Evaluation of the Nutrient Digestibility at Each Age in Dogs Diet by In vitro and In vivo Methods

The objective of this study was to evaluate <italic>in vitro</italic> predictions of digestibility at each age (puppy, adult, and senior) in dogs of dry matter (DM), organic matter (OM), crude protein (CP), gross energy (GE), crude fiber (CF), and ether extract (EE) using dog diets. First, to determine the digestibility of dog diets using pepsin and pancreatin incubations, conduct the <italic>in vitro</italic> method. Later, 18 mixed-sex beagles were used in this experiment to compare <italic>in vivo</italic> digestibility. Beagles are divided into 3 groups according to their age and body weight: six puppies (under 1-year-old; 6.21 ± 0.56 kg), six adult dogs (2 to 7 years old; 8.16 ± 0.64 kg), and six senior dogs (over 8 years old; 6.95 ± 1.39 kg). Except for DM in puppies and adult dogs, in all cases, <italic>in vitro</italic> digestibility values were higher than <italic>in vivo</italic> digestibility values (p &lt; 0.05). In puppies, there were strong relationships for DM and GE with r² values of 0.95 and 0.84, respectively, between <italic>in vitro</italic> and <italic>in vivo</italic> digestibility. Also, in adult dogs, there were strong relationships for DM and GE with r² values of 0.97 and 0.84, respectively, between <italic>in vitro</italic> and <italic>in vivo</italic> digestibility. However, in senior dogs, there was a lower relationship for DM, OM, CP, GE, CF, and EE with r² values of 0.18, 0.42, 0.01, 0.02, 0.11, and 0.04, respectively, between <italic>in vitro</italic> and <italic>in vivo</italic> digestibility. In conclusion, <italic>in vitro</italic>, the prediction of nutrient digestibility of DM and GE in puppies and adult dogs seems to have significant potential for practical application. However, additional research is needed to compare senior dogs with the <italic>in vitro</italic> method.