Aguiar, M. do S.M., Silva, F.F. da, Donato, S.L.R., Schio, A.R., Souza, D.D. de, Meneses, M. de A. and Lédo, A.A. 2015. Microbial protein synthesis and concentration of urea in dairy heifers fed diets with cactus forage Opuntia. Semina: Ciências Agrárias. 36, 2 (Apr. 2015), 999–1012. DOI:https://doi.org/10.5433/1679-0359.2015v36n2p999.