Utilization of the n-alkane marker technique to estimate dry matter intake and digestibility in grazing dairy cows

Studies were conducted to evaluate the potential use of the n-alkane marker technique as a tool to improve the nutrition of grazing animals. A grazing experiment consisting of two completely randomized trials was conducted to compare the n-alkane marker technique to the well-accepted Cr₂ O₃ marker technique for estimating dry matter intake and digestibility. Each trial had 15 primaparous Holstein lactating cows that were randomly allocated to one of three dietary treatment groups, with concentrate fed at 20% (L), 35% (M) or 50% (H) of pre-trial total dry matter intake (DMI). Cows grazed a primarily orchardgrass (Dactylis glomerata L.) pasture and were moved to a new section of pasture daily. Indigestible faecal markers, Cr₂O₃ and n-alkane (C₃₂ and C₃₆) controlled-release capsules were placed into the cow's reticulo-rumen by oral administration. Three Jersey steers were fed freshly cut forage from the same pasture to establish in vivo n-alkane recovery rates. An in vitro method to determine n-alkane recovery rates was tested and results were compared with the actual in vivo n-alkane recovery rates. (Abstract shortened by UMI.)...