilical clamp (plastic bag clamps are useful). The cord should not be tied with string, etc.


• Dress the navel (e.g. with teat dip or povidone iodine solution, chlorhexidine or antibiotic spray) within 30 minutes of delivery. Recent work suggests that the best results are obtained with chlorhexidine and that povidone iodine may not be as effective as was first thought.13 Ensure thorough soaking of the navel but avoid over-handling. Aerosol sprays may give a false impression of their effectiveness because they are under mild pressure and their cover is more defined and can be seen, but the antibacterial effects are probably poor and nonpersistent. The antibiotic may not be effective against the organisms present (many significant Gram-negative bacteria, including Escherichia coli, are tetracycline-resistant).


• Full hygiene measures are imperative for anyone handling the foal. It is remarkable how few stud personnel have any concept of cleanliness when handling foals and parturient mares.


• It is advisable to wear gloves and overalls that can be changed frequently on every occasion when dealing with neonatal foals (preferably protective clothing should be changed between different foals). Washing hands and changing overalls frequently also minimizes cross-contamination between mares foaling at the same time.


• All reasonable hygiene precautions should be in effect at all times, including the provision of freshly washed or disposable aprons/gowns for each mare/foal and for each stud. It is best to advise the stud to maintain a stock of these for their own personnel and for visiting veterinarians.




EVALUATION OF THE NEWBORN FOAL


Evaluation of the newborn foal is very important as it provides the first and earliest opportunity to assess its potential viability. It also allows a veterinarian to assess whether there is anything that needs to be addressed immediately, such as provision of oxygen, artificial (positive-pressure) ventilation, blood transfusion, antibiotics, etc.


Foals are best scored at 1–3 minutes of age. Note, however, that foaling mares exhibit a natural period of tranquility following the expulsion of the foal (the foal usually still has its hind legs in the birth canal). During this stage the foal’s umbilical circulation is still very active (a pulse is still palpable in the umbilical artery) and the uterus is actively contracting. This causes a progressive arterial resistance and an active return of the foal’s venous blood into its systemic circulation. This is a very important stage of delivery and disturbances to assess the foal at this stage may be counterproductive. Early rupture of the cord resulting from early disturbance of the mare may result in significant deprivation for the foal. Up to 1 liter of circulating blood may be left in the placental circulation when rupture is rapid. Adaptation must under these circumstances be abrupt and this allows little scope for interference in the event of a problem.




The APGAR scoring system14


The APGAR system is a scoring system that is used to assess Appearance, Pulse (rate), Grimace (response), Activity (muscle tone), and Respiration (rate). It is a simple method that can be used for the immediate assessment of the foal during the first 3 minutes of birth (see Table 11.4). A more complex system in which muscular activity parameters carry a higher loading can be used in specialist hospitals for older foals (up to 2 hours) (see Table 11.5).





• Provided problems are recognized early, even some seriously depressed foals can be saved with effective intensive care. Some conditions arise before birth, so accurate history and careful clinical assessment is vital. Owners can be taught to assess the foal at birth; this does not reduce the necessity for a full examination as soon after birth as possible.


• Many high-risk foals look relatively normal at birth and up to 12–18 hours of age. Once problems develop, deterioration is usually rapid. This makes early recognition of problems an important management procedure.


• Newborn foals that are high-risk or that show any evidence of respiratory or neurological (or other) compromise, should be subjected to APGAR scoring at regular intervals over the first 30 minutes. Apparently normal foals should be scored only once and then left alone.



ROUTINE VETERINARY AND MANAGEMENT PROCEDURES FOR A NEWBORN FOAL


In performing the following procedures, the groom/veterinarian must balance the need to interfere against the possible disturbance that this creates. If a foal is delivered in a safe clean environment, little interference should be required and routine procedures can be delayed until the foal is standing and has bonded with the mare.










3. Administration of colostrum by nasogastric tube




• At birth, oral nutrient intake becomes the sole source of nutrition and the importance of colostral antibody transfer cannot be overstated.



Note:




• Newborn foals can easily be intubated. A soft rubber tube (diameter <1 cm) is best and can be passed up the ventral meatus of the nose. Passage up the middle meatus is more difficult and tends to induce significant ethmoidal damage and bleeding.


• Always use as small a tube as possible that is consistent with requirements. Enteral feeding tubes are very much smaller and well tolerated, even allowing normal feeding to take place with the tube in situ.


• Usually the act of swallowing can be felt and the tube advanced gently but swiftly.



Note:



• Do not introduce any material down the tube until it is certain that the tube is in the esophagus.


• If you can blow and suck on the end of the tube, it is likely that it is in the trachea.


• If you cannot blow or suck, it is likely that the tube is kinked over itself and must be carefully withdrawn. Severe trauma can occur when this happens.


• If you can blow but cannot suck, the tube is most likely in the esophagus.


• The passage of the tube down the esophagus can usually be seen in the left jugular furrow.


• The tube can usually easily be palpated in the neck.


• There is usually some resistance to the passage of the tube in the esophagus.


• There is no resistance to the tube in the trachea and it may be ‘rattled’ within it.


• If the foal coughs it is likely that the tube is in the trachea.


• Aspiration of stomach contents means that the tube is correctly placed.



Long-term enteral nasogastric tubes can be introduced through a wider tube, which can then be removed. Enteral feeding tubes are commercially available (Nutrifoal Tubes®). These tubes have a bag attachment for feeding up to 3 liters of liquid feed. It is essential to measure the length required before insertion; there have been occasions when extra length inserted into the stomach has caused the tube to tie itself into a knot, making removal impossible. The end of the tube should preferably be in the distal esophagus. Suture the end of the tube into the nostril or glue are tape to head collar (foal slip) to prevent rub removal. When using a long-term tube there is no need for the tube to reach the stomach; there is a slight risk of knotting if too much length is introduced. Wide tubes make for easier insertion but have a higher incidence of pharyngeal damage (including necrosis, abscessation, and inflammation); thin tubes are more inclined to blockage and can be rejected from the esophagus.


Once the tube is in position it should be briefly flushed with warm water and the end plugged. Aspiration of air can be a serious complication of long-term stomach tubes if the tube is left open.


Larger tubes can be left in situ for 24–36 hours (not longer), but enteral feeding tubes are well-tolerated for up to 4 days. Indicators for removal and replacement of the tube include:



It is important to remember that a foal needs very small feeds repeated at regular intervals to try to mimic the natural state of feeding.


Nasal oxygen tubes are well tolerated by sick foals but less so as the foal gets better. The tube should be inserted so that the tip lies just within the internal nares. If the tube is advanced further it may induce repeated swallowing and less induces repeated sneezing/rejection.





6. Laboratory


The foal should be blood sampled (see below) at 12–16 hours for estimation of colostral transfer (IgG) and for routine hematology and biochemistry (see Table 11.6). At this stage the earliest evidence for impending problems can often be detected. If there is any suspicion of a problem, blood culture should be set up immediately. Cultures routinely take over 24 hours to yield any useful results. Although this can be a valuable prophylactic measure, it is an expensive procedure.




Blood sampling



Venous sampling

Foals are very liable to venous/jugular thrombosis and thrombophlebitis and every care needs to be taken to ensure that:




Note:




Suitable venepuncture sites, which can also be used for catheter placement, include:



The umbilical vein(s) can be used in foals less than 24 hours of age but this carries a significant risk of navel infection/septicemia.


The placental vessels provide a good source of blood without the need to interfere with the foal at all immediately after delivery (within 2 minutes). The samples will need to be taken from the ruptured placental vessels immediately the foal is delivered so that the breaking of the cord can be directly observed. Sampling from the intact umbilical vessels before cord separation is simple but may disturb the mare. Placid, experienced mares may allow this to be performed without making any attempt to rise.



Note:




Samples for blood culture should be placed immediately in biphasic blood culture medium in full aseptic manner. Other samples collected in conventional blood collection vials are of no value for blood culture. Swabs are even worse and should not be taken for culture purposes.



Note:



For example:


A platelet count can only be reliably estimated from a citrated sample, whereas blood glucose should be performed on a fluoride–oxalate sample.




Arterial sampling

Arterial blood can be obtained from:



Alternative sites include the median artery, the facial artery and the umbilical artery (in foals less than 24 hours old). The umbilical artery can easily be located by close examination of the navel. It is sometimes necessary to cut across the very end of the severed cord to reveal the three major structures. The artery is obvious and can be cannulated easily; a long catheter needs to be used (at least 30 cm). The risk of infection is very high.




CLINICAL EXAMINATION OF THE NEWBORN FOAL


It is impossible to perform a clinical examination of the foal without reference to the history relating to the dam, the pregnancy, and the foaling. The use of a proforma makes the examination simpler and the recording of the findings is important for subsequent examinations. Such a form helps ensure complete examination without serious omissions or errors. Events can change rapidly in foals and so repeated examinations are important to detect trends in physiological and pathological processes.



Disease is easily spread from stud to stud by fomites (fomites are substances, such as clothing, that are capable of absorbing and transmitting the contagium of disease) and contamination, so appropriate care needs to be exercised and demonstrated to lay persons. This has a beneficial effect upon the disease status of the studs in general and emphasizes the need for hygiene to the owners themselves.



PROTOCOL FOR EXAMINATION OF THE NEWBORN OR NEONATAL FOAL


The objective of a clinical examination (including the history) (see Fig. 11.2) is to establish:




Symptomatic treatments for unknown conditions that have no identifiable diagnosis are commonplace and almost inevitable in practice. However, if a full history is obtained and a thorough clinical assessment performed it should be possible to establish at least a list of the problems that are present. From this list a presumptive diagnosis may be possible, although further diagnostic tests may be needed to eliminate some of the differential diagnoses. The main problem with many foal diseases is that delays in waiting for the results of tests may be harmful and could in some cases be too long to save the foal. Therefore, there are few opportunities for short cuts or presumptive tests. In every case, regardless of the possible diagnosis, the IgG concentration in the foal’s blood must be established.





Examination of behavior


The behavior of the foal vis à vis the dam and its environment should be assessed early and certainly before any disturbances to either the dam or the foal.



Note:





• Does the foal recognize the dam and is teat-seeking direct and effective?


• Does the foal appear to see normally? (Does it bump into walls, etc.?)



Note:




• Is feeding normal?


• Is there milk on the foal’s face (indicating that the foal has at least been in the right vicinity)?


• Is the mare’s udder full or empty, and is there evidence of milk loss over the lower hindlimbs?


• Is there evidence of nasal reflux of milk during or after feeding?


• The respiratory rate should be measured before handling the foal if at all possible.


• Is there any evidence of abnormal breathing pattern, rate or is there a nasal discharge?


• Observe and assess restraint (e.g. ‘flop’ reflex) (see Fig. 11.3).




Examination of vital signs


The vital signs should be recorded early, as they are likely to alter significantly with handling.



• Respiratory rate and character can be measured and should be assessed before restraint. After the foal has been restrained the chest should be auscultated carefully with a stethoscope.


• Heart and pulse rate/quality should be measured (it is wise to check multiple arteries if possible). An abnormally low heart rate is usually a serious indicator of compromise; a very high rate can indicate anemia, pain, infection, or toxemia.


• Mucous membrane color and capillary refill time should be measured and recorded. Normal mucous membranes are a uniform salmon-pink color, and the capillary refill time is normally less than 2 seconds. Again it is wise to use all the mucous membranes available as some may be misleading (e.g. a bruised eye). Furthermore, the mucous membrane color may not be a good indicator of the oxygenation status of blood. The mucous membranes may be pale as a result of loss of blood, or icteric if internal hemorrhage, red cell destruction or liver disease is present. The presence of petechial hemorrhage is usually significant and can indicate toxemia or serious septicemic infection.


• The rectal temperature is an important parameter for the foal. Subnormal temperatures can be serious but can be the result of errors of technique. Ideally, a digital thermometer should be used and it should be pressed gently against the rectal mucosa. Any abnormal temperatures should be repeated to test the accuracy. The extremities (feet/limbs and ears, nose, tail) should be palpated to detect altered temperature.


• Bodyweight should be obtained routinely, but this is unfortunately not commonly done. The weight of a foal can usually be obtained simply by deduction from the total of a handler and the foal on normal bathroom scales.


• The body condition score may be very difficult to assess in a newborn foal as the usual parameters are not easy to identify. However, it should be possible to establish if the foal is reasonably covered with muscle and the extent of fat can sometimes be assessed.


A logical anatomical or systems approach is essential for the clinical examination, and the examination should always be performed in the same way. This will ensure that nothing is missed out. With experience some short-cuts can be taken but even then this may be unwise. There is much to commend the ‘body systems’ type of examination technique because, although it is more time-consuming, it does ensure that every system is examined carefully and, in the process, allows every anatomical site to be examined more than once.



Note:


A proforma for clinical examination is a very useful aid to both the examination and the subsequent clinical assessment. Recording the results of the clinical examination in an understandable form is important so that:





DETAILED EXAMINATION OF THE BODY SYSTEMS



Cardiovascular system




• The heart rate should be 40–80 immediately after delivery, with rises up to 130–150 while attempting to stand. Over the first 7 days the rate should gradually fall to 60–70. Foals are easily excited or stressed, so handling may cause increases in the heart rate.


• Sinus arrhythmia may be present in the first few hours but should then stabilize.


    Murmurs are common. The ductus arteriosus frequently remains patent for up to 48–72 hours; a characteristic ‘machinery murmur’ (often grade 3–4/5) may be heard predominantly at the level of the base of the heart (i.e. around the mid-point of the chest at the level of ribs 4–5). [The machinery murmur is a continuous, often vibratory, sound that increases and decreases with the changes in arterial blood pressure but which does not disappear at any stage in the cardiac cycle.]


• Serious heart defects may or may not have accompanying murmurs, and the associated signs may be subtle or dramatic.


• The normal pulse in a peripheral artery is usually only just palpable. Usually the facial, metatarsal and median arteries can be felt with the fingertips. It may be possible to feel the carotid pulse fairly easily deep in the lower quarter of the jugular groove.


• Normal blood pressure (measured from a tail cuff applied with the foal in lateral recumbency) is 35–45/85–90.


• The distal extremities such as the ears and feet should be warm.


• A jugular pulse is not normal. The distensibility of the jugular vein should be assessed; it should fill briskly unless the foal is hypovolemic.


• There are few palpable lymph nodes in the normal foal. Enlarged glands may be significant directly or they may be more noticeable if the foal is in poor bodily condition.


• As blood is also a part of the cardiovascular system, the color of the mucous membrane and the specific characteristics of a blood sample can be important aspects of the examination.



Respiratory system



Note:






• The resting respiratory rate and regularity of rhythm are best observed from a distance, without restraint or excitement. Thoracic/respiratory function should be very carefully assessed to ensure that nothing is missed.


• Immediately after birth the respiratory rate is normally >60 breaths/minute, but this falls after 1–2 hours to 20–40 breaths/minute.


• Breathing should require minimal effort, and should be smooth with passive elastic recoil during expiration. There should be equal airflow from both nostrils.


• Rapid respiration can be the result of many systemic conditions, including:



• Significant respiratory difficulty can also arise from congenital deformity of the airway (choanal atresia, subepiglottic cyst formation, laryngeal deformity or functional disability, tracheal collapse).


• During rest and sleep, respiration can become irregular and there may be some snoring/stertor.


• Beware of paradoxical chest patterns (the chest moves in and the abdomen moves out during inspiration). Excessive chest or abdominal movement is best regarded as abnormal and should be investigated. The patency of the airway MUST be assessed in any foal showing respiratory difficulty.


• Auscultation of the chest is much easier in the foal than in the adult horse, but even in severe pathology (e.g. Rhodococcus equi abscessation) there may be few abnormal sounds. The dependent lung of a recumbent foal may be almost silent.


• Percussion of the chest is very useful and under-utilized.


• Absence of sounds is possibly more sinister than obvious adventitious noises.


• Foals seldom cough or have nasal discharges even in severe disease.


• Too few foals are subjected to blood gas studies, ultrasonography, endoscopy and radiography.


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Jun 18, 2016 | Posted by in EQUINE MEDICINE | Comments Off on THE NEWBORN FOAL

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