Evaluation of ruminal escape potential of crab meal and other protein supplements and influence of steam explosion of ruminal degradability of crab meal

Four experiments were conducted, three to study the value of crab meal and other protein supplements, and the other to explore the potential of steam explosion technique to improve the nutritive value of crab meal. In Expt. 1, 48 Angus x Hereford and Angus x Simmental steers (avg. BW, 223 kg) were used in a 126-d growth study. Diets were formulated to contain 10.5% CP and 63% TDN, DM basis. In each diet, one third of the N was supplied by the protein supplement. Steers were randomly allotted to the following six supplements: 1) soybean meal (SBM); 2) supplement based on industrial byproducts of both plant and animal origin (IPA); 3) experimental supplement based on byproducts of animal origin (ESA); 4) hydrolyzed supplement No. 3 (HESA); 5) commercial supplement (Pro-Lak®) based on animal protein (CS) and 6) crab meal (CM). There were no significant positive responses in performance and feed efficiency for any of the protein supplemented groups compared to SBM. There was a trend for a positive response in gain to feed for steers fed CS and IPA. Lower weight gain and gain:feed were recorded for the steers fed HESA supplement. Steers fed CM diet had numerically higher growth and gain:feed than those fed SBM.

In Expt. 2, two metabolism trials were conducted, each with 24 wether lambs (avg. BW, 25 kg). In addition to the six diets that were used for the growth trial, two other diets were used, a negative control (NC) with no supplemental N, and a diet supplemented with urea (U). The supplements supplied one third of the total dietary N. There were no differences in DM and OM digestibilities among the lambs fed the different protein supplements. Lower (P < .05) apparent absorption of N was recorded for the lambs fed the HESA and NC diets. There were no differences in ruminal fluid pH among the sheep fed different protein supplements. Sheep fed CM tended to have higher total VFA compared to other supplements. Highest (P < .05) ruminal NH₃ N and blood urea N were observed in lambs fed the U diet.

In Expt. 3, the ruminal degradability of DM and CP of crab meal and other protein supplements were estimated in situ, in a ruminally cannulated steer. The highest DM degradability was for SBM. The ruminal escape of protem was lowest (P < .05) for SBM (23.2%) and the highest (P < .05) for the ESA supplement (79.8%). The respective values for IPA, HESA, CS and CM were, 60.6, 67.3, 69.8, and 48.4%. The IVDMD of feather meal and blood meal combinations (ESA and HESA) were lowest (P < .05). The IVDMD of crab meal was 67%.

In Expt. 4, the potential of steam explosion technique to enhance the nutritive value of crab meal was explored. Crab meal was steam exploded in a batch steam explosion reactor at two levels of severities. Steam explosion decreased (P < .05) N content of crab meal by 20%, and did not improve DM degradability nor increase escape of CP. A 60% increase in chitin degradability, from 21.5 to 34.2% was observed for steam exploded CM. Steam explosion improved IVDMD of CM from 65.9% to 75.2%.

These studies illustrated that substituting other protein supplements used in this study for SBM did not elicit a significant positive response in steer performance. Crab meal is comparable to SBM or other commercial products as a protein supplement for steers. Steam explosion does not seem to be a promising processing method for improving utilization of crab waste for ruminants.