CONSERVATION OF SPRING CUT ITALIAN RYEGRASS AS ROUND BALE SILAGE - EFFECT OF STAGE OF MATURITY ON ENSILING CHARACTERISTICS AND FORAGE NUTRITIVE-VALUE

Spring cut Italian ryegrass was harvested at two different stages of m aturity: lake vegetative (EARLY) and flowering (LATE). The wilted fora ge was round baled and then ensiled by wrapping in plastic film. EARLY harvest reduced dry matter (DM) yield significantly as compared to LA TE (5.6 vs. 10.5 t ha(-1); P < 0.01). However, forage quality both bef ore and after ensiling was better for EARLY with higher crude protein (CP) and non-structural carbohydrates content and a lower amount of ce ll walls (NDF). Higher pH and the fermentation characteristics confirm ed the poor quality of LATE silage, having higher content of butyrate, propionate and acid detergent insoluble nitrogen and a lower concentr ation of lactic acid. Dry matter intake of EARLY silage by sheep (aver age 65.0 +/- 7.3 kg LW) fed solely forage ad libitum was 37% higher th an LATE (1386 vs. 1011 g DM day(-1); P < 0.05) due to its better palat ability and digestibility. In vivo DM digestibility of EARLY silage wa s 76.1% while it decreased to 58.2% for LATE silage. Estimated metabol izable energy content of EARLY silage (11.5 MJ kg(-1) DM) was 29% high er than LATE (8.9 MJ kg(-1) DM) resulting as similar to the reference value of a high quality perennial ryegrass silage. The forage conserva tion system of ensiled round bales is effective and recommended when s pring cut Italian ryegrass is harvested at an early stage of maturity.