The effects of wilting of grass prior to ensiling on the response to bacterial inoculation .1. Silage fermentation and nutrient utilization over three harvests

Four silages were prepared from perennial ryegrass swards at each of first (primary growth), second (first regrowth) and third (second regrowth) 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 silages within a single harvest, were offered as the total diet at maintenance levels to 12 wether sheep for 3 weeks to determine nutrient apparent digestibilities. They were also give to 12 lactating dairy cows together with a concentrate supplement, in a three-period change-over study with experimental periods of 8-weeks duration, to examine dry matter (DM) apparent digestibility and utilization of nitrogen (N) and energy in the diets. Inoculation tended to improve silage fermentation with on average lower pH and ammonia-N/total-N across the three harvests, while wilting of grass prior to ensiling significantly increased silage pH (P<0.001) and ammonia-N/total-N (P<0.001). Neither inoculation nor wilting had any significant effect on mean nutrient apparent digestibilities, assessed through sheep, across the three harvest. However, at the second harvest inoculation significantly decreased apparent digestibilities 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 DM (P<0.05) at the second harvest. However, the mean apparent digestibilities of DM (P<0.05) at the first harvest. The efficiencies of metabolizable energy utilization for lactation (k(1)) were similar between the four silages at each of the first and second harvests, with the average being 0.50. The results of the present study indicated that inoculation tended to improve silage fermentation and significantly increased mean N apparent digestibility of mixed diets across the three harvests, while wilting significantly reduced mean DM, N and energy apparent digestibilities of mixed diets. Neither inoculation nor wilting had significant effects on k(1) value.