Digestibility Is Similar between Commercial Diets That Provide Ingredients with Different Perceived Glycemic Responses and the Inaccuracy of Using the Modified Atwater Calculation to Calculate Metabolizable Energy

Abstract

Dietary starch is required for a dry, extruded kibble; the most common diet type for domesticated felines in North America. However, the amount and source of dietary starch may affect digestibility and metabolism of other macronutrients. The objectives of this study were to evaluate the effects of 3 commercial cat diets on in vivo and in vitro energy and macronutrient digestibility, and to analyze the accuracy of the modified Atwater equation. Dietary treatments differed in their perceived glycemic response (PGR) based on ingredient composition and carbohydrate content (34.1, 29.5, and 23.6% nitrogen-free extract for High, Medium, and LowPGR, respectively). A replicated 3 × 3 Latin square design was used, with 3 diets and 3 periods. In vivo apparent protein, fat, and organic matter digestibility differed among diets, while apparent dry matter digestibility did not. Cats were able to efficiently digest and absorb macronutrients from all diets. Furthermore, the modified Atwater equation underestimated measured metabolizable energy by approximately 12%. Thus, the modified Atwater equation does not accurately determine the metabolizable energy of high quality feline diets. Further research should focus on understanding carbohydrate metabolism in cats, and establishing an equation that accurately predicts the metabolizable energy of feline diets.

True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay1

“…Those estimates led to the use of modified Atwater factors (3.5, 8.5, and 3.5 kcal/g for protein, fat, and digestible carbohydrate, respectively). Although those values provide a better estimate of ME for pet foods than do the Atwater factors, they underestimate the energy content of highly digestible foods, including today’s premium or super-premium diets ( Laflamme, 2001 ; Asaro et al, 2017 ).…”

Carbohydrate level and source have minimal effects on feline energy and macronutrient metabolism

“…It is probable that differences in carbohydrate content and resulting intake of the experimental diets in the present study stimulate variable lipid synthesis, and therefore different postprandial EE among treatments. Furthermore, we previously determined that the calculated ME from which feeding recommendations were developed was inaccurate (Asaro et al, 2017). When caloric intake was reanalyzed using the true ME of the diets, we found that cats were unintentionally offered nonisocaloric provisions, with more energy being consumed by cats fed the high PGR diet (Table 3).…”

“…Cats were fed to maintain BW using individual historical data of energy intake. Dietary ME was calculated using the modified Atwater calculation, though it was later determined that the Atwater equation consistently underestimated true ME of the experimental diets (AAFCO, 1997;Asaro et al, 2017). Cats followed an 8-d prefeeding schedule followed by calorimetry and glucose measures.…”

“…Considering the limited research regarding the effects of carbohydrates on the feline glycemic response, the present study discusses the perceived glycemic response (PGR) which refers to the expected theoretical glycemic response that would result from consumption of each diet (Asaro et al, 2017). The objectives of the present study were to measure effects of 3 diets differing in their PGR and ingredient composition on 1) RQ and EE in healthy adult cats and 2) interstitial glucose and serum glucose and insulin in healthy adult cats.…”

“…Calculated with modified Atwater equation(AAFCO, 1997): ME (kcal/kg) = [3.5 × CP (%) + 3.5 × NFE (%) + 8.5 × crude fat (%)] × 10.3 Using analyzed ME fromAsaro et al (2017).…”