The effects of the proportions of dietary macronutrients on the digestibility, post-prandial endocrine responses and large intestinal fermentation of carbohydrate in working dogs

Abstract

AIM: To compare the effects of feeding diets varying in the proportions of macronutrients on the digestibility, post-prandial endocrine responses and large intestinal fermentation of carbohydrate in working dogs.

METHODS: The apparent digestibility of two test diets, one comprising low-carbohydrate, high-protein dry biscuits (Diet 1), and one comprising high-carbohydrate, low-protein dry biscuits (Diet 2), fed to 12 adult Harrier Hounds (n=5 female), was determined using the indigestible-marker and total-collection methods. Serial breath samples were collected from each dog before and after feeding, and analysed for concentrations of hydrogen. Concentrations of glucose and insulin in plasma were established from serial blood samples obtained after feeding.

RESULTS: The apparent dry matter, protein, fat and energy digestibility of Diet 1 were higher, but the carbohydrate digestibility was lower (p<0.05), than those of Diet 2. The apparent digestibility values determined using the total-collection method were lower (p<0.05) for carbohydrates, and tended to be lower for dry matter and energy (p<0.10) than those determined using the indigestible-marker method, but the values for protein and fat digestibility were similar using the two methods of determination. The maximum concentration (C_max) of hydrogen detected in the breath of the dogs occurred earlier for Diet 1 than Diet 2 (p<0.01). However, the C_max and area under the curve (AUC) for breath hydrogen were higher in the dogs fed Diet 2 than Diet 1 (p<0.01). The C_max for glucose and insulin in plasma occurred earlier in dogs fed Diet 2 compared with those fed Diet 1 (p<0.05). However, the C_max for glucose, and AUC for glucose and for insulin were not different between the two diets. The C_max for insulin was greater for Diet 2 compared with Diet 1 (p<0.05).

CONCLUSIONS: The low-carbohydrate, high-protein diet (Diet 1) appeared to offer certain advantages to working dogs, including higher apparent nutrient digestibility, slower release of glucose into the bloodstream, and reduced large intestinal fermentation of carbohydrate.

CLINICAL RELEVANCE: A low-carbohydrate, high-protein diet may be beneficial for specific groups of dogs, including working dogs subjected to prolonged bouts of exercise requiring a sustained energy source, or those with diabetes mellitus requiring better glycaemic control.

KEY WORDS:

• Macronutrients
• apparent digestibility
• glucose
• insulin
• large intestinal fermentation
• breath hydrogen
• working dogs

Acknowledgements

The authors wish to thank Kelly O'Flaherty, Maggie Honeyfield-Ross and Claire Browne for their excellent technical assistance throughout this study. We would also like to thank Desanka Palevich for providing veterinary skills on sampling days. Funding for this study was provided by Heinz Watties New Zealand Limited.