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The aim was to estimate the ME content of TMR samples for lactating dairy cows based on 24 h gas production (GP) measured in two TMR fractions obtained by sieving that were considered proxy representations of their forage and concentrate contents. Samples of TMR for lactating cows, collected at 15 Italian dairy farms, were dried and fractionated using an apparatus composed of four sieves (mesh diam. of 6.00, 2.36, 1.18, 0.60 mm) and a bottom pan. The particles retained by the 6.00, 2.36 and 1.18 mm sieves were bulked to create a fraction named “Long” (L), while particles retained by the 0.60 mm sieve and the bottom pan created a fraction named “Fine”(F). Samples of whole TMR and of F and L fractions were fermented in rumen fluid (220 mg of dried sample into graduated 100 ml glass syringes with 30 ml of diluted rumen fluid) to measure GP at 0, 1, 2, 4, 6, 8, 12, 24, 48 and 72 h of incubation, and GP at 24 h was used in multiple equations to predict the ME content. The L fraction was the main part of the TMR (633 ± 61.7 g/kg DM) and contained more aNDFom (391 vs 185 g/kg DM; P < 0.01), less starch (213 vs 394 g/kg DM; P < 0.01) and less CP (132 vs 181 g/kg DM; P < 0.01) than the F fraction. The 24 h GP measured on the F fraction was 17% higher (P < 0.01) than in the L fraction lending to a 25% increase in the predicted ME content of the F fraction (12.1 vs 9.7 MJ/kg DM, P < 0.01). When the GP of the two fractions were summed on the basis of their relative weights in each TMR to obtain a calculated GP of the whole TMR, this did not differ from that directly measured on the original TMR sample. The ME values of the TMR had substantial variability among samples and the highest ME values measured for the F and L fractions were 13.23 and 10.82 MJ/kg DM, respectively. The inclusion of these F and L fraction values in TMR samples that had the lowest ME concentrations (e.g. 10.0–10.4 MJ/kg DM), as an hypothetical consequence of an improvement in nutritive quality of the dietary feed components, resulted in a calculated ME increment of about 0.5–0.6 and 0.8–1.0 MJ/kg DM, respectively. These simulations suggest appreciable ME variations in cases of substituting nutritionally extreme forages and/or concentrates with corresponding feeds of different nutritive quality. [ABSTRACT FROM AUTHOR]

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]

The aim of the trial was to compare two dietary levels of whole ear corn silage (ES), fed in two physical forms (coarse or after wet milling), on growth, slaughter traits and stomach development of heavy finishing pigs. Fifty six “Italian Large White × Italian Duroc” (about 5 months of age and 78–80 kg of live weight (LW) were divided into pairs homogeneous and were kept in 28 pens (1.2 × 3 m, partially-slatted) equipped with two separate troughs to avoid competitions for feeding and with free access to water. Four dietary treatments resulted from the combination of two ES inclusion levels (300 and 400 g/kg dry matter (DM), ES30 and ES40, respectively) and two physical forms of the silage (coarse and wet milled). Seven pairs of pigs were randomly assigned to each dietary treatment and the animals were slaughtered at an average LW of 163.0 kg (±1.9 kg). The coarse ES had particles longer than the milled silage (4.4 vs 2.7 mm) and when it was fed to pigs the pH of fecal samples were lower (P<0.01) than that from pigs fed the milled ES, at both dietary inclusion levels (6.00 vs 6.20 for the ES30 diets and 5.97 vs 6.14 for the ES40 diets). There were no significant differences in organic matter total tract digestibility, average daily gain, DM intake and gain:feed ratio among the dietary treatments (0.81, 764 g/d, 77.1 g DM/kg LW 0.75 , 0.266 g/g DM, on average, respectively). The ES40 diets reduced the Longissimus dorsi thickness (56.4–59.8 vs 62.7–64.1 mm, P<0.011) and increased the stomach weight (0.0040 vs 0.0038 of the LW, P<0.05), while the coarse dimension of silage particles increased the DM content of the material in the stomach (from 142–171 to 179–183 g/kg DM, P<0.045) and the surface of the pyloric region (from 214–216 to 225–232 cm 2 , P<0.029). The two dietary inclusion levels and physical forms of ES do not differentiate growth and slaughter traits of the heavy finishing pigs. However, the coarse form of the silage modifies the development of the stomach by increasing the internal surface of the pyloric region as a possible consequence of a longer retention time in the stomach. [ABSTRACT FROM AUTHOR]