THE EFFECT OF FORMIC-ACID, SULFURIC-ACID AND A BACTERIAL INOCULANT ON SILAGE FERMENTATION AND THE FOOD-INTAKE AND MILK-PRODUCTION OF LACTATING DAIRY-COWS

Herbage from first and second regrowths of perennial ryegrass based swards was directly ensiled following treatment with formic acid (850 g/kg) at 2.53 and 2.58 l/t, sulphuric acid (45% w/w) at 3.09 and 3.04 l/t, an inoculant of Lactobacillus plantarum (Kickstart, United Distillers Ltd) at 2.24 and 2.14 l/t, or no additive (control). First regrowth herbage had mean dry matter (DM) and water-soluble carbohydrate concentrations of 168 and 27-0 g/kg fresh weight with comparable values for second regrowth herbage of 164 and 16.9 g/kg respectively. All silages preserved well, although both the rate and extent of fermentation, as indicated by pH and lactic acid levels, were greater in control and inoculant-treated silages. Additive treatment had little effect on nutrient recovery following ensilage with the exception of a slightly greater recovery of both DM and energy with inoculant treated, second regrowth material. The silages were evaluated in two experiments, with 9 and 4 week periods for first and second regrowths respectively, using 48 British Friesian dairy cows. Animals were housed in individual stalls and, in addition to the treatment silages, received 5 kg/day fresh weight of a supplement containing 197 g crude protein per kg DM. Treatment of first regrowth material with formic acid significantly increased silage DM intake (P < 0.01) with a smaller, though positive effect being obtained with inoculant treatment. Treatment with either formic acid or inoculant had no significant effect on DM intake with second regrowth material. In contrast sulphuric acid tended to depress intake of first regrowth material whereas a marginal increase in intake was obtained with second regrowth material. Inoculant treatment had no significant effect on milk yield with either first or second regrowth material, although there was a tendency for small, though consistent, increases in milk fat and protein concentrations. Formic acid treatment resulted in marginal increases in fat plus protein yield whereas effects of sulphuric acid were less consistent with animal performance being decreased with first regrowth material and little effect observed with second regrowth material.