Estimation of faecal output, digestibility, and intake using a controlled release capsule of alkanes in early and late lactation dairy cows fed two levels of concentrate

Abstract

Thirty-two dairy cows (663 ± 70; kg of BW ± SD) were allotted to a 2 × 2 factorial arrangement of treatments to evaluate the controlled release alkane capsule (CRC; C32 and C36) to estimate digestibility and dry matter (DM) intake in early and late lactation for diets based on low (LC, 30%) or high (HC, 60%) proportions of concentrate. Cows were dosed orally with a CRC into the rumen and digestibility was measured by total collection and estimated from the ratios of alkanes in the diet and faeces. Recoveries of endogenous (C31 and C33) and exogenous (C32 and C36) alkanes were higher and lower, respectively, for LC compared with HC. The effects of diet and the interaction between diet and lactation stage were well estimated (P < 0.05) when measured released rates of C32 and C36 were used to estimate DM digestibility although estimation with both alkanes indicated an effect of lactation stage, which was not observed when using data of measured DM digestibility. The faecal ratio of C31/C32 or C33/C32 showed no diet effect on DM intake estimation while measured DM intake was 22.6% higher for cows fed HC than for those fed LC. In conclusion, estimation of DM intake was inadequate although digestibility of DM was estimated from alkanes contained in the CRC. Key words: Dairy cows, alkane, intake