Willow browse blocks for drought protection and for sustainable management of internal parasites

Abstract

Browse blocks were developed on wet rush-infested areas of Riverside Farm, near Masterton, by planting 6,000 willow stakes/ha over the winter periods of 2000, 2001 and 2002. This was followed by light grazing in the first year after planting and then more intensive grazing in later years. After 18 months the areas dried out, due to evapotranspiration from the trees, and a herbage sward developed from volunteer species. The quality of the herbage progressively improved over a 4 year period and the browse blocks now support year-round grazing by sheep. In Experiment 1, ewes that grazed willow browse blocks for 86 days in 2004 (including mating) had higher reproductive performance than ewes that were mated on short, drought affected pasture. However, reproductive performance was lower than that from ewes mated on a sole diet of long herbage similar to that growing in the browse blocks. It was calculated that 15 and 65% of the metabolisable energy and condensed tannins consumed by ewes grazing browse blocks was provided by willow trees. In Experiment 2, undrenched lambs grazing either control pasture or browse blocks for 98 days in 2005 had lower liveweight and carcass gains than lambs regularly drenched with anthelmintic. Lambs grazing browse blocks consistently had lower dag scores and undrenched lambs grazing on browse blocks had reduced worm burdens of some economically important internal parasites compared with undrenched lambs grazing pasture. It was concluded that the benefits of browse blocks could be due to both direct and indirect effects and that any benefits in internal parasite management may be accompanied by reduced rates of carcass growth. Guidelines are presented for the grazing management of willow browse blocks over a complete 12 month period. Keywords: willow (Salix), fodder tree, drought, internal parasites.