Objective—To determine whether water content in a canned food diet induces decreases in voluntary energy intake (EI) or body weight (BW) in cats fed ad libitum. Animals—16 sexually intact male domestic shorthair cats. Procedures—Maintenance EI was determined for 2 months in 10 weight-stable cats consuming a control diet (typical colony diet). Cats were allocated into 2 groups of equal BW and fed a canned diet (with-water [WW] diet) or a freeze-dried version of the canned diet (low-water [LW] diet) twice daily. Diets were identical in nutrient profile on a dry-matter basis. Each dietary treatment period of the crossover experiment lasted 3 weeks, with a 3-week washout period between diets. Body composition measurements were determined by use of deuterium oxide at the end of each dietary treatment. Daily food intake was measured for determination of dry-matter intake and EI. Six other cats were used in preference tests for the 3 diets. Results—EI was significantly decreased for the WW diet (mean ± SD, 1,053.0 ± 274.9 kJ/d), compared with EI for the LW diet (1,413.8 ± 345.8 kJ/d). Cats had a significant decrease in BW during consumption of the WW diet. Body composition was unaltered by diet. In short-term preference tests, cats ate significantly more of the WW than the LW diet. Conclusions and Clinical Relevance—Bulk water in the WW diet stimulated decreases in EI and BW in cats. The impact of water content on energy density and food consumption may help promote weight loss in cats.

Objective-To determine whether transitional cell carcinoma (TCC) cells incubated in media containing 5-aminolevulinic acid (ALA) would produce sufficient protoporphyrin IX (PpIX) to cause lethal phototoxic effects when exposed to 635-nm light. Sample Population-Canine TCC cells (K9TCC). Procedure-Cultured K9TCC cells were exposed to graded doses of ALA, and PpIX concentrations were determined. Cells then were exposed to various doses of 635-nm light from a diode laser, and cell viability was assayed. Results-Production of PpIX was dependent on time and dose of ALA. The K9TCC cells incubated with ALA produced sufficient PpIX to cause lethal phototoxic effects when exposed to 635-nm light. Phototoxic effects were dependent on time and dose of ALA. Increasing laser power density and energy density decreased cell survival. Conclusions and Clinical Relevance-ALA is an effective photosensitizer for in vitro photodynamic treatment of K9TCC cells. Further studies are warranted to assess the safety and efficacy of ALA as a photosensitizer for use in treating dogs with TCC. Impact for Human Medicine-On the basis of this study, dogs with TCC may be useful in the development of protocols for ALA-based photodynamic therapy of humans affected with muscle-invasive bladder cancer.