I. Sánchez herrera, E. Posadas Hernández, E. Sánchez Ramírez, B. Fuente Martínez, J. L. Laparra Vega, and E. Ávila González, “Effect of sodium butyrate on productive performance of laying hens in a semi-free range system”, Vet Mex OA, vol. 42, no. 3, Jul. 2013.