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The aim of this study was to assess the chemical composition and rumen degradability of ensiled soybean forage harvested at three plant vegetative stages ( i.e. , R4, R5, R6) and wilted for 20 or 28 h. The wilted forages were chopped from 1 to 2 cm and then manually pressed into 6 kg bags of fresh material (two bags for each combination of maturity stage and wilting duration) prior to storage under anaerobic condition for 90 days. The soybean silages were analysed for fermentative parameters and manually separated into leaves, stalks and pods. Whole forage and separated plant components were chemically analysed and the in vitro neutral detergent fibre (NDF) ruminal degradation (NDFD) was determined. Only whole plant silages were assessed for in vitro gas production (GP) and in vitro crude protein degradability (CPD). The dry matter (DM) content of the ensiled whole plants increased (P=0.005) from 454 to 485 and 518 g/kg from the R4 to R5 and R6 vegetative stages and was higher for forages wilted at 28 h than those at 20 h (528 vs 444 g/kg, P<0.001). Advancing plant maturity increased (P<0.001) the crude protein (CP) and ether extract (EE) content from 164 to 199 and from 18 to 53 g/kg DM, respectively, but reduced ash (P=0.011) from 71 to 63 g/kg DM. The NDFD increased with plant maturity from 0.319 to 0.465 (P<0.001). The GP did not differ among maturity stages of forages or wilting lengths, while CPD increased from 0.391 to 0.548 (P<0.001) with advancing maturity and slightly decreased with the longer wilting duration (P<0.008). The DM content of the pods and stalks increased (P<0.01) with the vegetative stage and CP content increased in pods and decreased in leaves. Results indicate that harvesting soybean forage at an advanced maturity stage ( e.g. , from R4 to R6) greatly increases the protein, the fat and the degradable NDF contents. Moreover, the wilting soybean forage has to be targeted to achieve a DM content of ensiled forage of about 440 g/kg (between about 410 and 480 g/kg, according to the maturity stage), and a further wilting determines no fermentative improvements at ensiling or relevant modification of silage nutritional contents. [ABSTRACT FROM AUTHOR]

The capability of maintaining protozoa populations and reduce the accumulation of undigested material was investigated in two experiments using a stratified continuous-culture rumen fermenter (CCF) at various setting. The CCF consists of 8 × 2 L glass bottles, warmed at 39 °C and placed on a waterproof magnetic stirrer. Bottles are closed with a rubber stopper, with an insert for the inflow of artificial saliva and have the outflow at the base. In Experiment 1 the effect of two stirring frequencies (continuous vs intermittent, S1 and S2) and two dilution rates ( D , 1.29 vs 1.04) on the pH values and on the counts of the protozoa in the fermentation fluid was evaluated. The pH reached a steady state after 4 d of fermentation and S1 bottles had lower pH than those S2 (6.50 vs 6.57, P<0.001). The protozoa in the fermentation fluid (2.92 × 10 5 /ml at the beginning) declined sharply in the first 2 d of fermentation and stabilized at about 13 × 10 3 /ml in the S2 flasks, while the S1 flasks had lower protozoa concentrations (about 0.8 × 10 3 /ml, P<0.001). The D had no effects on pH and protozoa. Experiment 2 aimed to test effects of varying the daily diet ( F ) amount (15, 20, 25, 30 g DM/d of a diet with 50:50 forage: concentrate ratio) on the organic matter (OM) digestibility (OMD) and on the fermentative patterns. In two fermentation runs of 8 d each, bottles were inoculated with 450 ml of rumen fluid and 1050 ml of artificial saliva, which was then pumped at a rate of 78 ml/h. Lowering F reduced the OM accumulated inside the vessels (from 5.06 to 0.68 g/d; P<0.001) but did not affected the OMD for any of the dietary treatments (range between 0.460 and 0.510). The reduction of F led to a linear decrease (P<0.001) in volatile fatty acids concentration (from 65.8 to 45.3 mM) and to an increase of acetate:propionate ratio (from 2.91 to 3.42) and of pH (from 6.0–6.1 to 6.4–6.5). Lowering F tended to increase the number of protozoa (from 72 to 198 × 10 3 /ml, P=0.082). The tested CCF reaches stable conditions of fermentation after some days of adaptation, allows the survival of protozoa population and has a limited accumulation of undigested materials in the glass bottles. [ABSTRACT FROM AUTHOR]