Estimating forage intake and quality in grazing cattle: a reconsideration of the hand-plucking method.

Abstract

The hand-plucking method for estimation of bite size and nutritive quality was tested for steers grazing at low stocking rates on heathland and in riverine grassland. Vegetation height, standing crop, and cover of distinct plant categories were determined in 13 sampling periods over 2 years. In each period bite size was estimated with 4 esophageally fistulated steers. Bite counts on different plant categories were made during sampling. The plant categories were sampled separately by hand-plucking and weighed to determine plucking size. Extrusa and hand-plucked samples were analyzed for concentrations of nitrogen and calcium. Vegetation height was a more accurate predictor of plucking size than standing crop. A curvilinear relationship was derived between plucking size and bite size. The nutritive quality of extrusa and hand-plucked samples was not significantly different. It is concluded that the application of the hand-plucking method appears successful when a stratified sampling approach to hand-plucking is followed. Future studies should examine operator-biases and how these can be minimized.