The utilization of Hyparrhenia veld for the nutrition of cattle in the dry season III. Studies on the digestibility of the produce of mature veld and veld hay, and the effect of feeding supplementary protein and urea

Abstract

Indigenous (Bos indicus) oxen fed ad lib. were used to measure the changes in the apparent digestibility of mature Hyparrhenia veld during the dry season, and also the apparent digestibility of late-cut veld hay and nitrogen-fertilized veld hay. The forages were those used in a field trial, and the present results complement previous work.1. Mature Hyparrhenia veld harvested at the end of the rains as veld hay or green forage, contains approximately 50% digestible o.m. and 0·6% digestible c.p. The low level of approx. 3% c.p. resulted in a low apparent c.p. digestibility and consequent protein deficiency.2. The nutritive value of the mature Hyparrhenia grassland as ‘standing hay’ progressively dropped to 38% digestible o.m. and negative c.p. digestibility by mid-dry-season in July.3. There was an accompanying decline in voluntary intake of forage from approximately 12 lb. d.m./1000 lb. animal/day at the end of the rains to 8 lb. d.m./1000 lb. animal/day in mid dry season.4. The seasonal drop in digestibility values is accentuated by the drop in dry-matter intake so that a diet of mature veld herbage in mid dry season is grossly deficient in both energy and protein.5. The feeding of supplementary protein or urea resulted in a 40–60% increase in the intake of mature Hyparrhenia forage. Urea and groundnut meal were of equal value in their effect on herbage intake at the level of feeding used in this trial.6. The main factor limiting the utilization of the mature Hyparrhenia veld appears to be a dietary protein deficiency. Increasing the dietary protein level, either by using nitrogen fertilizers to raise the herbage crude protein, per cent, or by supplementary feeding of protein or urea, not only relieved the dietary protein deficiency, but, due to the resultant increase in forage intake, also corrected the deficiency in dietary energy. The nutritive value of mature Hyparrhenia forage was thus raised from a submaintenance to a supra-maintenance level.