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EXPANDED ABSTRACT There are numerous anecdotal reports of the beneficial effects of various nutritional supplements for horses that, from a scientific basis, are unlikely to be effective. The present study was to investigate placebo effects on subjectively perceived parameters in sport horses. Because deficiencies of vitamin E and selenium may cause nutritional myopathy (1), German sport riders often presume that problems with their horses such as unresponsiveness or stiff back (back muscles do not relax and contract in the rhythm of the movement but remain permanently contracted, a condition that impairs the movements of the horse and gives the rider a very bumpy and uncomfortable ride) are caused by problems of muscle metabolism and may be alleviated by supplementation of extra vitamin E and/or selenium. These popular theories were used to investigate the potential of placebo effects.

The effect of starch and sugars on blood sugar level and renal excretion of sugars and galactitol was investigated. Fifty-nine adult cats were divided into seven dietary groups (carbohydrate content in dry matter): STARCH (29-37% starch, decomposed or raw), SUC (36% sucrose), LAC1 and LAC2 (11 and 28% lactose, respectively), GLUC (40% glucose), GAL (39% galactose) and a carbohydrate-free control diet, FAT. Diet STARCH did not significantly influence postprandial blood glucose level (3.65 +/- 0.68 mmol/l +/- SD, n = 16) compared with diet FAT (3.20 +/- 0.77 mmol/l, n = 14) 1, 3 or 6 h after feeding (weighted means). Diet GLUC led to a steep rise in blood glucose concentration 1 h after feeding (5.08 +/- 0.69 mmol/l, n = 6). Diet SUC induced a mild persistent hyperglycemia without marked postprandial changes (4.52 +/- 0.52 mmol/l, n = 15, weighted mean of 0, 3 and 6 h post-prandially). Diet GAL induced persistent hypoglycemia before and after feeding (2.58 +/- 0.38 mmol/l, n = 13) and considerable postprandial galactosemia (3.26 +/- 1.38 mmol/l, n = 7). In the groups STARCH and FAT, glucose was only detectable in traces in urine, whereas all diets containing sugars led to glucosuria. In group SUC, fructose and sucrose were found in urine and in both lactose groups galactose and lactose were found. Diet GAL led to galactosuria (140 mmol galactose/l). In group LAC1, and especially in group GAL, galactitol was detected in urine. These results point to a rather limited capacity of the cat to metabolize sugars.

Six healthy adult cats were fed a basal minced beef meat and rice diet (one meal per day) with varying amounts or combinations of acidifying and alkalixing additives (ammonium chloride, calcium and sodium carbonate). The base excess in the food (mmol/kg dry matter) was calculated (data on food compounds in g/kg dry matter) as follows: base excess=49.9*Ca+82.3*M8+43.5*Na+25.6*K-64.6*P13.4*met-16.6*cys-28.2*Cl, Base excess in the experimental diets amounted to between +305 and -1079 mmol/kj dry matter. After an adaptation period of 5 d, urine and blood pH as well as water and mineral balance were determined in the cats over a 10-15-d period. The daily mean urine pH ranged between 6.1 and 7.8. There was a highly significant correlation between the base excess in the food and the mean urine pH. The regression line was linear down to a base excess in the diet of ∼-400 to -500 mmol/kg dry matter and a pH in the urine of 6.2. The postprandial increase of urine pH was suppressed either by large amounts of ammonium chloride (>780 mmol/kg dry matter) alone or in combination with calcium carbonate but not in combination with sodium carbonate. The relationship between the decrease of the blood pH and the amount of ammonium chloride added to the diet was more marked than the relationship between blood pH and base excess in the food. To avoid health risks from long term feeding of acidifying diets, it is recommended that struvite diets with low base excess be formulated and that they contain as few alkalixing compounds as possible that must be neutralized by acidifiers

In diets specifically designed for obese dogs and cats, fiber is considered important to reduce energy density and therefore energy intake. However, there is contradictory evidence on the effects of high fiber diets on food intake. Butterwick and Markwell (1997) found no influence of soluble or insoluble fiber on the energy intake in energy-restricted dogs. In contrast, Jewell and Toll (1995) noted decreased energy and dry matter intake in dogs after they were fed a medium or high fiber diet. These differences may be due to different composition or palatability of basic experimental diets. In this investigation, we studied the interactions between diet composition (especially high fat content) and fiber (cellulose) on dry matter intake. Digestibility of macronutrients and organic matter was also determined in some high fiber diets.