No abstract

The object of this series of investigations is to secure detailed information concerning the composition, digestibility and nutritive value of pasture herbage in its different stages of growth. The results which were obtained in these respects by cutting the herbage of the experimental pasture plot at weekly, fortnightly and 3-weekly intervals have been described in previous communications. During the seasons of the present investigations (1929 and 1930), the trials have been carried a stage further by the adoption of a system of cutting at monthly intervals. The results, therefore, are invested with special significance, in that a period of four weeks has been tentatively adopted in this country as the interval which is allowed to lapse, in rotational grazing practice, between successive grazings of pasture enclosures.

The main conclusions from the present investigation, which was undertaken in order to obtain an insight into the consequences of the adoption of a 5-weekly rotational close-grazing system, may be summarized as follows:The lengthening of the interval between successive cuts from a month to 5 weeks leads to a definite, though not very serious, reduction in the digestibility of the herbage. This reduction is most noticeable during the flush period of growth, and the constituent most affected is the crude protein. During the fore-flush and post-flush periods, it appears to be immaterial, from the standpoint of digestibility, whether a system of monthly or 5-weekly cutting is adopted. The falling off in digestibility is not connected with the onset of lignification in the herbage, since the digestion coefficient of the fibrous constituent remains high throughout the season, and it may be concluded that, during a season of favourable rainfall, it is possible by cutting (or close-grazing) at intervals of 5 weeks, to prevent the herbage from becoming lignified and of greatly reduced digestibility. The possibility, however, during seasons of a droughty character, of a premature onset of lignification under a system of cutting (or close-grazing) at 5-weekly intervals is discussed.

The present communication is the second contribution to the study of the nutritive characters of the lucerne crop. It deals with investigations that are the outcome of certain preliminary trials carried out in the 1932 season and reported on in an earlier communication(1). The primary object of the present trials was to investigate the composition, digestibility and nutritive value of the first, second and third growths of lucerne under conditions of systematic cutting at the stages of (1) bud and (2) flower. A determination of the digestibility and nutritive value of lucerne in its pre-budding stage of growth was also made. In addition, account has been kept of the effect of cutting lucerne systematically at certain definite stages of growth, namely, pre-budding, budding and flowering, on the yields per acre of dry matter, starch equivalent and digestible protein, and on the health and vigour of the crop.

The object of this series of investigations is to secure detailed information concerning the composition, digestibility and nutritive value of pasture grass in its different stages of growth. The results which were obtained in these respects by cutting the herbage of the experimental pasture plot at weekly and at fortnightly intervals have been described in previous communications. During the season of the present experiment, the trials have been carried a stage further by the adoption of a system of cutting at 3-weekly intervals. The main findings of the 1928 investigation are recorded below:(1) Chemical composition of 3-weekly pasture cuts: The adoption of a more lenient system of cutting at 3-weekly intervals led to a slight lowering of the percentage of crude protein in the grass and a slight raising of the percentages of crude fibre and N-free extractives. On the other hand, no corresponding effect was noted in respect of the ether extract, SiO2-free ash, lime and phosphate, the percentages of these constituents being very similar in the weekly and 3-weekly pasture samples obtained in 1928. The falling off of the percentage of crude protein in the 1928 3-weekly-mown herbage, as compared with the weekly and fortnightly-mown herbage of 1925 and 1927 respectively, was not wholly the consequence of the more lenient system of cutting, but was also due in part to the protein-depressing influence of the droughty periods which were experienced in the 1928 season.