Endogenous N‐losses in piglets estimated by a [15N]‐isotope dilution technique: Effect of xylanase addition to a wheat and rye based diet

The nitrogen pool of piglets weighing 19.4 ± 1.4 kg at the beginning of the experiment was labeled with an oral application of ([15N]H4SO4 (1.26 [l5N]‐atom percent excess of dietary N) over a period of 7 d. The labeling period was followed by an equilibration period of 7 d without feeding the labeling compound. The two experimental diets were based on wheat (53%) and rye (25%) and were fed either with or without a xylanase containing enzyme preparation over both experimental periods. Additionally, diets were supplemented with an indigestible marker during the 2nd period of the experiment to allow the calculation of endogenous N‐Iosses in subsequent segments of the digestive tract of the pigs. These endogenous N‐losses were estimated at the end of the experiment by analyzing feces, ingesta and urine for [15N]‐enrichment assuming that [l5N]‐enrichment of urine represents the [15N]‐enrichment of the precursor pool. Endogenous N‐losses were not significantly affected by xylanase addition at any measurement site (stomach, 3 sections of the small intestine, total digestive tract). Endogenous N‐proportions of total nitrogen amounted on average for the six pigs to 42 ± 11% and 56 ± 5% at the last section of the small intestine and over the whole digestive tract, respectively, which corresponded to endogenous N‐losses of 2.8 ± 1.3 g N/kg DM and 2.0 ± 0.3 g N/kg DM, respectively.