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Some aspects of energy, protein and vitamin E nutrition of the performance horse are discussed. The amount, dietary source and time of ingestion of energy before exercise can influence performance. In 1989 the National Research Council (NRC) increased their estimates of energy required by racehorses. Recent studies indicate that the increase was reasonable. Many factors, however, can influence energy requirements. Therefore, the best measure would be body weight and composition of the horse. A proper balance of soluble carbohydrate, fiber, fat and protein is essential. Some guidelines are presented. The amount and type energy source given before exercise can influence level of plasma glucose and free fatty acids during exercise, but the effects of these changes in the concentration of metabolites remains to be determined. There is no evidence that increased dietary concentrations of protein are needed and, in fact, may impair performance. Supplemental histidine (to enhance carnosine levels) or carnitine appear to be of limited value for horses fed conventional diets. Dietary concentrations of vitamin E less than the 80 IU/kg recommended by NRC seem to adequately protect against exercise-induced peroxidation. The NRC value may be justified on the basis of immune response, but further studies are needed. Vitamin E has been shown to be involved with familial equine degenerative myeloencephalopathy and may be involved with equine motor neuron disease, a condition considered to be similar to amyotrophic lateral sclerosis in humans. [ABSTRACT FROM AUTHOR]

Two giant pandas were used to assess the utilization of bamboo as a feedstuff. Three 1-week-long digestion trials were conducted during which feed intake and fecal output were recorded. Passage of digesta was measured from both fluid and particulate markers administered at feeding. Results indicate that the giant panda, although highly specialized for the consumption of bamboo, is a very inefficient digester of bamboo. The pandas consumed up to 6% of body weight in dry matter per day, with bamboo dry matter digestibility averaging less than 20%. Apparent digestion coefficients for the structural carbohydrates of bamboo (27% for hemicellulose and 8% for cellulose) indicate that, unlike most herbivores, pandas do not rely heavily on the microbial degradation of plant material to fulfill their nutritional requirements. Additionally, the passage of digesta through the gastrointestinal tract of the panda was extremely rapid, with complete clearance of markers in less than 12 hours. The giant panda seems to have specialized to a feed source high in plant fiber without extensive modification of the digestive tract by selectivity in feeding, effective mastication, ingestion of large quantities, digestion of cellular contents rather than cell walls and rapid fecal excretion of the undigested residue.

Changes in the mineral composition of mare milk during lactation were studied. Milk samples were obtained from five Thoroughbred mares one to three times weekly from the first to the eighth week of lactation and from two of the mares for an additional 8 wk. Samples averaging 500 mL were obtained after oxytocin was administered to the mares. Each sample was analyzed for total solids, ash, calcium, phosphorus, magnesium, sodium, potassium, copper and zinc. The concentration of all constituents except sodium and potassium decreased throughout lactation. The rates of decline of ash, calcium, phosphorus and magnesium concentration were similar, but the rates of decline of the other elements differed. Thus, the mineral composition of mare milk should be described in terms of the stage of lactation of the mare. The total solids and ash content of mare milk were 12 and 0.61% respectively, at the end of the first week of lactation, 10.5 and 0.45% at 4 wk, 10 and 0.38% at 8 wk and 10.2 and 0.32% at 16 wk. The calcium, phosphorus and magnesium concentrations at the end of the same periods were 1345, 943 and 118 micrograms/g of milk at 1 wk; 1070, 659 and 86 at 4 wk; 831, 574 and 58 at 8 wk and 700, 540 and 43 micrograms/g of milk at 16 wk. Copper and zinc concentrations were 0.85 and 3.1, 0.55 and 2.2, 0.29 and 1.9 and 0.28 and 1.8 microgram/g of milk at 1, 4, 8 and 16 wk, respectively.

The effects of copper intake on stable copper and 64Cu metabolism and on the excretory pathways of absorbed copper were examined in ponies. Bile and feces collected from two bile duct-cannulated ponies following an intravenous dose of 64Cu showed that bile was the main route of endogenous copper excretion. Stable copper and 64Cu metabolism were examined in three intact ponies fed dietary copper to provide 5.6, 16.6 and 25.7 mg Cu/100 kg body weight/day. The amount of copper excreted in urine was not influenced by dietary treatment. Stable copper absorption and 64Cu retention significantly increased when ponies were fed the low copper ration. A direct linear relationship was observed between 64Cu excretion in feces and copper intake. Isotope dilution methods and regression analyses of data from balance studies were used to estimate an obligatory copper loss in ponies of approximately 3.5 mg Cu/100 kg body weight per day. The estimated dietary copper requirement for maintenance of mature ponies was 3.5 ppm.

Pony foals were injected intramuscularly with 0, 0.5, or 5.0 mg dexamethasone per 100 kg body weight daily for up to 11 months. True absorption of dietary calcium was inhibited by treatment at 18 days (57% versus 14% of intake; P less than .01) and 10 months (72% versus 55% versus 43%: P less than .01), but not at 2 or 7 months, and was independent of age and treatment related decreases in intestinal calcium binding protein activities. Uninary excretion of calcium was increased by treatment through 7 months but decreased at 10 months. Treatment for 18 days resulted in total calcium excretions equivalent to 127% of dietary intake. All animals were in positive calcium balance thereafter. Endogenous fecal calcium excretion was not affected by treatment, age, or sex, averaging 18.0 mg per kg body weight per day. At 2 months, rates of calcium deposition into bone were 13.02, 7.01 and 6.83 g per 100 kg per day in ponies treated with 0, 0.5 and 5.0 mg per 100 kg, respectively. Corresponding rates of calcium removal from bone were 5.41, 1.88, and 2.69 g per 100 kg per day. These rates remained significantly inhibited in the treated ponies at 7 and 10 months. The net effect of dexamethasone treatment was an inhibition of bone turnover: calcium removal was suppressed more than inhibition of bone turnover: calcium removal was suppressed more than calcium deposition.

The effects of molybdenum ingestion on copper metabolism were investigated in bile duct-cannulated ponies fed diets containing 1.01, 27.4 and 107.3 ppm molybdenum. Copper metabolism was assessed by examination of 64Cu and stable copper excretion in feces, bile and urine. The addition of molybdenum to the diet decreased copper absorption and retention as a consequence of increased excretion of dietary copper in feces and increased excretion of absorbed copper in bile. Only 5% or less of the absorbed copper was excreted in urine regardless of dietary treatment. Biliary molybdenum excretion was only 0.86 mg per 100 kg of body weight per day even when ponies were fed the highest level of molybdenum. However, increased molybdenum ingestion produced elevations in protein bound copper in bile. Molybdenum was absorbed by ponies but urinary excretion was effective in eliminating most of the element from the body.

Milk samples averaging 500 ml were collected weekly from 10 to 54 days postpartum from five lactating mares. Samples were obtained by hand milking after oxytocin administration and while the foal nursed. Dry matter, protein and gross energy were higher in samples obtained at 10 and 17 days postpartum than those obtained during the midlactation period of 24-54 days. Midlactation samples averaged 10.5% dry matter, 1.29% fat, 1.93% protein, 6.91% sugar and 50.6 kcal/100 g. Protein comprised 22% of milk energy. Milk intake was estimated in five foals from deuterium oxide (D2O) turnover to be 16, 15 and 18 kg/day at 11, 25 and 39 days postpartum. Milk intake differed significantly among foals and at the various postpartum ages, whether intake was expressed as a daily amount, as a percent of foal body weight, per kilogram0.75 or per gram of foal body weight gain. Milk production was equivalent to 3.1% of the mare's body weight at 11 days postpartum, 2.9% at 25 days and 3.4% at 39 days. On the basis of metabolic body size milk output by the mare was 149 g/kg0.75, 139 g/kg0.75 and 163 g/kg0.75 at 11, 25 and 39 days postpartum, respectively. Nutrient intakes by foals were calculated from milk composition and intake data. At 11, 25 and 39 days postpartum, respectively, dry matter intake equaled 3.1, 2.1 and 2.0% of foal body weight, and daily gross energy intake was 9380, 7590 and 8910 kcal. For each gram of body weight gain, foals ingested 0.37 g protein and 8.3 kcal at 11 days, 0.26 g protein and 6.7 kcal at 25 days, and 0.30 g protein and 7.8 kcal at 39 days of age.