回归法测定生长猪内源磷排泄量及磷真消化率研究

为了确定多重线性回归法是否能应用于测定生长猪内源磷排泄量及菜粕和豆粕磷的真消化率,试验选用5头平均质量为(21.6±1.43)kg的健康大白×长白阉公猪为试验动物,采用5×5拉丁方设计,设5个磷水平(1.8,2.7,3.6,4.5和4.7 g/kg);日粮以豆粕、葡萄糖、玉米淀粉等为基础,以菜粕为待测植物性饲料,配制半纯合试验日粮,菜粕和豆粕为磷惟一来源。通过测定日粮和粪中的干物质(DM)、磷和氧化钛含量,计算出日粮、豆粕和菜粕磷的表观消化率。再应用多元线性回归分析,推导出生长猪内源磷的排泄量及豆粕和菜粕磷的真消化率。结果表明,以每kg干物质采食量(DMI)计,生长猪粪磷的排出量与日粮磷的摄入量呈线性关系(P<0.000 1);采食豆粕加菜粕日粮的生长猪内源磷的排泄量为(1.24±0.29)g/kg DMI,菜粕磷的真消化率为(46.46±11.33)%,豆粕磷的真消化率为(61.87±7.79)%;相对于表观消化率(-0.45%～35.15%),日粮磷真消化率(56.60%～59.03%)更稳定。说明多元线性回归法可以应用于同时测定猪内源磷排泄量和饲料磷的真消化率;在配制日粮时,磷表观消化率可加性差,而真消化率具有很好的可加性。     

春季大棚与露地蔬菜蜗牛的发生规律比较

文章介绍了对2013年浙江省温岭市春季设施大棚与露地蔬菜蜗牛发生情况调查,并进行比较统计分析。结果表明:浙江省温岭市大棚内的蜗牛发生早,为害严重,对两季蔬菜大棚与露地的蜗牛株为害率和蜗量两者呈极显著相关关系,2013年3月20日播种蜗牛株为害率,y=0.042 2x2-0.278 4x+0.144 2,R2=0.963 54(n=9,R20.01=0.734 79),5月12日播种,y=0.736 9x-0.904 9,R2=0.986 3(n=5,R20.01=0.834 34);3月20日播种每平方米蜗牛量,y=0.376 4x-0.093 6,R2=0.900 7(n=9,R20.01=0.734 79),5月12日播种,y=1.000 0x-0.800 0,R2=0.984 0(n=5,R20.01=0.834 34)。     

日粮真可消化磷水平对生长猪氮磷消化率和排泄量的影响

选用5头平均体重为27.86 kg健康三元(杜×长×大)杂交阉公猪,采用5×5拉丁方设计,以真可消化磷(True digestiblephosphorus,TdP)为指标,配制了5种日粮真可消化磷含量不同的生长猪试验日粮,并使其总钙与TdP的比例为2∶1,来研究日粮真可消化磷水平对氮、磷的消化率及其排泄量的影响。结果表明,在日粮真可消化磷含量低于0.26%时,日粮磷的真消化率随着日粮真可消化磷含量的上升而升高,当日粮真可消化磷含量超过0.26%后达到0.39%时,磷的真消化率陡然下降,由52.69%下降到49.56%。由试验结果可以推导出,当日粮真可消化磷含量在0.34%左右时日粮磷的真可消化率达到最高56.6%。但是各试验日粮之间磷的真消化率差异并不显著。当以g.kg-1 DMI为单位时,粪磷排泄量随着日粮磷摄入量的增加线性增加,线性方程为:y=0.493x+1.140 9,r2=0.957 4。x表示日粮磷的摄入量,g.kg-1,DMI(DryMatter Intake);y表示粪磷排泄量,g.kg-1,DMI。日粮5对应的粪磷排泄量极显著高于日粮1(P<0.001)、日粮2(P<0.001)、日粮3(P=0.001)和日粮4(P<0.001),试验日粮1、2、3和4之间没有显著差异。当以g.kg-1 feces DM为单位时,日粮5对应的粪磷排泄量最高(25.82),极显著高于日粮1(P<0.001)、日粮3(P=0.005)和日粮4(P<0.001),显著高于日粮2(P=0.021),日粮4对应的粪磷排泄量最低(21.28),除了显著低于日粮5以外,还显著低于日粮2(P=0.006)和日粮3(P=0.029)。日粮粗蛋白的平均表观消化率为81.6%,且各组之间受日粮真可消化磷含量的影响差异不显著(P=0.679 4),而氮的总排泄量平均为12.14 g.d-1,各组之间没有显著差异(P=0.259 6),氮的沉积率在66%￣74%之间,各组之间差异也不显著,可见日粮真可消化磷水平并不影响氮的消化吸收利用。     

粤北高寒山区茄子测土施肥技术指标体系研究和建立

在不同肥力耕地设置高寒山区茄子田间肥料试验,对施肥量、土壤有效养分含量(碱解氮、有效磷、有效钾)和茄子相对产量等试验数据进行相关统计分析,并求取相应的回归方程,建立合适的数学模型,以此建立高寒山区茄子土壤有效养分丰缺指标和不同肥力土壤的推荐施肥量指标。结果表明:高寒山区茄子的碱解氮、有效磷、速效钾丰缺指标的数学模型分别为:y(相对产量)=28.117ln(x)-47.985(R2=0.818 7,n=12)、y(相对产量)=47.412ln(x)-67.4(R2=0.620 5,n=12)、y(相对产量)=31.877ln(x)-43.403(R2=0.931 9,n=12)。高寒山区茄子的推荐施氮、磷、钾肥总量数学模型分别为:y=-4.537 5ln(x)+32.024(R2=0.199 2,n=12)、y=-1.777ln(x)+12.939(R2=0.24,n=12)、y=-7.438 4ln(x)+40.164(R2=0.539 7,n=12)。并根据推荐施肥量数学模型计算出高寒山区茄子不同土壤有效养分含量的推荐施肥总量。当土壤碱解氮含量分别为:<32、32~79、79~161、>161 mg/kg时,推荐的总施氮量分别为:>16.2、16.2~12.2、12.2~9.9、<9.9 kg/666.67 m2;当土壤有效磷含量分别为:<12、12~20、20~31、>31 mg/kg时,推荐的总施磷量分别为:>8.5、8.5~7.6、7.6~6.8、<6.8 kg/666.67 m2;当土壤有效钾含量分别为:<19、19~41、41~77、>77 mg/kg时,推荐的总施钾量分别为:>18.4、18.4~12.5、12.5~7.9、<7.9 kg/666.67 m2。     

粤北山区柰李测土配方施肥技术指标体系研究

在不同地点、不同肥力的果园,设置柰李肥料试验,对施肥量、土壤有效养分含量(碱解氮、有效磷、速效钾)和柰李相对产量等试验数据进行相关统计分析,并求取相应的回归方程,建立合适的数学模型,以此初步建立粤北山区柰李土壤有效养分丰缺指标和不同肥力土壤的推荐施肥量指标。结果表明:柰李的碱解氮、有效磷、速效钾丰缺指标的数学模型分别为:y(相对产量)=37.334 ln(x)-89.905(R2=0.549 2,n=15)、y(相对产量)=11.149 ln(x)+37.141(R2=0.915 7,n=15)、y(相对产量)=32.779 ln(x)-65.621(R2=0.902,n=15)。柰李的推荐施氮、磷、钾肥总量数学模型分别为:y=-18.763 ln(x)+98.391(R2=0.669 9,n=15)、y=-2.611 2 ln(x)+16.07(R2=0.767 1,n=15)、y=-15.601 ln(x)+83.701(R2=0.750 9,n=15)。并根据推荐施肥量数学模型计算出粤北山区柰李不同土壤有效养分含量的推荐施肥总量。当土壤碱解氮含量分别为:<42.41、42.41~82.84、82.84~114.56、>114.56 mg/kg时,推荐的总施氮量分别为:>28.08、15.52~28.08、9.43~15.52、<9.43 kg/667 m2;当土壤有效磷含量为:<3.17、3.17~29.84、29.84~179.40、>179.40 mg/kg时,推荐的总施磷量分别为:>13.06、7.21~13.06、2.52~7.21、<2.52 kg/667 m2;当土壤速效钾含量分别为:<34.03、34.03~72.96、72.96~134.30、>134.30 mg/kg时,推荐的总施钾量分别为:>28.67、16.77~28.67、7.25~16.77、<7.25 kg/667 m2。     

槟榔芋测土施肥技术指标体系研究

在不同肥力耕地设置槟榔芋田间肥料试验,对施肥量、土壤有效养分含量(碱解氮、有效磷、有效钾)和槟榔芋相对产量等试验数据进行相关统计分析,并求取相应的回归方程,建立合适的数学模型,以此初步建立槟榔芋土壤有效养分丰缺指标和不同肥力土壤的推荐施肥量指标。结果表明:槟榔芋的碱解氮、有效磷、速效钾丰缺指标的数学模型分别为:y(相对产量)=27.318ln(x)-33.433(R2=0.76,n=9)、y(相对产量)=21.36ln(x)+12.254(R2=0.888 7,n=9)、y(相对产量)=13.883ln(x)+30.815(R2=0.858 9,n=9)。槟榔芋的推荐施氮、磷、钾肥总量数学模型分别为:y=-8.544 5ln(x)+50.957(R2=0.799 7,n=9)、y=-1.858 3ln(x)+13.178(R2=0.804 9,n=9)、y=-5.468 5ln(x)+35.937(R2=0.934 9,n=9)。并根据推荐施肥量数学模型计算出槟榔芋不同土壤有效养分含量的推荐施肥总量。当土壤碱解氮含量分别为:<21、21~53、53~110、>110 mg/kg时,推荐的总施氮量分别为:为>24.86、24.86~17.05、17.05~10.78、<10.78 kg/666.67 m2;当土壤有效磷含量分别为:<4、4~24、24~101、>101 mg/kg时,推荐的总施磷量分别为:>9.91、9.91~7.73、7.73~5.98、<5.98 kg/666.67 m2;当土壤有效钾含量分别为:<6、6~19、19~48、>48 mg/kg时,推荐的总施钾量分别为:>28.36、28.36~18.53、18.53~10.66、<10.66 kg/666.67 m2。     

绵羊冬春放牧采食量的测定（1报）

进行三期放牧采食量测定,探讨绵羊冬春放牧采食量测定的有效方法;补料对放牧采食量的影响,以及羯羊和空怀母羊在放牧采食量上的差异。从采食牧草有机物质(OM)的消化率(n=10)来看,在冬春放牧采食量测定中,全部收粪,模拟采摘牧草样品,木质素(L)为内源指示剂,粪中干物质(DM)排出数量为计算依据的方法是基本可行的。补料明显影响绵羊的放牧采食量(p<0.01),羯羊和空怀母羊的放牧采食量无明显差异(p>0.05)。绵羊DM采食量与代谢体重(W~(075))呈正相关,(n=15,r=0.770),利用y=146x-928可估计各W~(075)的DM采食量。粪中OM％与粪能(FE)cal/g间(n=20)有强的线性关系(r=0.871),根据y=1063 40x可从OM％推算FE(cal/g)。     

转基因耐热植酸酶对肉鸡生产性能、钙磷平衡和磷排放量的研究

试验选用1日龄爱拔益加(AA)肉仔鸡900只,采用玉米-豆粕型日粮,研究不同水平植酸酶对肉鸡生产性能、钙磷平衡和磷排放量的影响.研究显示:AP降低0.15%后,添加500～750 FTU/kg(在37℃,pH 5.5条件下,每分钟释放出1 μmol无机磷所需的植酸酶数量为1 FTU)转基因耐热植酸酶不影响肉鸡采食量、增重、料重比、屠体品质、骨骼质量、血清碱性磷酸酶(ALP)活性及血清钙磷水平(P>0.05);添加750 FTU/kg转基因耐热植酸酶提高了28日龄肉鸡胫骨强度(P<0.05);添加500和750 FTU/kg转基因耐热植酸酶,可以使肉鸡粪尿磷排放量降低10.60%和12.64%(P<0.05).结果表明:肉鸡日粮中AP降低0.15%后,添加500～750 FTU/kg转基因耐热植酸酶在不影响生产性能、屠体品质,保证钙磷平衡的前提下,每1 kg日粮磷的排泄量可以降低0.53 g和0.63 g,粪尿磷排放量降低10.60～12.64%,有利于环保.     

北京市通州区芹菜氮磷钾肥料量级研究

为了找出通州区设施农业主栽作物芹菜的施肥模型,2008年北京市通州区农业技术推广站选择潞城镇小营高肥力地区和展示基地中肥力、八各庄中肥力的保护地进行了芹菜氮磷钾肥不同施肥量的研究。试验结果:1)在高肥力小营地区的芹菜氮肥肥料效应函数y=3814.4+106.75x-2.8524x2,R2=0.7308。最高施肥量x=18.71kg/667m2,最佳施肥量x=18.26kg/667m2;磷肥效应函数y=4209.5+99.992x-3.2527x2,R2=0.7704。最高施肥量x=15.37kg/667m2,最佳施肥量x=14.87kg/667m2;钾肥效应函数y=4222.6+69.77x-4.4996x2,R2=0.3688。最高施肥量x=7.75kg/667m2,最佳施肥量x=7.31kg/667m2。2)在中等肥力八各庄的芹菜氮肥肥料效应函数y=3318.7+136.67x-3.2955x2,R2=0.7368。最高施肥量x=20.74kg/667m2,最佳施肥量x=20.34kg/667m2;磷肥效应函数y=3873.8+197.13x-9.5952x2,R2=0.8509。最高施肥量x=10.27kg/667m2,最佳施肥量x=10.10kg/667m2;钾肥效应函数y=4058.7+97.69x-6.1234x2,R2=0.4462。最高施肥量x=7.98kg/667m2,最佳施肥量x=7.65kg/667m2。     

太湖地区规模奶牛场粪尿年产生量估算

为了估算规模化奶牛养殖场产污与排污量,采用源强估算法监测与估算奶牛场的泌乳牛和育成牛4个季节的粪尿产生量,同时监测了奶牛饲料氮磷摄入量与奶牛在运动场的粪尿产生量。结果表明:①每头泌乳牛日平均排泄粪便32.03 kg、尿20.93 kg,育成牛日平均排泄粪便13.58 kg、尿7.60 kg;泌乳牛日平均氮、磷产生量分别为274.23 g和95.93 g,育成牛每日氮、磷产生量分别为54.15 g和18.05 g,泌乳牛排泄量明显大于育成牛。②泌乳牛磷摄入量与磷排泄量呈线性相关(P0.05),r=0.935 9;氮排泄量与饲料氮摄入量相关性不显著。③奶牛夏季在运动场上粪尿产生量占粪尿总产生量的30%左右,冬季占10%左右。     

规模化奶牛场泌乳牛粪便氮磷含量预测模型研究

为了探讨基于泌乳牛日粮营养成分及其基本生产状况预测粪便氮磷含量的可行性,建立粪便总氮（fecal nitrogen,FN）、粪便总磷（fecal phosphorus,FP）含量的预测模型。本试验以中国荷斯坦奶牛为研究对象,选取天津市具有代表性的 7 家规模化奶牛场为采样点,利用问卷调查收集了 20 组泌乳期奶牛日粮营养成分及基本生产状况等基础数据,并采集了 60 份粪便样品,测定其氮磷含量。选取其中 14 组泌乳期奶牛日粮营养成分及基本生产状况等基础数据和 48 份泌乳牛粪便的氮磷含量,利用 SAS 统计分析软件,对其进行相关性分析和回归分析,建立预测模型。结果表明：日粮有机质摄入量（organic matter intake,OMI）和粗脂肪摄入量（crude fat intake,CFi）与泌乳牛粪便总氮含量有显著的正相关性,相关系数分别为 0.836 和 0.705。泌乳牛体重（body weight,BW）与粪便总磷含量呈负相关性,相关系数为-0.525。利用多元线性回归分析建立的预测模型的决定系数 R² 显著高于一元线性回归方程。其中基于泌乳牛产奶量（milk yield,MY）,产奶天数（days in milk,DIM）,日粮有机质摄入量 OMI 和氮摄入量（nitrogen intake,NI）建立的粪便总氮含量的预测模型的决定系数 R² 可达 0.96（P约0.001）,预测方程为：y=0.43+0.29×MY+0.02×DIM+0.92×OMI-13.01×NI。粪便总磷含量的预测模型的决定系数 R² 相对低于总氮含量的预测模型,最高为 0.62（P约0.10）,预测方程为：y=22.97-0.026×BW-4.02×NI+14.63×PI（phosphorus intake,PI）。最后利用 6 组泌乳牛日粮营养成分及其基本生产状况的基础数据和对应的 18 份粪便样品的氮磷含量对最优预测模型进行了外部验证。结果表明,粪便总氮含量和总磷含量的预测值与测定值间的相对误差分别为1.62%和 3.81%,预测标准差分别为 0.70 mg·g^-1 和 0.68 mg·g^-1,模型取得较理想的预测结果。     

Effects of yeast and yeast cell wall polysaccharides supplementation on beef cattle growth performance,rumen microbial populations and lipopolysaccharides production

This experiment was conducted to investigate the effects of live yeast and yeast cell wall polysaccharides on growth performance, rumen function and plasma lipopolysaccharides(LPS) content and immunity parameters of beef cattle. Forty Qinchuan cattle were randomly assigned to one of four treatments with 10 replicates in each treatment. The dietary treatments were: control diet(CTR), CTR supplemented with 1 g live yeast(2×1010 live cell g–1 per cattle per day(YST1), CTR supplemented with 2 g live yeast per cattle per day(YST2) and CTR supplemented with 20 g of yeast cell wall polysaccharides(30.0%≤β-glucan≤35.0%, and 28.0%≤mannanoligosaccharide≤32.0%) per cattle per day(YCW). The average daily gain was higher(P=0.023) and feed conversion ratio was lower(P=0.042) for the YST2 than the CTR. The digestibility of neutral detergent fiber(P=0.039) and acid detergent fiber(P=0.016) were higher in yeast supplemented groups. The acetic acid:propionic acid of the YST2 was lower compared with the CTR(P=0.033). Plasma LPS(P=0.032), acute phase protein haptoglobin(P=0.033), plasma amyloid A(P=0.015) and histamine(P=0.038) were lower in the YST2 compared with the CTR. The copies of fibrolytic microbial populations such as Fibrobacter succinogenes S85, Ruminococcus albus 7 and Ruminococcus flavefaciens FD-1 of the YST2 were higher(P0.001), while the copies of typical lactate producing bacteria Streptococcus bovis JB1 was lower(P0.001) compared with the CTR. Little differences were observed between the CTR, YST1 and YCW in growth performance, ruminal fermentation characteristics, microbial populations, immunity indices and total tract nutrient digestibility. It is concluded that the YST2 could promote fibrolytic microbial populations, decrease starch-utilizing bacteria, reduce LPS production in the rumen and LPS absorption into plasma and decrease inflammatory parameters, which can lead to an improvement in growth performance in beef cattle.     

Nitrogen nutrition diagnosis for cotton under mulched drip irrigation using unmanned aerial vehicle multispectral images

Remote sensing has been increasingly used for precision nitrogen management to assess the plant nitrogen status in a spatial and real-time manner. The nitrogen nutrition index (NNI) can quantitatively describe the nitrogen status of crops. Nevertheless, the NNI diagnosis for cotton with unmanned aerial vehicle (UAV) multispectral images has not been evaluated yet. This study aimed to evaluate the performance of three machine learning models, i.e., support vector machine (SVM), back propagation neural network (BPNN), and extreme gradient boosting (XGB) for predicting canopy nitrogen weight and NNI of cotton over the whole growing season from UAV images. The results indicated that the models performed better when the top 15 vegetation indices were used as input variables based on their correlation ranking with nitrogen weight and NNI. The XGB model performed the best among the three models in predicting nitrogen weight. The prediction accuracy of nitrogen weight at the upper half-leaf level (R²=0.89, RMSE=0.68 g m^–2, RE=14.62% for calibration and R²=0.83, RMSE=1.08 g m^–2, RE=19.71% for validation) was much better than that at the all-leaf level (R²=0.73, RMSE=2.20 g m^–2, RE=26.70% for calibration and R²=0.70, RMSE=2.48 g m^–2, RE=31.49% for validation) and at the plant level (R²=0.66, RMSE=4.46 g m^–2, RE=30.96% for calibration and R²=0.63, RMSE=3.69 g m^–2, RE=24.81% for validation). Similarly, the XGB model (R²=0.65, RMSE=0.09, RE=8.59% for calibration and R²=0.63, RMSE=0.09, RE=8.87% for validation) also outperformed the SVM model (R²=0.62, RMSE=0.10, RE=7.92% for calibration and R²=0.60, RMSE=0.09, RE=8.03% for validation) and BPNN model (R²=0.64, RMSE=0.09, RE=9.24% for calibration and R²=0.62, RMSE=0.09, RE=8.38% for validation) in predicting NNI. The NNI predictive map generated from the optimal XGB model can intuitively diagnose the spatial distribution and dynamics of nitrogen nutrition in cotton fields, which can help farmers implement precise cotton nitrogen management in a timely and accurate manner.     

吉林省不同生态区玉米施磷的增产效应差异

【目的】明确吉林省玉米施用磷肥的增产效应在生态区及县域尺度上的差异,为优化区域磷肥的施用与配置,实现粮食进一步增产和提高磷肥效率提供依据。【方法】选取2005—2013年吉林省玉米"3414"田间试验中不施磷和推荐施磷处理数据,通过分析区域与县域尺度的作物产量反应、磷肥的农学利用率和肥料贡献率等指标,评估不同生态区玉米施用磷肥的增产效应及其差异。另外,通过建立不施磷处理玉米产量与施磷处理产量、磷肥贡献率的关系,分析不同生态区土壤基础供磷能力的差异对玉米施磷增产效应的影响。【结果】施用磷肥对保障吉林省玉米高产具有重要作用,东部湿润山区、中部半湿润平原区和西部半干旱平原区玉米施磷后分别增产1.4 t·hm~(-2)(18.4%)、1.2 t·hm~(-2)(14.5%)和1.7 t·hm~(-2)(24.7%)。当前推荐施磷条件下,东、中、西部生态区玉米施用磷肥的平均农学利用率分别为23.2、17.5和24.1 kg·kg~(-1),而平均肥料贡献率分别为14.6%、11.9%和18.3%。统计分析结果显示,西部地区玉米施磷的增产效果和肥料贡献率高于东、中部地区,而农学利用率东部地区低于中、西部地区。回归分析结果显示,各生态区玉米施磷产量与基础产量之间存在正相关关系,均符合显著的线性模型,东部地区为y=0.855x+2605(R~2=0.697**),中部地区为y=0.846x+2658(R~2=0.739**),西部地区为y=0.761x+3545(R~2=0.623**)。各生态区玉米的磷肥贡献率与基础产量之间均存在负相关关系,均符合显著的对数模型,东部地区为y=-21.8 ln(x)+211.7(R~2=0.248**),中部地区为y=-18.8 ln(x)+183.3(R~2=0.230**),西部地区为y=-26.7 ln(x)+257.4(R~2=0.342**)。随着土壤基础供磷能力的提升,西部地区玉米施磷产量的增幅和肥料贡献率的降幅较东、中部地区更为明显。【结论】不同生态区的自然环境特点和土壤地力条件显著影响了玉米的磷肥增产效应,生产中应根据区域磷素供应能力和施磷反应特征合理配置和施用磷肥。相比东、中部地区,吉林省西部地区农田的基础磷素供应能力偏低,因而其玉米施磷的增产效应较高,该地区需重视磷肥的科学管理和调控,同时结合其他栽培管理措施以协同提高产量水平和肥料效率。     

饲粮尿素添加水平对生长育肥牛生长性能和血液生化指标的影响

【目的】利用肉牛饲养试验研究饲粮尿素添加水平对生长育肥牛生长性能和血液生化指标的影响,为肉牛生产中合理添加尿素提供理论依据。【方法】选择60头利木赞×复洲杂交的F1公牛,随机分为6组,每组10头,分别接受1个尿素添加水平的饲粮处理。设置6个粗蛋白和代谢能值相近（14% CP,11.3 MJ•kg-1,DM基础）的饲粮处理,其中尿素添加量分别为0%（对照）、0.4%、0.8%、1.2%、1.6%和2.0%。试验期14周,其中预饲期1周,正试期13周。【结果】随尿素添加水平的提高,干物质摄入量（dry matter intake,DMI）无显著变化（P＞0.1）,但日增重呈线性规律显著下降（L,P＜0.05）,饲料转化效率（DMI/ADG（average daily gain））呈现线性规律显著上升（L,P＜0.05）。其中,尿素添加水平在0.8%以内未见日增重和饲料转化效率（DMI/ADG）有显著变化。提高饲粮尿素添加水平,血氨浓度线性上升（L,P＜0.001）;而血浆总蛋白和血浆尿素氮（plasma urea-N,PUN）浓度呈二次曲线规律升高（Q,P＜0.001）,其中血浆总蛋白和PUN浓度分别在1.50%和0.64%（%DM）尿素添加水平下出现拐点。提高饲粮尿素添加水平对谷丙转氨酶活性没有显著影响（P＞0.1）,但会导致谷草转氨酶活性呈线性升高（L,P＜0.001）。在反映肉牛应激状况的激素指标中,除肾上腺素外,肌酸激酶活性、去甲肾上腺素、皮质醇、皮质酮和醛固酮浓度等均呈显著的二次曲线规律上升或下降（Q,P＜0.05）;其中,上升或下降趋势的变化出现在0.8%-1.2%尿素添加水平。【结论】生长育肥牛饲粮中尿素添加水平在0.8%以内,或尿素氮占总氮比例在16%以内,可认为是适宜的安全添加水平。     

Effects of Dietary Isoflavone Supplementation on Meat Quality and Oxidative Stability During Storage in Lingnan Yellow Broilers

To investigate the effects of a synthetic isoflavone （SI） on meat quality and oxidative stability, 1 500 43-d-old Lingnan yellow male broilers were randomly assigned to five dietary treatments： diets supplemented with 0, 10, 20, 40, or 80 mg SI kg-1, fed ad libitum for a period of 3 wk. After refrigerated storage, a＊ value of the meat increased with dietary SI supplementation using 10 and 40 mg kg-1 level （P〈0.05）, L＊ value decreased （P〈0.05）, and 40 mg kg-j increased the pH （P〈0.05）. Supplementation with SI, at all levels, increased water holding capacity （P〈0.05） and decreased lactic acid content of meat （P〈0.05）. The concentration of malondialdehyde at 72 h decreased linearly （P=0.005） and quadratically （P=0.004） with increasing levels of SI. Dietary SI at 20 and 40 mg kg-1 levels enhanced total superoxide dismutase activity in meat （P〈0.05）. Meat pH quadratically decreased as the storage time increased （P〈0.05）, with the highest value at 24 h （P〈0.05）. Lactic acid and malondialdehyde concentrations of meat increased over time, with value at 96 h being far higher than at earlier times （P〈0.05）. Supplemental SI linearly and quadratically increased the mRNA abundance ofglutathione peroxidase （GPX） （P=0.001 and P=0.002） and catalase （CAT） （P=0.003 and P=0.006） in breast muscle. The results from this study indicate that dietary supplementation with SI can improve meat quality during refrigerated storage by decreasing lipid peroxidation and enhancing oxidative stability and, for male broilers from 43 to 63 d of age, the optimal level of SI was 40 mg kg-1.     

The effects of step-wise improvement of forage combination in total mixed rations on fatty acid profile in the rumen and milk of Holstein cows

Five lactating Holstein cows in a 5×5 Latin square experiment were fed five high-concentrate total mixed rations(TMRs) to investigate the effects of step-wise improvement of forage combination on ruminal and milk fatty acid profiles. The ratio of concentrate to forage was fixed as 61:39, and the step-wise improvement of forage combination was applied as: TMR1, a ration containing corn stover; TMR2, a ration containing corn stover and ensiled corn stover; TMR3, a ration containing ensiled corn stover and Chinese wild ryegrass hay(Leymus chinensis); TMR4, a ration containing the ryegrass hay and whole corn silage; TMR5, a ration containing the ryegrass hay, whole corn silage and alfalfa hay. The TMRs were offered to the cows twice daily at 0700 and 1900 h. The entire experiment was completed in five periods, and each period lasted for 18 days. Diurnal samples of rumen fluids were collected at 0100, 0700, 1300 and 1900 h(day 16); 0300, 0900, 1500 and 2100 h(day 17); and 0500, 1100, 1700 and 2300 h(day 18). The step-wise improvement of forage combination increased energy and crude protein contents and decreased fibre content. As a result, the step-wise improvement of forage combination increased dry matter intake and milk yield(P0.05). The step-wise improvement increased dietary content of linolenic acid(C18:3 n-3), but did not alter dietary proportions of palmitic acid(C16:0), stearic acid(C18:0), oleic acid(C18:1 cis-9), linoleic acid(C18:2 n-6) and arachidic acid(C20:0). In response to the forage combination, ruminal concentration of C16:0, C18:2 n-6 and C18:3 n-3 linearly increased against their dietary intakes(P0.10). The step-wise improvement increased milk contents of C10:0, C12:0, C14:0, C16:0, C18:2 n-6 and C18:3 n-3(P0.10) and decreased milk contents of C18:0 and C18:1 cis-9(P0.05). Milk yields of C16:0, C18:1 cis-9, C18:2 n-6 and C18:3 n-3 were linearly increased by the increase of these fatty acids in the rumen(R2≥0.79, P0.05), and milk yields of C18:2 n-6 and C18:3 n-3 were also positively correlated with dietary intake of these fatty acids(R2≥0.85, P0.05). The step-wise improvement increased the transfer efficiencies from feed to milk for C18:2 n-6 from 11.8 to 14.2% and for C18:3 n-3 from 19.1 to 22.3%. In a brief, along with the step-wise improvement of forage combination, more dietary linoleic and linolenic acids might escape microbial hydrogenation in the rumen and consequently accumulated in milk fat though these fatty acids were present in low concentrations in ruminal fluids. The step-wise improvement of forage combinations could be recommended as a dietary strategy to increase the transfer efficiency of linoleic and linolenic acids from feed to milk.     

Effects of dietary forage to concentrate ratio and wildrye length on nutrient intake,digestibility, plasma metabolites,ruminal fermentation and fecal microflora of male Chinese Holstein calves

Twenty-eight male, weaned Chinese Holstein calves((156.8±33.4) kg) were used to investigate the effects of dietary forage to concentrate ratio(F:C) and forage length on nutrient digestibility, plasma metabolites, ruminal fermentation, and fecal microflora. Animals were randomly allocated to four treatments in a 2×2 factorial arrangement: whole-length forage(WL) with low F:C(50:50); WL with high F:C(65:35); short-length forage(SL) with high F:C(65:35); and SL with low F:C(50:50). Chinese wildrye was used as the only forage source in this trial. The grass in the SL treatments was chopped using a chaff cutter to achieve small particle size(~50% particles 19 mm). Dry matter intake(DMI) and organic matter(OM) intake was increased by increasing both F:C(P0.01) and forage length(FL)(P0.05), while acid detergent fiber(ADF) and neutral detergent fiber(NDF) intakes were only increased by increasing the F:C(P0.01). The digestibility of NDF was increased as the FL increased(P0.01), and it was also affected by interaction between F:C and FL(P0.05). Cholesterol(CHO)(P0.01), leptin(LP)(P0.05), and growth hormone(GH)(P0.01) concentrations in plasma were increased as dietary F:C increased. A significant increase in plasma triglyceride(TG)(P0.01), insulin(INS)(P0.05), and GH(P0.01) levels was observed with decreasing dietary FL. Ruminal p H values of calves fed with low F:C diets were significantly lower than those in high F:C treatment(P0.05). Increasing the F:C enhanced ruminal acetic acid(P0.05) and acetic acid/propionic acid(P0.01). Fecal Lactobacillus content was significantly higher, while Escherichia coli and Salmonella contents were significantly lower in WL and high F:C groups(P0.05). Lower fecal scores(higher diarrhea rate) were observed in calves fed with SL hay compared to WL hay(P0.05). Denatured gradient gel electrophoresis(DGGE) bands and richness index(S) were significantly affected by the interaction between F:C and FL(P0.05), under high F:C, band numbers and richness index from WL group were higher than that from SL group(P0.05), whereas there were no differences between WL andSL groups under low F:C(P0.05). Microflora similarity was 50–73% among the different treatments. It is concluded that the WL with high F:C(65:35) diet is suitable for weaned calves.     

青藏高原草地地下生物量与环境因子的关系

青藏高原草地生物量大部分分布于地下,地下生物量在其碳循环研究中起着重要的作用.基于大规模野外样地调查数据,分析比较了青藏高原南北和东西样带上草地地下生物量与环境因子的相关关系,探讨了环境因子对地下生物量控制作用的区域差异.研究结果表明:对于所有采样点而言,青藏高原草地地下生物量的环境控制因素主要有土壤含水量、表层土壤有机碳和全氮含量.通过比较南北和东西样带研究结果发现,草地地下生物量与土壤含水量、土壤表层有机碳和全氮含量相关的显著性水平,在东西样带上明显高于南北样带.同时,东西样带上草地地下生物量与降水量有显著正相关关系,这种关系在南北样带上不显著,表明水分对东西样带草地地下生物量的控制作用较强.气温与南北样带草地地下生物量呈显著负相关,但与东西样带草地地下生物量相关不显著,由此说明环境因子对青藏高原草地地下生物量的控制存在显著区域差异.     

谷子苗期氮高效品种筛选及相关特性分析

【目的】评价不同基因型谷子苗期氮素吸收利用差异性,筛选谷子氮高效利用基因型材料,为谷子氮高效利用品种选育和机理研究提供理论依据。【方法】采用沙培盆栽试验,以具有代表性生态类型的79个谷子品种为材料,分析其在低氮(0.2 mmol·L~(-1))和高氮(6 mmol·L~(-1))处理下茎叶干物重、含氮量、氮素吸收量、氮素吸收与利用效率的差异及相关性,并划分不同生态类型品种的氮效率类型。【结果】供试谷子品种在2个氮素水平条件下的茎叶干物重(CV_(N0.2) 35.39%和CV_(N6) 50.83%)、氮素含量(CV_(N0.2) 11.52%和CV_(N6) 11.22%)、氮素吸收量(CV_(N0.2) 32.82%和CV_(N6) 48.46%)、氮素吸收效率(CV_(N0.2) 32.82%和CV_(N6) 48.45%)、氮素利用效率(CV_(N0.2) 11.53%和CV_(N6) 11.27%)和氮效率(CV_(N0.2) 35.35%和CV_(N6) 50.61%)均存在较大差异。不同生态类型谷子品种的氮素吸收和利用效率差异显著,西北春谷类型氮素吸收效率的变化(CV_(N0.2) 39.99%和CV_(N6) 54.38%)显著高于华北夏谷类型(CV_(N0.2)29.31%和CV_(N6) 45.68%)和东北春谷类型(CV_(N0.2) 29.49%和CV_(N6) 40.30%),而氮素利用效率以华北夏谷类型品种间差异最大(CV_(N0.212.03%和CV_(N6) 12.70%)。茎叶干物重与氮素吸收和氮素利用效率呈极显著正相关(P0.01),相关系数分别为R~2_(N0.2)=0.1827**和R~2_(N6)=0.1027**及R~2_(N0.2)=0.8985**和R~2_(N6)=0.9442**;氮效率与氮素吸收量极显著正相关,与氮含量极显著负相关,相关系数分别为R~2_(N0.2)=0.8985**和R~2_(N6)=0.9442**及R~2_(N0.2)=0.1962**和R~2_(N6)=0.0998**;氮素利用效率与氮含量极显著负相关,相关系数分别为R~2_(N0.2)=0.9924**和R~2_(N6)=0.9910**。氮素吸收效率与氮素含量和氮素利用效率间无显著相关性。以两氮素水平条件下茎叶干物重和氮效率的平均值为标准,将3种生态类型的谷子品种划分为4种氮效率类型,双高效型、双低效型、高氮高效型和低氮高效型。其中,东北春谷双高效型和高氮高效型品种所占比重最高(P_(东北)52.9%P_(西北)36.0%P_(华北)29.7%和P_(东北)23.5%P_(华北)18.9%P_(西北)4.0%),双低效型比重最低(P_(东北)17.6%P_(华北)32.4%P_(西北)36.0%),而低氮高效型在西北春谷类型中所占比重最高(P_(西北)24.0%P_(华北)18.9%P_(东北)5.9%)。【结论】不同谷子品种苗期氮效率差异显著,且西北春谷类型品种间氮素吸收效率差异最大,华北夏谷类型品种间氮素利用效率差异最大;氮素吸收效率和利用效率之间无显著相关性,应作为2个独立的氮效率指标进行评价和改良。