The study was carried out at the genetic centre of the
Italian Simmental Breeders Association located in Fiume
Veneto in the Friuli region of Italy. Twelve male calves of
AG, BU, RE and IS respectively were selected by the experts of
their breeders association and transferred to the experimental
farm at an average age of 113.9± 12.4 days and an initial
body weight of 138.0± 20.2 kg. After arrival, all calves of each
breed were housed in a single pen for a 70-day adaptation
period. The experimental fattening period started on May
2006 when the animals had an average live weight of 204±
6 kg. The calves of each breed were assigned to 3 multiple
pens of 4 animals each balanced according to their body
weight. All the pens had a straw bedded indoor area with a
space allowance of 3 m2
/head plus an outdoor run on
concrete (3 m2
/head) which was available from 07:00 to
17:00. Pens were contiguous and located in the same side of
the barn and the space at manger was 75 cm/head. Each pen
was equipped with two waterers and water was always
available. All the animals were fed ad libitum the same diet
distributed as total mixed ration in the morning at 08:30. Feed
and chemical composition of the diets fed during adaptation