Beef production as influenced by stage of maturity of grass for silage and level and type of supplementary concentrates

Abstract

The aim of this study was to examine the effects ofstage ofmaturity of grass for silage (EC = early cut, LC = late cut), and level (LL = low level, i.e., 1.5 kg dry matter (DM) d-1, HL = high level, i.e., 3.0 kg DM d-1) and type (B =barley, BRSM = barley and heatmoisture treated rapeseed meal) of supplementary concentrates on feed intake, animal performance and diet digestion in Finnish Ayrshire bulls. The study was conducted as a 23 factorial experiment with six randomized complete blocks. The average initial and final live weights of the bulls were 123 kg and 494 kg, respectively. The crude protein content of the ad libitum fed EC and LC silages, cut at an interval of eight days, was 159 and 131 g kg-1 DM. However, the difference in the estimated content of AAT (= amino acids absorbed in the small intestine) between the two silages was small, whereas there was a large difference in PBV (= protein balance in the rumen). The respective values for crude fibre were 278 and 304 g kg-1 DM. At the beginning of the experiment the voluntary grass silage intake of the EC bulls was higher than that of the LC bulls. Towards the end of the experiment the difference in silage intake between the two stages of cut disappeared. This change in voluntary grass silage intake was followed by a similar change in the rate of daily live weight gain (LWG): the EC bulls started to grow faster than the LC bulls, but the initial slower LWG of the LC bulls had been compensated by the end of the experiment. The LL bulls had a higher intake of silage than the HL bulls. The substitution rate was 0.63 kg silage DM per concentrate DM, regardless of the stage ofcut. HL feeding resulted in faster LWG. Owing, at least partly, to the improved diet digestibility, inclusion of rapeseed meal in the diet increased the silage intake throughout the experiment followed by a faster LWG. The positive effect of rapeseed meal was unaffected by the stage ofmaturity of the grass for silage and the level of concentrate supply. The animals were not able to take full advantage of the high protein content of the EC silage. The inclusion of rapeseed meal in the diet, however, improved the rate of gain and resulted in more efficient feed conversion.