RESPONSES OF RATS AND SWINE TO ALFALFA SAPONINS

Abstract

Leaf meal from Ranger alfalfa selected for low saponin content and from unselected Ranger alfalfa was fed to rats as a protein supplement to corn. Average daily gains of rats fed either leaf meal type did not differ, but gains of alfalfa-fed rats were lower (P < 0.01) than those for rats fed soybean meal or cottonseed meal. There were no differences in apparent digestibility by rats of crude protein or ether extract from either alfalfa type; values were about 64% for crude protein and 84% for ether extract. Alfalfa saponin was compared to quinine sulfate (a bitter compound) in a feed preference trial with rats. In two-choice feed preference tests, the control diet was preferred over the quinine-containing diets at levels of dietary quinine sulfate ranging from 0.001 to 0.1%. Similarly, the control diet was preferred over alfalfa saponin-containing diets at saponin levels above 0.8%. In an experiment with growing pigs, low saponin (1.01%), unselected (1.91%) and high saponin (2.80%) alfalfa meals were fed at levels of 20 and 40% of the diets. At the 40% level, average daily gains were greater with low saponin than with high saponin alfalfa. Correlations between saponin levels were linear and positive (P < 0.01) for feed efficiency and linear and negative (P < 0.01) for average daily gains. When fed at 40% of the diet, the low saponin alfalfa gave results equivalent to unselected alfalfa fed at 20%, but all alfalfa treatments produced gains that were lower (P < 0.05) than for the soybean meal.