Forage quality of leaf fodder from the main woody species in Iceland and its potential use for livestock in the past and present

Abstract

Woody species played, and in many Nordic regions still play, a very important role in livestock feeding. However, forage quality (contents of macroelements and fibre fractions) of the leaves of common woody species is often inadequate. The aim of our study was to determine forage quality of leaves of Betula nana, Betula pubescens, Salix lanata, Salix phylicifolia and Sorbus aucuparia from Iceland and to compare it with the forage quality of the common native grass Deschampsia cespitosa and the introduced grass Alopecurus pratensis used by contemporary Icelandic farmers for forage production. Samples were collected at four localities in Iceland in late June 2013 and analysed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), neutral and acid-detergent fibre and lignin concentration. Analyses were compared with the optimum range for cattle and sheep nutrition. The nutritive value of leaves of the Icelandic woody species was relatively high, and analysis showed their nutritive content satisfied both cattle and sheep nutrient requirements for N, P, K, Ca and Mg, but the relatively high content of indigestible lignin in all woody species could cause problems for livestock metabolism. Grasses were characterized by lower P, Ca and Mg, but substantially higher K concentrations, and higher N:P and K:(Mg + Ca) ratios. The forage quality of leaves of woody species increased in the order B. nana < B. pubescens < S. phylicifolia < S. Aucuparia < S. lanata. Results are discussed in relation to use of leaf fodder in the past, when woody species, particularly Salix spp., are likely to have played an important role in livestock feeding.