Neonatal Behavior
Most spontaneous births (≈80%) occur between 8 p.m. and 6 a.m., with a peak foaling time between 10 and 11 p.m.1 A normal foal should have righting reflexes and sufficient muscle tone to be able to right itself to sternal recumbency within 2 to 3 minutes of birth.
By 5 minutes the foal should be bright, alert, and responsive to visual, auditory, and tactile stimuli. Over the next 20 to 25 minutes the normal foal will be restless, alternating periods of sternal recumbency with lateral recumbency before beginning lurching attempts to stand. During this period the foal will often vocalize in response to maternal sounds or contact. Once standing, the initial posture is an unsteady basewide rocking stance, but this slowly improves such that by 60 minutes most foals should be standing securely without assistance. The mean time to stand in a recent study of Thoroughbred foals was 52 minutes (±30 minutes standard deviation).1 Colts typically take slightly longer to stand than fillies. The suckle reflex is present within minutes of birth in most foals and should be present in all foals by 30 minutes. Once standing, the foal will seek the udder, a process that is initially very clumsy but improves once the foal has successfully sucked. There will be repeated nudges of the udder in order to facilitate milk letdown. The foal should be nursing from the mare by around 2 hours (mean reported times of 111 and 125 minutes; ranges 35 to 420 minutes and 30 to 600 minutes), and most have nursed twice by 2.5 hours of age.1,2 Sucking periods vary in duration between 1 and 5 minutes and are interspersed with periods of sleep that last around 7 minutes. It is important to watch the foal during sucking to confirm appropriate teat contact and swallowing movements. A foal that spends long periods at the udder may do so because of inability to nurse from the mare or inadequate milk from the mare. The daily milk consumption of most newborn foals is estimated between 21% and 25% of their body weight.3 This equates to around 12 to 12.5 L/day for a 50-kg foal. On the basis of the caloric density of milk, this reflects a daily intake of 120 to 150 kcal/kg body weight, half used for basal metabolism and thermoregulation and half for growth.Sleep periods first occur between 90 minutes and 4 hours after birth and last for about 7 minutes.4 The foal spends one-third of its time lying down during the first 2 months of life, compared with 5% to 10% for adults, most of which occurs overnight. Foals do not learn to follow their dams to the exclusion of any other moving object for the first 1 to 2 weeks of life. Foals identify their dams by sight and smell and during the first week of life spend 85% of the time within 1 m of the dam, 94% to 99% within 5 m, and only rarely more than 10 m away from the dam.5 Loss of affinity for the mare in a foal that seems otherwise healthy may be an early sign of the neurologic form of hypoxic ischemic syndrome.
Recommendations to clients as to when veterinary intervention should be sought vary from practice to practice. The “1-2-3” rule states that foals should be standing unassisted by 1 hour, sucking from the mare by 2 hours, and the mare should have passed her fetal membranes by 3 hours. Clients may adopt a similar “2-4-6” rule to seek veterinary attendance, where intervention should be sought if the foal has not stood by 2 hours, not sucked by 4 hours, or the fetal membranes are still in place by 6 hours. These recommendations are only used as a rough guide and will obviously be influenced by peripartum conditions and client experience. A recent study from New Zealand reported that 95% of mares had passed the fetal membranes within 4 hours of parturition.1
■ TABLE 16.1
Apgar Score: Assessment of Neonatal Asphyxia
| Parameter | 0 Points | 1 Point | 2 Points |
| Appearance Pulse (beats per minute) Grimace | Gray or blue mucous membranes Absent | Pale pink mucous membranes 60, regular | |
| Nasal stimulation Ear tickle Thoracolumbar stimulus Activity (muscle tone) Respiration (breaths per minute) | No response No response No response Limp, lateral recumbency Absent | Grimace Head and neck motion Head and neck motion Semisternal, some limb flexion 30, regular, can whinny |
A modified Apgar score (Table 16.1) has been used in foals to semiquantitate the severity of signs that occur in response to peripartum asphyxia.6 The acronym used in equine practice differs from that used in human medicine and refers to appearance, pulse, grimace, activity, and respiration.
Appearance refers to oral mucous membrane color; pulse uses 60 beats per minute (bpm) as a cutoff; grimace is assessed in response to stimulation of the nasal mucosa, inside of the pinnae, and over the thoracolumbar area adjacent to the spine; attitude reflects the degree of muscle tone; and respiration refers to ventilation rate and rhythm with 30 breaths/min as the cutoff. Each category is scored from 0 to 2 points with a score of 10 being optimal. A score of 0 to 3 indicates marked depression; 4 to 6, moderate depression; 7 to 8 reflects mild asphyxial injury; and normal foals have a score of 9 or 10. Ideally the modified Apgar calculation should be made within the first minute after birth, but certainly within 15 minutes of delivery. Repeating the score 4 minutes later is recommended. Foals with low scores typically require aggressive resuscitation, whereas mildly affected foals may respond to vigorous rubbing, stimulation of the nasal mucosa, and limb movement.