Effect of ageing on resting energy expenditure in cats

Introduction of adult cats to indirect calorimetry respiration chambers causes increased energy expenditure and respiratory quotient that decrease following acclimation

OBJECTIVE

To replicate a previously defined behavioral procedure to acclimate adult cats to temporary restriction in indirect calorimetry chambers and measure energy expenditure and respiratory quotient changes during acclimation.

ANIMALS

8 healthy adult cats (4 spayed females, and 4 neutered males; mean ± SEM age, 2.5 ± 1.5 years; mean body weight, 4.8 ± 1.8 kg).

PROCEDURES

Cats underwent a 13-week incremental acclimation procedure whereby cats were acclimated to the chambers in their home environment (weeks 1 to 3), to the study room (weeks 4 to 6), and to increasing lengths of restriction within their home environment (weeks 7 to 8) and the chambers (weeks 9 to 13). Cat stress score, respiratory rate, fearfulness (assessed with a novel object test), energy expenditure, and respiratory quotient were measured. Data were analyzed by use of a repeated-measures mixed model.

RESULTS

Stress, based on cat stress scores, fearfulness, and respiration, peaked at weeks 4, 9, and 10 but returned to baseline levels by week 11. Energy expenditure and respiratory quotient peaked at weeks 10 and 11, respectively, but were reduced significantly by weeks 11 and 13, respectively. All cats returned to baseline by the end of the study and were deemed fully acclimated.

CLINICAL RELEVANCE

Changes in perceived stress level, energy expenditure, and respiratory quotient at various stages of the acclimation procedure suggest that stress should be considered a significant variable in energy balance measurements when indirect calorimetry is used in cats. An incremental acclimation procedure should therefore be used to prepare cats for the temporary space restriction necessary for indirect calorimetry studies.

Energy requirements of adult dogs: a meta-analysis

A meta-analysis was conducted to determine the maintenance energy requirements of adult dogs. Suitable publications were first identified, and then used to generate relationships amongst energy requirements, husbandry, activity level, methodology, sex, neuter status, dog size, and age in healthy adult dogs. Allometric equations for maintenance energy requirements were determined using log-log linear regression. So that the resulting equations could readily be compared with equations reported by the National Research Council, maintenance energy requirements in the current study were determined in kcal/kg(0.75) body weight (BW). Ultimately, the data of 70 treatment groups from 29 publications were used, and mean (± standard deviation) maintenance energy requirements were 142.8±55.3 kcal·kgBW(-0.75)·day(-1). The corresponding allometric equation was 81.5 kcal·kgBW(-0.9)·day(-1) (adjusted R2 = 0.64; 70 treatment groups). Type of husbandry had a significant effect on maintenance energy requirements (P<0.001): requirements were greatest in racing dogs, followed by working dogs and hunting dogs, whilst the energy requirements of pet dogs and kennel dogs were least. Maintenance energy requirements were less in neutered compared with sexually intact dogs (P<0.001), but there was no effect of sex. Further, reported activity level tended to effect the maintenance energy requirement of the dog (P = 0.09). This review suggests that estimating maintenance energy requirements based on BW alone may not be accurate, but that predictions that factor in husbandry, neuter status and, possibly, activity level might be superior. Additionally, more information on the nutrient requirements of older dogs, and those at the extremes of body size (i.e. giant and toy breeds) is needed.

Digestibility and metabolizable energy of raw soybeans manufactured with different processing treatments and fed to adult dogs and puppies

The objective of this study was to evaluate the apparent total tract digestibility (ATTD), ME, and fecal characteristics of adult dogs and puppies fed raw soybeans (RSB) and their by-products. Six treatments were evaluated: 1 reference diet (REF), based on a maize-poultry by-product meal, and 5 extruded diets containing 70% of the ingredients of the REF diet and 30% of a soybean processed product [defatted soybean meal (DSM), micronized soybeans (MSB), soybean meal (SBM), RSB, or toasted soybeans (TSB)]. Six adult dogs (5.8 yr old) and 6 puppies (5.1 mo old) were used in a study with a double Latin square design (6 × 6). Urease was reduced in all diets after extrusion, but trypsin inhibitor was reduced only in the diets containing SBM, DSM, and RSB. The ATTD of CP in DSM, SBM, MSB, TSB, and RSB were 85.1%, 85.2%, 88.4%, 84.7%, and 78.9%, respectively, for adult dogs. Soybean meal and DSM had the lowest ATTD of acid-hydrolyzed fat (AHF; 84.3% for both ingredients in adult dogs). The ATTD of DM and AHF in DSM and AHF in all soybean products were greater in puppies than adult dogs (P < 0.05). The ME content was greatest in MSB (21.39 MJ/kg) and least in DSM (15.23 MJ/kg). The feces of dogs fed soybean products were softer and had a lower pH (average of 5.91 vs. 6.05 for adult dogs fed soybean products and REF diets, respectively) and ammonia content (average of 3.82 vs. 4.32 g/kg for adult dogs fed soybean products and REF diets, respectively), except those fed RSB, which had similar fecal pH and ammonia values, compared with those fed the REF diet. Soybean products are good protein sources for both adult and growing dogs, provided they are heat treated before diet extrusion.

Seasonal and age effects on energy requirements in domestic short-hair cats (Felis catus) in a temperate environment

There is little information known about the energy requirements of cats in temperature climates. Energy requirement of domestic short-haired cats was determined using three groups of mixed gender - old kept outside (approximately 9.9 years of age; 4.8 kg; n = 9), young kept outside (approximately 3.1 years of age; 3.9 kg; n = 8) or young kept inside (approximately 3.1 years of age; 3.9 kg; n = 8). Cats were housed individually for 5 weeks during summer (18.5 ± 0.5 °C) and winter (8.5 ± 0.4 °C) and were fed a commercially available maintenance diet ad libitum. In both periods, energy expenditure was determined from the rates of (2) H and (18) O elimination for blood H2 O over a 12 day period, from a doubly labelled water bolus (2) H2 O (0.7 g/kg BW) and H2 (18) O (0.13 g/kg BW) administered intravenously. During the summer period, macronutrient digestibility was determined. Older cats had a reduction (p < 0.05) in apparent digestibility of dry matter (approximately 9%), energy (approximately 8%) and protein (6%). There was a significant effect of age and season on energy intake and energy expenditure. While lean mass was affected by age and season, there was no effect of age or season on energy expenditure when expressed as a proportion of lean mass. Possible seasonal differences in nutrient digestibility may explain these results.

Feeding old cats--an update on new nutritional therapies

Aging is associated with a wide variety of physiological changes that compromise the ability of the body to respond to stress or change, and ultimately contribute to morbidity and mortality. Much research has been done on the aging process in humans and experimental animals, and the impact of diet, but there is relatively little data from companion animal studies. However, although many of the aging changes are likely to be similar between different mammals, it is known that there are some differences with cats. In contrast to dogs and humans, elderly cats experience an increase in their maintenance energy requirements rather than a continued decline, which may be mediated partly through a better-maintained basal metabolic rate but also through progressive compromise in fat and protein digestion. Old age is also associated with a progressive loss of lean body mass that may be mitigated in part by feeding higher protein levels. Diets designed for healthy elderly cats should therefore concentrate on being energy dense, highly digestible and with an increase in the proportion of protein calories, and being fed with the aim of supporting optimal body weight. There is also strong evidence emerging that dietary manipulation in cats may be able to modify aspects of the aging process, with a long-term longitudinal study of cats demonstrating both survival and health benefits from feeding a diet supplemented with antioxidants, fatty acids, and a prebiotic source.

Energy requirements of adult cats

A meta-analysis was carried out in order to establish the energy requirements of adult cats. Publications that identified cat body weight (BW) were used to generate allometric relationships between energy requirements and BW of healthy adult cats, using log-log linear regression. Energy requirements were expressed in kcal/kg BW to be consistent with those reported by the National Research Council. Mean maintenance energy requirements were 55·1 (se 1·2) kcal/kg BW (115 treatment groups). Three allometric equations were identified to predict the energy requirements for maintenance of BW in the cat based on BW: light (53·7 kcal/kg BW− 1·061), normal (46·8 kcal/kg BW− 1·115) and heavy (131·8 kcal/kg BW− 0 ·366). When reported on lean mass, the allometric equation revealed maintenance requirements were 58·4 kcal/kg lean mass− 1·140 (adjusted R2 0·694; thirty-six treatment groups). The present review suggests that values for maintenance energy requirements based on BW alone may not be an accurate prediction and more detailed information on the age, sex and neuter status, BW and composition would enhance the ability to interpret the maintenance energy requirements of cats.

Nonexercise movement in elderly compared with young people

The association between free-living daily activity and aging is unclear because nonexercise movement and its energetic equivalent, nonexercise activity thermogenesis, have not been exhaustively studied in the elderly. We wanted to address the hypothesis that free-living nonexercise movement is lower in older individuals compared with younger controls matched for lean body mass. Ten lean, healthy, sedentary elderly and 10 young subjects matched for lean body mass underwent measurements of nonexercise movement and body posture over 10 days using sensitive, validated technology. In addition, energy expenditure was assessed using doubly labeled water and indirect calorimetry. Total nonexercise movement (acceleration arbitrary units), standing time, and standing acceleration were significantly lower in the elderly subjects; this was specifically because the elderly walked less distance per day despite having a similar number of walking bouts per day compared with the young individuals. The energetic cost of basal metabolic rate, thermic effect of food, total daily energy expenditure, and nonexercise activity thermogenesis were not different between the elderly and young groups. Thus, the energetic cost of walking in the elderly may be greater than in the young. Lean, healthy elderly individuals may have a biological drive to be less active than the young.

Aging on the job

The older population is growing faster than the population as a whole. Paid work is the main mechanism for physical activity in humans. We, therefore, wanted to ascertain whether work practices (such as employment status and the types of tasks workers perform) follow the biological decline in physical activity that occurs with aging in humans and many other species. We recorded work practices in 3352 adults in the Ivory Coast to establish how work burdens are distributed across different age groups in a community that is minimally fettered by legal constraints. We found a decrease in the amount of work performed with increasing age, and we found that elderly persons performed more skilled, less exothermic tasks than younger workers. These data mirror global workforce distribution trends expressed by age. If the trend continues, a major portion of the population will be unlikely to contribute to the labor force in the near future, producing potentially adverse economic consequences in some populations. Although the problem might be averted or at least minimized by implementing different employment policies, biological factors could overlay and supervene any economic planning.

Gastrointestinal transit times in young and old cats

Ageing results in a decrease in apparent nutrient digestibility in the gastrointestinal (GI) tract. The aim of this study was to investigate whether the rate of gastric emptying or total GI transit times differed between young (3.0+/-0.9 years) and senior (11.6+/-1. 4 years) cats. Gastric emptying rates were measured using [1-(13)C]octanoic acid and total transit times with chromium oxide. No significant differences (P>0.05) were observed in either the rate of gastric emptying or total transit time between young and senior cats although senior cats exhibited a larger variability in total transit time compared to the younger cats (35.71+/-14.06 and 26. 46+/-5.80 h, respectively). The results of this study indicate that the observed reduction in nutrient digestibility in ageing cats is not due to alterations in the rate of passage of digesta through the GI tract.