Effects of two protein sources and energy level of diet on the performance of young Marchigiana bulls. 1. Infra vitam performance and carcass quality.

摘要

The aim of this trial was to evaluate the influence of 2 protein sources and the energy levels of the diet on growth performance and carcass quality of young Marchigiana bulls. 18 weaned young bulls (129 days of age) were equally divided into 3 groups. Until the slaughter weight (620 kg) was achieved, the 2 groups were fed diets with the same protein and energy concentrations but differing in protein sources (faba bean-FB vs. soyabean meal s.e.-SB), and the last group was fed high-energy diets (HE) with both protein sources in the concentrates. Body weight, daily weight gain and biological efficiency of growth at different ages and periods and feed conversion indices were calculated from individual growth curves. Beginning at 180 days of age, group HE always showed a significantly (P<0.01) higher body weight and daily weight gain than groups FB and SB. Moreover, group HE reached the slaughter weight and conformation earlier than the other 2 groups (500 vs. 540 days, respectively). The protein sources only affected the growth in the first phase after weaning (body weight at 180 days: 173 vs. 186 kg for groups FB and SB, respectively; P<0.01). The highest energy diets appreciably improved the growth rate but worsened feed conversion indices. Animal and carcass measurements were not influenced either by energy intake or dietary protein source. Group HE showed the lowest incidence of long bones (6.2 vs. 6.7 vs. 5.8% of cold carcass for FB, SB and HE groups, respectively; P<0.01) and the highest percentage of fat (5.1 vs. 4.7 vs. 7.1% of cold carcass for FB, SB and HE groups, respectively; P<0.01). With respect to the protein sources, only the incidence of long bones resulted to a significant difference between FB and SB groups (6.2 vs. 6.7% of cold carcass, respectively; P<0.05). These data demonstrated that faba beans could be used as alternative sources to soyabean meal s.e. as it did not influence the growth rate and feed conversion indices in the entire experimental period. Nevertheless, immediately after weaning, the association of faba beans with another protein source richer in rumen undegradable protein would be preferable. Moreover, the utilization of high energy feeding planes could improve the growth dynamics of young Marchigiana bulls, although in the final phase, it might be suitable to reduce the energy intake in order to decrease fat deposition.