EFFECTS OF INOCULANT TREATMENT ON SILAGE FERMENTATION, DIGESTIBILITY AND INTAKE BY GROWING CATTLE

A changeover design experiment involving thirtysix 3-month-old Friesian male calves (mean initial live weight 127 kg) was carried out to evaluate a bacterial inoculant based on a single strain of Lactobacillus plantarum (Ecosyl, ICI) as a silage additive. On 25-31 August 1988, nine silages were harvested using double-chop forage harvesters from the second regrowth of three swards, namely permanent pasture which had received 100 kg N ha-1 and perennial ryegrass which had received either 100 or 150 kg N ha-1. Herbages (mean DM and WSC concentrations 144 and 11.2 g kg-1 respectively) from each sward were treated with either no additive, formic acid (2.4 l t-1) or the inoculant (3.3 1 t-1) and were ensiled in 126 silos of 0.8 t capacity. The only effects of the inoculant on chemical composition of the silages were a decrease in modified acid detergent fibre and an increase in endotoxin and crude and true protein concentrations. Silages were offered ad libitum and supplemented with 1.0 kg of concentrates per head daily for three periods each of 3 weeks in a partially balanced changeover design experiment. Digestibilities of the total diets were determined at the end of the experiment. For the untreated, formic acid-treated and inoculant-treated silages, silage dry matter intakes were respectively 3.58, 3.66 and 3.67 (s.e. 0.044) kg d-1, estimated metabolizable energy (ME) intakes were 46.1, 46.7 and 47.1 (s.e. 0.44) MJ d-1, energy digestibilities were 0.727, 0.727 and 0.738 (s.e. 0.0046) and organic matter digestibilities were 0.770, 0.771 and 0.788 (s.e. 0.0042). Rumen degradabilities of the silages were determined using two rumen-fistulated cows. Mean dry matter and nitrogen degradabilities for the control, formic acid-treated and inoculant-treated silages, assuming an outflow rate of 0.05 h-1, were 10.508, 0.49, 0.491 and 0.702, 0.676 and 0.729. It is concluded that the inoculant significantly increased the digestibility of the silages but did not affect dry matter or ME intake.