Dietary Lysine: Calorie Ratios and Their Influence on Nitrogen Metabolism and Digestibility in Moderately Obese Mature Dogs

Abstract

Problem statement:A goal during weight loss is to reduce body fat while maintaining body protein. We hypothesized that an increased dietary lysine: calorie might be beneficial during periods of caloric restriction. Approach: Two experiments were conducted to determine if changing the ratio of lysine: calories (lysine g/kg: Mcal ME/kg) while maintaining an ideal profile of amino acids will change nitrogen metabolism and weight loss in obese mature dogs. Results: The results of these experiments imply that if all essential amino acids are in adequate supply in the food, foods with an optimal balance of nutrients can reduce muscle degradation during periods of caloric restriction. Conclusion: Our optimum food for decreasing protein degradation was the food containing 3.0 lysine: calorie. However, the present experiments were relatively short and these results may not be sustained over longer periods of restriction.

The effects of added sulphur amino acids, threonine and an ideal amino acid ratio on nitrogen metabolism in mature, overweight dogs

“…Total urine was collected at 07:00 h and 19:00 h during the sampling period as described previously (Reeder et al 2011). Dogs were weighed on days 7, 14, 21 and 28 of each period.…”

“…Whole body protein turnover was measured using the 15 N-glycine single-dose urea end-product method (Waterlow et al 1978) as described earlier (Reeder et al 2011). …”

“…However, previously, it was shown that increasing lysine to achieve a ratio of 0.72 g lysine/MJ ME, in a diet composed mainly of brewer's rice, cornstarch, and low ash poultry meal, was optimal in mature, overweight dogs (Reeder et al 2011). However, previously, it was shown that increasing lysine to achieve a ratio of 0.72 g lysine/MJ ME, in a diet composed mainly of brewer's rice, cornstarch, and low ash poultry meal, was optimal in mature, overweight dogs (Reeder et al 2011).…”

“…Nutrient contents of the experimental diets (Table 1) were analysed as described previously (Reeder et al 2011). Faecal samples were combined for each dog, within a period, and thoroughly mixed.…”

“…After determination of urea content, individual urine samples collected from 07:00 h on day 25 through 07:00 h on day 28 were processed and analysed for 15 N enrichment as described previously (Reeder et al 2011). After determination of urea content, individual urine samples collected from 07:00 h on day 25 through 07:00 h on day 28 were processed and analysed for 15 N enrichment as described previously (Reeder et al 2011).…”