B. G. Cottyn

Microbial protein synthesis in growing-finishing bulls estimated from the urinary excretion of purine derivatives

Abstract In the frame of a feeding experiment with three periods, balance trials were carried out with 18 double-muscled Belgian White–blue bulls, allocated to one of four feeding regimes. The ration consisted of maize silage and concentrate in the ratio of 35:65 on DM basis. Six concentrates were formulated to supply three levels of protein and energy. The three periods corresponded to distinct live weight intervals of 360–460, 460–570 and 570–680xa0kg. In the first feeding regime, low protein and intermediate energy level were given during the whole trial; in the second regime, protein level decreased at a constant intermediate energy level; in the third regime, the energy level increased at a constant high protein level; in the fourth regime, protein level decreased simultaneously with an increase in the energy level. Total daily intake varied from 6.2 to 9.7xa0kg for dry matter (DM), from 65 to 106xa0MJ for metabolisable energy (ME) and from 719 to 1326xa0g for crude protein (CP) (50 animal observations). At the end of each period, the excretion of the purine derivatives (PD), allantoin and uric acid, was measured after total urine collection during 4 days to estimate microbial nitrogen supply to the duodenum (MNPD). The effect of the intake of DM, organic matter (OM), digestible OM (DOM), digestible carbohydrates (DCHO), total digestible nutrients (TDN), rumen fermentable OM (FOM), metabolisable energy (ME), fermentable ME (FME), CP, digestible CP (DCP) and rumen degradable protein (RDP) on PD and MNPD was examined. Further, the relationship of MNPD to MN, calculated according to different systems, was examined. The amount (mean±SD) of allantoin excreted in urine was 147±23xa0mmol day−1 and of uric acid 11±3xa0mmol day−1. The MNPD amounted to 97±21xa0g day−1, varying from 57 to 154xa0g day−1, and significantly increased with all measures of nutrient intake. The correlation coefficients, ranging from 0.45 for DCP to 0.57 for DOM and FME, were, however, not significantly different. MNPD showed a larger variation and was on average lower than the potential MN values calculated from the intake of FOM (108±13xa0g day−1), DCHO (141±16xa0g day−1) and FME (109±13xa0g day−1), similar to that calculated from the intake of RDP (99±14xa0g day−1) and higher than the MN value calculated from the intake of TDN (84±11xa0g day−1). The correlations of MNPD to the calculated MN values ranged from 0.47 for MNFOM to 0.59 for MNFME, but were not significantly different.

Phase-feeding to optimize performance and quality of Belgian Blue double-muscled bulls.

To optimize performance and carcass quality of Belgian Blue double-muscled bulls four phased feeding regimens were evaluated. All diets were offered ad libitum and consisted of 650 g concentrates and 350 g maize silage per kg dry matter (DM). Total period was divided into three phases (ca. 360 to 460, 460 to 570 and 570 to 680 kg). All four groups received the same maize silage but the different energy and protein densities were applied using different concentrates. During the three phases, the negative control (NC) group constantly received a diet with a low protein and a moderate energy density; the second group (DP) received with each phase diets with decreasing protein density while the energy density remained moderate; the third group (IE) received diets with increasing energy density at a constantly high protein density and the last group (DPIE) received diets which decreased in protein and increased in energy density. The NC group grew significantly slower during the first interval (1·37 v. 1·62 kg/day for the other groups), resulting in a significantly longer total finishing period. During the third period IE had the slowest growth. The NC group needed 21 and 20 days more than the DP and DPIE groups, respectively, to reach the same slaughter weight. The NC group had the lowest DM intake during the first interval, the IE group during the third interval. No significant differences (P > 0·05) were found for food conversion, when expressed as DM or NEF (net energy for fattening). IE had the worst protein conversion while NC had the best, with the two other groups being intermediate. The only important significant difference concerning carcass quality was the improved dressing proportion of the IE and DP groups. Although significant, differences in the fat content of the m. longissimus thoracis are of minor importance. These results proved that for Belgian Blue double-muscled bulls, protein density of the diet can be decreased with increasing live weight, while energy should be increased to give optimal performance.

Effect of dietary protein level on performance of early-weaned double-muscled calves

Abstract The effect of the protein content of the concentrate on the performance during a 20-week rearing period was investigated, using thirty-two male and thirty-seven female newborn double-muscled calves, belonging to the Belgian White–Blue breed. A restricted milk diet was fed. Weaning occurred when daily concentrate consumption reached 0.5 kg. The crude protein content of the concentrate amounted to 15% (LP) or 18% (HP) on an as-fed basis. Concentrate and grasshay were fed from a 2-week age onward. Daily concentrate intake was limited to a maximum of 3 kg, while hay was freely available. Weaning occurred at a similar live weight (LP: 80.1 vs. HP: 80.7 kg) and after a similar number of experimental days (LP: 60.5 vs. HP: 57.4 days). Total dry matter (DM) intake during the entire period (LP: 260.2 vs. HP: 267.2 kg) was not affected by dietary crude protein. Liveweight gain after weaning (LP: 0.98 vs. HP: 1.05 kg/d) and during the entire rearing period (LP: 0.78 vs. HP: 0.84 kg/d) was increased when the HP concentrate was fed. DM and net energy were more efficiently used in calves fed the HP concentrate, while protein was less efficiently converted at the higher dietary protein level. Higher dietary protein also increased serum urea concentration. Based on an increased liveweight gain and a better conversion of DM and net energy, on the one hand, and a reduced protein efficiency and a higher serum urea concentration on the other hand, it is concluded that a dietary level of 200 g crude protein (CP) or 114 g true protein digested in the small intestine (DVE) per kg DM is near the optimum in early-weaned double-muscled calves. It improved daily liveweight gain and feed conversion, compared to 167 g CP or 100 g DVE per kg DM. These results give evidence that the optimal dietary protein level in early-weaned double-muscled calves seems to be higher than in non-double-muscled calves.

Growth promoters and meat yield

Abstract The development of a number of growth promoters, such as antibiotics, hormones and β-agonists, and the use in poultry, pigs, sheep and cattle has improved meat production through a positive effect on growth rate and/or feed efficiency. The combined use of different growth promoters can result in additivity of effects. The anabolic steroid trenbolone and also β-agonists increase dressing percentage, while it was mostly unaffected by other steroid hormones and antibiotics, or often decreased by growth hormone. β-agonists and growth hormone repartition feed energy towards less fat and more lean tissue in the carcass, irrespective of animal species.

Monensin-Sodium and Lasalocid-Sodium as Growth Promoters for Grazing Young Beef Bulls

The contribution to beef production in Belgium expressed in carcass weight amounted to 7.8% from steers, 34.0% from bulls, 34.1% from cows and 24.1% from heifers in 1982 (INS, 1983). Bull beef production is mostly practised in a semi-intensive system. The inclusion of a pasture period is more profitable than continuous indoor feeding (Boucque et al, 1978). An energy supplementation during this period is worthwhile for young calves (Fiems et al, 1979). This paper deals with the effect of monensin and lasalocid on the performance of young grazing bull calves.