Levels of inclusion of spineless cactus (Nopalea cochenillifera Salm Dyck) in the diet of lambs

The objective of this study was to evaluate the intake of nutrients and water, digestibility, nitrogen balance, microbial protein synthesis, performance and blood parameters of lambs fed increasing levels (0, 150, 300 and 450 g/kg of DM basis) of fresh spineless cactus cv. Miuda (Nopalea cochenillifera Salm Dyck) included in the diet. Forty male (noncastrated) crossbred Santa Ines lambs, averaging 18.6 +/- 2.8 kg body weight (BW) at the beginning of the study, were used in this trial. A completely randomized design was used, with ten replicates per treatment and initial BW as a covariate. Quadratic behaviour was observed for dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), total carbohydrates (TC) and metabolizable energy (ME) intake, with maximum values estimated with 242.9, 236.4, 229.2, 218.2, 238.2 and 284.5 g/kg of spineless cactus inclusion, respectively. Non-fibrous carbohydrates (NFC) and neutral detergent fibre (NDF) intakes presented higher and lower values respectively in lambs fed 450 g/kg of spineless cactus. Voluntary water intake decreased with increasing quantities of spineless cactus, however, water intake from feed and total water intake increased. The digestibility of DM, OM, NFC and TC presented higher values with 450 g/kg of spineless cactus. Total weight gain and daily weight gain showed an increasing linear effect, while feed conversion decreased. Urine volume and microbial protein were higher for lambs fed 450 g/kg of spineless cactus, while urea excretion was lower. There was a quadratic effect on serum glucose and calcium levels with maximum values for inclusion of spineless cactus of 368.9 and 150 g/kg respectively, whereas beta-hydroxybutyrate and blood urea decreased linearly; phosphorus and magnesium concentrations increased, with lower and higher values in animals fed the highest levels of spineless cactus, respectively. The inclusion of spineless cactus by up to 450 g/kg of DM improves the microbial efficiency, nutrient utilization and the performance of the animals, without causing adverse effects on blood parameters.