Maize as a summer supplement in dairy cattle feeding

In the early stages of growth grass is an energy rich food of high digestibility, but as growth advances towards the hay stage the protein content falls and the fibre content increases, thus reducing the feeding value. Supplementary feeds in the form of cereals or as green forage provide additional nutrients at this stage. In New Zealand farmers rely almost solely on pasture herbage as food for sheep and cattle. The growing of special forage crops as green feed is gradually declining because of improved pasture position brought about by the use of better strains of grasses and clovers which are productive throughout the year. However, very considerable seasonal fluctuations in pasture production still occur in New Zealand and the growing of supplementary green feed will contribute to the complete utilization of the pasture. As it is well established that a major portion of the difference in milk production is because of environmental variation, particularly feeding, this situation is aggravated more in summer. The main reason is non-availability of readily available energy for production. Maize growing in New Zealand has been confined mostly in some districts of North Island where the climate is most suitable for the purpose. Milk production is well maintained on the green succulent, leafy stalks. Yields of 35 tons per acre of green material have been achieved even in Canterbury (Davies 1961). The object of this experiment was to see the effect of additional green maize supplements on production of milk, butter fat and S.N.F. P.C. In doing this it is important to know the quantity of useful energy consumed by the animal. This will be determined by the daily dry matter consumption and the proportion of that dry matter available as nutrients to the animal; the simplest measure of the latter is the percentage of the herbage dry matter which is digested. Accurate methods of measuring both feed intake and herbage feeding value are available for indoor animals, but for Field experiment as in case of New Zealand grassland farming systems indirect methods have to be adopted. During the last few years many techniques have been proposed and the literature on that subject is voluminous. Considerable attention has been given at Ruakura Agricultural Research Centre, Hamilton, to the development of methods measuring the pasture intake of free-grazing dairy cows by an indirect method, depending on estimating first the faeces output and accordingly the 'intake factor' or 'feed to faeces ratio' for the feed from which the faeces was derived. The literature on the estimation of digestibility faecal output and feed consumption has therefore, been reviewed in Part A and Part B will deal with green feed supplements.