Abigail E. Stevenson

Effect of dietary water intake on urinary output, specific gravity and relative supersaturation for calcium oxalate and struvite in the cat

It has been reported that daily fluid intake influences urinary dilution, and consequently the risk of urolithiasis in human subjects and dogs. The aim of the present study was to investigate the role of dietary moisture on urinary parameters in healthy adult cats by comparing nutritionally standardised diets, varying only in moisture content. A total of six cats were fed a complete dry food (6.3 % moisture) hydrated to 25.4, 53.2 and 73.3 % moisture for 3 weeks in a randomised block cross-over design. Urinary specific gravity (SG), urine volume, water drunk and total fluid intake were measured daily; relative supersaturation (RSS) for calcium oxalate (CaOx) and struvite was calculated using the SUPERSAT computer program. Cats fed the 73.3 % moisture diet produced urine with a significantly lower SG (P < 0.001) compared with diets containing 53.2 % moisture or lower. Mean RSS for CaOx was approaching the undersaturated zone (1.14 (sem 0.21); P = 0.001) for cats fed the diet with 73.3 % moisture and significantly lower than the 6.3 % moisture diet (CaOx RSS 2.29 (sem 0.21)). The effect of diet on struvite RSS was less clear, with no significant difference between treatment groups. Total fluid intake was significantly increased (P < 0.001) in the 73.3 % moisture diet (144.7 (SEM 5.2) ml, or 30 ml/kg body weight per d) compared with the 6.3 % (103.4 (SEM 5.3) ml), 25.4 % (98.6 (SEM 5.3) ml) and 53.3 % (104.7 (SEM 5.3) ml) moisture diets, despite voluntary water intake decreasing as dietary moisture intake increased. Cats fed the 73.3 % moisture diet had a higher total daily fluid intake resulting in a more dilute urine with a lower risk of CaOx when compared with the lower-moisture diets.

The Influence of Feeding Frequency on Growth and Body Condition of the Common Goldfish (Carassius auratus)

The optimal frequency for feeding ornamental fish species has yet to be clearly defined and this has led to uncertainty in the feeding routines used by many aquarists. Both overand underfeeding can be detrimental to the health of the fish and may cause a marked deterioration in water quality, reduced weight, poor food utilization, and increased susceptibility to infection. Consequently, specific growth rates and the efficiency of feed conversion can be directly related to feed ration and frequency. Therefore, it is important to be able to predict the most favorable feeding frequency relative to the species and size of fish. Although it is often postulated that feeding ornamental fish little and often throughout the day will result in more efficient feed utilization, research has not yet been conducted to validate this hypothesis. Published literature on frequency of feeding ornamental fish is limited when compared with that available from cultured fish species. Data from aquaculture research is commonly extrapolated and applied to ornamental species, which often proves to be unsatisfactory because of the differences in fish species and variation in diet formulations. In addition, the majority of research has focused on feeding fish to satiation, measuring the food intake, and linking this to growth performance and utilization. Research conducted with the ornamental Red Swordtail (Xiphophorus helleri) indicated that feeding 2 meals/d (where a meal is defined as providing food until fish stop eating [the point of satiation]) resulted in the greatest growth and reproductive success of this species in a cultured system, when compared with 4 alternative feeding regimens (1 meal in 3 d, 1 meal in 2 d, 1 meal/d, and 2 meals/d) (1). Further investigations by the same researchers using the Siamese Fighting Fish (Betta splendens. Regan) showed that 2 meals/d fed to satiation elicited maximum growth and reproductive output for this ornamental fish species when compared with 1 meal in 3 d, 1 meal in 2 d, 1 meal/d, and 3 meals/d (2). Additional research on commercially cultured fish species such as the Black Rockfish (Sebastes schlegeli) suggested that feeding to satiation once a day resulted in optimum growth and food utilization when compared with 1 meal every 2 d or 2 meals/d (3). In addition, juvenile Atlantic Halibut (Hippoglossus hippoglossus) displayed improved growth rates when fed to satiation 5 times/d, compared with 1/d (4), and African Catfish (Clarias gariepinus) exhibited greater growth rates when fed to satiation twice compared with 3 times/d (5). In one study where a set amount of food was offered, Giberson and Litvak (6) established that Shortnose Sturgeon (Acipenser brevirostrum) grew significantly better when offered a food ration of 3% of the tank biomass divided into 4 or 8 feedings/d compared to one. However, in the same study, growth and feeding efficiencies of Atlantic Sturgeon (Acipenser oxyrinchus) were unaffected by the frequency of feeding. Currently there appear to be no data available that directly relates feeding frequency to growth and efficiency of food utilization in the Common Goldfish (Carassius auratus). However, the closely related subspecies, Gibel Carp (Carassius auratus gibelio), exhibited significant increases in growth rate and feed efficiency when feeding frequency increased from 2 to 3, 4, 12, and 24 feedings/d, with the authors recommending an optimal feeding frequency of 24 meals/d for this species (7). However, fish were juvenile and fed to satiation, confirming that feeding frequency in part is a function of fish size, with larval and juvenile fish needing to eat more frequently because of their high energy demands. This current study aimed to assess the effects of feeding a set amount of food at a variety of meal frequencies on growth parameters of the Common Goldfish (Carassius auratus) and to identify the optimum number of feeds/d to maximize utilization of the food ration. 1 Published in a supplement to The Journal of Nutrition. Presented as part of The WALTHAM International Nutritional Sciences Symposium: Innovations in Companion Animal Nutrition, held in Washington, DC, September 15–18, 2005. This conference was supported by The WALTHAM Centre for Pet Nutrition and organized in collaboration with the University of California, Davis, and Cornell University. This publication was supported by The WALTHAM Centre for Pet Nutrition. Guest editors for this symposium were D’Ann Finley, Francis A. Kallfelz, James G. Morris, and Quinton R. Rogers. Guest editor disclosure: expenses for the editors to travel to the symposium and honoraria were paid by The WALTHAM Centre for Pet Nutrition. 2 Author disclosure: no relationships to disclose. 3 To whom correspondence should be addressed. E-mail: abigail.stevenson@ eu.effem.com.

Methods for Predicting Food Allowances from Body Length in Tropical and Temperate Ornamental Fish Species

Aquarists often overlook the importance of feeding an appropriate amount of a balanced diet for fish health and maintenance of water quality in an aquarium. Although most commercial food manufactures do offer an on-package feeding guide containing statements like ‘‘feed between 2–4 times per day, sprinkling a few flakes per fish on the water until the fish stop feeding,’’ such guidelines are vague, and may result in overfeeding. The overfeeding of fish in an aquarium results in increased pollution (ammonia and/or nitrite) and ultimately causes system failure if the tank is not maintained properly through husbandry procedures like water changes. These onpackage instructions are deliberately vague mainly because of the limited information available on factors such as different species requirements for size, activity, age, environment, and water temperature. The aim of this research is to establish simple mathematical models that can predict body weight (BW) from body length in fish. By linking predicted BW with a known energy requirement and energy density of the food, it becomes possible to calculate accurate food allowances. This is particularly useful because, although BW cannot easily be determined by owners of ornamental fish, an estimate of body length is usually possible.