Effect of dietary additions of hydrochloric and lactic acid on feed intake and metabolism of sheep and cattle

The effects of hydrochloric acid (HCl) and lactic acid on feed intake and metabolism of cattle and sheep were studied. The acids were added to a pelleted grassmeal control diet fed to five steers and five wethers in a double Latin-square design experiment. Each acid was given at two levels: lactic acid at 500 and 700 m mol/kg dry matter and HCl at 300 and 500 m mol/kg dry matter, giving dietary pH values of 4.2, 4.0, 4.4 and 3.8 respectively. Feed intake as a percentage of the control intake for cattle was 96.6, 93.4, 78.6 and 66.2 and for sheep 84.2, 86.7, 87.0 and 71.4 for the low and high levels of lactic acid and hydrochloric acid in that order. The interaction on feed intake between species and treatment was not significant (p > 0.05). Blood pH and plasma CO₂ concentration were depressed by the HCl treatments in both species, while lactic acid treatments did not affect blood pH, although plasma CO₂ concentration was lowered in sheep fed the high level of lactate. There were significant treatment effects on the molar percentages of rumen volatile fatty acids. The major effects were that lactic acid supplementation decreased the proportion of acetic acid in both cattle and sheep, increased the proportion of butyric and valeric acids in cattle, and increased the proportions of propionic and valeric acids in sheep.