The effect of grazing severity during winter on herbage regrowth and quality

Abstract

Grazing management is concerned with managing the interactions between plants and animals. Two management factors that require consideration are the optimal grazing time and the effect of grazing severity on subsequent regrowth. The objective of the current study was to quantify the effect of grazing severity in winter on leaf appearance r ate , herbage accumulation and quality, and plant energy r eserves. Ten pasture areas were grazed to two different residual masses (1260 ± 101 and 1868 ± 139 kg dry matter (DM)/ha, Severe and Lax, respectively) over five consecutive days by dry dairy cows. Neither growth rate (average 15 kg DM/ha/day), nor leaf appearance rate (average 16 days/new leaf) differed between treatments. As a result, herbage accumulated over the 49-day regrowth period was similar between grazing treatments (736 and 715 kg DM/ha for Severe and Lax, respectively), although herbage mass when three new leaves had emerged on regrowing tillers (third leaf stage) was greater on the laxly grazed treatment. Perennial ryegrass plants defoliated more severely displayed a trend for lower levels of water-soluble carbohydrates (WSC) than plants defoliated more laxly, but this difference had disappeared by the third leaf stage of regrowth. Pasture quality was improved in the severely defoliated treatment, with higher digestibility, WSC and metabolisable energy (ME) concentrations, and (ADF) lower acid and neutral detergent fibre (NDF) concentrations. Keywords: grazing sever ity, herbage production, water-soluble carbohydrates