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Exercise but Not Supplemental Dietary Tryptophan Influences Heart Rate and Respiratory Rate in Sled Dogs.

ABSTRACT: Tryptophan (Trp), an indispensable amino acid for dogs, is the precursor of serotonin, a neurotransmitter with a variety of effects throughout the body, including the ability to modulate cardiac and pulmonary activity. This study aimed to investigate the effects of a 12-week incremental exercise regimen and supplemental dietary Trp on heart rate (HR) and respiratory rate (RR) in client-owned sled dogs. Sixteen Siberian huskies were randomly allocated to either treatment or control diet groups. Both groups were fed a control diet (Trp to large neutral amino acid ratio of 0.047:1); however, treatment dogs received a Trp supplement to achieve a Trp to large neutral amino acid ratio of 0.075:1. Every three weeks, external telemetry equipment was used to non-invasively measure and record HR and RR at a resting, working, and post-exercise state in a controlled exercise challenge. A mixed model was used to test differences between diet, activity parameter, and week. Dietary Trp supplementation had no effect on HR or RR. Independent of diet, resting, working, post-exercise HR, and time to recover post-exercise HR decreased from week -1 to week 11 (p < 0.05). Resting HR had the greatest reduction from week -1 to week 11 (21%, p < 0.05). Working RR did not change with exercise (p > 0.10), but rRR and postRR decreased from week -1 to week 11 (p < 0.05). These data suggest that the exercise regimen the dogs were subjected to may have positively impacted the dogs' capacity to sustain aerobic exercise, whereas Trp supplementation had no effect on HR or RR.

SUBMITTER: Thornton E

PROVIDER: S-EPMC7559096 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Exercise but Not Supplemental Dietary Tryptophan Influences Heart Rate and Respiratory Rate in Sled Dogs.

Thornton Emma E Templeman James R JR Bower Michael M Cant John P JP Holloway Graham P GP Shoveller Anna K AK

Veterinary sciences 20200723 3

Tryptophan (Trp), an indispensable amino acid for dogs, is the precursor of serotonin, a neurotransmitter with a variety of effects throughout the body, including the ability to modulate cardiac and pulmonary activity. This study aimed to investigate the effects of a 12-week incremental exercise regimen and supplemental dietary Trp on heart rate (HR) and respiratory rate (RR) in client-owned sled dogs. Sixteen Siberian huskies were randomly allocated to either treatment or control diet groups. B ...[more]

PMID: 32717797

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Project description:Dietary fiber affects canine physiology in many ways, such as increasing colonic absorption of water and improving gut health, both of which may positively impact exercise performance. The objectives of this study were to investigate the effects of increased dietary soluble fiber and incremental training on respiratory rate (RR), internal body temperature (BT), body composition, and fecal metabolites in mid-distance training sled dogs. Fourteen dogs (12 Siberian and 2 Alaskan Huskies) were blocked by age, sex, and body weight (BW) and then randomly allocated into one of two diet groups. Seven dogs were fed a dry extruded control diet (Ctl) with an insoluble:soluble fiber ratio of 4:1 (0.74% soluble fiber on a dry-matter basis), and seven dogs were fed a dry extruded treatment diet (Trt) with an insoluble:soluble fiber ratio of 3:1 (2.12% soluble fiber on a dry-matter basis). Fecal samples were taken once a week. All dogs underwent 9 weeks of incremental exercise conditioning where the running distance was designed to increase each week. Every 3 weeks, external telemetry equipment was used to non-invasively measure and record RR and internal BT at resting, working, and post-exercise recovery states. Body composition was measured on weeks -1 and 9 using quantitative magnetic resonance. Body composition, RR, BT, and fecal metabolites were analyzed using a mixed model with dog as a random effect and week and diet group as fixed effects. Dogs on Trt had lower working and post-exercise BT than Ctl (P < 0.05). In addition, Trt dogs had lower recovery BT at weeks 2 and 5 than Ctl dogs (P < 0.05). Treatment dogs had greater fecal short-chain fatty acid concentrations than Ctl (P < 0.05). Diet had no effect on RR or body composition (P > 0.10), but exercise resulted in an overall 7% increase in lean and 3.5% decrease in fat mass (P < 0.05). These data suggest that increasing dietary soluble fiber may positively influence BT and gut health; however, it has no effect on RR or body composition. Soluble fiber did not negatively impact any measures of overall health and performance and should be considered for use in performance dogs.

Project description:Exercise improves the health of dogs; however, the extreme exertion experienced by sled dogs may lead to variable metabolic and fecal characteristics. Nutritional interventions, such as dietary tryptophan (Trp), may reduce the prevalence of these exercise-induced disturbances. Sporting diets tend to have high crude protein concentrations in contrast to adult maintenance diets and this results in less Trp relative to other amino acids (AA). Therefore, sporting dogs represent an ideal cohort to assess the effects of supplemental Trp. The objective was to evaluate the effects of supplemental dietary Trp and an incremental training regimen on AA and serotonin status, fecal scores and metabolites, and body composition in client-owned Siberian huskies. Sixteen dogs (nine females and seven males) were used, with a mean age of 4.8 ± 2.5 yr and body weight (BW) of 24.3 ± 4.3 kg. Dogs were blocked for sex, age, and BW and randomly allocated into two groups with eight fed a dry extruded control diet (Ctl) and eight fed Ctl supplemented with Trp to reach a Trp:large-neutral AA (LNAA) ratio of 0.075:1 (treatment, Trt). The exercise regimen was designed to increase in distance each week, but weather played a role in setting the daily distance. Each week BW was recorded and food allotments were adjusted to maintain initial BW. Pre and post-exercise blood samples were taken every 3 wk, dogs then received a meal followed by 1, 2, and 4 h post meal blood collections (serum AA, serotonin). Stool collection and scoring occurred each week and body composition was measured on weeks -1 and 11. Serotonin, AA, fecal metabolite, and body composition data were analyzed using PROC MIXED of SAS with dog as a random effect and week and Trt as fixed effects. Stool score data were analyzed using PROC FREQ to compare stool score and Trt, and PROC CORR was used to analyze associations between fecal score, temperature, humidity, and run distance. Dogs on Trt had greater fasted Trp compared with baseline, greater post-meal Trp and serotonin compared with baseline, greater post-meal Trp compared with fasted, and greater post-meal Trp and serotonin compared with Ctl (P < 0.05). Fecal data indicated that Trp improved stool scores (P < 0.05) yet had no effect on fecal metabolites. An overall increase in lean and decrease in fat mass was found (P < 0.05), but Trt had no effect on body composition. Optimization of the dietary Trp:LNAA ratio may help to improve GI health without compromising performance in actively training sled dogs.

Project description:Background: Muscle responses to exercise are complex, and potentially include acute responses to exercise-induced injury as well as longer-term adaptive training responses. Using Alaskan sled dogs as an experimental model, changes in muscle gene expression were analyzed to better understand the temporal changes that occur after severe exercise. Methods: Dogs were randomly assigned to undertake in a 160 km run (n=9), or to remain at rest (n=4). Biceps femoris muscle was obtained by needle biopsy from the unexercised dogs and two dogs at each of 2, 6 and 12 hours after the exercise and from 3 dogs 24 hours after exercise. RNA was extracted and microarray analysis used to define gene transcriptional changes. Results: Nine hundred sixty three transcripts exhibited statistically significant change over time after exercise as compared to the unexercised dogs. The changes in gene expression after exercise occurred in a clear temporal pattern and included transcripts with increased expression 2 hours after exercise with a return towards resting levels by 6 hours after exercise. Other transcripts demonstrated increased expression which peaked at six hours after exercise, while other transcripts showed sustained induction or repression over the 24 hours after exercise. Increases in a number of known transcriptional regulators, including PPAR-Î±, CERM and CEBPD, were observed 2-hours after exercise. Pathway analysis demonstrated coordinated changes in expression of genes with known functional relationships, including genes involved in muscle remodeling and growth, intermediary metabolism and immune regulation. Conclusion: Sustained endurance exercise by Alaskan sled dogs induces coordinated changes in gene expression with a clear temporal pattern. RNA expression profiling has the potential to identify novel regulatory mechanisms and responses to exercise stimuli. Subjects were 13 Alaskan sled dogs aged 4.5 + 2.5 years (mean + SD) and weighing 23.3 + 2.5 kg. Dogs were randomly assigned to two groups â one group of 9 dogs subsequently ran 160 km in 24 hours as 2 sessions of 80 km, separated by a 6 hour rest period. The second group consisted of four dogs housed in unheated kennels, their usual housing, for the duration of the experiment. All dogs were from the same kennel. Dogs were fed a commercial kibble (Eukanuba, Iams Company, Dayton, OH) supplemented with frozen meat during the 8 weeks preceding the study and throughout the study period. The dogâs diet was consistent before, during and after the exercise bout. All dogs had completed 1590 + 100 km of training runs in the 3 months before the study. The dogs had not exercised for 72 hors before the start of this study. Dogs in the exercise group ran as a team pulling a lightly laden sled and driver over packed snow. Ambient temperatures were -20o to -10o C with no wind. Dogs completed the two 80 km runs in 23 hours, including the 6 hour rest period. Blood samples were collected by jugular venepuncture from all dogs the day before exercise, and within a 10 minute window at 2, 6, 12, and 24 hours after completing the second run. Samples were collected into evacuated glass tubes containing a clot enhancer. Muscle samples were collected from each of two dogs within a 10 minute window at 2, 6 and 12 hours after completing exercise and from three dogs 24 hours after completing exercise. Muscle samples were collected from each of the four unexercised dogs within two hours of the other dogs initiating their exercise bout. Each dog had only one biopsy procedure performed. Muscle samples were collected from the biceps femoris muscle using a needle biopsy that yielded approximately 40-60 mg of muscle. The biopsy was performed after clipping and aseptic preparation of the skin overlying the biopsy site. The dog was anesthetized with propofol (6 mg/kg, IV, maintained as necessary with 2 mg/kg additional boluses), a cuffed orotracheal tube placed and the dog ventilated with a hand-held ventilation bag. When adequate anesthesia had been obtained a 5 mm incision was made in the skin. A sterile biopsy needle (12 g PGI EZ Core, Products group International, Inc. Lyons, CO) was then inserted through the incision and a sample of muscle collected. If necessary, repeated collections of muscle were made until a minimum of 40 mg of muscle has been collected from an individual dog. The skin incision was closed with tissue glue and an antibiotic ointment applied. The dog was monitored closely until recovery from anesthesia was complete. Carprofen (4.4 mg/kg, orally) was administered when the dog had recovered sufficiently from anesthesia to have a gag reflex.

Project description:Heart rate variability (HRV) is the variation of cardiac inter-beat intervals over time resulting largely from the interplay between the sympathetic and parasympathetic branches of the autonomic nervous system. Individual differences in HRV are associated with emotion regulation, personality, psychopathology, cardiovascular health, and mortality. Previous studies have shown significant heritability of HRV measures. Here we extend genetic research on HRV by investigating sex differences in genetic underpinnings of HRV, the degree of genetic overlap among different measurement domains of HRV, and phenotypic and genetic relationships between HRV and the resting heart rate (HR). We performed electrocardiogram (ECG) recordings in a large population-representative sample of young adult twins (n=1060 individuals) and computed HRV measures from three domains: time, frequency, and nonlinear dynamics. Genetic and environmental influences on HRV measures were estimated using linear structural equation modeling of twin data. The results showed that variability of HRV and HR measures can be accounted for by additive genetic and non-shared environmental influences (AE model), with no evidence for significant shared environmental effects. Heritability estimates ranged from 47 to 64%, with little difference across HRV measurement domains. Genetic influences did not differ between genders for most variables except the square root of the mean squared differences between successive R-R intervals (RMSSD, higher heritability in males) and the ratio of low to high frequency power (LF/HF, distinct genetic factors operating in males and females). The results indicate high phenotypic and especially genetic correlations between HRV measures from different domains, suggesting that >90% of genetic influences are shared across measures. Finally, about 40% of genetic variance in HRV was shared with HR. In conclusion, both HR and HRV measures are highly heritable traits in the general population of young adults, with high degree of genetic overlap across different measurement domains.

Project description:Although emerging data suggests a greater influence of gluconeogenic precursors, endurance sled dogs have long appeared to rely heavily on fatty acid oxidation for sustained energy production. However, much of the research investigating lipid utilization during exercise in sled dogs has been carried out with dogs subjected to extended bouts of endurance exercise. Less is known about changes in fatty acid composition in endurance training sled dogs subjected to short bouts of exercise, and fewer data define how fatty acid composition may change in distinct lipid fractions. As such, the study objective was to assess whether short bouts of submaximal exercise would affect fatty acid profiles of serum lipid fractions in endurance training sled dogs. Fifteen privately-owned Siberian huskies were used (8 females: 4 intact, 4 spayed; 7 males: 2 intact, 5 neutered), with an average age of 4.6 ± 2.5 years and body weight of 24.8 ± 4.2 kg. Throughout the diet acclimation and remainder of the study, all dogs were fed a dry extruded diet that met or exceeded all AAFCO nutrient recommendations. Dogs were weighed weekly and fed to maintain baseline body weight. A 12-week exercise regimen was designed to incorporate weekly increases in running distance, but weather played a role in setting the daily distance. On weeks 2, 5, and 11, an exercise challenge was implemented whereby dogs would run 4 km at 15 km/h in teams of 4. Pre- and post-exercise blood samples were taken, and gas chromatography was used to evaluate fatty acid profiles of all identified serum lipid fractions (cholesterol ester, diacylglycerol, free fatty acid, phospholipids, triglyceride). Data were analyzed using PROC MIXED of SAS, with dog as a random effect and week and sampling time point as fixed effects. Composition of oleic (18:1n9), linoleic (18:2n6), and alpha-linolenic (18:3n3) acids in the free fatty acid fraction decreased by ~9, 10, and 60%, respectively, following exercise (P ≤ 0.05). The results presented herein suggest that aside from a degree of depletion of these 18-carbon unsaturated fatty acids, short bouts of submaximal exercise do not induce considerable changes to sled dog fatty acid profiles.

Dataset Information

Exercise but Not Supplemental Dietary Tryptophan Influences Heart Rate and Respiratory Rate in Sled Dogs.

Publications

Exercise but Not Supplemental Dietary Tryptophan Influences Heart Rate and Respiratory Rate in Sled Dogs.

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