THE INFLUENCE OF AN INOCULANT ENZYME PREPARATION AS AN ADDITIVE FOR GRASS-SILAGE OFFERED IN COMBINATION WITH 3 LEVELS OF CONCENTRATE SUPPLEMENTATION ON PERFORMANCE OF LACTATING DAIRY-COWS

Three silages were prepared from the primary growth of a predominantly perennial ryegrass sward (dry matter (DM) 175 g/kg; crude protein 142 g/kg DM; water-soluble carbohydrates (WSC) 243 g/kg DM). Herbage was wilted for 24 h and then treated with either an inoculant/enzyme prepa ration (Lactobacillus plantarum, Streptococcus faecium and Pediococcus acidilactici), formic acid applied at 4.2 l/t (Add F, BP Chemicals) o r no additive. Time series analysis of laboratory silages revealed tha t different patterns of fermentation had been achieved: formic acid tr eatment resulted in high levels of residual WSC and low levels of lact ic acid, indicative of an inhibited fermentation, whilst treatment wit h the inoculant/enzyme preparation resulted in high levels of lactic a cid with a low level of residual sugars, as expected with an enhanced fermentation. Analysis of the material 'as fed' showed that losses in the WSC content of the formic acid-treated silage had occurred in the clamp. Secondary fermentation of lactic to acetic acid was apparent in the untreated silage, but not in the inoculant/enzyme-treated silage. Digestibility, as determined using Greyface wether lambs, was margina lly higher for both additive treatments when compared with the untreat ed silage. An evaluation of the silages for milk production was carrie d out at three levels of concentrate supplementation using 18 Ayrshire X British Friesian cows in a replicated 3 X 3 Latin-square design exp eriment. Treatment with formic acid resulted in significantly higher D M intakes, but this was not reflected in milk energy output. Cows offe red the inoculant/enzyme-treated silage partitioned energy away from m ilk production toward body tissue deposition (average milk yields 19.9 , 19.9 and 15.2 kg/day, and weight gain 0.26, 0.38 and 0.81 kg/day for the untreated, formic acid and inoculant/enzyme-treated silages respe ctively). The reason for this is not clear, but it is postulated that microbial capture of degraded nitrogen may have been impaired with the inoculant/enzyme-treated silage, resulting in an imbalance in metabol izable protein : metabolizable energy.