RELATIONSHIP OF FORAGE MATURITY TO DIGESTIBILITY AND ANIMAL GAIN WHEN SILAGE IS UNTREATED OR TREATED WITH FORMIC ACID

Abstract

Four crops were compared as unwilted silage for beef cattle weight gain: (a) grass harvested 10 June, vegetative stage, yield 3.29 tonnes/ha (T/ha) of 74% digestible dry matter (DM) (in vitro); (b) similar grass, harvested 20 June, early head, yield 4.46 T/ha of 66% digestible DM; (c) similar grass, harvested 10 July, bloom stage, yield 5.96 T/ha of 56% digestible DM; (d) alfalfa–bromegrass, harvested 23 June, early head–full bud, yield 4.94 (T/ha) of 64% digestible DM. Formic acid (4.5 liters/T) was applied to the forage stored in the bottom half of each of the four upright silos. The apparent digestibilities of the DM as determined with sheep for the four untreated silages were: (a) 74.4, (b) 64.7, (c) 55.2, and (d) 61.3%. Yearling steers fed the silages as the sole ration gained (a) 1.25, (b) 1.07, (c) 0.40 and (d) 0.72 kg/day; when supplemented with 1 kg barley/day, gains were (a) 1.24, (b) 1.17, (c) 0.51 and (d) 1.04 kg/day. The formic-acid-treated silage produced animal gains of (a) 1.17, (b) 1.06, (c) 0.78, and (d) 0.96 kg/day; when supplemented with 1 kg barley/day gains were (a) 1.31, (b) 1.08, (c) 0.79, (d) 1.06 kg/day. The greatest weight of beef cattle gain per tonne of DM was obtained with the (a) crop, but beef production per hectare was greatest from the grass crop harvested at the early head (b) stage of development. It was concluded that the production of over 1 tonne of beef gain per hectare per season is possible from a temperate climate grass crop, harvested in the vegetative stage of development.