LAUSR

Spineless cactus is an important part of dairy cow diet in the semiarid Brazilia. Severe infestation of cochineal (Dactylopius opuntiae Cockerell) destroyed a vast area of the most common species of cactus planted in the region; Opuntia ficus-indica Mill. resistant varieties with superior agronomic performance were recently selected, but they still need to be tested with dairy cows. We evaluated the use of a resistant variety, ‘Orelha de Elefante Mexicana’ (OEM, Opuntia spp.), in dairy cow diet. We tested its effect on intake, nutrient digestibility, microbial protein, blood parameters and performance of lactating cows. Ten cows with an average milk yield of 20 kg/day were assigned to an experiment using a double 5 × 5 Latin square design. The experimental diets consisted of five replacement levels of Nopalea cochenillifera Salm Dyck cv. (‘Miúda’) by ‘OEM’ (0%, 25%, 50%, 75% and 100%) on a dry-matter (DM) basis) and were formulated considering the ingredient composition. The roughage:concentrate ratio was 70:30 on a DM basis. The replacement of ‘Miúda’ by OEM did not change the intake (kg/day) of DM (18.0), organic matter (16.3), crude protein (CP, 2.8), total digestible nutrients (11.6), non-fibre carbohydrates (7.6) and neutral detergent fibre (5.7), or the apparent digestibility (g/kg) of DM (655), organic matter (694), CP (739) and non-fibre carbohydrates (950), whereas apparent digestibility of neutral detergent fibre increased linearly. Microbial protein production (1.5 g/day), microbial protein efficiency (129.2 g CP/kg total digestible nutrients), plasma urea nitrogen (21.4 mg/dL), nitrogen balance (123 g/day), feed efficiency (1.1), nitrogen efficiency (0.2), milk production (20.0 kg/day), fat-corrected milk production (20.1 kg/day) and milk composition were not influenced by the replacement. Therefore, we recommend the use of OEM in the diet of lactating cows with an average milk yield of 20 kg/day.