Twenty four Simmental calves, initially weighing 405.5:!:,18.7 kg and
approximately 11 months old, were random ely assigned into two dietary groups,
based on live weight, to study the effect of different fattening regimes on the animal
performance, carcass merits and composition. The first group (n=12, F) was fed grass
silage plus concentrate mixture which consisted of 97.1% sugar beet pulp and 2.9%
minerals, fibers was the main source of energy. The second group (n=12, S), where
starch was the main source of energy, was offered maize silage plus concentrate
mixture that composed of 51% corn, 45% soybean and 4% minerals. Diets were fed
ad libitum as a total mixed ration for 157 day. All diets consisted of 65% roughages
(grass silage or maize silage) plus 35% concentarte mixture. Claves fed S diet
Significantly grew faster and reached higher final body weight (1485 g1d and 637 kg)
in comparison with F diet (1261 g/d and 605 kg). Although both groups consumed
almost the same amount of ration (average 9.2 kg OM/d) without significant
differences, S group was more efficient for converting feed to gain compared to F
group (6.07 vs. 7.39 kg OM! kg gain). Hot carcass weight, dressing percentage and
scores of carcass conformation and fatness were similar for both Sand F groups.
Only kidney fat weight was significantly higher fer S (10.2 kg) than F group (7.74 kg).
No significant differences were detected between Sand F groups in the percentages
of lean, fat, bone and lean: fat ratio of the whole carcass. This study showed that although the fiber based-diet as a dietary energy source
did not improve animal performance compared to the starch based-diet, but it
produced similar carcass merits with the same content of lean, fat and bone. More
researches are needed to study the energy pathways, partitioning and deposition in
the different body tissues when fiber based-diets are used in beef production rations.