The effect of increasing the acidity or osmolality of grass silage by the addition of free or partially neutralised lactic acid on silage intake by sheep and upon osmolality and acid-base balance

A well fermented grass silage was mixed with 9·3 g lactic acid per kg silage supplied either as the free acid (lactic acid) or partially neutralized to pH 5·2 with sodium hydroxide (sodium lactate) to give three dietary treatments. Treatment with lactic acid reduced silage pH (P H to 4·15 and osmolality (P Wlien fed in a randomized-block design to either six intact lambs or to four rumen fistulated sheep lactic acid treatment reduced (P 0·75 ) from 34·7 to 27·8 for intact sheep and from 35·5 to 29·9 for fistulated sheep. Intakes of the sodium lactate-treated silage tended to be higher (39·2, intact and 40·1, fistulated sheep, g/kg weight0·75) than the control silage. Silage DM intake was correlated more closely with neutralizing value (r 2 = 0·34) than p H (r z = 0·24). Treatment of silage with lactic acid or sodium lactate did not change rumen p H , volatile fatty acid patterns or osmolality. Blood p H , pCO 2 and bicarbonate concentrations were not changed by the diets offered and were within normal ranges. Urine acid-base balance was not affected by lactic acid treatment whereas urine pH, and bicarbonate and sodium excretion were (P