LAUSR

Abstract Cactus is an important fodder option for semiarid regions of the world. The energy and water supplied by this forage has long been used by livestock, and cactus cultivation has increased food security and reduced hunger and poverty in semiarid areas. The environmental and management practices affect the nutritive value of cacti and animal performance. The major species of cacti used for livestock includes Opuntia ficus-indica Mill., O. lindheimeri Engelm, O. ellisiana, O. engelmannii Salm Dyck, O. chrysacantha Berg, O. amyclae, O. rastrera Weber, O. stricta Haw, and Nopalea cochenillifera Salm Dyck. Under similar environmental conditions, N. cochenillifera usually presents greater dry matter (DM), water-soluble carbohydrates, and in vitro digestible organic matter concentrations, and lesser crude protein (CP) when compared with O. ficus-indica. The planting density also affects cactus growth and its chemical composition: a greater plant N concentration was observed in a population of 5000 plants/ha (11.2 g/ kg) compared to a population of 40000 plants/ha (9.0 g/kg). Young cladodes are present in greater proportions in less dense plant populations, presenting greater nutrient concentration and lesser DM than older cladodes. Fertilizer application also affects the chemical composition. Nitrogen fertilization increased cladode N concentration (ranging from 6.7 g/kg to 13.9 g/kg) in Opuntia ficus-indica, with a positive linear response (0 up to 300 kg N/ha/year) occurring in three out of four locations in NE Brazil. The harvest management may affect the nutritive value, as a reduced harvest intensity will increase the proportion of younger cladodes. However, as cactus maintains its nutritive value for a longer period compared to other forages, the harvest frequency has little influence on overall nutritive value. Cladodes may be stored in a dry and shaded location without losing its nutritive value for at least two weeks, which may facilitate the logistics of transportation, reducing the total costs. Therefore, this review provides an overview of how agronomic and environmental factors affect the chemical composition and nutritive value of cacti with the potential to improve livestock productivity in arid environments.