- In part one, levels of dehydrated alfalfa meal greater than 60% of the diet significantly (P < 0.01) reduced the growth of rats fed isocaloric diets. Purified cellulose fed to provide the same amount of acid detergent fiber as contributed by the alfalfa did not affect growth. Feed intake was reduced at high alfalfa levels, indicating that palatability, rather than fiber level, was the factor responsible for reduced performance. In experiment two, the avoidance of heat during drying of alfalfa meal, through the use of freeze drying, resulted in improved growth and feed conversion. The results are consistent with the hypothesis that during conventional drying methods, bitter compounds are formed. No difference in crude protein, dry matter, or acid detergent fiber digestibility was found with oven dried (95°) compared to freeze dried alfalfa meal. In part two, five experiments with rats and one with Japanese Quail were conducted to evaluate a commercially prepared alfalfa protein concentrate (APC) as a protein supplement. It was found to contain 36% crude protein with 5. 5 g lysine and 2. 5 g methionine plus cystine per 100 g amino acids. Levels of up to 20% APC did not decrease performance of rats; APC as the sole protein source gave poor results. The Protein Efficiency Ratio (PER) of APC was significantly lower (P < 0.01) than those for herring meal, casein, or soybean meal (1. 23, 2. 82, 2. 67, and 2.54 respectively). Upon supplementation with lysine and methionine the PER was significantly increased (P < 0. 01) to 2. 54. Lys ine was the first-limiting amino acid; methionine was also deficient. With rats the crude protein digestibility was 65% for APC, which was significantly lower (P < 0.01) than for soybean meal (88%). The low digestibility of APC protein contrasts with other reported values of about 80%. The availability of lysine in APC was determined by using a bioassay with both rats and Japanese Quail. Low protein basal diets were used. To the basal diets the lysine references (casein for rats, lysine HCl for the quail) and APC were added as the lysine sources. The results were extrapolated from a graph of reference values using g gain vs. g lysine consumed. The availability of lysine was found to be about 80% for rats when compared to casein and about 86% for quail when compared to lysine HC1. In part three, three swine studies were conducted. APC gave excellent results when used in grower-finisher rations. Carcass evaluation showed no significant differences; however, there was a trend towards lower market grades with higher dietary APC levels. With young growing swine (18 kg to 47 kg), gains with 20% APC were significantly lower (P < 0. 05) than for the controls. In creep-starter rations, APC fed at levels of 6. 5 and 13% gave good results. Levels of 14, 28, and 34% which provided 29, 58, and 70% of the total dietary crude protein, significantly reduced growth (P < 0.05) in one trial but not another. In all tests with starter rations the feed conversion increased for the APC rations. The experiments with swine indicate that the APC may be better utilized by growing-finishing swine than by younger animals. The growth performance indicates the APC can be a useful protein supplement for all classes of growing swine.