Effect of dosing regime on intake estimation using then-alkane technique in sheep fed pelleted grass meal

Abstract

An experiment was carried out to evaluate the n-alkane technique for estimating the voluntary intake of pelleted grass meal by sheep. Two groups of 12 Scottish Blackface sheep were dosed once daily or twice daily with paper pellets containing 130 mg of C32 alkane. Mean daily intakes over a 5 day period were estimated from n-alkane concentrations in faeces and compared with actual intakes measured by weighing of food. Two faecal sampling frequencies were compared (once or twice daily) at each dosing frequency. Diurnal patterns of intake were determined by weighing food residues every 3 h for 4 days. Diurnal patterns of faecal n-alkane concentration were determined from rectal grab samples collected every 3 h for 2 days. There was no effect of dosing frequency on actual intake. Estimated intake was higher for twice-daily than once-daily dosed animals when twice-daily faecal sampling was employed (P < 0.05), although differences between mean actual and estimated intakes were not significant. The accuracy of estimation of individual intakes was better for sheep dosed once daily, at both faecal sampling frequencies, than for sheep dosed twice daily. This may have been due to diurnal variation in food intake and digesta outflow from the rumen, demonstrating the importance of matching n-alkane dosing and sampling regimes to the digesta kinetics of the diet fed. © 2000 Society of Chemical Industry