MANAGED CARE DIET FORMULATION

The nutritional requirements of production, laboratory and companion animals for optimum growth, health and reproductive fitness are well defined (Lebas et al. 2010; NRC 1995, 2001, 2006, 2007a, 2007b, 2012).

Digestive system physiology in domestic animals may provide an appropriate model for a particular non­domestic species (Fig. 14.1-14.3). Many nutrient require­ments are similar between species and domestic animal models can provide a basis for formulating diets (Table 14.1). For example, it is assumed that all mammals will require calcium to phosphorus in a ratio between 1:1 and 2:1 in the diet to support skeletal health. Commercial products and supplements formulated for domestic spe­cies may be used to provide minimum nutrient levels for non-domestic species. However, not all Australian mam­mals have a truly representative domestic animal model. In those cases, further information is gained from dietary field studies and managed care studies on nutrient utili­sation. Stable isotope analysis, DNA metabarcoding and microbiome studies are providing more detailed infor­mation on digestion and nutrient assimilation. Vitamin and mineral deficiencies, obesity, periodontal disease and acidosis are still common in managed care and more research is required to formulate appropriate diets for dietary specialists such as insectivores, nectarivores and browsers.

The nutrient composition and/or form of natural diets can be difficult to replicate in managed care. Compro­mises are made to accommodate management and train­ing needs or mixed species habitats where animals have different diets and feeding strategies.

Basal metabolic rate (BMR) is used to calculate the minimum energetic expenditure of an animal at rest within its thermoneutral zone (TNZ). Field metabolic rate (FMR) is the metabolic rate for a free-ranging animal in the wild and may vary widely for individuals within the same species.

Fig. 14.1. a) Examples of gastrointestinal tracts from Australian mammal foregut-fermenting herbivores and the domestic sheep (Ovis aries) as a comparative domestic animal model. b) Examples of gastrointestinal tracts from Australian mammal hindgut-fermenting herbivores and the horse (Equus caballus) as a comparative domestic animal model. Domestic sheep, dugong (Dugong dugon), bare-nosed wombat (Vombatus ursinus) and horse images from Stevens and Hume (1995); koala (Phascolarctos cinereus) image modified from Hume (1999).

with many inherent errors (Tomlinson 2016). However, BMR and FMR can be used as an estimate of energy needs to formulate daily diets (Table 14.2). Nutrient and energy recommendations vary for individuals within a group and will depend on several factors including size, physio­logic state, age, group dynamics, activity level, health, weight management goals, environmental conditions and climatic adaptations. Healthy managed animals, within their TNZ and at minimal activity levels, will be expected to have low metabolic requirements at or even below the calculated range for FMR. Sick or post-operative patients may have increased demands but limited intake, so diets may need to be adjusted to increase energy and/or protein density to maintain weight during recovery.

Animal diets are not meant to be static and need to be reviewed regularly to ensure they are reaching the goals set out for each group or individual. Goals may be related to managing a health concern such as diabetes or main­taining ideal body condition and faecal consistency. Just as serum glucose levels can be monitored and assessed against baseline values, establishing parameters to assess body condition and faecal consistency for each species can be used to monitor diet. A general faecal scoring guide, grading faeces from 1 (extremely dry) to 5 (liquid diarrhoea) can be adapted for use when species-specific guides are not available (Stannard et al.

Body condition refers to the relative ratios of an ani­mal’s weight, size, muscle and fat in proportion with its age, health and physiological state. Regular weighing and palpation are generally considered the most accurate methods of monitoring and determining body condi­tion. Where animals are intractable and handling is

Fig. 14.2. Examples of gastrointestinal tracts from Australian mammal omnivores and the pig (Sus scrota) as the comparative domestic animal model. Long-nosed bandicoot (Perameles nasuta) and greater bilby (Macrotislagotis) modified from Hume (1999). Pig image from Stevens and Hume (1995).

problematic, visual body scoring is a useful tool to iden­tify trends to determine necessary corrective action. Training and practice will reduce individual bias regard­less of which scale is employed. Additional information on body condition and faecal scoring is available from the American Zoo Association Nutrition Advisory Group website (NAG 2024).

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