A data frame with 36 observations on the following 4 variables.
treatment
a factor with levels ABC
period
a numeric vector
animal
a numeric vector
gain
a numeric vector
References
SAMPAIO, I. B. M. Estatistica aplicada a experimentacao animal. 3nd Edition. Belo Horizonte: Editora FEPMVZ, Fundacao de Ensino e Pesquisa em Medicina Veterinaria e Zootecnia, 2010. 264p.