This study was approved by the Ethical Committee of the Faculty of Veterinary Medicine, Ghent University, Belgium (EC 2011/056). Twelve healthy Beagles with a mean age of 6.0 years old were included in this study. Six Beagles (one spayed and three intact females; two intact males) were lean, with a body condition score of 4–5/9, and six Beagles (two intact females and two intact males) were obese, with a body condition score of 8–9/9. Obesity was induced ∼1 year before the present study by feeding the dogs a high-fat commercial diet as described by Van de Velde et al. (2013 (link)). Before the study, dogs were deemed healthy (apart from obesity in four dogs), based on physical exams, complete blood counts, and serum biochemistry.
Two isocaloric experimental diets, a high-protein/low-carbohydrate (HPLC) diet consisting of 50.0 g crude protein, 12.2 g ether extract, and 32.2 g nitrogen-free extract on 100 g dry matter basis, and a low-protein/high-carbohydrate (LPHC) diet consisting of 17.8 g crude protein, 13.6 g ether extract, and 62.3 g nitrogen-free extract on 100 g dry matter basis were formulated with the same ingredients (Co. NV Versele-Laga, Deinze, Belgium). Full details of the ingredients and dietary composition were described previously (Xu et al. 2017 (link)), and the main ingredients are presented inSupplementary Table S1 . Both diets met the minimal requirement for adult dogs according to the National Research Council (2006 ). The initial amount of feed offered was calculated based on individual maintenance energy requirements according to individual history and adjusted to maintain a stable body weight throughout the study. Dogs were fed twice daily and had free access to water.
The study was designed as a crossover with two 4-week periods. The first 3 weeks consisted of an adaptation period and samples were taken in the fourth week (on day 27). In the first period, three lean and obese dogs were randomly selected and assigned to the LPHC diet first, whilst the other three lean and obese dogs received the HPLC diet. In the second period, diets were switched. Each dog was therefore assigned to one of four groups (group 1: lean dogs received the LPHC diet first; group 2 lean dogs received the HPLC diet first; group 3 obese dogs received the LPHC diet first; group 4 obese dogs received the HPLC diet first). On day 27 of each period, fresh faecal samples were collected within 10 min after spontaneous voiding. An aliquot of ±2 g was placed into a sterile plastic tube, frozen immediately on dry ice, lyophilized as soon as possible, and stored at −80 °C in preparation for metabolomics analysis. Two obese dogs were excluded from the metabolomics analysis due to an insufficient amount of faecal samples, and as such, each group ended up containing three lean and two obese dogs.
Two isocaloric experimental diets, a high-protein/low-carbohydrate (HPLC) diet consisting of 50.0 g crude protein, 12.2 g ether extract, and 32.2 g nitrogen-free extract on 100 g dry matter basis, and a low-protein/high-carbohydrate (LPHC) diet consisting of 17.8 g crude protein, 13.6 g ether extract, and 62.3 g nitrogen-free extract on 100 g dry matter basis were formulated with the same ingredients (Co. NV Versele-Laga, Deinze, Belgium). Full details of the ingredients and dietary composition were described previously (Xu et al. 2017 (link)), and the main ingredients are presented in
The study was designed as a crossover with two 4-week periods. The first 3 weeks consisted of an adaptation period and samples were taken in the fourth week (on day 27). In the first period, three lean and obese dogs were randomly selected and assigned to the LPHC diet first, whilst the other three lean and obese dogs received the HPLC diet. In the second period, diets were switched. Each dog was therefore assigned to one of four groups (group 1: lean dogs received the LPHC diet first; group 2 lean dogs received the HPLC diet first; group 3 obese dogs received the LPHC diet first; group 4 obese dogs received the HPLC diet first). On day 27 of each period, fresh faecal samples were collected within 10 min after spontaneous voiding. An aliquot of ±2 g was placed into a sterile plastic tube, frozen immediately on dry ice, lyophilized as soon as possible, and stored at −80 °C in preparation for metabolomics analysis. Two obese dogs were excluded from the metabolomics analysis due to an insufficient amount of faecal samples, and as such, each group ended up containing three lean and two obese dogs.
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