Obesity in captive animals

  1. Adipose tissue
    • Obesity is dependent on the amount of adipose tissue (fat) in the body NOT on weight
    • White adipose: most common, found subcutaneously (under deepest layer of skin; insulation) as well as around organs (protective cushioning)
    • Brown adipose: found between the shoulder, common in babies, mostly lost by adulthood. Can 'vibrate' to generate heat (thermogenesis)
    • Image Upload 1
    • Made up of adipocytes
  2. Adipokines
    • Type of cytokine (adipocytokine) -> cell signalling protein
    • Adipocytokines send signals all over the body (brain, reproductive system, gut) and give information on the exernal environment (availability of resources)
    • The amount of adipose tissue influences the brain and body
    • Leptin: (thin) hormone. Secreted by adipocytes and sends signals to the hypothalamus.
    • > As it's secreted by adipocytes the amount of hormone in the body is dependent on the amount of adipose tissue.
    • > Also known as the 'satiety' hormone; high levels inhibit appetite and increase energy expenditure while low levels increase appetite and decrease energy expenditure.
    • > Leptin receptor KO mice, when given blood transfusion from healthy mice begin to show weightloss
    • > Leptin resistance in hypothalamus can contribute to obesity; resistance can be caused by too high a level in the blood
    • Adiponectin: most important adipose secretion
    • > Decreases with increased body fat (negatively associated with adiposity)
    • > Anti-inflammatory (so prevents cardiovascular disorders)
    • > Increases fatty acid oxidation AND insulin sensitivity
    • > Low levels increase risk for Type 2 diabetes, CVD, metabolic sydrome, hyperlipidaemia (high levels of triglycerides, cholesterol in blood) -> increases bad cholesterol, decreases good.
  3. Clinical consequences of obesity
    • Hyperlipidaemia: Higher triglyceride and/or cholesterol levels
    • > Diabetes associated with hypertriglyceridemia (and hypercholesterolemia)
    • Consequences
    • ● Insulin resistance
    • ● Hepatobiliary disease
    • ● Pancreatitis
    • ● Ocular diseases
    • ● Seizures and neurologic disorders (?)

    • Hyperinsulinaemia: high levels of blood insulin
    • > leads to resistance/weaker sensitivity
    • > lean dogs had less insulin but are significantly more sensitive (HOMA)
    • > weight loss leads to increased insulin sensitivity in cats and dogs

    • Laminitis: Affliction of the hoof lamellar interface (HLI)
    • > Dermoepidermal junction that serves to attach the hoof capsule to the connective tissue and the distal phalanx
    • > Sinking = detached distal phalanx is forced downwards under weight to eventually compress the sole
    • > Rotation = detached distal phalanx rotates and disrupts weight distribution
    • > Laminitis can cause lameness and other locomotion difficulties

    • Adipokines: at high levels, leptin acts as an inflammatory molecule.
    • > Weight loss increases adiponectin which increases anti-inflammatory response
  4. Prevalence of obesity
    • Dogs: 24% (1986) -> 29/34% (2006) -> ~54%
    • Cats: 6/12% (1973) -> 19/25% (2005) -> ~59%
    • Horses: up to 45%
  5. Assessing obesity
    • By body weight: for dogs, >15% optimal weight HOWEVER not a great method, differences among breeds
    • Body mass index (BMI): dogs (weight/height sq) accounting for breed; cats (weight/height x length); equine BMI gives range of healthy values
    • Body composition: horses = use of ultrasonography to assess subcutaneous fat thickness in tail area
    • Body condition score (BCS): Body score, fat coverage and ability to palpate ribs
    • > scores 1-9
    • > Reliable and consistent, validated by DEXA (X-ray method)
    • 1 Emaciated: No discernible body fat; prominent bones; evident loss of muscle mass
    • 2 Very thin: No palpable body fat; visible bones; slight loss of muscle mass
    • 3 Thin: No palpable body fat; visible bones; waist and abdominal tuck are obvious
    • 4 Underweight: Minimal fat over palpable ribs; waist and abdominal tuck present
    • 5 Ideal: Little fat over palpable ribs; waist and abdominal tuck present
    • 6 Overweight: Fat over ribs, still palpable; waist and abdominal tuck discernible from behind (w) and side (a)
    • 7 Heavy: Fat covering ribs (palpable with difficulty), lumbar area and base of tail; waist and abdominal tuck not detectable
    • 8 Obese: Heavy fat deposits; ribs palpable when applying pressure; no waist or abdominal tuck; abdominal distension
    • 9 Grossly obese: Massive fat depots also on neck and limbs; ribs not palpable; no waist or abdominal tuck; obvious abdominal distension
    • Assessing obesity in horses
    • Image Upload 2
  6. Causes of obesity
    • Longer life span: easier to put on weight with age
    • Neutering/Spaying: change in body composition (especially testosterone which promotes synthesis of lean mass)
    • > also reduces metabolic rate
    • > rapid increase in weight and blood insulin in weeks/months following neutering/spaying
    • Breed disposition: particularly dogs and horses
    • > dogs = Labrador, dachshunds, cocker spaniels, beagle, basset hound, shetland sheepdog
    • > horses = ponies
    • Owners under-recognition, Environment and Negligence: More common in pets of owners who are older or present overweight, due to
    • > Low levels of exercise; Home-cooked meals; Table scraps, treats, snacks
    • > More common in dogs whose owners observe them eating (psychological/behavioural)
    • Environment - Thrifty gene hypothesis: horses genetically predisposed to storing energy
    • > Natural selection: Metabolism optimized for native grass and long-distance travel
    • > Hindgut fermentation
    • > Yearly cycles of fat storage and use; Increased intake and adiposity during autumn (chronobiology adaptation); Fat stores depleted through winter
    • > Neuroendocrine regulation linked to seasonal shifts in forage availability
    • > Current husbandry practices: Energy-rich rations, physically inactive horses; Genetically improved grassland optimized for rapid weight gain
  7. Treatment
    • Cats and dogs: weight loss improves respiratory function, mobility, metabolic profile and quality of life
    • Gradual weight loss
    • o Minimize lean tissue loss
    • o Avoid weight rebound (yo-yo) effect, common in dogs
    • Traditional approach: decrease intake, increase exercise
    • o Low energy, high nutrient density
    • o High-protein and fibre for satiety = especially in dogs; Cats -> (too much) fibre can reduce palatability; protein can increase intake
    • o High micronutrient content (vitamins/minerals)
    • Higher energy restriction in females
    • Shift focus toward wellbeing
    • Main barrier = OWNER
    • > reluctance to admit to problem; lack of compliance during diet, difficulty recognising appropriate behaviour; poor cooperation of family members; inability to resist animal begging (feelings of guilt)
    • Pharmacological options: amphetamines (clenbuterol, ephedrine); side effects - increased BP, temp; decreased gastrointestinal motility; tachycardia, anorexia, anxiety, death
    • L-carnitine -> takes triglycerides to mitochondria for oxidisation. Evidence of effectiveness for weight loss in cats with hepatic lipidosis. Standard supplement in dogs but no research
    • Orlistat -> lipase inhibitor. Side effects; steatorrhea, flatulence, discomfort, leakage
    • Mitratapide, dirlotrapide (lipoprotein synthesis inhibitors) -> tops fat from being reassembled for storage. Withdrawn from market in 2010. 

    • Horses
    • Diet: Hay as primary source of energy
    • > Should be analysed for energy and nutrient content
    • > Food must amount to 1.5-2% body weight
    • > No grain, limited access to pasture, low-sugar, low-starch pellets treats
    • > Further restriction for ponies and horses with EMS
    • > Vitamin and mineral supplements required
    • Increase exercise
    • Pharmacological options:
    • ● Levothyroxine
    • ● Insulin-sensitizing drugs (metformin; safety studies lacking)
Card Set
Obesity in captive animals
Obesity in cats, dogs, horses