John M. Rawlings

A Simple, Reliable Tool for Owners to Assess the Body Condition of Their Dog or Cat

Numerous methods exist for quantifying body composition and body fat mass in companion animals. In a clinical setting, the most widely accepted and practical method of body condition evaluation is condition scoring using visual assessment and palpation (1). All such systems attempt to partition a body composition continuum into a finite number of categories. Currently, 3 main systems exist, all of which use similar visual and palpable characteristics, but which differ by the number of integer categories within the scoring system (e.g., 5 points, 6 points, and 9 points) (2–8). The most widely accepted system is the 9-integer scale system, which has previously been shown to correlate well with body fat mass determined by dual-energy X-ray absorptiometry (DXA) (2–4). To aid decision making, a series of animal silhouettes are also provided that illustrate the visual characteristics for a typical (e.g., Labrador morphology) dog and cat. Scores determined by different operators have also been shown to correlate well (2–4), although a degree of expertise is required, rendering this system less accessible to untrained pet owners. S.H.A.P.E (Size, Health And Physical Evaluation) is a new algorithm-based system that uses similar visual and palpable characteristics as existing scoring systems (see http://www.petslimmers.com/shape.htm). A series of questions are followed that direct the operator to examine the animal in a sequential fashion. The questions instruct the operator to perform examinations that will determine the presence and amount of subcutaneous fat (over the ribcage and spine, etc.), and the amount of abdominal fat (by determining the presence and degree of abdominal tuck). Ultimately, 1 of 7 categories of body condition is chosen, each of which is assigned an alphabetical character from A (underweight) to G (obese). Letters were chosen for this new system to avoid confusion with current body condition score systems. This approach is designed to minimize interoperator variability and expertise required, allowing owners to evaluate their animals in the home and consult the veterinarian accordingly. The aim of the current study was to assess the performance of the algorithm system in predicting body composition in dogs and cats, and to acquire preliminary data on how the system performed in the hands of both experienced and inexperienced operators.

Role of Dietary Antioxidants to Protect against DNA Damage in Adult Dogs

We studied the effects of feeding an antioxidant blend of vitamins, minerals and carotenoids to a mixed adult dog population (n = 40, mean 4.4 +/- 1.85 y) for a 16-wk period. Compared to the control group of dogs (n = 20), the antioxidant (AOX)-supplemented group of dogs (n = 20) demonstrated significant increases in plasma levels of vitamin E and taurine by 4 wk of supplementation (P < 0.01) and total antioxidant activity (as measured by ferric-reducing antioxidant power assay) by 8 wk of supplementation (P < 0.05). Following 8 wk of supplementation, the AOX-supplemented dogs also showed significant reductions in both endogenous and exogenous DNA damage (P < 0.005) compared to that of the control dogs, as measured by the comet assay. Over an 8-wk rabies vaccination course that started at 8 wk supplementation, the AOX-supplemented dogs also demonstrated significantly higher vaccine-specific virus-neutralizing antibody levels at 2, 4 and 6 wk postvaccination (P < 0.05) and a tendency toward establishing a vaccine-specific antibody response quicker than did the control group of dogs. These findings in dogs suggest that antioxidant supplementation can achieve sustained increases in circulating levels of antioxidants that exert a protective effect by a decrease in DNA damage, leading to improved immunological performance. These findings also have implications in a wider context where free-radical damage has been associated with a variety of degenerative disorders and the aging process in general.

Application of Single-Cell Gel Electrophoresis (Comet) Assay for Assessing Levels of DNA Damage in Canine and Feline Leukocytes

Increasing evidence suggests involvement of free-radical species in the development of oxidative DNA damage, the consequences of which have been implicated in a number of degenerative disorders associated with the aging process. Here we report the application of a single-cell gel electrophoresis (comet) assay for assessing levels of DNA damage in canine and feline leukocytes. Leukocytes were collected from 24 healthy adult cats and dogs and subjected to DNA damage ex vivo by exposure to a range of hydrogen peroxide (H(2)O(2)) concentrations (0-250 micromol/L). The optimal concentration of H(2)O(2) to induce a significant increase in DNA damage was 100 micromol/L for both canine and feline leukocyte samples. Levels of DNA damage were assessed and quantified by visual and computer image analysis. The results obtained showed high correlations between visual scoring and computer image analysis for feline samples (percentage DNA in tail, R(2) > 0.99; tail moment, R(2) > 0.95; tail length, R(2) > 0.90) and canine samples (percentage DNA in tail, R(2) > 0.97; tail moment, R(2) > 0.95; tail length, R(2) > 0.91). In conclusion, this method provides a way of assessing levels of DNA damage utilizing visual and/or computer image analysis in the feline and canine systems. With the capacity of the comet assay to be able to measure end products of free-radical reactions, it is a useful tool for determining the optimal effects of dietary antioxidants on a reliable biomarker of oxidative stress such as cellular DNA status in cats and dogs.

Effects of two commercially available feline diets on glucose and insulin concentrations, insulin sensitivity and energetic efficiency of weight gain.

A low-carbohydrate, high-protein (LCHP) diet is often recommended for the prevention and management of diabetes in cats; however, the effect of macronutrient composition on insulin sensitivity and energetic efficiency for weight gain is not known. The present study compared the effect in adult cats (n 32) of feeding a LCHP (23 and 47 % metabolisable energy (ME)) and a high-carbohydrate, low-protein (HCLP) diet (51 and 21 % ME) on fasting and postprandial glucose and insulin concentrations, and on insulin sensitivity. Tests were done in the 4th week of maintenance feeding and after 8 weeks of ad libitum feeding, when weight gain and energetic efficiency of each diet were also measured. When fed at maintenance energy, the HCLP diet resulted in higher postprandial glucose and insulin concentrations. When fed ad libitum, the LCHP diet resulted in greater weight gain (P < 0.01), and was associated with higher energetic efficiency. Overweight cats eating the LCHP diet had similar postprandial glucose concentrations to lean cats eating the HCLP diet. Insulin sensitivity was not different between the diets when cats were lean or overweight, but glucose effectiveness was higher after weight gain in cats fed the HCLP diet. According to the present results, LCHP diets fed at maintenance requirements might benefit cats with multiple risk factors for developing diabetes. However, ad libitum feeding of LCHP diets is not recommended as they have higher energetic efficiency and result in greater weight gain.

Effect on Canine Oral Health of Adding Chlorhexidine to a Dental Hygiene Chew

A study to compare the effect of a dental hygiene chew with or without 0.2% chlorhexidine on the development of gingivitis and the accumulation of dental deposits was performed using 11 small dogs. Confirming previous data, the daily addition of a standard chew to a dry diet resulted in significantly less gingivitis and calculus after 3 weeks compared with feeding the dry diet alone. Addition of chlorhexidine to the chew made no difference to the degree of gingivitis or the amount of calculus that accumulated, but did result in significantly less plaque accumulation after 3 weeks. The abrasiveness of the chew, rather than the antibacterial activity of chlorhexidine, is likely to have contributed the most to the maintenance of oral health in dogs with mild gingivitis.

Oral Malodor and its Relevance to Periodontal Disease in the Dog

Oral malodor has been studied extensively in humans but very little work has been done in dogs where it constitutes a significant problem. In this article we review its causes, methods of detection, and strategies for preventing it. Oral malodor arises from microbial metabolism of exogenous and endogenous proteinaceous substrates in the oral cavity and is exacerbated by periodontal disease and poor oral hygiene. Gram negative bacteria found in plaque, in periodontal pockets, and on the dorsum of the tongue are primarily responsible for odor production. The volatile sulfur compounds (VSCs) hydrogen sulfide and methyl mercaptan, which are produced by these bacteria, are not only primarily responsible for the objectionable odor but have been implicated in the pathogenesis of periodontal disease. Assessment of malodor by portable sulfide monitors correlates well with organoleptic measurements. Reduction of microbial load in the oral cavity due to good oral hygiene practices (such as tooth-brushing) or by the use of appropriate diets or chews may reduce malodor formation.

Adiponectin profiles are affected by chronic and acute changes in carbohydrate intake in healthy cats.

Adiponectin is a key adipokine that regulates carbohydrate and lipid metabolism. It circulates in stable low (LMW) and high molecular weight (HMW) forms. The aims of this study were to characterize baseline adiponectin profiles (total, LMW and HMW multimers) in healthy cats and to assess the effects of varying dietary carbohydrate content on adiponectin profiles. Cats were maintained on a diet with moderate carbohydrate content (37% metabolisable energy [ME]) for 4 weeks and then randomly allocated to either a low carbohydrate (19% ME) or high carbohydrate (52% ME) diet for 4 weeks. Fasting and postprandial plasma adiponectin profiles were measured by ELISA and sucrose gradient/Western blot. After consuming the moderate carbohydrate diet for 4 weeks, fasting total, HMW and LMW plasma adiponectin concentrations were 5.0±0.6, 2.5±0.5 and 2.6±0.2 μg/mL, respectively. After changing to the low carbohydrate diet, fasting total adiponectin was unchanged but HMW adiponectin increased and LMW adiponectin decreased. No significant postprandial changes were observed. Cats consuming the high carbohydrate diet had increased fasting total and LMW adiponectin with no change in HMW adiponectin. In the postprandial state total adiponectin was reduced and there was a trend towards a decrease in HMW (p=0.086) but not LMW multimers. These data indicate that feline adiponectin multimer profiles are similar to those reported in other species and demonstrate that changes in plasma adiponectin occur in response to chronic and acute carbohydrate intake and these reflect differential changes in adiponectin multimers.

Energy Intake in Cats as Affected by Alterations in Diet Energy Density

Whether mammals have the ability to regulate total intake or intake of specific macronutrients is controversial. The definition of an animal that can regulate is one that will alter its ingestive behavior to maintain (‘‘defend’’) adequate nutrient intake (1). Locusts, for example, alter the volume ingested to maintain intake of protein and carbohydrate in the face of dilution of foods with nondigestible bulk, a range of macronutrient combinations, or variation in the frequency of, and differing distances between macronutrients (1). Another striking example comes from the work of Theall et al. (2). In those experiments, rats ingested amounts of protein and carbohydrate within a tight range when challenged with foods containing 8 different macronutrient combinations. Rapid compensation for dietary dilution was also observed in many omnivorous and herbivorous species such as chickens (3), horses (4), cows (5), and humans (6). Anecdotally, it was believed that cats were also able to regulate intake to maintain adequate macronutrient and energy intake. Small-scale studies suggested that cats consuming feed ad libitum will eventually reach a stable energy intake, but the weight at which this occurs is not predictable (7). This has important implications for feline health because the incidence of obesity is estimated at;25% (8) and is predicted to rise. If cats merely regulate to the volume eaten, then a potential solution to obesity is the production of less energy-dense foods. If cats regulate to energy or macronutrient target, however, this approach will be unsuccessful. Previous studies were conducted over short periods and without adequate power, making it difficult to draw firm conclusions (9–12). The aim of the current study was to examine the effect of dietary dilution on intake in a large population of cats over an extended period of time.

Insulin-like growth factor-I (IGF-I) and its association with lymphocyte homeostasis in the ageing cat

Ageing affects feline lymphocyte homeostasis in a similar pattern to that observed in other long-lived mammalian species, contributing to increased levels of morbidity and mortality in the ageing cat. Insulin-like growth factor-I (IGF-I) is now recognised as an important endocrine regulator of immunity and has been shown to decline with age in humans and rodent species. Analysis of plasma IGF-I in adult and senior cats confirmed that the older cats had significantly lower circulating levels of IGF-I. In order to determine whether an association existed between lymphocyte subpopulations and IGF-I levels in the cat, each parameter was measured and subjected to regression analysis. A highly significant association was found in vivo between plasma IGF-I and CD4(+) T-cell values in the senior group, but no such association was observed in the adult group. In order that this relationship could be examined further, in vitro studies were undertaken to investigate the effects of physiologically relevant concentrations of recombinant human IGF-I (rhIGF-l) on peripheral blood lymphocyte (PBL) cultures from adult and senior cats. While rhlGF-I induced low-level thymidine incorporation in the lymphocytes isolated from the senior group, it did not enhance the proliferative response to T-cell mitogens, Con A and PHA in either group, nor did it rescue cells from oxidatively induced apoptosis. Furthermore, the proliferative response of PBL from seniors did not attain the magnitude of that from the adults at any concentration of rhIGF-l. We propose that the observed association is not a direct effect of IGF-I on PBL, but may be mediated through an effect of IGF-I on the thymus.

Studies of Oral Malodor in the Dog

We compared currently used methods for assessing oral malodor and found a significant, positive correlation between the concentration of volatile sulfur compounds (VSCs) in breath and the human perception of malodor, but only within a limited range of VSC production. Daily tooth-brushing from an early age maintains a low and consistent level of oral malodor that does not differ significantly throughout the day. In contrast, dogs with elevated concentrations of VSC production suffer from the highest level of malodor early in the morning, prior to feeding and daily activities. Even in older dogs, periodontal therapy can result in a substantial reduction of oral malodor that remains significantly below pre-treatment values for up to 3 months after treatment.