E. Jean Harper

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.

Changing perspectives on aging and energy requirements : Aging and digestive function in humans, dogs and cats

When considering the question of energy balance, it is important to take into account energy provision and the ability of aging animals to digest macronutrients and thus obtain their maintenance energy requirement. A large number of studies have been conducted in humans in an effort to establish whether aging of the gastrointestinal tract has a significant effect on availability of dietary energy. The results of these studies have been conflicting, with indications that some aspects of gut functionality do decline with age, but little evidence overall to suggest that aging humans are at risk of energy deficit due to compromised digestive efficiency. A number of digestibility studies carried out with dogs confirm that there is no evidence of an age-related decline in digestive efficiency. This knowledge makes the determination of energy provision to senior dogs relatively straightforward to calculate. Many senior cats appear to exhibit quite a marked reduction in their ability to digest macronutrients, particularly fat, efficiently. Because this reduces the overall capacity to obtain energy from the diet, it is recommended that old cats should not routinely be offered reduced energy diets. For senior cats, the feeding regimen in later life should be to offer highly digestible diets that provide as much energy as adult maintenance rations.

Clinical nutrition of small psittacines and passerines

There is an increasing volume of work on the nutritional requirements of small psittacine and passerine species and this, together with the extensive nutritional studies of poultry, provides a basis for nutritional guidelines for pet birds. Most of the small psittacine and passerine species are granivorous, but not all the nutritional requirements can be met by an unsupplemented seed diet. Macronutrient and energy requirements can usually be met by a seed-based diet, but during reproduction and growth, the requirement for macronutrients, particularly protein, is considerably increased. Diets should be designed to provide a minimum of 10% to 14% of dietary protein for adult birds and 15% to 20% for growing birds. There is no advantage in providing excess dietary protein, and levels of 25% and greater have been shown to have detrimental effects in growing birds. With respect to micronutrients, imbalances in calcium, phosphorus, and vitamin D are some of the more commonly observed nutritional disorders, particularly in reproducing and growing birds. Seed-based diets tend to have a low calcium-phosphorus ratio, which should be adjusted to an optimal ratio of 2:1 through supplementation. Further mineral imbalances that have been documented in pet birds include iodine insufficiency, which causes goiter, and iron, which is more often associated with symptoms of toxicity. The other micronutrient imbalance that most commonly affects birds is vitamin A, and both insufficiency and toxicity are frequently observed. Seed-based diets do not contain enough s-carotene to prevent vitamin A deficiency, and oversupplementation with very rich sources, such as cod liver oil, can result in hypervitaminosis A. This article reviews the latest information on the specific macro- and micronutrient requirements of small psittacines and passerines. It provides guidelines on the minimum and maximum requirements for maintenance, growth, and reproduction and discusses the clinical conditions commonly associated with malnutrition in birds.

Aging Does Not Influence Feeding Behavior in Cats

The aim of this investigation was to see whether aging influences feeding behavior in cats. Two studies were carried out. In the first study, a standard canned cat food was fed to six young adult and six senior cats for 10 d on an ad libitum basis. Feeding behavior was monitored during the final 5 d. In the second study, diets enriched with beef tallow, olive oil or sunflower oil were fed at an equivalent energy intake for 21 d. Feeding behavior was monitored during the final 5 d. The results of both studies indicated no significant differences between the young and old cats in the number of meals consumed, the amount consumed at each meal or the duration of each meal when fed either ad libitum or at equivalent energy intakes. Daily feeding patterns were similar for each of the 5 d for each cat, with cats tending to consume regular small meals throughout the day and night. The only significant differences noted were among the fat-enriched diets. The diet enriched with beef tallow had fewer refusals compared to the diets enriched with olive oil and sunflower oil, indicating a possible palatability differential. It was concluded that cats of all ages are habitual feeders with similar daily feeding patterns, which may be altered only with a change in diet. Given that no differences were seen between the young and senior cats, it cannot be assumed that feeding patterns are responsible for the previously observed age-related decreases in apparent digestibility.