Passage kinetics of dry matter and neutral detergent fibre through the gastro-intestinal tract of growing beef heifers fed a high-concentrate diet measured with internal ?13C and external markers

J. B. Daniel, H. Van Laar, D. Warner, J. Dijkstra, A. Navarro-Villa, W. F. Pellikaan
2014 Animal Production Science  
Fractional rumen passage rates (K 1 ) are fundamental in feed evaluation systems for ruminants to predict the extent of nutrient degradation. Data on passage kinetics of growing beef cattle fed high-concentrate diets are scarce and mainly rely on external passage markers which do not provide nutrient-specific K 1 estimates. The present study describes the use of carbon stable isotopes (d 13 C) as an internal marker to estimate K 1 of dry matter (DM) and neutral detergent fibre (NDF) fractions
more » ... e (NDF) fractions of a compound feed in a high-concentrate diet, and compares them to the external markers ytterbium (Yb)-actetate and chromium mordanted fibre (Cr-NDF). Four rumen-fistulated Holstein heifers received four times per day a basal diet consisting of barley straw and pelleted compound feed offered separately (ratio 10 : 90, DM basis). Compound feed in the basal diet was mainly based on wheat of low natural 13 C enrichment (À28.4 d 13 C), which was exchanged with a single dose of a maize-based compound feed of higher natural 13 C enrichment (À18.9 d 13 C). This difference in natural 13 C abundance was used to determine K 1 values from faecal 13 C excretion patterns. At the same time Yb-Acetate and Cr-NDF were introduced into the rumen to determine K 1 values from faecal excretions. Faeces were collected over 90 h after pulse dosing. The K 1 of d 13 C-marked DM (0.062/h) did not differ (P = 0.745) from d 13 Cmarked NDF (0.060/h). The d 13 C-based K 1 values also did not differ from Cr-NDF (0.056/h; P = 0.315). These results indicate similar passage behaviour of these fractions in the rumen of beef heifers fed a high-concentrate diet.
doi:10.1071/an14354 fatcat:pvypkqemxfgihc3fyrjxlb6j6u