Animal Feed Science and Technology 177 (2012) 161–171 Contents lists available at SciVerse ScienceDirect Animal Feed Science and Technology journal homepage: www.elsevier.com/locate/anifeedsci Estimation of feed intake and digestibility in cattle consuming low-quality tropical roughage diets using molasses-based n-alkane boluses M. Bezabih a,b,∗ , W.F. Pellikaan a , A. Tolera b , W.H. Hendriks a,c a Animal Nutrition Group, Department of Animal Sciences, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands b Department of Animal and Range Sciences, Hawassa University, P.O. Box 5, Hawassa, Ethiopia c Animal Nutrition Division, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80151, 3508 TD Utrecht, The Netherlands a r t i c l e i n f o Article history: Received 26 January 2012 Received in revised form 10 August 2012 Accepted 24 August 2012 Keywords: Ruminant Intake Digestibility Prediction Grazing n-Alkane a b s t r a c t A feeding experiment was conducted to measure the faecal recovery rates of n-alkanes and to evaluate molasses-based alkane boluses for feed intake and digestibility estimations in cattle consuming low-quality tropical roughages. The experiment was performed in a cross-over design with four experimental diets, four 21-day feeding runs and eight bulls. The animals received a measured amount of the experimental diets that resulted in little refusal throughout the experiment. After seven days of adaptation, the animals were dosed with molasses-based alkane boluses (each containing 200 g C 32 and 150 g C 36 ) twice daily at 07:00 and 18:00 h. Concurrent with the alkane dosing, faecal spot samples were taken twice daily until the end of each run. In addition, total faecal collections were performed over the last 5 days of each run. The mean faecal recovery rate of both natural and dosed n-alkanes ranged between 0.61 and 0.86, with the recovery showing an upward trend with increasing carbon-chain length. The recovery rate of dosed alkanes was considerably higher than that of adjacent odd-chain alkanes. Whilst diets did not differ (P≥0.23) in the recovery of even-chain n-alkanes, an effect of diet (P≤0.01) was observed in the recovery of odd- chain n-alkanes. The faecal concentration of dosed alkanes reached equilibrium 3.30 days into the alkane dosing. On the assumption of similar faecal recovery of adjacent n-alkanes, intake was underestimated by 12% (P<0.001) when C 31 /C 33 and C 33 /C 32 alkane pairs were used and by only 1.5% (P≥0.42) when C 35 /C 36 was used. Correction for differences in the faecal recovery of adjacent n-alkanes considerably improved the intake prediction when C 31 /C 32 and C 33 /C 32 pairs were used. Digestibility of diets was accurately predicted using either C 36 as external marker or C 35 as internal marker corrected for incomplete recovery. The results showed that molasses-based boluses administered twice daily are suitable, and that knowledge of the faecal recovery rates of adjacent n-alkanes improves the reliability of the predictions. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The production performance of farm animals within their genetic limits depends on the level of intake and the quality of the diet ingested (Coleman and Moore, 2003). Accurate measurement of feed intake and digestibility are, in this respect, important to meet nutritional requirements of the animal and optimise production (Mayes and Dove, 2000). Feed intake, diet ∗ Corresponding author at: Animal Nutrition Group, Department of Animal Sciences, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands. E-mail address: derseh7@yahoo.com (M. Bezabih). 0377-8401/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.anifeedsci.2012.08.014