Dietary factors have a major role in the maintenance of healthy coat and skin, and are significant in the etiology and therapy of certain skin diseases. Nutritional deficiencies are now uncommon as a result of the widespread feeding of complete and balanced pet foods. Deficiencies of (n-6) polyunsaturated fatty acids, zinc and vitamins, however, do arise in certain animal- or product-related instances. Supraphysiologic doses of vitamin A have been used in the management of vitamin A-responsive dermatosis in Cocker spaniels; other keratinization defects and seborrheic conditions may respond to retinoid therapy. Much interest has been paid to the therapeutic value of polyunsaturated fatty acid supplements in the management of dermatologic conditions associated with hypersensitivity reactions or keratinization defects. These studies have generally yielded disappointing results, which may reflect shortcomings in the design of some trials. Nevertheless, a placebo-controlled, double-blind, cross-over study has demonstrated a clear benefit of high dose (n-3) fatty acids in the management of pruritic skin disease. There is also preliminary experimental evidence that specific dietary (n-6):(n-3) fatty ratios are useful in the dietary management of inflammatory diseases. Although results of controlled clinical trials are awaited, the argument exists that it is the absolute amount of (n-3) fatty acid intake rather than ratio that is responsible for potential health benefits.

The background, clinical signs, blood biochemistry and management of 18 cases of equine hyperlipaemia are described. Eleven of the animals were Shetland ponies, four were Welsh mountain ponies or their crosses, one was a fell pony and two were riding ponies of mixed breeding. Their average age was nine years. Fourteen of the cases were mares, of which nine were in foal and two were lactating; the remainder were geldings. Underlying or concurrent diseases were identified in only six animals, but in one other animal the hyperlipaemia appeared to have been precipitated by stress, and in another by undernutrition to prevent laminitis. Twelve of the animals were considered obese. There was no age, seasonal, or geographic bias to the distribution of cases. Plasma triglyceride concentrations were increased by between five- and 80-fold, and ranged from 4.7 to 78.8 mmol/litre. There was biochemical evidence of hepatic damage in 17 cases, of renal insufficiency in 15, and pancreatic pathology in three cases. Four animals were euthanased without therapy. The others were treated with oral glucose solutions, which were supplemented with injections of insulin and heparin in four cases, and insulin alone in two cases. Eight of the treated animals died, to give an overall mortality of 67 per cent. The outcome of the treatment was unrelated to the degree of hypertriglyceridaemia, to the presence and severity of hepatic, renal or pancreatic pathology or to the therapeutic regimen.

VLDL1, VLDL2, IDL, and LDL and its subfractions (LDL-I, LDL-II, and LDL-III) were quantified in 304 normolipemic subjects together with postheparin plasma lipase activities, waist/hip ratio, fasting insulin, and glucose. Concentrations of VLDL1 and VLDL2 rose as plasma triglycerides (TGs) increased across the normal range, but the association of plasma TGs with VLDL1 showed a steeper slope than that of VLDL2 (P < .001). Plasma TG level was the most important determination of LDL subfraction distribution. The least dense species, LDL-I, decreased as the level of this plasma lipid rose in the population. LDL-II in both men and women exhibited a positive association with plasma TG level in the range 0.5 to 1.3 mmol/L, increasing from about 100 to 200 mg/dL. In contrast, within this TG range the LDL-III concentration was low (approximately equal to 30 mg/dL) and changed little. As plasma TGs rose from 1.3 to 3.0 mmol/L there was a significant fall in LDL-II concentration in men (r = .45, P < .001) but not in women (r = .1, NS). Conversely, above the TG threshold of 1.3 mmol/L there was a steeper rise in LDL-III concentrations in men than in women (P < .001); 42% of the men had and LDL-III in the range associated with high risk of heart disease ( > 100 mg lipoprotein/dL plasma) compared with only 17% of the women. Other influences on the LDL subfraction profile were the activities of lipases and parameters indicative of the presence of insulin resistance. Men on average had twice the hepatic lipase activity of women. This enzyme was not strongly associated with variation in the LDL subfraction profile in men, but in women it was correlated with LDL-III (r = 39, P = .001) and remained a significant predictor in multivariate analysis. Increased waist/hip ratio, fasting insulin, and glucose were correlated negatively with LDL-I and positively with LDL-III, primarily, at least in the case of LDL-III, through raising plasma TGs. On the basis of these cross-sectional observations we postulate the following model for the generation of LDL-III. Subjects develop elevated levels of large TG-rich VLDL1 for a number of reasons, including failure of insulin action. The increase in the concentration of VLDL1 expands the plasma TG pool, and this, via the action of cholesteryl ester transfer protein (which facilitates neutral lipid exchange between lipoprotein particles), promotes the net transfer of TGs into LDL-II, the major LDL species.(ABSTRACT TRUNCATED AT 400 WORDS)

Gastric emptying time in Scophthalmus maximus, when fed friable artificial pellets based on fishmeal. is composed of two phases: (a) a delay time ( I d ) during which the meal forms a bolus and which shortens with temperature, and (b) an emptying phase (duration tend) which varies with meal size (8, body weight ( W ) and temperature (0 according to: log, tcnd=4.66+0.448 log, S-0.2664 log, W-0.051 7 (where tend is in h, S is in g, W is in g and Tis C). During the emptying phase, stomach contents decrease curvilinearly according to: S,O.448 = S00.448 -0.448 K (where S, & So is in g and I is in h) in which the instantaneous digestion rate, K , varies with fish weight and temperature as: ~= 0 . 0 2 1 ~0 . 2 6 6 4 p 5 1 iFood pellets were prepared which remained separate and did not form a bolus in the stomach; K increased if a given meal size was subdivided to increase surface area. If meal size was increased by ingestion of identical pellets, K decreased. After a satiation meal, appetite in young turbot returns in direct relation to the degree of stomach emptiness. When food is regularly available, young turbot feed steadily at a rate which maintains their stomachs at c. 85% maximum fullness.When trained to use demand feeders, the fish interact a s a group to feed rhythmically. but feeding rate falls 33% to only two-thirds of the previous rate since stomach fullness, and hence digestion rate (g h-I). i s maintained at a lower level. Reduction in dietary energy density below I kCal g -' increases gastric emptying rate and the turbot demonstrate partial compensation by increasing food intake. On energy-rich diets, protein nitrogen and energy assimilation efficiencies remain high (97.5% and 91 YO respectively) irrespective of feeding rate and frequency.