THE EFFECTS OF WILTING OF GRASS PRIOR TO ENSILING ON THE RESPONSE TO BACTERIAL INOCULATION .1. SILAGE FERMENTATION AND NUTRIENT UTILIZATIONOVER 3 HARVESTS

Four silages were prepared from perennial ryegrass swards at each of f irst (primary growth), second (first regrowth) and third (second regro wth) harvests during the 1993 growing season. At each harvest the four silages included two unwilted (without and with inoculant at 2.4 l/t) and two wilted (without and with inoculant at 2.4 l/t). The four sila ges within a single harvest, were offered as the total diet at mainten ance levels to 12 wether sheep for 3 weeks to determine nutrient appar ent digestibilities. They were also give to 12 lactating dairy cows to gether with a concentrate supplement, in a three-period change-over st udy with experimental periods of 8-weeks duration, to examine dry matt er (DM) apparent digestibility and utilization of nitrogen (N) and ene rgy in the diets. Inoculation tended to improve silage fermentation wi th on average lower pH and ammonia-N/total-N across the three harvests , while wilting of grass prior to ensiling significantly increased sil age pH (P<0.001) and ammonia-N/total-N (P<0.001). Neither inoculation nor wilting had any significant effect on mean nutrient apparent diges tibilities, assessed through sheep, across the three harvest. However, at the second harvest inoculation significantly decreased apparent di gestibilities of DM (P<0.05) and N (P<0.001). At this harvest, wilting also significantly decreased apparent digestibilities of DM (P<0.05) at the second harvest. However, the mean apparent digestibilities of D M (P<0.05) at the second harvest. However, the mean apparent digestibi lities of DM (P<0.05) at the first harvest. The efficiencies of metabo lizable energy utilization for lactation (k(1)) were similar between t he four silages at each of the first and second harvests, with the ave rage being 0.50. The results of the present study indicated that inocu lation tended to improve silage fermentation and significantly increas ed mean N apparent digestibility of mixed diets across the three harve sts, while wilting significantly reduced mean DM, N and energy apparen t digestibilities of mixed diets. Neither inoculation nor wilting had significant effects on k(1) value.