Chitinous products were investigated by in vivo rumen fermentation. Samples of cockroaches, grasshoppers, shrimp shells, crabmeal, and purified chitin were placed in the rumen of fistulated steers. Average rumen solubility (weight loss from a nylon bag) of 66.5. 32.0, 17.4, 35.7, and 21.5%, respectively, were observed. Measurements of water solubility in a non-rumen system indicated that the rumen system was solubilizing 8, 7, and 12% of cockroaches, grasshoppers, and crabmeal, respectively, over that in water. A feeding trial was conducted where crabmeal was evaluated at 0, 10, and 20% of a basal diet. The experiment was conducted by using six ruminating calves in two replications of a 3 x 3 Latin square design. In each 4-week period, nitrogen balance data was collected during the third week. Crabmeal nutritive value was established. It substituted equally for base ration at the levels studied. No treatment differences were detected for gain, feed intake, absorbed and retained nitrogen, dry matter, or crude fiber digestibility (P<.05). In a second feeding trial using a 2 x 2 Latin square design, a zero and 20% diet were fed to two groups of five ruminating calves for two time periods. Nitrogen balance data collected as in Trial I on two animals of each group, further established crabmeal nutritive value. There was no difference between groups for all performance parameters measured except that animals fed crabmeal had a lowered nitrogen retention (P<.05). Chitin digestion in Trial I averaged 58 ± 19% and 69 ± 22% for 10 and 20% crabmeal diets, respectively; for Trial II, chitin digestion averaged 72 ± 12%. In in vitro incubations of purified chitin and insect skins in strained rumen fluid for three hours, there was no apparent deacetylation of chitin beyond that observed in positive and negative control samples. / Ph. D.