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The goals of this study were to have an improved understanding of milk composition and to help create a suitable milk formula for cubs raised in captivity. Milk samples were evaluated for fat, fatty acids, carbohydrate, vitamin D(3), 25(OH)D(3), vitamin A (retinol), vitamin E (α-tocopherol), protein, and amino acids. Total lipids in milk did not differ for cubs (mean ± SEM = 26.60 ± 1.88 g/100 ml vs. yearlings 27.80 ± 2.20 g/100 ml). Milk lipids were of 23.6% saturated fatty acid for cubs and 22.4% for yearlings. Milk consumed by cubs and yearlings contained 43.8 and 42.0% mono-unsaturated fatty acids and 23.4 and 21.9% polyunsaturated fatty acids, respectively. Carbohydrate content was higher in milk for cubs (4.60 ± 0.64 g/100 ml) than for yearlings (2.60 ± 0.40 g/100 ml). Vitamin D(3) concentration of milk was 18.40 ± 5.00 ng/ml in early lactation compared with 7.60 ± 2.00 ng/ml for mid-lactation. 25(OH)D(3) was lower in milk consumed by cubs (162.00 ± 6.70 pg/ml) than in milk consumed by yearlings (205.00 ± 45.70 pg/ml). Vitamin A concentrations were 0.06 ± 0.01 and 0.03 ± 0.01 µg/ml for cubs and yearlings, respectively. Vitamin E was higher in milk consumed by cubs (20.16 ± 4.46 µg/ml) than by yearlings (7.30 ± 1.50 µg/ml). Protein content did not differ in milk available to cubs (11.40 ± 0.80 g/100 ml compared with milk for yearlings 11.80 ± 0.40 g/100 ml). Taurine was the most abundant free amino acid at 3,165.90 ± 192.90 nmol/ml (0.04% as fed basis).

Growth assays were performed to determine lysine bioavailability for kittens and rats in untreated and heated casein; these values were compared with estimates obtained with an in vitro method. Body weight, food intake, nitrogen and dry matter digestibility, and plasma lysine were determined during an 80-day growth trial using kittens (n = 16). Body weight and food intake were determined during a 21-day growth trial using weanling rats (n = 80). The growth data showed bioavailable lysine to be 102.4% and 100.2% (for untreated casein) and 66.1% and 51.7% (for heated casein) for kittens and rats, respectively. There was no relationship between plasma lysine and dietary lysine concentrations for kittens. There were no significant differences in nitrogen or dry matter digestibility among diets for kittens. The chemically reactive lysine content of untreated casein was 99.6%, and of heated casein was 67.1%. Heat treatment of casein resulted in significantly decreased lysine bioavailability as estimated by all methods. For untreated casein, both growth assays showed good agreement with the in vitro method for available lysine. For heated casein, the rat growth assay significantly underestimated bioavailable lysine as determined in kittens while the in vitro method closely approximated this value for the cat.

Two days after castration, urinary free felinine plus N-acetylfelinine decreased 24% in male cats, but, by day 5, the concentration had not decreased to that routinely found in males that have been castrated for several months. In a second experiment, three groups of castrated adult male cats received different subcutaneous injections: control (carrier), testosterone, testosterone plus estradiol. A fourth group of intact adult female cats received a testosterone injection. Urine was collected and analysed for free felinine, N-acetylfelinine and 3-methylbutanolglutathione. Baseline blood testosterone and estradiol concentrations were low during the pre-period, but increased sharply after hormone injections. The concentration of all three urinary metabolites increased as a result of testosterone injections with estradiol not modulating the effect. The effect of testosterone was not gender dependent. The concentration of free felinine, N-acetylfelinine and 3-methylbutanolglutathione in the urine remained low in the placebo control group throughout the study. The relative molar contribution of free felinine to the total amount of felinine containing compounds increased due to testosterone treatment, while the contribution of 3-methylbutanolglutathione and N-acetylfelinine decreased. Testosterone increases free felinine, N-acetylfelinine and 3-methylbutanolglutathione excretion in castrated adult male and intact female cats, whereas estradiol does not modulate this effect.

The objective of this study was to determine if the methionine (met) requirement of kittens is correlated with the concentration of dietary crude protein (CP). The study used 48 male kittens in two replications of six 4 x 4 Latin squares, each representing one concentration of met (1.5, 2.5, 3.5, 4.5, 6.0 or 9.0 g/kg diet) with four CP concentrations (150, 200, 300 and 500 g/kg diet) in 2-week periods. Cystine was present in the lowest CP diet at 5.3 g/kg diet and increased as dietary CP increased. Body weight gain, food intake, nitrogen balance and plasma amino acids, glucose, insulin, cortisol, somatomedin C, T(3) and T(4) concentrations on day 12 were measured. From breakpoint analysis of the nitrogen retention curves, the met requirement of kittens was found to be 3.1, 3.8, 3.1 and 2.4 g met/kg for the 150, 200, 300 and 500 g CP/kg diets, respectively. When met was limiting (1.5 or 2.5 g/kg diet), increasing dietary CP did not decrease, but rather increased food intake, body weight gain and nitrogen retention. Plasma met concentrations increased as dietary met increased and at 2.5-3.5 g met/kg diet were not different among kittens fed the various CP diets. Total plasma T(3) and T(4) increased significantly as dietary CP increased in kittens given the 2.5 and 4.5 g met/kg diets. Results indicate that food intake and possibly altered hormonal secretion play a role in this growth response. In conclusion, the met requirement of growing kittens, unlike omnivores and herbivores studied, was not positively correlated with the concentration of dietary CP.

Diet-induced (taurine deficiency) dilated cardiomyopathy is reported more in large than small dogs possibly because taurine biosynthesis rate (TBR) is lower in large than small dogs. The TBR in 6 mongrels (37.9 +/- 2.1 kg) and 6 beagles (12.8 +/- 0.4 kg) was determined from the fractional dilution rate of urinary [1,2-(2)H(2)]-taurine, (d4-tau). All dogs were given a 15.6% protein, 0.60% sulfur amino acid (SAA) diet in amounts to maintain an ideal body condition score. After 3 mo, 14.6 mg/kg body weight of d4-tau was given orally and TBR determined from d4-tau to taurine ratio in urine collected each d for 6 d. Enrichments of d4-tau were determined by GC-MS. Thereafter, mongrels and beagles were paired by ranking of SAA intake per metabolic body weight per kg(0.75). Each pair received the same amount of diet/kg(0.75) for 2 wk, then TBR was again determined. Concentrations of taurine in plasma, blood, and urine and concentrations of plasma thiols were measured during each TBR determination. In Expt. 1, TBR and taurine concentrations in plasma and urine of mongrels were lower (P < 0.05) than those of beagles. In Expt. 2, TBR and taurine concentrations in blood and plasma of mongrels were lower (P < 0.05) than beagles. Together, the results support the hypothesis that large compared with small dogs have lower TBR when fed diets near-limiting in dietary SAA, but adequate to maintain ideal body condition.

To determine the effectiveness of dietary lysine supplementation in cats with enzootic upper respiratory disease (URD), 50 cats were fed a ration containing 11 or 51 g lysine/kg diet for 52 days. Food intake, body weight, clinical signs, plasma amino acid concentrations and presence of Chlamydophila felis or feline herpesvirus (FHV)-1 DNA within the conjunctival fornix were assessed. Food and lysine intake of both dietary groups decreased between days 17 and 22, coinciding with peak disease and viral presence. Mean disease score for cats fed the supplemented ration (0.94) was higher than for those fed the basal diet (0.21); however, this could be attributed to a small subset of male cats which demonstrated fighting behavior that may have contributed to stress within that cage. FHV-1 DNA was detected on 12 occasions in six cats receiving the supplemented diet and on one occasion in one cat fed the basal diet. C felis DNA was never detected. Mean plasma arginine concentration was lower and plasma lysine concentration was higher in supplemented cats. Mean plasma arginine concentration declined throughout the study in both dietary groups. Data from the present study raise important questions but do not permit a definitive conclusion regarding the efficacy of dietary lysine supplementation in cats with enzootic URD.

Although taurine is not dietarily essential for dogs, taurine deficiency and dilated cardiomyopathy (DCM) are sporadically reported in large-breed dogs. Taurine status and husbandry were examined in 216 privately owned Newfoundlands, a giant dog breed with high incidence of idiopathic DCM (1.3-2.5%). Plasma taurine concentration was positively correlated (P < 0.01) with plasma cyst(e)ine (r = 0.37) and methionine (r = 0.35) concentrations and was similar across age, sex, neutering status, body weight, and body-condition scores. Plasma taurine concentration was low (< or =40 micromol/L) in 8% of dogs. Dogs with low plasma taurine were older, less active, had more medical problems and treatments, and had lower plasma albumin, cyst(e)ine, tryptophan, and alpha-amino-n-butyric acid concentrations than the other dogs (P < 0.05). Of 9 taurine-deficient, clinically evaluated dogs, 3 had DCM that was reversed by taurine supplementation and 1 had retinal degeneration. When given a diet apparently adequate in sulfur amino acids (5.4 g/kg) for 3 wk, 6 Newfoundlands (52.5 +/- 2.3 kg, 3.5-7 y), compared with 6 Beagles (13.2 +/- 2.3 kg, 5.5 y), had lower (P < 0.01) concentrations of plasma taurine (49 +/- 16 vs. 97 +/- 25 micromol/L) and cyst(e)ine and blood glutathione, lower (P < 0.01) de novo taurine synthesis (59 +/- 15 vs. 124 +/- 27 mg x kg(-0.75) x d(-1)), and greater (P < 0.05) fecal bile acid excretion (1.7 +/- 0.2 vs. 1.4 +/- 0.2 micromol/g). Newfoundlands would appear to have a higher dietary sulfur amino acid requirement than Beagles, a model breed used in nutrient requirement determinations.

Copper deficiency has been reported to cause a decrease in urinary taurine excretion in rats. We determined whether Cu deficiency would decrease taurine status and the hepatic activities of cysteine dioxygenase (CDO) and/or cysteine sulfinic acid decarboxylase (CSAD) in rats. Ten weanling male rats were assigned to either a Cu-adequate (+Cu) or Cu-deficient (-Cu) group. All rats consumed a Cu-deficient purified diet and water ad-libitum for 16 wk. The water for the (+Cu) group contained 20 mg Cu/L as CuSO(4). At wk 16, the groups differed (P < 0.05) in the following variables (means +/- SEM, -Cu vs. +Cu): body weight (BW), 375 +/- 19 vs. 418 +/- 2.9 g; food intake, 16.2 +/- 0.7 vs. 18.5 +/- 0.4 g/d; hematocrit, 0.294 +/- 0.027 vs. 0.436 +/- 0.027; hemoglobin, 95.2 +/- 9 vs 134 +/- 10 g/L; liver Cu, 8.7 +/- 2.0 vs. 65.9 +/- 2.5 nmol/g; plasma Cu, 0.38 +/- 0.09 vs. 13.4 +/- 0.61 micromol/L; plasma ceruloplasmin activity, 1.75 +/- 1.0 vs. 67.9 +/- 8.4 IU; relative heart weight, 0.56 +/- 0.04 vs. 0.35 +/- 0.02% BW; relative liver weight, 4.06 +/- 0.23 vs. 3.37 +/- 0.06% BW; and liver CSAD activity, 18.8 +/- 1.37 vs. 13.5 +/- 1.11 nmol x min(-1) x mg protein(-1). The groups did not differ at wk 16 in: plasma taurine, 249 +/- 14 vs. 298 +/- 63 micromol/L; whole blood taurine, 386 +/- 32 vs. 390 +/- 25 micromol/L; urinary taurine excretion, 82.5 +/- 15 vs. 52.0 +/- 8.3 micromol/d; liver taurine, 2.6 +/- 0.7 vs. 2.8 +/- 0.4 micromol/g; liver total glutathione, 6.9 +/- 0.48 vs. 6.3 +/- 0.40 micromol/g; liver cyst(e)ine, 96 +/- 7.1 vs. 99 +/- 5.3 nmol/g and liver CDO activity, 2.19 +/- 0.33 vs. 2.74 +/- 0.21 nmol x min(-1) x mg protein(-1). These findings support the conclusion that Cu deficiency does not affect body taurine status.

Essential amino acid (EAA) requirements of omnivores and herbivores (e.g. chicks, lambs, pigs and rats) are directly related to the concentration of dietary crude protein (CP). When an EAA is limiting in the diet, addition of a mixture of EAA lacking the limiting one (which increases dietary CP) results in a decrease in food intake and weight gain. This interaction has been referred to as an AA imbalance and has not been studied in depth in strict carnivores. The objectives of these experiments were to examine the effects on growing kittens (2-week periods) of the addition to diets of a mixture of AA lacking the limiting one. The control diets were at the requirement of the respective limiting EAA (or about 85% of the 1986 National Research Council requirement). In experiment 1, with the dietary EAAs at the minimally determined requirements, the concentration of the essential or dispensable amino acids was increased to determine if CP or an EAA was limiting. Results of growth rates (n = 12) and plasma AA concentrations indicated that tryptophan was limiting, but increased body weight gain also occurred when the concentration of CP was increased as dispensable amino acids without additional tryptophan. Experiment 1 was repeated in experiment 2 using a crossover design. Again, when tryptophan was limiting additional concentrations of dispensable AAs increased body weight gain. This response is the opposite of that in herbivores and omnivores. Experiment 3 consisted of 10 separate crossover trials, one for each of the 10 EAA and examined the effect of two concentrations of dietary CP (200 and 300 g CP/kg diet) on body weight gain of kittens (n = 8) offered diets limiting in each respective EAA. Body weight gain was numerically greater when diets contained 300 g CP/kg than 200 g CP/kg for eight of 10 EAAs (p < 0.05 for only isoleucine and threonine) when each amino acid was limiting. This response is the reverse of that which occurs in chicks, lambs, pigs and rats when an EAA is limiting and dietary CP lacking the limiting EAA is increased. These results indicate that the EAA requirements of kittens are not positively correlated with dietary CP concentrations.

Indispensable amino acids are neither synthesized nor stored in animals and are rapidly depleted when not provided by the diet. To maintain homeostasis, organisms must sense deficiency of an indispensable amino acid and implement a repletion strategy. In rats and birds, the anterior piriform cortex houses the detector, but its mechanism has evaded description for >50 years. Recently, rapid detection of amino acid depletion was shown behaviorally when naive animals, pre-fed a low nitrogen diet, terminated their first deficient meal within 20 min. The general amino acid control system of yeast, which is activated by amino acid deprivation via deacylated tRNA, was found to be active in rodent brain, showing conservation of amino acid sensory mechanisms across eukaryotic species.

When pyrroloquinoline quinone (PQQ) is added to an amino acid-based, but otherwise nutritionally complete basal diet, it improves growth-related variables in young mice. We examined PQQ and mitochondrial function based on observations that PQQ deficiency results in elevated plasma glucose concentrations in young mice, and PQQ addition stimulates mitochondrial complex 1 activity in vitro. PQQ-deficient weanling mice had a 20-30% reduction in the relative amount of mitochondria in liver; lower respiratory control ratios, and lower respiratory quotients than PQQ-supplemented mice (2 mg PQQ/kg diet). In mice from dams fed a conventional laboratory diet, but switched at weaning to the basal diet, plasma glucose, Ala, Gly, and Ser concentrations were elevated at 4 wk (PQQ- vs. PQQ+), but not at 8 wk. The relative mitochondrial content (ratio of mtDNA to nuclear DNA) also tended (P

Three experiments were conducted to determine the effects of dietary arginine concentrations on plasma free amino acid (PAA) concentrations in rainbow trout, Oncorhynchus mykiss (Walbaum). The first experiment was conducted to determine appropriate post-prandial and food deprivation sampling times in dorsal aorta cannulated rainbow trout averaging 519′9.5 g (mean′SD) at 16°C. Blood samples were taken at 0, 2, 3, 4, 5, 6 and 24 h after feeding (0 and 24 h blood samples were taken from the same group of fish). PAA concentrations increased by 2 h post-feeding and the concentration of all essential amino acids except histidine peaked at 5 h and returned to 0 time values by 24 h. In the second experiment dorsal aorta cannulated rainbow trout averaging 528′11.3 g (mean′SD) were divided into 6 groups of 4 fish to study the effect of dietary arginine levels on PAA. After 24 h food deprivation, each group of fish was fed one of six L-amino acid diets containing graded levels of arginine (0.48, 1.08, 1.38, 1.68, 1.98 or 2.58%) by intubation. Blood samples were taken at 0, 5 and 24 h after feeding. Post-prandial (5 h after feeding) plasma-free arginine concentrations (PParg) showed a breakpoint at 1.03% arginine in the diet and post-absorptive (24 h after feeding) plasma free-arginine concentrations (PAarg) showed a breakpoint at 1.38% arginine. PAarg increased linearly from fish fed diets containing arginine between 0.48% and 1.38%, and the concentrations remained constant from fish fed diets containing arginine at or above 1.38%, but were all below PParg at all time points. Results of the third experiment confirm the results that PParg concentrations from fish fed arginine deficient diets were higher than PAarg (0 or 24 h values). Thus, in contrast to mammals and birds, the PParg when arginine is present in the diet as the most limiting amino acid such that it severely limits growth, increases in plasma rather than decreases.

Summary Many genes influencing mammalian coat colours are well conserved. While genes responsible for pelage phenotypes in one species provide strong evidence for a candidate gene in a different species, the X-linked orange phenotype of the domestic cat is unique within mammals. The orange locus (O) undergoes X-inactivation, producing females that express both wildtype black (wt) and orange (variant) phenotypes when heterozygous (tortoiseshell). The orange locus has not yet been localized on the X chromosome. Tortoiseshell male cats have been identified but have been shown to be sex chromosome trisomies (XXY). To localize the cat orange locus, 10 feline-derived X-linked microsatellites were analysed in two extended cat pedigrees consisting of 79 and 55 individuals, respectively, segregating for the orange phenotype. Linkage analyses excluded close association of orange in the vicinity of the nine informative X-linked microsatellites. One marker was not polymorphic within either family. Several markers suggested exclusion (Z < )2.0) at distances of 7.5‐33 cM. Exclusion analyses suggested a possible location for orange a1 4 cM region near Xcen. Recombination distances of markers in the segregating feline pedigrees were reduced as compared with the feline interspecies backcross family. Thus, the presented pedigrees may be useful as reference families for the domestic cat because more accurate recombination rates for domestic cats can be determined.

Background In human blood, the amino acid cysteine forms disulfide bonds with itself and with other sulfhydryl compounds in their free form and with sulfhydryls in protein. Protein-bound cysteine is lost when plasma proteins are removed before amino acid analysis. Objective The purpose of this study was to assess the time course and extent of cyst(e)ine (cysteine + half-cystine) loss in dog and cat plasma. Methods An equal volume of 6% sulfosalicylic acid was added to plasma aliquots at 0, 2, 4, 10, 16, 24, 36, 48, 60, and 72 hours after separation of blood cells. Tris-2-carboxyethyl-phosphine hydrochloride (TCEP - HCl), a reducing agent, was used to regenerate total plasma cyst(e)ine after 3 months of sample storage (-20 degrees C). Results Initial free cyst(e)ine concentrations (mean +/- SEM) were higher in canine plasma (77 +/- 4 micromol/L) than in feline plasma (37 +/- 3 micromol/L). Free plasma cyst(e)ine concentrations in dogs and cats decreased after first-order kinetics, with a half-life of 23 and 69 hours, respectively. Total plasma cysteine after TCEP - HCl treatment was similar for dogs (290 micromol/L) and cats (296 micromol/L), but the percentage of free cysteine was higher (P = .02) in dogs (27%) than in cats (13%). Over half of the cyst(e)ine, homocysteine, cysteinylglycine, and glutathione were bound in vivo to plasma proteins. Conclusion These results emphasize the importance of removing plasma proteins within 1 hour after blood collection for reliable assay of free plasma cyst(e)ine.

Three experiments were conducted using a total of 15 male and 15 female weaned specific pathogen-free kittens given amino acid-based purified diets containing varying concentrations of lysine (from 4.0 to 11.3 g/kg diet) in a Latin square design of 10 day periods. In experiment 1, the predicted lysine requirement was 7.7 g/kg diet, and in experiments 2 and 3, maximal weight gain occurred at 8.0 g lysine/kg diet. In experiment 3, nitrogen balance was not different for kittens given diets containing 8.0 and 9.0 g lysine/kg. These experiments support a requirement of 8.0 g lysine (free base)/kg diet, in a diet with a calculated metabolizable energy value of 4.7 kcal/g.

Milk from 11 domestic shorthair cats (Felis catus; n=7 fed dry low-fat diet, n=4 fed dry high-fat diet) was collected weekly for 6 weeks following parturition, and analysed for total solids (TS), crude protein (CP), fat, lactose and ash. Samples were collected in 1-ml sequential fractions to determine whether within-sampling changes in composition existed Samples of extracted milk fat were also analysed for fatty acid content. Two commercia kitten milk replacers were analysed according to the same procedures utilized for mil samples. In statistical analyses individual cat, diet, stage of lactation, litter size, and teat position influenced concentrations of milk components; parity and sequential sampling had no effect. Averaged cat milk was 27.9% TS, and 8.7% CP, 12.7% fat, 4.2% lactose and 1.3% ash (on a wet basis). Milk protein percentage increased over lactation for both diet groups, but fat percentage increased only for queens fed the high-fat diet. Milk replacers were lower in fat and protein content than milk from queens, and had considerably lower levels of arachidonic acid. Data from this study contribute to the limited information available regarding the composition of domestic cat milk, and give possible reasons for poor growth occasionally observed in kittens fed unsupplemented commercial milk replacers.

The percentage of protein that dogs voluntarily choose and the effect of palatability on the quantity selected were determined. Six beagles were offered a choice of two isoenergetic purified diets containing 0 vs. 25, 9 vs. 32, 18 vs. 32, 18 vs. 48 and 25 vs. 48% metabolizable energy from protein (MEp). To examine whether palatability modifies the choice, the dogs were offered 0 vs. 25% MEp, with the 0% protein diet containing 2.9 times more sucrose than the diet containing 25% MEp. To determine the effect of concentration of protein in the diet on dietary choice and plasma amino acid concentrations (PAA), dogs were adapted to 9% MEp, followed by a choice of diets containing 9 vs. 32% MEp. The choice was repeated after adaptation to a diet containing 32% MEp. Dogs selected diets to obtain 21-27% of the MEp (mean, 25% MEp; median, 27% MEp) when sucrose was kept at 6.4%. When the protein-free diet contained 25% sucrose, dogs selected 17% of MEp, but increased food intake to ingest about the same amount of protein per day. PAA did not correlate linearly with protein intake. Food intake and total PAA were the lowest after consumption of the 9% MEp diet. We conclude that when fed equally bland diets, dogs select food to ingest approximately 25% MEp. As a palatability enhancer, sucrose increases food intake and selection of the diet containing the higher sucrose concentration.

The purpose of this study was to determine the selenium (Se) requirement in kittens. Thirty-six specific-pathogen-free kittens (9.8 weeks old) were utilized in a randomized complete block design to determine the Se requirement in cats with gender and weight used as blocking criteria. Kittens were fed a low Se (0.02 mg/kg Se) torula yeast-based diet for 5 weeks (pre-test) after which an amino acid-based diet (0.027 mg Se/kg diet) was fed for 8 weeks (experimental period). Six levels of Se (0, 0.05, 0.075, 0.10, 0.20 and 0.30 mg Se/kg diet) as Na2SeO3 were added to the diet and were used to construct a response curve. Response variables included Se concentrations and Se-dependent glutathione peroxidase activities (GSHpx) in plasma and red blood cells (RBC) as well as plasma total T3 (TT3) and total T4 (TT4). No significant changes in food intake, weight gain or clinical signs of Se deficiency were noted. Estimates of the kitten's Se requirement (i.e. breakpoints) were determined for RBC and plasma GSHpx (0.12 and 0.15 mg Se/kg diet, respectively), but no definitive breakpoint was determined for plasma Se. Plasma TT3 increased linearly, whereas plasma TT4 and the ratio of TT4 : TT3 decreased in a quadratic fashion to dietary Se concentration. The requirement estimate determined in this study (0.15 mg Se/kg) for kittens is in close agreement with other species. As pet foods for cats contain a high proportion of animal protein with a Se bioavailability of 30%, it is recommended that commercial diets for cats contain 0.5 mg Se/kg DM.

The aim of this study was to determine the taurine content in a variety of animal feeds. There is very little information on the taurine content of ingredients used in home-prepared diets for dogs and cats, and foods fed to wild animals in captivity. This study reports the taurine content of both common and alternative feed ingredients, and compares taurine loss as a result of different methods of food preparation. Foods were selected based on their use in commercial and home-prepared diets. Animal muscle tissue, particularly marine, contained high taurine concentrations. Plant products contained either low or undetectable amounts of taurine. The amount of taurine that remained in a feed ingredient after cooking depended upon the method of food preparation. When an ingredient was constantly surrounded by water during the cooking process, such as in boiling or basting, more taurine was lost. Food preparation methods that minimized water loss, such as baking or frying, had higher rates of taurine retention.

BACKGROUND There is little published information on plasma copper and whole blood copper concentrations in cats, and except for extracellular superoxide dismutase (EC SOD), we are unaware of published values for cat cuproenzyme activities. OBJECTIVE In this study we determined plasma and whole blood copper concentrations, plasma ceruloplasmin (CP), EC SOD and diamine oxidase (DAO) activities, and erythrocyte superoxide dismutase (RBC SOD) activity in a specific pathogen-free colony of cats. Results were evaluated for differences based on age and sex. METHODS Blood was obtained from 20 adult cats (10 males, 10 females; >1 year of age) and 20 immature cats (10 males, 10 females

Breath hydrogen (H(2)) concentration, an indicator of intestinal microbial abundance, was determined in cats given purified and commercial canned and dry-type diets. Before measurements, the cats were fed diets for more than 2 wk and habituated to a daily feeding interval of 4 hr. Breath H(2) concentrations were determined before a meal (approximately 25% daily MER) and then every 20 min for 8 hr or hourly for 10 hr. A clear rise above baseline breath H(2) concentrations, 1-2 ppm, was not observed in 6 males given a casein-based purified diet. A mean (+/- SEM) peak breath H(2) concentration of 22 +/- 4 ppm was observed in 6 other males, 6.3 hr after ingestion of a canned diet with protein, fat, and carbohydrate proportions similar to those of the purified diet. Area-under-the-curve (AUC) breath H(2) responses to the canned diet were substantially greater (p0.05) than responses observed in 5 males given a dry-type diet, but similar to responses observed in 12 males given an uncooked form of the canned diet. Gamma irradiation to inactivate microbes in the uncooked diet did not affect the breath H(2) response. Breath H(2) responses to 2 other canned and 2 other dry-type diets were evaluated in 8 adult females using a 4 x 4 Latin-square design. Peak and AUC responses to the canned diets were similar but approximately 2 times greater (p0.05) than responses to the dry diets. Relative to dry-type diets, canned diets induce a substantially greater breath H(2) production, and therefore appear to support a greater intestinal microbial population.

Nutrition most certainly affects health and may play a role in the etiology of growth and reproductive problems in captive cheetah (Acinonyxjubatus) populations. The objective of our research was to examine nutritional differences between two dietary regimens and quantify their physiologic effects on cheetahs held in captivity. Twelve cheetahs were randomly assigned to either a commercial diet (COM) or a supplemented meat diet (SMD) group. These cats were physically examined and had blood samples taken three times over the course of a year. Representative samples of COM and four separate components of the SMD treatment were analyzed over the same time frame for proximate nutrient composition, digestibility, and concentrations of taurine, fat-soluble vitamins, and selected minerals. Concentrations of fat, vitamins A and E, Se, Fe, Cu, Na, and Mn were significantly higher in COM compared with those in SMD samples, with the exception of fat content in turkey. Mg content was lower in COM than in SMD; other nutrients did not differ. Mean concentrations of vitamins A and E in COM were markedly higher than in SMD samples (408,140 vs. 29,696 IU/kg dry matter [DM] and 431 vs. 48 IU/kg DM, respectively) and varied dramatically between sampling periods. Percent crude protein and protein-to-fat ratios were high for SMD compared with either whole prey-based or commercial food preparations. Blood urea nitrogen and serum creatinine levels were above normal reference means for domestic cats. Plasma concentrations of vitamins A, D, and E were significantly higher in COM-fed than in SMD-fed cheetahs. Both plasma retinol and tocopherol levels were almost three times higher in COM-fed cats (1.26 +/- 0.06 vs. 0.53 +/- 0.03 microg/ml and 17.5 +/- 0.7 vs. 6.4 +/- 0.02 microg/ml, respectively) and exceeded the normal ranges expected for domestic felids. Significant differences between male and female cheetahs were found for plasma concentrations of vitamin E, Se, and Fe after allowing for effects of diet and time of collection. Excess fat-soluble dietary vitamins can result in direct toxicities as well as nutrient antagonisms and may be linked to reproductive and health issues in captive cheetahs. The high protein levels found in SMD may be linked to chronic renal disease, which was detected in some of these cheetahs.

The effect of a low-selenium diet on thyroid hormone metabolism was investigated in growing kittens. Twelve specific-pathogen-free kittens with ages ranging from 16 to 18 weeks were divided into two groups of equal number with equal sex distribution in each group. One group was fed a yeast-based low-selenium diet (0.02 mg Se/kg diet) while the other group was fed the same diet supplemented with Na2SeO3 at 0.4 mg Se/kg diet for 8 weeks. Food intake, body weight and body weight gain were not affected by the low-Se diet during the study period. However, kittens given the low-Se diet had significantly reduced plasma selenium concentration and glutathione peroxidase activity. Plasma total thyroxine (T4) increased and total 3,5,3'triiodothyronine (T3) decreased significantly in kittens fed the low-Se diet at the end of the study. These results suggest that type I deiodinase in cats is a selenoprotein- or a selenium-dependent enzyme.

The relationship between taurine concentrations of plasma, whole blood, serum and skeletal muscle during taurine depletion and repletion was investigated in cats, to identify the most useful indicators of taurine status. Sixteen cats were fed a purified diet containing either 0 or 0.15 g/kg taurine for 5 months. Treatments were then reversed and the taurine concentration was measured during repletion and depletion phases. Plasma taurine exhibited the fastest rate (slow component) of depletion (t 1/2 = 4.8 wk), followed by serum (5.3 wk), whole blood (6.2 wk), and skeletal muscle (11.2 wk). Whole blood taurine was the first to replete at a rate of 0.74 wk to 1/2 maximal repletion, followed by serum (2.1 wk), skeletal muscle (3.5 wk), and plasma (3.5 wk). Whole blood more closely reflected skeletal muscle taurine concentrations than plasma during depletion, while plasma taurine concentrations appear to be the most valuable predictor of skeletal muscle taurine concentrations during repletion. This study suggests that the best clinical method to evaluate the taurine status of the cat is the determination and interpretation of both plasma and whole blood taurine concentrations.

Objective—To determine the effectiveness of 3 antioxidants in preventing Heinz body anemia in cats. Design—Prospective study. Animals—44 specific-pathogen-free healthy cats. Procedure—Cats were housed individually, divided randomly into 4 groups, and given the following orally every 12 hours: empty gelcaps (control cats), Nacetylcysteine (NAC, 100 mg/kg of body weight), vitamin E (d,l-α-tocopherol; 400 IU), or ascorbate (250 mg). After 2 weeks, Heinz bodies were induced by dietary onion powder (OP; 1% or 3% of dry matter) or propylene glycol (PG, 8% wt/vol in drinking water) for an additional 3 weeks. Intake of treated water or food was recorded daily. Body weight, PCV, Heinz body and reticulocyte percentages, reduced glutathione concentration, and total antioxidant status were measured twice weekly in all cats. Results—Heinz body percentage and degree of anemia did not differ significantly among cats receiving antioxidants and control cats except in cats that ingested water containing PG, in which antioxidant supplementation was associated with a decrease in water intake. Of cats that were fed a diet that contained OP, cats that received NAC had significantly higher reduced glutathione concentrations, compared with other cats in the experiment. Total antioxidant status did not consistently correlate with antioxidant supplementation or type of oxidant administered (ie, OP or PG). Conclusions and Clinical Relevance—Although the effect of antioxidant supplementation on Heinz body anemia in cats was minimal, antioxidants may have subclinical biochemical effects such as GSH sparing that may be important against milder forms of oxidative stress. (Am J Vet Res 2001;62:370–374)

Objective—To assess effects of deficiency of lipoprotein lipase (LPL) on body condition scores and lean and fat body masses of adult cats. Animals—12 cats without LPL mutations and 23 cats that were heterozygous or homozygous carriers of the Gly412Arg LPL mutation. Procedure—Lean and fat body masses were estimated by use of body condition scores and change in enrichment of serum after IV administration of deuterium oxide. Mass spectroscopy and infrared absorbance methods were used to determine deuterium enrichment. Results—Fat body mass (mean ± SD; 0.2 ± 0.1 kg) and percentage body fat (6.2 ± 1.4%) of homozygotes were significantly less than those of clinically normal cats and heterozygotes (0.7 ± 0.1 kg, 18.2 ± 1.6% and 0.5 ± 0.1 kg, 15.6 ± 1.7%, respectively). Homozygous offspring of homozygous dams had significantly less fat body mass (0.1 ± 0.1 kg) and percentage body fat (2.1 ± 1.0%) than homozygous offspring of heterozygous dams (0.3 ± 0.1 kg and 9.2 ± 1.7%, respectively). Lean body mass did not differ significantly among groups. For all groups, percentage body fat was significantly correlated with body condition score (r = 0.65), and body condition scores supported findings for fat body mass. Conclusions and Clinical Relevance—Deficiency of LPL activity in cats diminishes stores of body fat. This is consistent with a low rate of de novo synthesis of fat. The effect of dam on body masses in mature LPLdeficient cats indicates nutrient programming of adipose formation during gestation or lactation. (Am J Vet Res 2001;62:264–269)

Objective—To validate a recently developed commercially available leptin radioimmunoassay (RIA) for use with feline serum and evaluate the relationship between serum leptin concentrations and body fat mass in domestic cats. Animals—19 sexually intact male specific–pathogenfree domestic cats that weighed 3.8 to 7.1 kg and were 1.1 to 3.5 years old. Procedure—Specificity for feline leptin was evaluated by use of gel filtration chromatography and reversephase high-performance liquid chromatography fractionation of serum. Body fat mass was determined by use of the deuterium oxide (D2O) dilution method. Serum water D2O enrichment was measured by use of gas-phase Fourier transform infrared spectroscopy. Results—Body fat mass and percentage body fat ranged from 0.3 to 2.3 kg and 7.5 to 34.9%, respectively. Serum leptin concentrations were lower in the unfed versus the fed state and ranged between 1.6 and 4.9 ng/ml human equivalent (HE); mean ± SD value was 2.9 ± 0.2 ng/ml HE. Leptin concentrations increased with increasing body fat mass and percentage of body fat. Conclusions—Leptin is in the serum of domestic cats in free (> 78%) and apparently bound forms. The relationship between body fat and serum leptin concentration was similar to that observed in humans and rodents and indicative of a lipostatic role for leptin in cats. Cats that have an overabundance of body fat appear to be less sensitive to the weight-normalizing action of leptin than cats of ideal body condition. (Am J Vet Res 2000;61:796–801)

The objective of this study was to determine the copper requirement of female cats (queens) for gestation. Cuproenzyme activities were evaluated to identify a noninvasive indicator of copper status. This study used a depletion-repletion model. Specific pathogen-free queens (n = 28) were adapted to a purified diet; after consuming a copper-depletion diet (0.8 mg Cu/kg diet) for 4 mo, they were randomly allocated to three dietary treatment groups receiving copper sulfate at 4.0, 5.8 or 10.8 mg Cu/kg diet. Four queens underwent liver biopsies at two time points during the study. Plasma samples were analyzed for copper concentrations, extracellular superoxide dismutase, ceruloplasmin and diamine oxidase activities. Only liver copper concentrations were responsive to dietary copper intake. The dietary concentration of copper had a significant effect on the time taken for queens to conceive (P = 0.04). There was a negative linear relationship between dietary copper (x = Cu mg/kg diet) and the mean time (y = days) for queens to conceive (y = 43.38-2.87x; R(2) = 0.97). The current NRC recommendation of 5 mg/kg diet copper for cats appears marginal for optimal reproduction.

BACKGROUND Polyunsaturated n-3 fatty acids have been shown to inhibit the growth and metastasis of tumors. This double-blind, randomized study was designed to evaluate the hypothesis that polyunsaturated n-3 fatty acids can improve metabolic parameters, decrease chemical indices of inflammation, enhance quality of life, and extend disease free interval and survival time for dogs treated for lymphoblastic lymphoma with doxorubicin chemotherapy. METHODS Thirty-two dogs with lymphoma were randomized to receive one of two diets supplemented with menhaden fish oil and arginine (experimental diet) or an otherwise identical diet supplemented with soybean oil (control diet). Diets were fed before and after remission was attained with up to five dosages of doxorubicin. Parameters examined included blood concentrations of glucose, lactic acid, and insulin in response to glucose and diet tolerance tests; alpha-1 acid glycoprotein; tumor necrosis factor; interleukin-6; body weight; amino acid profiles; resting energy expenditure; disease free interval (DFI); survival time (ST); and clinical performance scores. RESULTS Dogs fed the experimental diet had significantly (P < 0.05) higher mean serum levels of the n-3 fatty acids docosahexaenoic acid (C22:6) and eicosapentaenoic acid (C20:5) compared with controls. Higher serum levels of C22:6 and C20:5 were associated with lesser (P < 0.05) plasma lactic acid responses to intravenous glucose and diet tolerance testing. Increasing C22:6 levels were significantly (P < 0.05) associated with longer DFI and ST for dogs with Stage III lymphoma fed the experimental diet. CONCLUSIONS Fatty acids of the n-3 series normalize elevated blood lactic acid in a dose-dependent manner, resulting in an increase in DFI and ST for dogs with lymphoma. Cancer 2000;88:1916–28. © 2000 American Cancer Society.

Background We have previously described a colony of domestic cats with a naturally occurring mutation in the lipoprotein lipase (LPL) gene. We have now further characterized cats homozygous for LPL deficiency (LPL −/−, homozygotes), and have contrasted these with heterozygotes (LPL +/−) and normal cats (LPL +/+). Materials and methods Density gradient ultracentrifugation with subsequent lipid analysis, agarose and polyacrylamide gel electrophoresis was used to examine detailed liproprotein differences between the genotypes. Oral fat loading studies and breast milk fatty acid analysis were also performed to further characterize the phenotypic expression of LPL deficiency in this model system. Results Several lipid abnormalities associated with homozygosity for LPL deficiency were evident. Triglyceride-rich lipoprotein-triglycerides (TRL-TG) and cholesterol (TRL-C) were higher (TRL-TG 2.09 ± 1.14 vs. 0.15 ± 0.04 mmol L−1, P

EXPANDED ABSTRACT Experiments with rats (Heger 1990, Stucki and Harper 1962), chicks (Bedford and Summers 1985, Stucki and Harper 1961), turkeys (Bedford and Summers 1988) and pigs (Wang and Fuller 1989) have shown optimal growth rates when the dietary essential amino acid (EAA) 3 nitrogen to total nitrogen (E:T) ratios were between 0.4 and 0.65. It has been consistently found that diets containing only EAA (E:T 5 1.0) yield poor growth rates. Taylor et al. (1996) showed that in kittens fed diets that contain EAA as the sole source of nitrogen [E:T 5 1.0, with the EAA pattern proportionate to the NRC requirements (NRC 1986)], weight loss results. Plasma amino acid concentrations of methionine (and possibly arginine) suggested toxicities of these amino acids. Also, marked depressions in the concentrations of proline and asparagine suggested that these amino acids might be conditionally essential. A near-maximal growth rate for the group receiving all EAA (E:T 5 1.0) was achieved when methionine and arginine were limited to not more than 2.25 times the NRC requirements. No response was obtained with proline and/or asparagine supplementation to the all-EAA diet or when these two amino acids were removed from the control diet. Thus asparagine and proline are clearly dispensable under all conditions tested thus far. These results suggest that the poor growth rates recorded in other species given only EAA (E:T 5 1.0) diets are the result of an intolerance of one or more EAA, rather than a metabolic inability of animals to synthesize dispensable amino acids (DAA) at a rate fast enough for rapid growth, as previously suggested by Harper (1974). Here we report the results of weight gains of kittens fed a wide range of crude protein (CP) levels at various E:T ratios in which excesses of essential amino acids that depress weight gains were avoided. Materials and methods. A control purified diet (CD) was

Summary The medical records of 209 dogs receivingtotal parenteral nutrition (TPN) over a 84-month period were examined retrospectively to determine patient profiles, frequency and type of complications, and prognostic factors affecting clinical outcome. TPN administration accounted for 895 patient days. Dogs with diarrhea or vomiting associated with gastrointestinal disease, pancreatitis, or renal failure constituted the largest proportion of patient receiving TPN. The median duration of TPN administration was 3.5 days (range 0.05 to 25 days). The median length of hospitalization before initiation of TPN was 1.5 days (range 0.05 days to 15 days). and this durationwas not associated with survival. Metabolic complications were frequent (329 of 473 complications observed) and were due predominantly to hyperglycemia. Mechanical (118 of 473) and septic (26 of 473) complications occurred less commonly. The overall mortality rate for dogs receiving TPN was 48.8%. Our conclusion: TPN can be a beneficial mode of therapy for carefully selected dogs that have impaired gastrointestinal function (parvovirus, pancreatitis, or inflammatory bowel disease) and are expected to be anorectic for morethan 5 days.

Amino acid-imbalanced (IMB) diets induce an acute amino acid deficiency and hypophagic responses in most animals. The neural circuits underlying these responses are unknown. To ascertain potential neural circuits involved in the recognition of IMB, we measured the concentrations of norepinephrine, dopamine, serotonin, their metabolites and 20 amino acids in 14 rat brain areas in three studies. Rats were prefed a basal diet with L-amino acids as the protein source for at least 1 wk. For the experiments, either threonine or isoleucine IMB diet was offered for 2.5 or 3.5 h. Brains were taken before (using a mildly IMB diet) or after (using moderately or severely IMB diet) food intake was significantly (P < 0.05) depressed. Brain areas were dissected and analyzed for monoamines, metabolites and amino acids. Only in the anterior piriform cortex (APC), a brain area that may contain the amino acid chemosensor, was the limiting amino acid lower in IMB groups than in controls across all of the experiments. Before the onset of the anorectic response to the IMB diets, monoaminergic activity was affected in areas that have recognized monosynaptic connections with the APC. We propose a circuit for the neural responses in the initial recognition of acute amino acid deprivation that begins with activation of the APC and includes areas in the hindbrain and hypothalamus. After a significant hypophagic response, serotonergic indicators were altered in areas of the taste pathway and the limbic system. These results suggest that different circuits mediate the initial recognition and secondary conditioned responses to IMB diets.

Incomplete agreement exists on the relative potency of amino acids in stimulating endocrine secretion of cholecystokinin (CCK). Species and methodological variations have been suggested to account for the apparent inconsistencies. In the present research, the CCK-releasing potency of dietary amino acids was evaluated in cats using plasma CCK-like immunoreactivity (CCK-LI) as an indicator of CCK secretion rather than pancreatic protein and enzyme secretion, as has been used in past research. Oral-gastric administrations of a casein-simulating amino acid mixture increased (P < 0.05) plasma CCK-LI but not to the extent of that observed for casein or sodium oleate. The response in plasma CCK-LI to administrations of 50 mM solutions of amino acids was significant (P < 0.05) for tryptophan, phenylalanine, leucine, and isoleucine and the response increased linearly (P < 0.01) with increasing amino side-chain hydrophobicity. Control administrations of water and saline also evoked elevation in plasma CCK-LI, but the responses were so transient that amino acid effects were not obscured. This was substantiated by the finding of a significant linear (P < 0.001) dose response to phenylalanine administration. Cholecystokinin-8, 33 and 58 were among the CCK molecular forms identified by HPLC in plasma after administrations of phenylalanine and water. The present findings indicate that lipophilic amino acids released during digestion account for at least part of the endocrine CCK response in cats to ingested protein. The greater CCK-releasing potency observed for intact protein relative to free amino acids may have been the result of a slow digestive release of amino acids, elaboration of peptide secretogogues or protection of protease-sensitive releasing factors.

Kittens fed diets containing 0.75 × the NRC (1986) essential amino acid requirement (EAArq) and 210 to 560g crude protein(CP)/kg diet exhibited, with increasing CP: 1) decreasing weight gain, 2) decreasing plasma arginine concentrations, 3) increasing urinary orotic acid excretion, 4) increasing plasma glutamic acid concentrations, and 5) plasma isoleucine concentrations at levels that suggest a marginal isoleucine deficiency. Kittens fed a control diet (CD) containing 1.5 × EAArq and 350 g CP/kg diet had maximal weight gains and no orotic aciduria. It was concluded that the decreased weight gain and adverse metabolic effects were caused by arginine deficiency and possibly glutamic acid toxicity induced by high dietary dispensable amino acids. Kittens fed the diets containing 1.0 × EAArq and 350 and 560 g CP/kg diet had depressed plasma arginine and elevated glutamic acid concentrations and orotic aciduria. These results indicate that 10 g arg/kg diet is not adequate at CP concentrations above 280 g/kg and the calculated requirement of arginine is (0.02 g arginine/g CP) × (Y g CP/kg diet) + (4.0 g arginine/kg diet) where Y is the dietary CP level.

The effects of weight gain and subsequent weight loss on glucose tolerance and insulin response were evaluated in 12 healthy cats. Intravenous glucose tolerance tests (IVGTT) were performed at entry into the study, after a significant gain of body weight induced by feeding palatable commercial cat food ad libitum, after a significant loss of body weight induced by feeding a poorly palatable purified diet to discourage eating and promote fasting, and after recovery from fasting when body weight had returned to pre-study values and cats were eating commercial foods. A complete physical examination with measurement of body weight was performed weekly, a CBC and serum biochemistry panel were evaluated at the time of each IVGTT, and a liver biopsy specimen obtained 2 to 4 days after each IVGTT was evaluated histologically for each cat. Mean serum glucose and insulin concentrations after glucose infusion and total amount of insulin secreted during the second 60 minutes and entire 120 minutes after glucose infusion were significantly (P < .05) increased after weight gain, as compared with baseline. At the end of weight loss, cats had hepatic lipidosis and serum biochemical abnormalities consistent with feline hepatic lipidosis. There was a significant (P < .05) increase in mean serum glucose concentration and t1/2, and a significant (P < .05) decrease in mean serum insulin concentration and the glucose disappearance coefficient (K) after glucose infusion for measurements obtained after weight loss, compared with those obtained after weight gain and at baseline. Insulin peak response, insulinogenic index, and total amount of insulin secreted during the initial 10 minutes, 20 minutes, and 60 minutes after glucose infusion were decreased markedly (P < .05), compared with measurements obtained after weight gain and at baseline. In addition, the total amount of insulin secreted for 120 minutes after glucose infusion was decreased markedly (P < .05) in measurements obtained after weight loss, compared with those obtained after weight gain. At the end of recovery, all cats were voluntarily consuming food, serum biochemical abnormalities identified after weight loss had resolved, the number and size of lipid vacuoles in hepatocytes had decreased, and results of IVGTT were similar to those obtained at baseline. These findings confirmed the reversibility of obesity-induced insulin resistance in cats, and documented initial deterioration in glucose tolerance and insulin response to glucose infusion when weight loss was caused by severe restriction of caloric intake.

This study determined the effect of a commercial dry expanded (complex) diet and purified diet on methotrexate (MTX) toxicity and pharmacokinetics in the cat. Twelve cats were randomized to receive a purified diet or a complex diet for 21 days. They were then given an intravenous bolus injection of MTX at a dose of 10 mg/kg (160 mg/M2). Cats fed the purified diet had severe enteritis, characterized by depression, lethargy, diarrhea, and vomiting. Cats receiving the complex diet remained mentally bright, alert, and responsive throughout the post-chemotherapy period, and only one of six cats in this dietary group developed mild diarrhea 48 hr after MTX administration. Methotrexate was associated with a significant (P < 0.0001) reduction in the total white blood cell (WBC) counts in cats receiving the purified and complex diets. The elimination of MTX appeared to follow a three-compartment model of elimination. Plasma MTX concentrations at all time points examined were virtually identical in cats receiving the purified and complex diets. The terminal half-life of MTX in cats receiving the complex and purified diets was 1.75 ± 0.44 hr and 2.77 ± 0.8 hr, respectively. The similarity of plasma MTX concentrations and pharmacokinetic parameters in both dietary groups suggests that dietary alterations may influence enterotoxicity directly rather than altering exposure to MTX.

Most experiments conducted to determine the optimal essential amino acid (EAA) nitrogen to total nitrogen (E:T) ratio in rats, chicks and other species have shown that weight gain and nitrogen retention are optimal when the ratio is between 0.5 and 0.65. Two experiments were conducted to determine if weight gains of kittens fed EAA as a sole source of dietary nitrogen were equivalent to those of kittens fed a control diet that contained equal amounts of EAA and dispensable amino acids (DAA). In the first experiment, kittens fed diets that contained only EAA lost weight. Amino acid analysis of plasma showed that the concentration of methionine was 9.1 times that of controls, supporting the premise that the weight loss that occurred was the result of an adverse effect of excess methionine. Also, plasma threonine and arginine were elevated whereas proline and asparagine were very low. In the second experiment, feeding lower concentrations of methionine and arginine in a diet containing only EAA resulted in weight gains and nitrogen retention that were not significantly different from results for kittens fed the control diet (E:T ratio = 0.5). The addition of proline and asparagine to this EAA diet or their removal from the control diet did not improve or reduce weight gain or nitrogen retention. It is concluded that the decreased weight gain found in kittens (and probably other species) fed only EAA is the result of an adverse effect of excesses of methionine and possibly other EAA, and not the inability to synthesize DAA. If excesses of certain EAA are avoided, near-maximal weight gain can be achieved without any DAA in the diet.

Previous work indicates that the essential amino acid requirements for kittens are not positively correlated with the concentration of dietary nitrogen as they are in other species. In the studies presented here, the interaction between graded levels of threonine and dietary crude protein was investigated. Dose-response curves were generated using six 4 x 4 Latin squares. Each square represented one concentration of threonine (4.0, 5.0, 6.0, 7.0, 9.0 or 12.0 g/kg diet) and four concentrations of crude protein (150, 200, 300 and 500 g/kg diet). Food intake, weight gain, nitrogen retention and plasma amino acids were measured. There was no strong positive relationship between the threonine requirement of kittens and dietary crude protein. Increasing crude protein when threonine was limiting in the diet increased growth and food intake under some conditions, whereas under other conditions food intake and growth were decreased in a manner consistent with an amino acid imbalance response. An additional experiment was done to verify some of these findings. The requirement for threonine was found to increase from 5.0 g/kg diet at 150 and 200 g crude protein/kg diet to 6.0 g/kg diet when crude protein was 300 or 500 g/kg diet. The requirement for crude protein in the kitten appears to be between 200 and 300 g/kg diet.

The effect of acid–base status on self-selection of dietary protein was examined in three groups of adult male cats fed 20% soybean-protein and lactalbumin diets formulated to produce acidic, neutral or alkaline status. In two experiments, cats were offered a choice between the 20% protein diets or (1) the same diet with additional protein as casein (49% total crude protein) or (2) the same diet with added soybean-protein and lactalbumin (43% crude protein). Casein contained 0·63 mmol H + /g and caused all three groups to avoid the high casein diets by day 4. The high soybean-protein–lactalbumin diets did not contain added acid but would produce some extra acid upon catabolism of the sulfur-containing amino acids. Again, all three groups avoided the high protein diets by day 4. In a third choice trial, cats adapted to three low protein diets containing appropriate electrolytes to cause neutrality, acidemia or alkalemia, were offered a choice between: neutral vs. acidic; acidic vs. neutral or basic vs. acidic. The cats chose the neutral, neutral and basic diet respectively, restoring or maintaining acid–base homeostasis for each situation. The diets producing acidosis lowered serum sodium and potassium concentrations. We conclude that cats select appropriate diets in an attempt to maintain acid–base homeostasis.

In a crossover design, cats were fed a canned heat-processed diet (18 g dry matter/kg initial body wt) either with (+) or without (-) antibiotics [a mixture of penicillin G, procaine (25 mg/18 g diet) and tetracycline (50 mg/18 g diet)]. The (-/+) group received no antibiotics during the first 5-wk period and received antibiotics during the second 5-wk period; the (+/-) group received the reverse. Plasma, whole blood, urinary and fecal concentrations of taurine, fecal bile acid excretion and cholyltaurine hydrolase activities were measured. Consumption of antibiotics for 5 wk resulted in a lower rate of depletion of plasma taurine. Taurine concentrations decreased more over the first 5 wk in cats in the (-/+) group than in cats in the (+/-) group [from 116 +/- 26 to 26 +/- 6 mumol/L (-/+) and from 109 +/- 6 to 77 +/- 7 mumol/L (+/-) for plasma, and from 546 +/- 8 to 292 +/- 29 mumol/L (-/+) and from 560 +/- 11 to 431 +/- 20 mumol/L (+/-) for whole blood]. Urinary total taurine excretions during the 5th week were 54 mumol/d for the (-/+) group and 135 mumol/d for the (+/-) group (pooled SEM, +/- 13). Fecal total taurine excretions during the 5th week were 184 and 53 mumol/d for the (-/+) and (+/-) groups, respectively, (pooled SEM +/- 9). Most of the fecal taurine was unconjugated (free). Fecal bile acid excretions during the 5th week were 235 +/- 18 and 106 +/- 11 mumol/d for the (-/+) and (+/-) groups, respectively. Dietary antibiotics suppressed fecal cholyltaurine hydrolase activity of cats. Fecal cholyltaurine hydrolase activities during the 5th week were 279 +/- 54 and 42 +/- 10 nmol cholic acid released.min-1.g dry feces-1 in the (-/+) and (+/-) groups, respectively. After the crossover, mean values for the groups were reversed, showing that the observed changes were due to the antibiotic treatment. These results support the hypothesis that the dietary taurine requirement of cats is largely determined by the extent of microbial degradation of taurine in the gastrointestinal tract.

The purpose of this study was to evaluate the use of urinary 3-methylhistidine excretion as an index of in vivo skeletal muscle protein degradation in cats. The criterion for validation was the rapid and quantitative excretion of an intravenously administered dose of radiolabeled 3-methylhistidine (3-methyl-14C). Four adult cats were maintained in individual metabolism cages and allowed free access to a purified diet (43.5% protein) and water for 4 weeks. The cats were then injected intravenously with 740 kBq 3-[14C]methylhistidine dihydrochloride diluted in 1 mL of saline. Twenty-four-hour urine samples were collected for 7 days. Total radioactivity in each urine sample was determined by direct counting. Quench correction was determined by using an external standard. The mean (±SEM) cumulative urinary recovery of 3-[14C]methylhistidine from the four cats was 94.9 ±3.5% at 48 hr following radioisotope injection. The mean (±SEM) cumulative urinary recovery of radioactivity from the four cats was 103.9 ± 2.2% at 7 days following radioisotope administration. There was no detectable radioactivity found in expired CO2 and negligible amounts (mean ± SEM: 0.6 ± 0.5%) in the feces. Chromatography of urinary amino acids and radioactive urine metabolites revealed no significant radioactivity in any other peak besides 3-methylhistidine. Acid hydrolysis of urine resulted in no increase in 3-methylhistidine content or urine, indicating that there is no significant acetylation of 3-methylhistidine in this species. On the basis of these results, 3-methylhistidine does not appear to be metabolized and should therefore be a valid index of in vivo skeletal muscle protein degradation in the cat. Urinary 3-methylhistidine excretion should be useful for studying how nutritional, hormonal, and other physiological or pathological factors cause losses or gains in skeletal muscle protein in this species.

The effects of heat processing (Maillard reaction) and addition of antibiotics to diets on the metabolism of taurine in adult cats were studied. Groups of four cats were given daily 22 g/kg body weight one of four purified diets based on casein and starch. All diets contained the same major ingredients as the control (diet 1), except for starch substitutions. Diet 2 was autoclaved ; in diet 3, 50 g glucose replaced 50 g starch before autoclaving ; in diet 4, only the casein component was autoclaved with 50 g glucose before addition to the diet. Diets were fed for 5 wk, then a mixture of antibiotics was added to all diets and they were fed for a further 5 wk. In the first (no antibiotics) period, cats given the Maillard reaction products (diets 3 and 4) had a significant depletion of plasma and whole blood taurine and had twice the fecal, but less than half the urinary total taurine excretion of control cats. The addition of antibiotics to the diets restored plasma and whole blood concentration in cats given diets 3 and 4, reduced fecal and increased urinary taurine excretion, and decreased fecal cholyltaurine hydrolase activity. These results suggest that Maillard reaction products promote an enteric flora that favors degradation of taurine and decreases recycling of taurine by the enterohepatic route.

The nitrogen requirements of cats during gestation and lactation were determined. Purified diets containing 200, 250, or 300 g protein (N × 6.25)/kg diet, calculated ME = 20 kJ/g) and ≥ 1.5 times the minimal essential amino acid requirement of the growing kitten were fed for ≥ one month before mating and through gestation and lactation. Results during gestation showed that there were no significant differences among treatments in number and size of kittens at birth and suggested that 200 g protein/kg diet was adequate. Treatments had little effect on kitten weight gains at week one or two. By the third week, kitten weight gains were significantly higher for the higher levels of dietary protein. Queens fed the 200 g protein/kg diet had a lower PCV at 6 weeks lactation than queens fed the 250 or 300 g protein/kg diet. Essential amino acid concentrations in plasma at 3 week lactation indicated that two to five of the essential amino acids may have been limiting, even though they were all added in the diet at 1.5 times that of the kitten growth requirement. Results suggest that the protein requirement of the queen during gestation is not greater than 200 g protein/kg diet and the requirement during lactation appears to be between 250 and 300 g protein/kg diet containing 250 g fat/kg diet.

Freshly passed feces were collected from cats (n = 5-7) given cooked and uncooked commercial canned-type diets, casein and soy protein containing purified diets and a commercial extruded diet. The feces were anaerobically cultured in medium containing either taurine, taurocholic acid or [2-3H]taurine for 24 h at 37 degrees C. Taurine degradation in cultures was greatest for cultures from cats receiving diets reputed to cause taurine depletion. Diaminopimelic acid in feces indicated that differences in taurine degradation rate among groups was associated with differences in bacterial numbers in feces. After 6 h of incubation,10% of taurocholate and60% of taurine remained. Nearly all the tritium on the labeled taurine was recovered as water. These results indicate that deconjugation and deamination are the initial steps in microbial catabolism of taurocholic acid and that enteric microbial growth may be a major determinant of dietary taurine requirement of cats.

Despite the lack of precise information on the requirements for many of the nutrients essential for cats and dogs and the paucity of information on the availability of nutrients in foods, many commercial diets support excellent growth, reproduction, and maintenance. However, these diets use empirical information that cannot be readily applied to the formulation of new diets. Progress in companion animal nutrition requires more precise information on requirements for various life stages (especially reproduction and maintenance), along with values for the bioavailability of nutrients in dietary ingredients. There is virtually no information on the bioavailability of nutrients for companion animals in many of the common dietary ingredients used in pet foods. These ingredients are generally byproducts of the meat, poultry and fishing industries, with the potential for wide variation in nutrient composition. Claims of nutritional adequacy of pet foods based on the current Association of American Feed Control Official (AAFCO) nutrient allowances ("profiles") do not give assurances of nutritional adequacy and will not until ingredients are analyzed and bioavailability values are incorporated. The AAFCO feeding test provides a superior method for assessing nutritional adequacy to the profile, although the current protocol has procedural and interpretative limitations.

The aims of this study were to develop a gastroscopic food sensitivity testing (GFST) technique for clinical use in dogs and to determine if the results of GFST were influenced by the feeding of a hypoallergenic diet immediately before the testing period ("unmasking"). The technical requirements for GFST were devised during a total of eight endoscopies performed in four healthy dogs. GFST was performed in anesthetized dogs in sternal recumbency. Food extracts were dripped onto the dependent aspect of the body of the stomach via plastic tubing passed through the endoscope. Changes were observed within 2 to 3 minutes of application, and included localized mucosal swelling and erythema, generalized mucosal erythema, and hyperperistalsis. The influence of "unmasking" was then examined in 6 atopic and 2 healthy dogs, which underwent GFST on three occasions, 4 weeks apart. Before the first and third testing periods, the dogs consumed a commercial dry dog food. For 5 days before the second testing period the dogs were fed a hypoallergenic elemental diet. Oral challenges were performed to identify which of the dogs had clinically overt immediate food sensitivity. Localized swelling was most frequently correlated with positive challenge PO. No positive reactions occurred in response to the negative control extract (lamb). The number of positive GFST results increased after feeding the hypoallergenic diet. In conclusion, these preliminary results indicate that GFST holds substantial promise for the diagnosis of immediate food sensitivities affecting the gastrointestinal tract. The sensitivity of the procedure appears to be enhanced by preceding testing with a hypoallergenic diet.