Abstract
Freeze-dried pet foods represent a small segment of the pet food market, but its growth has been significant in recent years. Despite their increasing popularity, freeze-dried diets have not been well tested. Therefore, the objective of this experiment was to determine and compare the standardized amino acid (AA) digestibilities of freeze-dried dog foods using the precision-fed cecectomized rooster assay. Three formats of freeze-dried diets provided by Primal Pet Foods (Fairfield, CA) were tested: traditional freeze-dried nuggets (FDN), low-temperature freeze-dried nuggets (LTN), and a hybrid freeze-dried nugget (HN). All animal care procedures were approved by the University of Illinois Institutional Animal Care and Use Committee prior to experimentation. Twelve cecectomized roosters (4 roosters per substrate) were randomly assigned to the three test substrates. After 24h of feed withdrawal, roosters were tube-fed 12-13g of test substrates and 12-13g of corn. Following crop intubation, excreta (urine and feces) were collected for 48h. Endogenous corrections for AA were made using 5 additional cecectomized roosters. All data were analyzed using the Mixed Models procedure of SAS version 9.4. There were no significant differences in standardized AA digestibilities among diets, with digestibilities being high for all tested. For most of the indispensable AA, digestibilities were greater than 90% for all diets (arginine: 94.1%-95.6%; isoleucine: 91.2%-93.1%; leucine: 92.4%-95.3%; methionine: 92.8%-94.9%; phenylalanine: 90.8%-93.6%; tryptophan: 96.2%-98.6%; valine: 90.2%-92.9%). Histidine, lysine, and threonine were the exceptions, with digestibilities ranging from 81.7%-86.6%, 86.7%-91.7%, and 89.6%-91.7%, respectively. Moreover, the reactive:total lysine ratio, a measure of heat damage, ranged from 0.91 to 0.95. In general, the low-temperature nugget had thegreatest numerical AA digestibilities, likely due to reduced heat damage, but all diets performed very well.