生育期与品种对紫花苜蓿营养价值及瘤胃降解率的影响

选用3个品种(肇东、龙牧801和龙牧803)、3个不同生育期(现蕾期、初花期和盛花期)的紫花苜蓿,研究不同生育期与品种对苜蓿营养价值及瘤胃降解特性的影响。结果表明,粗蛋白质(CP)含量、粗灰分(CA)含量、CP和中性洗涤纤维(NDF)的瘤胃有效降解率及快速降解组分(a组分)含量均随生育期的延长而降低;NDF、酸性洗涤纤维(ADF)和CP的慢速降解组分(b组分)含量随生育期的延长而升高;肇东和龙牧803的CP含量、NDF有效降解率极显著高于龙牧801(P<0.01);ADF含量、CP有效降解率按肇东、龙牧801、龙牧803顺序显著降低(P<0.05);生育期与品种对CP含量、CA含量及CP、NDF有效降解率均有明显的互作效应。     

Effect of particle size and partial replacement of alfalfa hay by soya bean hulls on nutrient intake,total tract digestibility and rumen degradability of diets by Holstein steers

This study examined the effect of alfalfa hay (AH) particle size and the replacement of soya bean hull (SH) for AH within the diet of restricted fed Holstein steers on dry matter intake (DMI), total tract digestion, ruminal digestion, ruminal pH and ammonia nitrogen content, and faecal pH. Four rumen‐cannulated Holstein steers averaging 353 ± 9.6 kg of BW were assigned to a 4 × 4 Latin square experiment with four periods and a 2 × 2 factorial arrangement of treatments. Factor A was AH particle size (fine vs. coarse) and factor B was diet SH content (0% vs. 10%; substituted for AH). Steers were fed at 1% of body weight of TMR containing 400 g/kg forage and 600 g/kg concentrate. Chopping of AH to fine particles decreased (p = 0.01) amount of dietary materials retained on the medium sieve (8 mm). The inclusion of SH significantly increased (p = 0.01) materials retained on the 1.18‐mm sieve and tended to decrease (p = 0.07) materials on 19‐mm sieves. The inclusion of SH increased (p = 0.01) ether extract (EE) intake and increased (p = 0.07) DMI. Inclusion of SH increased (p = 0.01) EE digestion and decreased (p < 0.01) faecal pH. Neither AH particle size nor SH inclusion in diets affected (p > 0.10) the in situ ruminal degradability coefficients of DM (‘a’, ‘b’, ‘c’ or ‘a+b’). No interaction of AH×SH was seen on nutrient intake, digestibility and in situ ruminal degradability of Holstein steers.     

苎麻营养成分分析及瘤胃降解特性研究

为系统的研究苎麻的营养价值及其在山羊瘤胃中的降解特性,利用化学分析等方法检测了7个茬次苎麻的粗蛋白(CP)、氨基酸(AA)组成、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)等营养成分、单宁等抗营养成分的含量,并采用3只装有永久瘤胃瘘管的波尔山羊为试验动物,对苎麻的部分营养成分的降解率和降解参数进行测定。结果表明,7个茬次苎麻的CP含量均较高且品质较好,CP平均值达到了19.57%,而且呈现出随着茬次的增加,CP含量有所下降的趋势,但是第7茬和第6茬相比CP含量略有升高。AA总和平均值达到了16.40%,占CP平均值含量的83.80%,赖氨酸(Lys)的平均含量达到了0.84%,苏氨酸(Thr)的平均含量达到了0.82%。抗营养因子方面,单宁可能是苎麻最主要的抗营养因子,平均值达到了0.67%。苎麻的干物质(DM)、CP、有机物(OM)、NDF和ADF的降解率均随着瘤胃消化时间的延长而不断提高,有效降解率分别达到了47.00%,35.53%,44.29%,57.68%和38.59%。由此得出,苎麻的营养价值较高,主要体现在CP含量高且品质较好,主要营养成分的瘤胃降解率均较高,可以作为反刍动物优良的粗饲料资源加以开发利用。     

不同精粗比日粮添加甘露寡糖对绵羊瘤胃纤维降解率的影响

选取6只安装永久瘤胃瘘管羯羊(白萨福克♂×小尾寒羊♀)为瘤胃液供试动物,采用4×6二因子析因试验设计,共设2个因子,分别为不同精粗比日粮(A1(20:80)、A2(30:70)、A3(40:60)、A4(50:50))和不同甘露寡糖添加量(B1 (0)、B2 (0.4%)、B3 (0.8%)、B4 (1.2%)、B5 (1.6%)、B6 (2.0%)),进行尼龙袋半体内试验,旨在研究不同精粗比日粮中添加甘露寡糖对绵羊瘤胃中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)降解率的影响。结果表明,A因子对日粮中不同时间点NDF、ADF瘤胃降解率、降解参数及有效降解率均产生了显著影响(P< 0.05),A1处理组的NDF和ADF各个时间点(除3 h外)的瘤胃降解率均显著高于A3和A4处理组(P< 0.05);B因子对3、6、9、12、48 h的瘤胃ADF降解率均产生了显著影响(P< 0.05),其中B5处理组显著高于B1、B2处理组(P< 0.05);A3处理组的NDF有效降解率显著高于A1、A2处理组(P< 0.05),稍高于A4处理组(P >0.05)。综上所述,在精粗比为40:60时,NDF和ADF的瘤胃有效降解率处于较高水平。     

不同种类脲酶抑制剂对山羊饲粮养分瘤胃消失率和挥发性脂肪酸浓度的影响

选择装有永久性瘘管体重(20±0.5)kg的雄性山羊4只,采用拉丁方设计和尼龙袋方法研究脲酶抑制剂乙酰氧肟酸(25mg/kg)、对苯二酚(40mg/kg)和丝兰皂甙(36mg/kg)对饲料养分在瘤胃48小时的消失率和挥发性脂肪酸浓度的影响。试验结果表明,对苯二酚和乙酰氧肟酸使饲粮干物质在瘤胃48小时消失率分别提高16.58%和13.87%(P<0.05),而丝兰皂甙的影响未达到显著水平。对苯二酚和乙酰氧肟酸使饲粮中性洗涤纤维瘤胃48小时消失率分别提高13.44%和9.36%(P<0.05),使酸性洗涤纤维的瘤胃消失率分别提高13.67%(P<0.05)和7.15%(P>0.05)。对苯二酚显著提高瘤胃乙酸、丙酸和丁酸的浓度,分别提高8.66%、18.1%和32.9%(P<0.05),而乙酰氧肟酸和丝兰皂甙对瘤胃挥发性脂肪酸浓度的影响未达到显著水平。     

Photochemical oxidation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in soils — a tool to assess their degradability?

To determine the degradability of PAHs and PCBs for soil remediation or ecotoxicological risk assessment, a simple method is needed. We tested the suitability of photocatalytic oxidation for this purpose. We determined the concentrations of 20 PAHs and 12 PCBs in four mineral topsoil horizons, six organic horizons, and four particle‐size fractions of each of three soils before and after UV irradiation with TiO₂ as a catalyst in suspension. Preliminary experiments showed that in dry soil no photooxidation occurred, but after 48 h of irradiation in suspension the PCB concentrations decreased by up to 40—50 %, while the PAH concentrations did not change significantly. In contrast to this, 95—100 % of PAH and PCB standards spiked on quartz sand were degraded within 8 h, indicating that sorption to organic matter limited degradation of PAHs and PCBs in soil suspensions. There was no difference in the degradation among different individual PAHs and PCBs, respectively, indicating that the degradation did not occur in dissolved state, but in association with soil organic matter. In all samples except one, the degradation of PCBs (10—80 % loss of initial concentrations) was higher than those of the PAHs (0—40 % loss). This suggests that the accessibility of PCBs for OH· radicals generated during irradiation was higher, or the oxidation of PAHs was limited by the properties of the sorbing organic matter. Thus, the tested method was not suitable to predict biodegradability, because it did not reflect the differences in degradability of individual compounds.     

六种狼尾草营养成分及瘤胃降解动态研究

对6种狼尾草的营养成分及瘤胃降解动态进行了研究,结果表明:杂交狼尾草和桂牧1号的干物质和中型洗涤纤维的有效降解率均较高,闽牧6号的干物质有效降解率最低,台农2号中型洗涤纤维的有效降解率最低。狼尾草属牧草的干物质的潜在降解程度同粗蛋白呈正相关,同中性洗涤纤维呈负相关,干物质潜在降解程度同粗蛋白和中性洗涤纤维的潜在降解程度均呈正相关,而且同中性洗涤纤维的潜在降解程度相关性更高,说明通过改善狼尾草属牧草纤维的降解能力而提高其利用程度更有效。     

高寒牧区天然草地牧草干物质的瘤胃降解率动态变化

选用5只安装有瘤胃瘘管,体重和体质相近,健康无病的德国美利奴×小尾寒羊为试验羊只,采用瘤胃尼龙袋法测定2010~2012年不同月玛曲高寒草地天然牧草瘤胃降解率动态变化,结果表明,天然牧草在瘤胃中降解48h后其干物质瘤胃降解率趋于平缓。牧草瘤胃干物质降解率随生育期的推移先升高后降低,在6、7月出现了峰值,2010年7月,2011和2012年6月分别达到67.05%,60.9%和71.56%。此时牧草营养价值较高,完全可以满足家畜对营养素的需求,8、9月逐渐下降;不同年份相同草地牧草干物质降解率也不同。     

In situ ruminal amino acid degradability of green and ensiled Italian rye-grass according to particle transit model and microbial contamination correction

The ruminal degradation of amino acids (AA) of a green Italian rye-grass (GRG) and its silage (ERG) was determined on three wethers cannulated in rumen and duodenum using in situ and particle passage techniques. Wethers were fed a diet of ERG, corn silage and concentrate (1:1:1, DM basis) at 40 g DM/kg BW^0.75. Two rumen incubations (at 0, 2, 4, 8, 16, 24, 48 and 72 h) with freeze-dried samples (3 g) in nylon bags were performed for each feed. The microbial contamination of incubated residues was corrected using ¹⁵N enriched solid associated bacteria isolates as reference. Two different estimates of undegraded AA were established: UP_p, considering the particle rumen outflow rate (k_p) of the ERG, and UP_cp, considering additionally the rate of comminution and mixing (k_c) of these particles. Microbial contamination resulted in large errors in the degradation kinetic parameters of all AA. As a result, non corrected UP_p and UP_cp included a large fraction of microbial origin. For essential AA plus cysteine these microbial proportions ranged 0.365–0.555 (UP_p) and 0.461–0.710 (UP_cp) in GRG. In ERG these values ranged: 0.403–0.666 (UP_p) and 0.481–0.804 (UP_cp). Cysteine always supplied minimum values whereas lysine showed maximum values in GRG or very close to these in ERG. Ensiling was associated with large changes in the AA profile. These variations conditioned, in turn, large differences in the changes made by the rumen microorganisms on the AA profile of both forages. However, ensiling only led to little changes in the profile of the rumen undegraded protein, especially when k_c was considered. Results show the need to correct for this contamination to obtain accurate AA valuations and also that the AA profile of the undegraded protein of a green forage may serve as a guide for this profile in its silages.