Effect of energy density of diets for intensive bull beef production on intake, growth rate and feed conversion

Abstract

The impact of the energy concentration (kg SU/kg DM) of ad libitum fed diets, on intake, growth rate and efficiency was investigated with 119 groups loose housed Belgian white-blue store bulls (I), 62 groups of individually tied up Belgian white-blue store bulls (II) and 42 groups of individually tied up Belgian white-red baby-beef bulls (III). We established a negative relationship between the energy density (x) and the dry matter intake (y -g DM/kg Woo 75 ).Within the studied range of energy density (0.53 to 0.89 kg SU/kg DM) the relationship with energy intake (y = g SU/kg Woo 75 ) was positive :The increasing energy intake with higher energy densities (x) resulted in an increasing growth rate (y = g/d) (except for group II) but the correlation was lower :The feed conversion (y = kg SU/kg gain) in function of the energy concentration (x) did not indicate a significant relationship for two of the three groups :Communication No. 428 (CALLOW, 1961 ;H ENRICKSON et al., 1965 ; GA RRIGUS et al., 1969 ;W ALDMAN et al., 1971 ; B OND et al., 1972 ; A NDERSEN , 1975 (G EAY et al., 1976 ; L EVY et al., 1976 ;R OHR and D AENICKE , 1978).This study will not investigate the influence of energy levels, but rather the impact of the ration energy concentration on feed intake, growth rate and feed conversion of fattening bulls. -ExperimentalThe bulls involved with this investigation can be divided in three groups : I: store bulls of the Belgian white-blue (BWB) (1969). ' The impact of the energy concentration on dry matter and net energy intake, growth rate and feed conversion was studied by regression analysis (DRAPER and SMITH, 1966 Our investigation always resulted in a decreasing DM intake (y = g/kg W O . 75 ) (figure 1) with increasing energy concentration (x = kg SU /kg DM).The relationship was respectively :These findings are in accordance with most of the literature data shown in (B OUCQUE et al., 1978). This statement helps to explain the lower r value for group II. -Daily liveweight gainBecause of the positive correlation between the energy concentration and the energy intake, we expect a higher growth rate (y = g/day) with increasing energy concentration. This was confirmed by our investigation (Figure 3), but the correlation coefficients were lower (especially for group II) than those for intake and concentration. The relationship was respectively : This is also in accordance with the data in Table 2, although some investigations (F LACHOWSKY and L 6HNERT , 1977 and F L AC HOW S KY , 1979), with high energetic rations but with a lack of fibrous material, resulted in a growth depression without a decreasing energy intake. L ANARI and S USMEL (1979) found that maize rations with increasing energy concentration clearly improved daily gains of beef breed bulls (r = 0.80), while the increase in daily gain was less evident for dairy breed bulls (r = 0.42), light steers (r = 0.26) and heavy steers (r = 0.67).In the case of store bulls only, there is a clearly better response on energy concentrat...