40 Feeding orphan and sick foals
Introduction
The neonatal foal has a high metabolic rate and low hepatic glycogen reserves that only last a few hours (Ousey 2003). Newborn foals are dependent on frequent ingestion of good quality colostrum and then milk. Foals that fail to nurse even for a few hours will rapidly become hypoglycemic, hypovolemic, hypothermic and start to break down body tissue to meet their metabolic needs. During the first week of life, healthy foals suckle five to seven times per hour with each bout lasting just under 2 minutes (Carson & Wood Gush 1983). Over the first month of life, the frequency and duration of the suckling bouts decreases as the foals suckle more efficiently.
During the first 24 hours post partum foals consume about 15% of their bodyweight as milk (8 liters for a 50-kg foal); this increases to 12–15 liters by the end of the first week of life (Ousey et al 1996). The first month of life is a period of very rapid growth. Thoroughbred foals gain 1.5–2 kg/day (Jelan et al 1996, Martin Rosset & Young 2007), and most Thoroughbred foals will have doubled their birthweight by a month of age. Growth rate in healthy foals is breed, age and month of birth dependent (Chapter 12 provides data on normal growth rates of foals).
It is well established that in order to produce a sound, healthy athlete a smooth growth curve should be maintained rather than periods of restriction and compensatory growth. Although moderate restriction in growth can be compensated for to some extent, capacity for compensation decreases with age. In general, differences in growth rates have little influence on mature size after the rapid neonatal growth phase is completed (Martin Rosset 2005). The reader is referred elsewhere in this book for a more complete discussion on foal growth and development (Chapter 12).
The orphan foal
How to feed
Ousey (1999, 2003) recommends that foals under 2 days of age are fed hourly, then every 2 hours for a further 12 days, after which there should be a gradual decrease in the frequency and increase in the volume fed such that by 8 weeks of age the foal is receiving four feeds daily.
Fostering
• Temperament – it is important that there is no risk of injury to the foal or personnel;
• Disease risk – the mare should be screened for risk of EHV 1, strangles and other infectious disease; and
• Stage of lactation – if there is a significant disparity between the stage of lactation and foal age it may be necessary to consider mineral supplementation as milk mineral levels change throughout lactation.
1. Withhold milk from the foal for 1–2 hours prior to introduction to the foster mare.
3. Ensure the mare has easy access to a plentiful supply of hay/feed and water.
4. Have plenty of assistance available when the foal is first introduced to the mare.
5. In some cases carefully fitted hobbles may be helpful.
6. Strip the mare’s udder and cover the foal with her milk.
7. Don’t allow the mare to sniff the foal until a bond is established.
8. Take the mare outside to hand graze her with the foal close by.
Kelly (1999) provides further details of fostering techniques.
Sick neonatal foals
Requirements of the sick neonatal foal
Healthy foals aged 1–4 days spend approximately 12 hours standing and active, increasing to nearly 14 hours per day by day 7, whereas sick foals are often recumbent for much of the time. This behavioral difference reduces energy expenditure by approximately two thirds. On the other hand, environmental temperatures below the lower critical temperature (24°C in sick foals) will increase metabolic rate and so can increase energy requirements for maintenance (Ousey 1997, Ousey et al 1997).
Although studies on the requirements of sick foals are sparse, research suggests that the energy requirements of sick neonatal foals are considerably less than their healthy counterparts. Studies of immature foals and foals with perinatal asphyxia syndrome showed they have a lower metabolic rate, requiring only 260–290 kJ/kg/day (13–14.5 MJ/day for a 50 kg foal) compared to 540–600 kJ/kg/day for healthy foals (Ousey et al 1996, Ousey 2003).
A recent study using indirect calorimetry in sick foals reported energy requirements of approximately 188 kJ/kg/day (Paradis 2001). Historically, it was thought that conditions such as sepsis and systemic inflammatory response syndrome (SIRS) in young as well as mature patients produced a hypermetabolic state and therefore increased energy requirements. However, recent studies (Taylor et al 2003, Turi et al 2001) in children have refuted this theory, finding that children do not become hypermetabolic during critical illness. Turi et al (2001) speculated that this is due to diversion of energy for growth into the recovery process.
Recent studies in humans having found that the overfeeding of critically ill patients has an adverse affect on outcome (Dandona et al 2005). Similarly, McKenzie & Geor (2009) have suggested a conservative approach to calorie provision for sick neonatal foals. Providing excess carbohydrate can result in hyperglycemia, which may increase production of proinflammatory cytokines and increase production of CO2, which can worsen hypercapnia in foals with respiratory compromise. Excessive dietary protein increases protein catabolism which can produce azotemia, while excessive feeding of lipids results in hypertriglyceridemia. One study reported that triglyceride concentrations >200 mg/l (>2.25 mmol/l) were associated with non-survival in neonatal foals receiving parenteral nutrition (Myers et al 2009).
Mare’s milk has high carbohydrate (lactose) content. Insulin secreted by the beta cells in the pancreas is essential for regulation and homeostasis of blood glucose in the face of high carbohydrate intake. Maturation of beta cells in the pancreas occurs very late in gestation and is dependent on the prepartum cortisol surge which prepares the fetus for birth in the few days before parturition (Holdstock et al 2004, Fowden et al 2005).
Buechner-Maxwell and Thatcher (2004) have suggested that crude protein requirements for neonates are 4–6 g protein/100 non-protein calories. However, other authors have recommended a lower protein requirement (2–5 g/kg/day) for foals with normal plasma protein concentrations, and a higher rate of provision (6.5 g/kg/day) for sick neonates that are hypoproteinemic (Stratton-Phelps 2008). The criteria for diagnosis of hypoproteinemia will depend on factors such as foal age, disease process, and laboratory reference ranges.
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