Nutritional evaluation of cardoon (Cynara cardunculus) seed for ruminants

Chemical composition, rumen degradability, and digestibility coefficients of whole cardoon (Cynara cardunculus L.) seed were studied on two different samples. Ruminal degradability of whole seed was determined by using the nylon bag technique in three rumen fistulated wethers. Four wethers were used to perform digestibility studies on a basal diet (0.5 hay and 0.5 concentrate) and three diets more where cardoon seed was included at rates of 0.1, 0.2, and 0.3 at the expense of the basal diet in a 4 x 4 Latin-square design. Additionally, the effects of three substitution rates (0, 0.1, and 0.25) on rumen fermentation patterns and fibrolytic activity, measured by the in sacco degradation of the lucerne hay included in the diets, were established using a 3 x 3 Latin-square design with three rumen fistulated wethers. Crude protein (CP), ether extract (EE) and neutral detergent fibre (NDF) contents of whole cardoon seed were 225, 250, and 338 g kg(-1) DM, respectively, the last being highly lignified (acid detergent lignin (ADF) = 104 g kg(-1) DM) as consequence of its high hull proportion (45%). Rumen DM degradability of whole seed was 56.8%, while CP degradability was 82.9%. Diet digestibility coefficients were maximum for 8.1 substitution rate, except for EE, that showed a linear and quadratic increase through all diets. The estimates of seed digestibility obtained by the substitution and extrapolation methods were only similar for the 0.3 substitution rate. Digestibility coefficients (%) obtained by substitution at this level were 83.8 for CP, 82.8 for EE, 20.3 for NDE 56.1 for OM, and 59.2 for energy. Seed inclusion in diets up to a 25% had not effect on rumen fermentation patterns or on ruminal fibrolytic activity, in spite of the high content of fat rich in unsaturated fatty acids (85.5% of total fatty acids) of this seed. (C) 2000 Elsevier Science B.V. All rights reserved.