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The indicator amino acid oxidation (IAAO) method has been used to determine metabolic availability (MA) of amino acids in feedstuffs for pigs, humans, and preliminarily for cats. Peas are a commonly used protein source in grain-free extruded dog diets. However, peas have a poor sulfur amino acid (AA) ratio (methionine (Met):cysteine) with Met being the first limiting AA. Furthermore, little is known about the MA of Met in peas fed to dogs. Therefore, our objective was to compare the MA of Met in peas to chicken meal (CM), as a gold-standard reference protein. The study was done as a replicated 5 x 5 complete Latin square design. Ten neutered male mixed-breed dogs (1.5 years old; 26.0 kg ±2.4 kg body weight; BW) fed to maintain ideal BW received all dietary treatments: BAS: lamb-based diet (deboned lamb and lamb meal) providing Met at 50% of its requirement (0.27 g/100g DM), CHK: CM and lamb-based diet, and PEA: ground dried pea and lamb-based diet both providing Met at 68% of its requirement (0.35 and 0.37 g/100g DM, respectively). Two other treatments were created by blending BAS with PEA (BAP) and the BAS with CHK (BAC) to create diets with Met at 59% of requirement (0.32 and 0.31 g/100g DM, respectively). This resulted in three graded levels of Met for both CM and peas to allow for a slope-ratio assay approach to quantify MA with the BAS diet as the common first point. All other AAs were provided to meet at least 120% of the AAFCO recommendations for adult dogs. The BAS diet, with supplemental DL-Met, was fed for a 2-wk wash-in period. After 2 days of diet adaptation IAAO was performed. Dogs were fed 13 small meals where meal 6 contained a priming dose (9.4 mg/kg BW) of L-[1-13C]-phenylalanine (Phe; 99%) as well as a constant dose (2.4 mg/kg BW) in meals 6-13. Breath samples were collected and enrichment of 13CO2 was measured using isotope-ratio mass spectrometry to calculate the rate of Phe oxidation (F13CO2 umol/kg BW/h). Oxidation was analyzed via SAS using proc GLIMMIX with dog and period as random effects, and diet, %Met, and their interaction as fixed effects. Unexpectedly, the slope of Phe oxidation, in response to increasing Met intake, from CM was 31% of that of peas, indicating a lower MA for Met in CM as compared to peas. This finding may be due to damage of AAs during rendering. At this time, CM in extruded diets is not an acceptable reference protein to determine MA of AAs in dogs and the MA of Met from peas cannot be confidently assessed.

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Feline obesity elicits a plethora of metabolic responses leading to comorbidities, with potential reversal during weight loss. The specific metabolic alterations and biomarkers of organ dysfunction are not entirely understood. Untargeted, high-throughput metabolomic technologies may allow the identification of biological components that change with weight status in cats, increasing our understanding of feline metabolism. The objective of this study was to utilize untargeted metabolomic techniques to identify biomarkers and gain mechanistic insight into the serum metabolite changes associated with reduced food intake and weight loss in overweight cats. During a four-wk baseline period, cats were fed to maintain body weight. For 18 wk following baseline, cats were fed to lose weight at a rate of ~1.5% body weight/wk. Blood serum metabolites were measured at wk 0, 1, 2, 4, 8, 12, and 16. A total of 535 named metabolites were identified, with up to 269 of them being altered (p- and q-values < 0.05) at any time point. A principal component analysis showed a continual shift in metabolite profile as weight loss progressed, with early changes being distinct from those over the long term. The majority of lipid metabolites decreased with weight loss; however, ketone bodies and small lipid particles increased with weight loss. The majority of carbohydrate metabolites decreased with weight loss. Protein metabolites had a variable result, with some increasing, but others decreasing with weight loss. Metabolic mediators of inflammation, oxidative stress, xenobiotics, and insulin resistance decreased with weight loss. In conclusion, global metabolomics identified biomarkers of reduced food intake and weight loss in cats, including decreased markers of inflammation and/or altered macronutrient metabolism.

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The objective of the present study was to evaluate the changes in blood metabolites, AA profile, and oxidative stress markers in American Foxhound dogs fed a nutrient-fortified endurance diet while undergoing unstructured endurance exercise over several months. Thirty-six adult American Foxhound dogs (mean age: 4.5, range 2 to 10 yr and mean BW: 34.7, range: 23.1 to 46.9 kg) were selected to participate in the study. Prior to the study, all dogs consumed a commercial diet for 16 wk. After collecting baseline blood samples, dogs were assigned to a standard commercial performance diet (control) or a nutrient-fortified dog food (test). Dogs were balanced by gender, age, body weight, and athletic performance between diets. During the study, dogs underwent 78 bouts of exercise, with approximately 22 km/bout. Blood samples were collected after 40, 75, 138, and 201 d on study (October 2012 to March 2013). All blood metabolites were similar at baseline and serum chemistry profile remained within normal ranges throughout the study. Over time, plasma taurine and vitamin E concentrations decreased (P < 0.05) in dogs fed the control diet but were maintained or increased (P < 0.05) in dogs fed the treatment diet. Also, plasma creatinine and triglycerides were lower (P < 0.05) and blood phosphorus and alkaline phosphatase were higher (P < 0.05) in dogs fed the treatment diet. Vitamin E and taurine status of dogs appear to be affected by extended endurance exercise. These data suggest dogs undergoing endurance exercise may benefit from supplementation of vitamin E and taurine to minimize oxidation and maintain taurine status.

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OBJECTIVE To determine effects of restriction feeding of a moderate-protein, high-fiber diet on loss of body weight (BW), voluntary physical activity, body composition, and fecal microbiota of overweight cats. ANIMALS 8 neutered male adult cats. PROCEDURES After BW maintenance for 4 weeks (week 0 = last week of baseline period), cats were fed to lose approximately 1.5% of BW/wk for 18 weeks. Food intake (daily), BW (twice per week), body condition score (weekly), body composition (every 4 weeks), serum biochemical analysis (weeks 0, 1, 2, 4, 8, 12, and 16), physical activity (every 6 weeks), and fecal microbiota (weeks 0, 1, 2, 4, 8, 12, and 16) were assessed. RESULTS BW, body condition score, serum triglyceride concentration, and body fat mass and percentage decreased significantly over time. Lean mass decreased significantly at weeks 12 and 16. Energy required to maintain BW was 14% less than National Research Council estimates for overweight cats and 16% more than resting energy requirement estimates. Energy required for weight loss was 11% more, 6% less, and 16% less than American Animal Hospital Association recommendations for weight loss (80% of resting energy requirement) at weeks 1 through 4, 5 through 8, and 9 through 18, respectively. Relative abundance of Actinobacteria increased and Bacteroidetes decreased with weight loss. CONCLUSIONS AND CLINICAL RELEVANCE Restricted feeding of a moderate-protein, high-fiber diet appeared to be a safe and effective means for weight loss in cats. Energy requirements for neutered cats may be overestimated and should be reconsidered.

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Our objective was to measure the proximate, starch, amino acid, and mineral compositions of grains, grain co-products, and other carbohydrate sources with potential use in pet foods. Thirty-two samples from barley (barley flake, cut barley, ground pearled barley, malted barley, whole pearled barley, pearled barley flakes, and steamed rolled barley); oats (groats, ground oatmeal, ground steamed groats, instant oats, oat bran, oat fiber, oat flour, quick oats, regular rolled oats, steamed rolled oat groats, and steel cut groats); rice (brown rice, polished rice, defatted rice bran, and rice flour); and miscellaneous carbohydrate sources (canary grass seed, hulled millet, whole millet, quinoa, organic spelt hull pellets, potato flake, sorghum, whole wheat, and whole yellow corn) were analyzed. Crude protein, amino acid, fat, dietary fiber, resistant starch, and mineral concentrations were highly variable among the respective fractions (i.e., barley flake vs. malted barley vs. steamed rolled barley) as well as among the various grains (i.e., barley flake vs. brown rice vs. canary grass seed). These ingredients not only provide a readily available energy source, but also a source of dietary fiber, resistant starch, essential amino acids, and macrominerals for pet diets.

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Dogs participating in endurance exercise, including herding, hunting and racing have a greater energy requirement and may be more susceptible to nutrient depletion, electrolyte imbalance and metabolic stress. The objective of the present study was to investigate the acute response to unstructured mixed exercise in American Foxhounds fed a nutrient-fortified endurance diet. Thirty-nine adult Foxhound dogs (median age: 5·0, range: 2-10 years and median body weight (BW): 36·4, range: 24·9-49·5 kg) were allotted to a standard performance diet (Control) or nutrient-fortified endurance diet for adult dogs (Test). Dogs were balanced by sex, age, BW and athletic performance between diets. All male dogs were intact, whereas all the female dogs were spayed. After 80 d on diet, blood samples were collected via jugular puncture at baseline (0 h), and at 3 and 25 h post-exercise (mean: 17·7 (sem 0·92) km run over 2-3 h). Plasma taurine concentration and complete amino acid (AA) profile, serum chemistry and creatine kinase were measured. Serum chemistry profile remained within normal ranges throughout the study. A significant (P < 0·05) diet by time interaction was observed for calcium, alkaline phosphatase and most AA. Plasma taurine and most essential AA were increased (P < 0·05) after exercise and remained greater (P < 0·05) in dogs fed the Test diet, including the branched-chain AA (isoleucine, leucine and valine). Creatine kinase increased (P = 0·01) after 3 h and returned to baseline after 25 h post-exercise, but was not altered by diet. These data indicate that dogs undergoing a moderate bout of exercise did not suffer from electrolyte imbalance, and that a nutrient-fortified diet resulted in greater plasma taurine and essential AA concentrations.

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The benefits of whole grain consumption have been studied in human subjects, but little research exists on their effects in dogs. The objective of the present study was to test the effects of resistant starch (RS) in the diet of healthy adult dogs. Twelve adult Miniature Schnauzer dogs (eight males, four females; mean age: 3·3 (1·6) years; mean body weight: 8·4 (1·2) kg; mean body condition score: D/ideal) were randomly allotted to one of three treatment groups, which consisted of different amounts of RS supplied in a biscuit format. Dogs received either 0, 10 or 20 g biscuits per d (estimated to be 0, 2·5 or 5 g RS per d) that were fed within their daily energetic allowance. A balanced Latin square design was used, with each treatment period lasting 21 d (days 0-17 adaptation; days 18-21 fresh and total faecal collection). All dogs were fed the same diet to maintain body weight throughout the study. Dogs fed 5 g RS per d had lower (P = 0·03) fat digestibility than dogs fed 0 gRS per d, but DM, organic matter and crude protein digestibilities were not affected. Faecal fermentative end-products, including SCFA and branched-chain fatty acids, ammonia, phenols and indoles, and microbial populations were not affected. The minor changes observed in the present study suggest the RS doses provided to the dogs were too low. Further work is required to assess the dose of RS required to affect gut health.

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In response to global economic duress and heightened consumer awareness of nutrition and health, sustainable and natural ingredients are in demand. Identification of alternative sources of nitrogen and amino acids, including taurine, may help meet dietary requirements while fostering sustainability and natural feeding approaches. Twenty plants, eighteen marine algae and five insect species were analysed. All samples were freeze-dried, hydrolysed and filtered prior to amino acid analysis. Samples for amino acids were analysed in duplicate and averaged. Nitrogen was analysed and crude protein (CP) determined by calculation. With the exception of taurine concentration in soldier fly larvae, all insects exceeded both the National Research Council's canine and feline minimal requirements (MR) for growth of all essential amino acids (EAA) and CP. Although some plants and marine algal species exceeded the canine and feline MR for growth for EAA and CP, only very low concentrations of taurine were found in plants. Taurine concentration in insects was variable but high, with the greatest concentration found in ants (6·42 mg/g DM) and adult flesh flies (3·33 mg/g DM). Taurine was also high in some macroalgae, especially the red algal species: Mazaella spp. (4·11 mg/g DM), Porphyra spp. (1·22 mg/g DM) and Chondracanthus spp. (6·28 mg/g DM). Preliminary results suggest that insects and some marine algal species may be practical alternatives to traditional protein and supplemental taurine sources in pet foods. Safety, bioavailability, palatability and source variability of alternative items as food ingredients should be investigated prior to incorporation into canine and feline diets.

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OBJECTIVE: To determine whether gonadectomy or age at gonadectomy was associated with the risk that dogs would subsequently become overweight. DESIGN: Retrospective cohort study. ANIMALS: 1,930 dogs gonadectomized between 1998 and 2001 at ≤ 6 months of age (n = 782), > 6 months to ≤ 1 year of age (861), or > 1 to ≤ 5 years of age (287) and 1,669 sexually intact dogs. PROCEDURES: Dogs were followed-up through medical records for ≥ 10 years or until a diagnosis of overweight (defined as overweight, obese, or having a body condition score ≥ 4/5) was recorded. Information extracted included age at study entry, sex, breed, breed-size category, hospital visit frequency, and diagnosis (yes or no) of overweight or diseases that might affect body condition. Relative risk of a diagnosis of overweight was assessed among age groups of gonadectomized dogs and between gonadectomized and sexually intact dogs. RESULTS: No difference was detected among dogs grouped according to age at gonadectomy with respect to the risk of being overweight. This risk was significantly greater in gonadectomized dogs than in sexually intact dogs, but only during the first 2 years after gonadectomy. Sexually intact male dogs were approximately 40% less likely to have this diagnosis (hazard ratio, 0.61; 95% confidence interval, 0.52 to 0.72) than were sexually intact female dogs; no difference in risk between the sexes was evident for gonadectomized dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Gonadectomized dogs had a greater risk of being overweight than did sexually intact dogs, but this risk was not influenced by age at gonadectomy. Opportunities exist for veterinarians to provide counseling during the first years after gonadectomy to help dogs maintain a healthy weight.

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Sustainable practices meet the needs of the present without compromising the ability of future generations to meet their needs. Applying these concepts to food and feed production, nutritional sustainability is the ability of a food system to provide sufficient energy and essential nutrients required to maintain good health in a population without compromising the ability of future generations to meet their nutritional needs. Ecological, social, and economic aspects must be balanced to support the sustainability of the overall food system. The nutritional sustainability of a food system can be influenced by several factors, including the ingredient selection, nutrient composition, digestibility, and consumption rates of a diet. Carbon and water footprints vary greatly among plant- and animal-based ingredients, production strategy, and geographical location. Because the pet food industry is based largely on by-products and is tightly interlinked with livestock production and the human food system, however, it is quite unique with regard to sustainability. Often based on consumer demand rather than nutritional requirements, many commercial pet foods are formulated to provide nutrients in excess of current minimum recommendations, use ingredients that compete directly with the human food system, or are overconsumed by pets, resulting in food wastage and obesity. Pet food professionals have the opportunity to address these challenges and influence the sustainability of pet ownership through product design, manufacturing processes, public education, and policy change. A coordinated effort across the industry that includes ingredient buyers, formulators, and nutritionists may result in a more sustainable pet food system.

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Endocrine characteristics of Quarter Horse-type mares were determined during a 68 h feed deprivation and again in the same mares following surgical thyroidectomy (THX). A crossover experimental design was implemented, in which mares received brome hay available ad libitum (FED) or were food deprived (RES) for 68 h. Blood samples were collected every 20 min for 48 h, beginning 20 h after the onset of food deprivation. Concentrations of triiodothyronine and thyroxine were undetectable post-THX. Plasma concentrations of thyrotropin were greater post-THX versus pre-THX (P<0 x 001). Plasma concentrations of leptin were greater in the THX FED group than in the THX RES group (P<0 x 01). The existence of leptin pulse secretion was found only in post-THX compared with the same horses pre-THX (P=0 x 02). We theorize that non-pulsatile secretion of leptin may have contributed to the survival of this species, as it evolved in the regions of seasonal availability of food. Lack of pulsatile secretion of leptin may contribute to the accumulation of energy stores by modulating leptin sensitivity.

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OBJECTIVE: To quantify changes in endothelium-derived factors and relate those changes to various aspects of digital hemodynamics during the prodromal stages of carbohydrate overload (CHO)-induced laminitis in horses. ANIMALS: 20 adult horses without abnormalities of the digit. PROCEDURES: Digital and jugular venous blood samples were collected at 1-hour intervals (for assessment of endothelin-1 [ET-1] immunoreactivity and measurement of glucose, insulin, and nitric oxide [NO] concentrations) or 4-hour intervals (CBC and platelet-neutrophil aggregate assessment) for 8 hours or 16 hours after induction of CHO-associated laminitis in horses treated with an ET-1 antagonist. Effects of treatment, collection site, and time and the random effects of horse on each variable were analyzed by use of a repeated-measures model. Where treatment and collection site had no significant effect, data were combined. RESULTS: Compared with baseline values, CHO resulted in changes in several variables, including a significant increase from baseline in digital blood ET-like immunoreactivity at 11 hours; digital blood ET-like immunoreactivity was significantly greater than that in jugular venous blood at 8, 9, 11, and 12 hours. Digital and jugular venous blood concentrations of glucose increased from baseline significantly at 3, 4, and 5 hours; insulin concentration increased significantly at 5 hours; and the number of platelet-neutrophil aggregates increased significantly at 12 hours. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, concurrent increases in venous blood ET-1 immunoreactivity, insulin and glucose concentrations, and platelet-neutrophil aggregates support a role of endothelial dysfunction in the pathogenesis of CHO-induced laminitis.

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Horses fed beyond their nutritional requirement and that are physically inactive will develop obesity, which is often accompanied by insulin resistance and heightened risk of laminitis. The use of pharmacologic agents in combination with nutritional restriction may promote weight loss in obese horses unable to exercise because of laminitic pain. This study shows that reducing feed intake of brome grass hay to 75% of ad libitum intake in obese pony mares reduces body weight without induced exercise. Additional supplementation of ractopamine hydrochloride for 6 weeks resulted in a tendency for increased weight loss. Subsequent modulation of obesity-associated hormones, leptin and insulin, as a result of caloric restriction was observed.

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