Composition, digestibility and rumen degradability of crab meal

Abstract

The nutritive value of dried shellfish waste (referred to as crab meal) produced in New Brunswick in the mid-1980s was evaluated by physical, chemical and biological assays. Typically the crab meal was high in ash content (about 50%), consisting mainly of calcium carbonate and contained about 20% chitin, 25% crude protein (CP) and less than 2% lipid material. The meal could be separated by screening into a coarse fraction high in ash and chitin and a fine fraction lower in ash and higher in CP. Although the reactivity rate of crab meal ash was not as high as that of similar sized limestone particles (42 vs. 30.4 min for particles that passed a 500-μm screen but were retained on a 300-μm screen), it was high enough to suggest crab meal could be a useful rumen buffer. The CP of crab meal was highly resistant to degradation in the rumen in sacco. Less than 18% of the crab meal CP disappeared from bags suspended in the rumen for 24 h, compared with more than 87% for soybean meal and full-fat canola seed. The digestibility of crab meal dry matter by sheep was only 34.3 ± 3.7%, but the CP digestibility was 69.6 ± 4.1%. The chemical and physical attributes assayed and the results of the in sacco and sheep digestibility trials all suggest that crab meal should be a useful supplement for diets low in digestible undergraded protein. However its inclusion in a supplement for beef calves fed legume silage resulted in lower feed consumption and rate of gain (P < 0.01). Feeding soybean meal or full-fat canola resulted in a significant increase (P < 0.01) in feed efficiency, compared with calves fed the control and crab meal supplements. It was concluded that crab meal produced in New Brunswick would be a useful supplement for beef cattle if problems of palatability could be overcome. Key words: Crab meal, rumen degradability, digestibility, protein, palatability