A study of the grazing preference of sheep on developed and undeveloped grassland at a high-country site

Abstract

There are now some 57 million sheep and 9 million cattle in New Zealand (N.Z. Meat and Wool Bds Econom. Serv. 1974). For most of the year almost all of them graze pasture of mixed botanical composition. New Zealand has achieved fame for its enlightened advances in the science and practice of efficient grazing management of improved pasture. Surprisingly, in a land so concerned with the relationship between animals and plants, there has been almost no research into the dietary preference of domestic animals for particular plant species – information which would seem to be fundamental to any assessment of the value of mixed swards in animal nutrition.

In fact the only published New Zealand work on this subject has been by three authors – L. Cockayne, J. M. Hercus, and Barbara H. Hercus (nee Croker) – all of whom did their major work in essentially unimproved montane tussock grassland. Of these authors, Cockayne (1919, 1920a, 1920b, 1926) recorded the plants which he observed sheep grazing and J. M. Hercus (1961, 1963) noted the degree of grazing of species in randomly-located ring quadrats. Only Croker (1959, Hercus 1960) attempted to estimate the diet of sheep from remnants of their ingesta and to translate it into quantitative terms.

That these studies of preference should have been focussed on sheep grazing tussock grasslands is, however, appropriate. Coop (1952) pointed out that while on lowland topdressable country cattle and sheep eat practically everything that grows, it is possibly only by practising selection that they manage to produce and reproduce at the level they do on the very poor quality pasture of the South Island hill and high country.