THE EFFECT OF INCREASING THE ACIDITY OR OSMOLALITY OF GRASS-SILAGE BYTHE ADDITION OF FREE OR PARTIALLY NEUTRALIZED 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 neu tralized to pH 5.2 with sodium hydroxide (sodium lactate) to give thre e dietary treatments. Treatment with lactic acid reduced silage pH (P < 0.05) from 4.03 to 3.80 and increased (P < 0.01) the amount of sodiu m hydroxide required to raise silage pH to 6.5 (neutralizing value) fr om 167 to 261 mmol/kg silage and osmolality (P < 0.01) from 712 to 854 mosmol/kg silage; sodium lactate treatment increased (P < 0.05) silag e pH to 4.15 and osmolality (P < 0.01) to 964 mosmol/kg silage but did not change neutralizing value. When fed in a randomized-block design to either six intact lambs or to four rumen fistulated sheep lactic ac id treatment reduced (P < 0.05) silage dry matter (DM) intake (g/kg we ight(0.75)) from 34.7 to 27.8 for intact sheep and from 35.5 to 29.9 f or fistulated sheep. Intakes of the sodium lactate-treated silage tend ed to be higher (39.2, intact and 40.1, fistulated sheep, g/kg weight( 0.75)) than the control silage. Silage DM intake was correlated move c losely with neutralizing value (r(2) = 0.34) than pH (r(2) = 0.24). Tr eatment of silage with lactic acid or sodium lactate did not change ru men pH, volatile fatty acid patterns or osmolality. Blood pH, pCO(2) a nd bicarbonate concentrations were not changed by the diets offered an d 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 < 0.01) increased by sodium lactate treatment of the silage.