Digestibility study
The animals were housed individually in metabolic cages (40×50×50 cm) which allow separation of faeces and urine; each cage was equipped with an automatic drinker nipple and a manual feeder. The experimental period lasted 14 d, feed consumption was accurately determined daily during the whole experimental period and feces were collected for four days as a collection period (Perez et al., 1995); the collection was performed at approximately 09:00 h each morning before the next daily ration was provided, and then the feces were dried at 60°C for 24 h. All collected feces for each animal were mixed, then representative feces samples were ground for chemical analyses. The apparent coefficients of nutrient digestibility were determined using two different methods (direct and indirect method).