The growth and nutritive value of autumn-saved pasture

Abstract

New Zealand’s economy depends mainly upon a primary production in which quality is kept high and costs low. To achieve the latter, along with maximum animal production, stocking must be at a rate proportional to the pasture growth at any one time (Eyles 1957). Also there must be as much natural grazing as possible. From a survey of farms in the United Kingdom (Davies 1957), farmers are realising this principle and are, with the aid of various practices, now grazing animals for a greater portion or the year than they previously had been doing.

Because winter is a period of reduced pasture growth it is necessary to fill the gap in food supply as efficiently as possible. The techniques available are, supplementary feeding including hay and silage, specially sown forage crops, bought in concentrates and the extension of the natural grazing season through the use or autumn-saved pasture. This practice is influenced by the plant species and the cultural practices imposed on them such as the use of nitrogen fertilizers and pest and disease reduction. Autumn-saved pasture is accomplished by removing the stock from an area in the autumn so allowing herbage to grow and stand from that time until used later on. The nutritive value of such pasture bas long been recognised both in the United Kingdom (Griffith and Hutton 1935, 1936) and New Zealand (Riddett 1938).

It is desirable that stock produce their young just prior to the spring flush of pasture growth. Wallace (1955) suggests feeding this saved pasture at late pregnancy and early lactation after feeding the hay and silage when these pastures were closed. By so doing, maximum use is made of the high nutritive value of the autumn-saved pasture at a time when most needed. This also reduces the incidence of metabolic disorders that are prevalent at this time of the year.

Essentially the whole problem revolves around the fact that pasture growth is the inelastic component of the animal pasture complex, with the animals’ demands being relatively elastic. As stated by Clarke (1959), both the animals and the pastures can stand a certain amount of abuse. Good management is avoidance of over-abuse of either of these components.

Some evaluation of autumn-saved pasture has been made in the North Island by using dairy cows (Mcllroy and Bartrum 1940, 1941), but a comparable study with any class of livestock is completely lacking from the cooler South Island. The work described in this thesis is an attempt to make such a study a using sheep as the experimental animals.