南疆地区青贮玉米中乳酸菌的分离与鉴定

为了从青贮玉米中筛选产酸能力强的乳酸菌菌株,利用MRS培养基从青贮玉米中筛选到两株乳酸菌菌株F和菌株J,对它们进行形态特征、生理生化特征、分子生物学鉴定。形态学和生理生化结果表明菌株F符合葡萄球菌属,菌株J符合芽孢杆菌属特征,经16S rDNA鉴定结果表明菌株F属于葡萄球菌属Staphylococcus sp,J菌株属于芽孢杆菌属Bacillus sp。     

甜菜块根和玉米秸秆混贮营养品质及有氧暴露期微生物数量分析

本试验旨在研究甜菜块根和玉米秸秆按照不同混合比例青贮后营养品质及有氧暴露期微生物数量的变化,筛选调制青贮饲料时二者最优的混合比例。结果表明：T2组粗蛋白、Ca和P的含量均显著高于T1、T3、T4组（P<0.05）,T1、T2组水溶性碳水化合物含量均显著高于其他3组（P<0.05）,而干物质损失率均显著低于其他3组（P<0.05）;T2组pH分别显著低于T0、T1组（P<0.05）,乳酸含量显著高于T0、T1组,NH₃-N含量显著低于其他4组（P<0.05）,T0、T1组未检测到丙酸、丁酸;在整个有氧暴露期,随着甜菜块根添加比例的增加,酵母菌和霉菌数量逐渐升高,乳酸菌数量逐渐降低,且T1组乳酸菌数量最高,酵母菌和霉菌数量最低。综合分析,二者比例为10：90时,更有利于甜菜营养品质的长期保存与利用。     

Impact of field fungal contamination of barley on ensiling properties,nutritional quality and the microbiome of barley silage

Barley varieties of differing fungal disease resistance were grown in triplicate plots at Lacombe and Lethbridge, Alberta with the disease resistant variety (FR) sprayed with a foliar fungicide to maximize differences in field fungal disease. Both varieties were harvested at soft dough and ensiled in minisilos to assess differences in fungal contamination on ensiling properties, nutritional quality, aerobic stability and associated bacterial and fungal microbiomes. Data were analysed as repeated measures with the effect of treatment × time (duration of ensiling or aerobic exposure) included in the model. The percentage leaf area diseased by net form net blotch was higher (p < 0.05) in the untreated barley cv. Sundre (UN, 59.1% leaf area affected at Lacombe and 25.2% at Lethbridge) than in the FR barley cv. Chigwell (0.7% leaf area affected at Lacombe and 0.1% at Lethbridge). Fungal resistant barley had a lower (p < 0.01) acid and neutral detergent fibre content. Relative abundance of Xanthomonadales was higher (p = 0.02) for FR than UN, while Lactobacillales dominated the bacterial microbiome after 60 day of ensiling in both silages. Bacillales dominated both FR and UN after 21 day of aerobic exposure. Fungal resistant fresh barley forage had a tendency (p = 0.10) for a greater relative abundance of Pleosporales, while UN had higher (p < 0.01) Hypocreales. Mould counts were lower (p = 0.01) for FR than UN after 7 day of ensiling. Fungal resistant barley had minimal influence on the fungal community that contributed to the aerobic deterioration of barley silage.     

Modelling feed intake and milk yield responses to different grass ley harvesting strategies

A meta‐analysis of feeding trials using grass silages was conducted to predict production responses for dairy cows fed grass silage. They were divided into two subsets: 69 diets from 11 studies were used for comparison of silages made from primary growth and regrowth grass (harvesting subset), and another 157 diets from 24 studies were used for comparison of digestibility influenced by the maturity of grass ensiled (D‐value, digestible organic matter in dry matter) (maturity subset). The minimum prerequisite for an experiment to be included in the data set was that milk production, feed intake, silage characteristics and concentrate ingredients were reported. Both subsets were analysed using the mixed model procedures of SAS. The mean response in dry‐matter intake (DMI) and silage DMI to improved silage D‐value was 0.0175 and 0.0161 kg per unit D‐value (g/kg DM) respectively. The average increase in milk and energy‐corrected milk yield was 0.30 and 0.37 kg per 10‐unit increase in silage D‐value respectively. Milk protein concentration increased, and fat concentration tended to increase with enhanced silage D‐value. Each 10‐unit increase in D‐value reduced milk yield by 0.092 kg at a given dietary metabolizable energy intake (MEI), suggesting that the ME concentration of high D‐value silages was overestimated. Cows fed regrowth silage produced 0.55 kg/day more energy‐corrected milk than those fed primary growth silage at a given dietary MEI. The prediction models can be used to improve ration formulation systems or incorporated into economic models for optimizing milk production in various farming systems.     

Field‐related quality management system for grass silage production

A model for the prediction of the silage quality was tested in several large farms in northeast Germany. The model uses data and information on the fresh grass and the application of silage additives at ensiling to evaluate the “ensilability.” During clamp filling, the model analyses information on the filling performance, activity of compacting machines and hermitic covering of the clamp and evaluates the “ensiling technique.” Both “ensilability” and “ensiling technique” are assessed as “good,” “medium” or “bad” and pooled in “silage evaluation grades” 1–5. In the present model version, the predicted silage net energy lactation (NEL) and crude protein (CP) content is between 3% (for the best grade 1) and 15% (for the weakest grade 5) lower than the fresh grass NEL and CP content. In our experiments, all the grass silage production systems were characterized by “good” “ensilability” and “ensiling technique.” Under those circumstances, the experimental results indicated a closer numerical relation between fresh grass and measured silage NEL and CP content than between predicted silage and measured silage NEL and CP content. The results reveal that the model prediction calculation should be changed compared to the present version. If “ensilability” and “ensiling technique” are evaluated as “good,” the predicted silage NEL and CP content should be forecasted in a range between 0% and 3% decrease compared to fresh grass.     

Occurrence of filamentous fungi and mycotoxins in wrapped forages in Sweden and Norway and their relation to chemical composition and management

A study was conducted on 124 farms in Sweden and Norway where fungal (all farms) and mycotoxin (100 of the 124 farms) presence was examined in wrapped forage bales. Samples were also analysed for chemical composition, and data on the bale production and storage system on each farm were collected. Fungi, analysed by three common sampling methods, were found in bales from 89% of the visited farms (110 farms). The most frequently isolated fungal species from the bale surface was Penicillium roqueforti. Mycotoxins were present in 39% of the 100 samples analysed. The most common mycotoxins present were enniatin B (14 farms) followed by deoxynivalenol (12 farms). The risk of finding fungi in baled forage samples was higher with odds ratio (OR) of 5.1 when less than eight layers of stretch film were applied, low seal integrity of wrapping (OR 172 at <10 s of seal integrity), higher dry‐matter content (OR 1.17–1.56 per % unit DM) and higher concentrations of acetic acid (OR 47.5 per g DM) and ethanol (OR 3.4 per g DM). Mycotoxin presence was not found to be correlated with any of the chemical characteristics of the baled forage, or with any forage production and management factors. A positive correlation was present between total fungal counts and general mycotoxin presence, but not between specific mycotoxins and the toxin‐producing fungal species.     

Impact of grass silage quality on greenhouse gas emissions from dairy and beef production

High‐quality grass silages may represent a mitigation option by reducing enteric methane production and by increasing productivity, thus reducing greenhouse gas emissions per kg of product (emission intensity). Two previous studies found considerable effects of three different silage qualities cut at different maturity stages (very early [H1], early [H2] and normal [H3]) offered ad libitum with various levels of concentrate supplementation, on animal performances of growing/finishing bulls and dairy cows in early lactation, indicating that emission intensities may also vary. Based on results from these previous studies, the aim of this study was to estimate emission intensities for milk and beef carcasses for the included combinations of silage qualities and concentrate levels, by using the farm‐scale model HolosNor. The emissions intensities were lowest for the H1 silage, and highest for the H3 silage, independent of concentrate levels for both milk and beef. Thus, increasing concentrate levels did not compensate for lower grass silage quality. Improvements in silage quality from H3 silage to H2 is realistic and has the potential to reduce emission intensities with approximately 10% while keeping the milk yield per cow constant and reducing the use of concentrates considerably. For beef production, the potential is even larger, with a reduction in emission intensity of approximately 17%. We conclude that improving grass silage quality may be a mitigation option that will also reduce the dependence on concentrates.     

Proteolysis and in situ ruminal degradation of lucerne ensiled with Cistus ladanifer tannins

The effects of ensiling lucerne with graded inclusion of Cistus ladanifer condensed tannins (CT) on in silo fermentative parameters, in vitro organic matter digestibility (IVOMD) and on in situ rumen degradability of dry matter (DM) and crude protein (CP) were studied. Lucerne forage ( Medicago sativa subsp. sativa ) was sprayed with different solutions of C. ladanifer CT extract in 60 ml of water in order for dose 0 (control), 40 (L40), 80 (L80) and 120 (L120) g of CT per kg of lucerne DM and was ensiled in lab‐scale silos. After 35 days, the silages were analysed for chemical composition, and the in situ ruminal degradability was determined in rams. The inclusion of CT in the silages caused an important dose‐dependent reduction in soluble‐N, NH₃‐N and a large increase in true protein content and N bound with neutral detergent fibre (NDF‐N), which indicates an effective proteolysis reduction during ensiling. Also, the rumen undegradable protein (RUP) increased linearly (P < 0.01) with CT inclusion. However, a linear decrease (P < 0.02) of 5%, 13% and 22% of IVOMD was observed for the silages L40, L80 and L120 respectively. The results obtained suggest that C. ladanifer CT can be used as silage additives to reduce proteolysis of high‐protein forages during ensiling. A level of CT of 40 g/kg DM seems to be the best compromise between the gains achieved by the protection of CP degradation in silo and in the rumen and the losses associated with the depression of the digestion and absorption.     

溶氧量及搅拌速率对青贮玉米秸秆微曝气水解效果的影响

为提高秸秆好氧水解的生物可降解性,试验选用切碎揉丝的青贮玉米秸秆,水解液按照体积比为10%的量添加,以水解液溶氧量(1、2、3、4、5、6mg/L)和搅拌速率(50、100r/min)为变化因素,温度控制在35～38℃、总固体为5%,进行优化设计。研究发现,进行8 d,pH值及氧化还原电位(oxidation-reduction potential,ORP)值趋近于稳定;搅拌速率为50 r/min、溶氧量为1～4 mg/L;以及搅拌速率为100 r/min、溶氧量为1～2 mg/L范围内,曝气量的提高,对脂肪酸的积累显著,且搅拌和曝气都可促进乙酸、丙酸和正丁酸的积累;搅拌速率为100 r/min,可溶性需氧量(soluble chemicaloxygendemand,s COD)的浓度整体呈现出高于搅拌速率为50 r/min时的状况;以纤维素降解为例,在搅拌速率为100 r/min条件下,溶氧为2 mg/L时,木质纤维素具有较高的降解率,达到48%。