Effect of different levels of cactus (Opuntia ficus-indica) inclusion on feed intake, digestibility and body weight gain in tef (Eragrostis tef) straw-based feeding of sheep

The study was conducted to determine the effect of different levels of cactus (Opuntia ficus-indica) inclusion on feed intake, diet apparent digestibility and live weight gain in tef (Eragrostis tef) straw-based feeding of sheep. A randomized complete block design was used to assign 24 male Highland sheep with initial live weight of 17.0 ± 3.9 kg (mean ± S.D.) in six replications to one of the four treatment feeds. The animals in T1 were offered 610 g tef straw on dry matter (DM) basis, and 57.6 g DM noug (Gouzotia abyssinica) seed cake, and those in T2, T3 and T4 were offered the same quantities of noug seed cake DM with replacement of one fourth, half and three fourths of tef straw DM with spineless cactus DM, respectively. The sheep were kept on the experimental feeds for 118 days. Spineless cactus and tef straw were offered separately to animals in two equal portions at 8:00 and 16:00 h. Common salt and fresh water were offered ad libitum throughout the experimental period.Spineless cactus had a high content of water (880 g/kg fresh weight), ash, especially calcium (45 g/kg DM), but the phosphorus concentration was 2.6 g/kg DM, making the ratio of calcium to phosphorus 17:1. The soluble carbohydrate of cactus was over 251 g/kg DM, whereas it was only 130 g/kg DM in the basal diet. The crude protein (CP) content of cactus (83 g/kg DM) was higher compared to that of the basal feed (76 g/kg DM). High contents of neutral detergent fiber (NDF) (705 g/kg DM) and acid detergent fiber (ADF) (386 g/kg DM) were determined in tef straw than in cactus that had NDF content of 392 g/kg DM and ADF content of 263 g/kg DM. Cactus was readily consumed and the animals preferred cactus to tef straw. The water intake was negatively correlated (r = −0.88) with cactus intake. Significant differences (P<0.05) were observed between treatments in daily live weight gain and the highest live weight gain (53 g/day) was recorded in sheep fed on T3, whereas the lowest live weight gain (23 g/day) was recorded in animals on T1. The digestibility coefficients for CP, NDF and ADF reduced as the cactus level increased in the diet. It is concluded that inclusion of cactus in the experimental diet or other comparable diets to up to 50% on DM basis for sheep fed tef straw promotes weight gain without causing digestive disturbances common in diets with high cactus inclusion.