Research Article Cats in Positive Energy Balance Have Lower Rates of Adipose Gain When Fed Diets Containing 188 versus 121 ppm L-Carnitine M. A. Gooding, 1 D. L. Minikhiem, 1 and A. K. Shoveller 1,2 1 Te Iams Company, Mars PetCare, 6571 State Route 503 North, Lewisburg, OH 45338, USA 2 Centre for Nutrition Modelling, Department of Animal Biosciences, University of Guelph, 50 Stone Road East, Guelph, ON, Canada N1G 2W1 Correspondence should be addressed to A. K. Shoveller; ashovell@uoguelph.ca Received 19 May 2016; Revised 12 July 2016; Accepted 2 August 2016 Academic Editor: Stephen D. Ginsberg Copyright © 2016 M. A. Gooding et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. L-carnitine (LC) is included in select adult feline diets for weight management. Tis study investigated whether feeding adult cats with diets containing either 188 ppm of LC (LC188) or 121 ppm of LC (LC121) and feeding them 120% of maintenance energy requirement (MER) resulted in diferences in total energy expenditure (EE), metabolic fuel selection, BW, body composition, and behavior. Cats ( = 20, 4 ± 1.2 yrs) were stratifed for BCS and randomly assigned to one of two dietary treatments and fed for 16 weeks. BW was measured weekly, and indirect calorimetry, body composition, physical activity, play motivation, and cognition were measured at baseline and throughout the study. A mixed, repeated measures, ANCOVA model was used. Cats in both treatments gained BW ( < 0.05) throughout the study, with no diferences between treatments at any time point ( > 0.05). Tere were no diferences in body composition between groups at baseline; however, body fat (g) and body fat : lean mass ratio were greater in cats fed LC121 in contrast to cats fed LC188 ( < 0.05) on week 16. No other outcomes difered between treatments ( > 0.05). Supplying dietary LC at a dose of at least 188 ppm may be benefcial for the health and well-being of cats fed above MER. 1. Introduction While there is no dietary requirement for L-carnitine (LC) in cats, as it is synthesized endogenously, LC is considered a conditionally essential nutrient, as defciencies can occur during certain disease states, during aging, and during weight loss/gain, as LC facilitates fatty acid metabolism [1] and energy metabolism [2]. Further, LC is believed to enhance cognition in humans [3] and animal models, such as rats demonstrating cognitive impairments [4]. L-carnitine is a cofactor that facilitates the transport of long chain fatty acids (LCFA) across the inner mitochondrial membrane for subsequent -oxidation. Furthermore, LC also acts as a cofactor in the transport of acetyl-CoA out of the mito- chondria. Increased concentrations of mitochondrial acetyl- CoA can inhibit further -oxidation. Together these actions regulate the intramitochondrial acetyl-CoA concentrations and release free CoA and acetyl-carnitine that favor the oxidation of pyruvate. Due to the mechanism of action by which LC exerts its efects on fatty acid metabolism, LC may also provide a mechanism for removal of excessive fatty acids that are released during weight loss [2]. Tis is critically important in cats because lipids released during weight loss are commonly deposited in the liver if they are not oxidized and result in hepatic lipidosis [5]. Weight gain and related metabolic indices in domestic cats are related to diminished physical activity, mainly in the light hours [6]. Similarly, obese cats have lower EE than lean cats [7], and we recently found that overweight and obese cats have reduced activity counts in contrast to lean cats [8]. Recently, dietary LC (100 ppm) fed to cats has been shown to increase EE and lipid oxidation in contrast to cats fed control (30 ppm) during controlled weight loss [9] and for overweight cats fed to weight maintenance [7]. We have previously demonstrated that dietary LC sup- plementation can positively impact motivation to play in overweight, but not lean, cats [7]. We hypothesized that LC, Hindawi Publishing Corporation e Scientific World Journal Volume 2016, Article ID 2649093, 7 pages http://dx.doi.org/10.1155/2016/2649093