Simple SummaryThe inevitable basal endogenous loss of nutrients from the body is closely associated with the animal’s metabolic functions. A purified diet formulated with highly refined feed ingredients lacking phosphorus is commonly used to determine the basal endogenous loss of phosphorus. However, such diets may alter metabolic functions, thereby affecting the basal endogenous loss of phosphorus. Moreover, feeding a purified diet for a long period of time may cause abnormal gut health, resulting in a decrease in empty gut weight and shorter intestinal segments. To the best of our knowledge, information on the effect of the feeding duration of a phosphorus-free diet on the basal endogenous loss of phosphorus is limited. We found that feeding broiler chickens a phosphorus-free diet for up to 4 days did not affect the amount of basal endogenous loss of phosphorus.AbstractThe study investigated the effects of feeding duration on the length and weight of the ileum, and basal endogenous loss (BEL) of phosphorus (P) on broiler chickens fed a P-free diet (PFD). A standard starter diet was fed to 384 birds for 15 days. On day 15, they were weighed and randomly allocated to one of three treatment groups in a randomized complete block design, with eight replicate cages per treatment and 16 birds per cage. The birds in each treatment group were fed the PFD for 2, 3, or 4 days. There was an increase in growth performance (p< 0.05) as the PFD feeding duration increased from 2 to 4 days. Although the relative dry weight of the ileum (mg/100 g of body weight) decreased linearly (p< 0.05) as the PFD feeding duration increased, the amount of dried ileal digesta (g/bird) was not affected. The BEL of P was 110.2, 128.2, and 133.6 mg/kg of dry matter intake in birds fed the PFD for 2, 3, and 4 days, respectively. Feeding a PFD to broiler chickens for 2, 3, or 4 days did not change P BEL.