Nutritive value of forage shrubs: Bituminaria bituminosa, Rumex lunaria, Acacia salicina, Cassia sturtii and Adenocorpus foliosus

Abstract

The nutritive value of three forage shrubs endemic from Canary Islands (Bituminaria bituminosa, Rumex lunaria, Adenocorpus foliosus) and two introduced shrubs (Acacia salicina, Cassia sturtii) was studied along the year. Mean organic matter, neutral detergent fibre and protein content (g kg(-1) dry matter (DM)) of four cuts along the year was, respectively, 910, 424 and 184 for B. bituminosa, 865, 329 and 149 for R. lunaria, 955, 452 and 159 for A. foliosus, 879, 412 and 123 for A. salicina, 937, 390 and 102 for C. sturtii. Mean calcium content (kg(-1) DM) was the highest for A. salicina (25.1 g), the lowest for A. foliosus (3.2 g), and moderate for the others (range 10.4-14.3 g). Mean phosphorus content of shrubs ranged 1.5-2.8 g kg(-1) DM. Mean tannin content (g catequins kg(-1) DM) was the highest for C. sturtii and R. lunaria (0.63 and 0.54 g, respectively) and moderate for A. salicina (0.24 g), while B. bituminosa and A. foliosus had only traces of tannins.Mean ruminal organic matter degradability, protein degradability and in vitro organic matter digestibility were, respectively, 57.5, 72.2 and 64.6% for B. bituminosa, 50.5, 57.0 and 56.2% for R. lunaria, 49.7, 55.4 and 59.6% for A. foliosus, 33.5, 30.4 and 37.4% for A. salicina, 53.5, 56.4 and 38.8% for C. sturtii. From these results, the net energy content of B. bituminosa, R. lunaria, A. foliosus, A. salicina and C. sturtii was estimated to be, respectively, 5.6, 4.7, 5.4, 3.2 and 3.3 MJ kg(-1) DM, with significant differences among species and seasons.