An animal's primary demand from its diet is for energy. Unlike an individual nutrient, there is no range of acceptable intakes, but rather a specific energy requirement for a given set of conditions. Accurate assessments of both food energy density and the energy needs of the animal are implicit in providing reliable feeding recommendations. The metabolizable energy content of a food is best measured using in vivo testing in the target species. However, the demands of biological testing mean that a set of factors is desirable to provide reasonable estimates. Assessment of energy requirement in dogs is confounded by their wide range of body weights. It should be expressed on an allometric basis, but the precise value for the exponent is still a matter of some debate. For cats recent studies suggest there may be an allometric relationship over a weight range of 2.5-6.5 kg. Energy requirement is dependent on a number of other factors, in particular, activity, environmental temperature and life stage. Demand increases most in lactation (four times) and growth (up to three times). Old animals show a decline in energy requirement, but this may reflect principally a decrease in activity, rather than any underlying change in metabolism.
Racing Greyhounds ran faster when fed a diet containing higher fat and protein and lower carbohydrate contents. Their maintenance metabolizable energy requirement was slightly higher than that of moderately active dogs.
Dogs are unique among mammals in having a 100-fold range in body weight for nonobese adults. This variation makes the calculation of the power function for metabolic body size and hence the allometry of energy requirements a particularly challenging subject. Several functions have been proposed from W0.68 to W0.88 (W = body weight in kg). In the present study we measured the heat output of 22 dogs representing seven breeds, aged 1-10 y with W from 5.8 to 48.8 kg, using a whole-body calorimeter specifically designed for this purpose. Regression of log energy output against log W gave the equation 678 W0.64 (r = 0.96; P less than 0.001), which is considered to represent resting energy expenditure (REE) as kJ/d. If estimates of the energy cost of activity are added to REE, new equations of 655 W0.69 (low activity) and 643 W0.73 (higher activity) are obtained, depending on the amount of activity included in the calculation. From these results we suggest that the allometry of energy requirements of adult dogs is a function of different exponents for REE and the energy cost of activity. It does not appear to exceed W0.75 and may be nearer to W0.67.
The literature on feline central retinal degeneration is reviewed and an experiment reported which investigates whether taurine is essential in cats fed a purified diet. The development of taurine deficiency retinopathy is described and illustrated. The histopathological, ultrastructural and ERG changes are also described. Other retinal degenerations in the cat are discussed.
Summary A study to evaluate the long term effects of feeding a fat supplemented diet during medium intensity, aerobic training was conducted over 7 months using 12, 2‐year‐old Thoroughbreds. The control group (n=6) was fed grass hay and a fortified sweet feed (CON) and the other group (FAT)(n=6) received hay, sweet feed, a supplement pellet and 400 ml of soybean oil that supplied about 12% of the DE intake of the FAT group. After 2, 4 and 7 months, the horses performed 2 standardised exercise tests (SETs) on a high speed treadmill. The first test (STEP) consisted of sequential steps of 800 m at speeds of about 4, 8, 9, 10 and 11 m/s. V200 and VLA4 increased with training, but were not different between treatment groups. During the last STEP, insulin was higher post feeding in the CON horses. Blood glucose was lower at the end of the STEP in CON horses. The second test (SET30) consisted of 30 min of trotting at about 4 m/s. Cortisol was elevated during exercise in the CON horses during the last SET30. T4 was unaffected by diet or exercise. Consuming a fat supplemented diet altered the insulin response after feeding and this may have prevented a fall in blood glucose during strenuous exercise. Feeding a fat supplemented diet to 2‐year‐old. Thoroughbreds during training did not change red or white blood cell numbers or liver function as measured by serum levels of AST, γGT and SDH. Fat supplemented diets can be fed safely for extended periods of time to horses in training.
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