Vet360 Vol 4 Issue 4 August 2017 Vet 360 - Page 38

NUTRITION rine. Diagnosis of taurine deficiency is confirmed by measurement of taurine in the blood (more reliable than plasma) with ranges > 320nmol/l being normal and those <150 nmol/L indicating deficiency. ii. Arginine Arginine can be synthesised from citrulline and or- nithine but these precursors are synthesised in only small amounts in the cat. Additionally the urea cycle cannot be down regulated during protein deficient intake, thus cats continually use large amounts of ar- ginine. Cats fed a diet deficient in arginine develop signs of hyperammonaemia. iii. Methionine and cysteine Methionine and cysteine are also required in greater amounts by cats as they are gluconeogenic amino acids in cats and are catabolised to pyruvate and then subsequently oxidised to provide energy. In dogs and other animals, methionine and cysteine are primarily converted to taurine, homocysteine and s-adenosyl –methionine (SAMe) and its metabolites, such as glu- tathione, which are important anti-oxidants. iv. Tyrosine Tyrosine is considered conditionally essential in cats, especially those with black pigmentation, as it is re- quired for the synthesis and homeostasis of melanin. v. Carnitine Carnitine is considered conditionally essential. Car- nitine is synthesised in the kidneys of cats whereas it is synthesised in the liver of dogs. Carnitine synthesis requires several B-vitamins and iron, thus synthesis may be limited in sick or anorectic cats. In humans, relative or absolute carnitine deficiency causes he- patic lipid accumulation and a link with hepatic lipi- dosis in cats is being investigated. Carnitine increases lean muscle mass and enhanc- es weight loss in obese cats. Supplemental carnitine (250 – 500mg/d) is recommended for obese cats and cats with idiopathic hepatic lipidosis. Carbohydrates Cats also have several physiological adaptations that reflect their expected low intake of carbohydrates. Cats do not have salivary amylase, the enzyme re- sponsible for initiating carbohydrate digestion. Cats have low activities of intestinal and pancreatic am- ylase and reduced amounts of intestinal disacchari- dases, which are responsible for breaking down car- bohydrates in the small intestine. Despite this, cats are extremely effective in their utilisation of small amounts of simple sugars, but high amounts of di- etary carbohydrates decreases protein digestibility in cats . Cats also have minimal hepatic gluokinase, the activ- ity of which cannot be upregulated, when this limits the amount of glucose which can be phosphorylated vet360 Issue 04 | AUGUST 2017 | 38 for storage or oxidation. Cats also have minimal activi- ty of hepatic glycogen synthetase which converts glu- cose to glycogen for storage. These hepatic changes are probably due to a metabolism designed to use protein and fats for energy rather than carbohydrates. Cats thus have a decreased ability to minimise hyper- glycaemia from a large dietary carbohydrate load. In carnivores, glucose is released in small amounts over a longer time from protein catabolism resulting in less blood fluctuations. Fats Fat typically provides most of the energy in a carniv- orous diet but it is also important for increasing the palat