INFLUENCE OF THE MATURITY STAGE OF WHOLE MAIZE PLANT HARVESTED FOR SILAGE ON THE COMPOSITION, APPARENT DIGESTIBILITY, FERMENTATION CHARACTERISTICS IN THE RUMEN AND ANIMAL PERFORMANCES IN GROWING FATTENING BULLS

Maize was harvested as whole plant to three different stages of maturi ty (S1, S2, S3) corresponding to dry matter contents of 25.1% (S1), 29 .8% (S2), 32.3% (S3). The yields were, respectively, 10.7, 11.1 and 11 .8 tons dry matter per ha. Each of these maize silages, offered to gro wing fattening bulls, was supplemented with dried sugar beet pulp, soy a bean meal, minerals and vitamins. The stage of maturity did not affe ct ash, insoluble ash, ether extract or protein contents; however, a s ignificant reduction of the fibre content was recorded with the late s tage (S3). The stage of maturity did not affect apparent digestibility of dry matter and organic matter either in the whole diet or in the m aize silage fraction measured in vivo on bulls maintained in metabolis m stalls. In contrast, the digestibility of fiber was significantly re duced (62.1 vs 67.2 or 65.6% in the diet; 54.1 vs 63.3 or 60.7% in mai ze silage). In terms of rumen potentiality to degrade the feedstuffs, it was noted that total degradability of the different feedstuffs incu bated was greater with the maize silage with a high dry matter content . There were no significant effects of the stage of maturity on animal performances during the ad libitum feeding trial lasting 5.5 months. From the feed conversion ratio, the total live weight gain and the yie ld of dry matter per ha, it was possible to estimate that 13.8, 14.2 a nd 15.7 bulls can be fattened, respectively, when maize was harvested in a early, medium or later stage of maturity.