牦牛血发酵的最佳菌种组合及最优发酵条件探究

为探究牦牛血发酵的最佳菌种及最优发酵条件,采用正交试验筛选出最佳的发酵菌种组合,以发酵时间、发酵温度、接种量、磷酸二氢钾添加量、麦麸添加量、菌种比例等条件为对象,在单因素试验基础上利用Box-Behnken试验设计原理,通过响应面法构建复合菌发酵牦牛血模型。结果表明:最适发酵组合为黑曲霉与酵母菌组合,在发酵时间为50h、温度为30℃、酵母与黑曲霉之比为0.4、接种量为0.3%的条件下,发酵后牦牛血可溶性蛋白质含量最高,最大预测值提高8.25%,实测值提高8.40%,且粗蛋白质含量增加,粗纤维含量减少。     

呼伦贝尔典型草原的利用方式对地上啮齿动物群落多样性的影响

2012年7、9月及2013-2014年5、7、9月,采用标志重捕法研究了连续放牧、季节轮牧和禁牧对呼伦贝尔典型草原啮齿动物捕获率、捕获量比例、多样性指数(丰富度指数、均匀性指数、Shannon-Wiener指数)的影响。结果表明,1)啮齿动物捕获率表现为连续放牧季节轮牧禁牧,连续放牧区显著高于禁牧区(P0.05)。2)不同放牧方式使啮齿动物群落结构发生了一定的变化。连续放牧区主要以草原黄鼠(Citellus dauricus)为主,捕获量比例为38.60%;季节轮牧区以黑线仓鼠(Cricetulus barabensis)和草原黄鼠占的比例较大,捕获量比例分别为37.30%和31.50%;禁牧区以黑线仓鼠为主,捕获量比例为38.89%。3)连续放牧区啮齿动物丰富度指数、Shannon-Wiener多样性指数均为最高;季节轮牧中均匀性指数为最高;禁牧中丰富度指数、Shannon-Wiener指数、均匀性指数均为最低。连续放牧中的丰富度指数和Shannon-Wiener指数显著高于禁牧(P0.05)。不同放牧方式明显改变了啮齿动物群落组成及多样性。综上,本研究结果表明,季节轮牧方式更利于合理利用草地资源并且能够抑制鼠害发生。     

Effect of dietary vanadium and vitamin C on egg quality and antioxidant status in laying hens

This study assessed the effect of dietary vanadium (V) and vitamin C (VC) on production performance, egg quality and antioxidant status in laying hens. A total of 360 laying hens (31‐week‐old) were randomly allotted into a 3 × 3 factorial arrangement treatments (four replicates and 10 chicks per replicate) with three levels of dietary V (0, 5 and 10 mg/kg) and three levels of vitamin C (0, 50 and 100 mg/kg) for 12 weeks. The effect of V and VC did not alter egg production, egg weight, average daily feed intake and feed conversion ratio during 1–12 week. Albumen height and Haugh unit value were linearly decreased (p < 0.001) by addition of V, whereas the effect of 100 mg/kg VC was observed to counteract (p < 0.05) this effect in V‐containing treatments during 1–12 week. Hens fed V‐containing diet laid lighter (linear effect, p < 0.05) coloured eggs (higher lightness value, lower redness and yellowness value), and the VC exerted no influence on it during 1–12 week. The serum superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐Px) activities, ability to inhibit hydroxyl radical, were significantly decreased, and the malondialdehyde (MDA) and V contents were increased (p < 0.05) by effect of V during 4, 8 and 12 week. The effect of VC alone and the interactive effect between VC and V were shown to increase serum (p < 0.05) SOD activity in 4 week and decrease MAD levels in 12 week. The result indicate that V decreased the egg quality and caused the oxidative stress at level of 5 mg/kg and 10 mg/kg, and the addition of 100 mg/kg vitamin C can alleviate its egg quality reduction effect and can mitigate the oxidative stress to some extent.     

肉鸡Trx1和Trx2蛋白的表达纯化及其抗氧化应激效果评价

试验旨在对肉鸡Trx1和Trx2蛋白进行表达和纯化,并评价其抗氧化特性。将原核表达载体GgTrx1-pET28a(+)和GgTrx2-nsp-pET28a(+)转入大肠埃希菌中进行蛋白表达;应用镍柱亲和层析的方法对该融合蛋白进行纯化;采用胰岛素还原法对重组肉鸡Trx1和Trx2蛋白(GgTrx1和GgTrx2)进行活性鉴定;通过细胞体外试验分析比较GgTrx1和GgTrx2对大鼠肝细胞BRL-3A氧化应激保护作用的影响。结果显示,试验成功获得两种重组蛋白:GgTrx1和GgTrx2,最适诱导条件分别为37℃、0.4mmol/L IPTG诱导4h和37℃、1.0mmol/L IPTG诱导4h;纯化的重组蛋白GgTrx1和GgTrx2纯度可达到90%,浓度分别达到4.0和5.0 mg/mL。重组蛋白GgTrx1和GgTrx2均具有较高的还原胰岛素二硫键的能力,并呈现出浓度效应。体外细胞试验发现,重组蛋白GgTrx1和GgTrx2均能显著降低过氧化氢诱导的BRL-3A膜脂过氧化,保护抗氧化酶SOD和CAT活性,且重组蛋白GgTrx2效果更明显。本试验结果表明,重组蛋白GgTrx1和GgTrx2均具有生物学活性和良好的抗氧化应激特性,且线粒体型Trx2为临床治疗氧化应激性疾病提供了更多可能。     

Pharmacokinetics of orbifloxacin in crucian carp (Carassius auratus) after intravenous and intramuscular administration

The pharmacokinetics of orbifloxacin was studied after a single dose (7.5 mg/kg) of intravenous or intramuscular administration to crucian carp (Carassius auratus ) reared in freshwater at 25°C. Plasma samples were collected from six fish per sampling point. Orbifloxacin concentrations were determined by high‐performance liquid chromatography with a 0.02 μg/ml limit of detection, then were subjected to noncompartmental analysis. After intravenous injection, initial concentration of 5.83 μg/ml, apparent elimination rate constant (λ_z) of 0.039 hr^?1, apparent elimination half‐life (T_1/2λz) of 17.90 hr, systemic total body clearance (Cl) of 75.47 ml hr^?1 kg^?1, volume of distribution (Vz) of 1,948.76 ml/kg, and volume of distribution at steady‐state (Vss) of 1,863.97 ml/kg were determined, respectively. While after intramuscular administration, the λ_z, T _1/2λz, mean absorption time (MAT ), absorption half‐life (T _1/2ka), and bioavailability were determined as 0.027 hr^?1, 25.69, 10.26, 7.11 hr, and 96.46%, respectively, while the peak concentration was observed as 3.11 ± 0.06 μg/ml at 2.0 hr. It was shown that orbifloxacin was completely but relatively slowly absorbed, extensively distributed, and slowly eliminated in crucian carp, and an orbifloxacin dosage of 10 mg/kg administered intravenously or intramuscularly would be expected to successfully treat crucian carp infected by strains with MIC values ≤0.5 μg/ml.     

Reference gene selection for reverse transcription quantitative polymerase chain reaction in chicken hypothalamus under different feeding status

This study was designed to investigate the stability of 10 candidate reference genes, namely ACTB, B2M, GAPDH, HMBS, LBR, POLR2B, RN18S, RPS17, TBP, and YWHAZ for the normalization of gene expression data obtained by quantitative real‐time polymerase chain reaction (qPCR) in studies related to feed intake of chicken. Samples were isolated from hypothalamus under three different nutritional status (ad libitum, fasted for 24 hr, fasted for 24 hr then refed for 2 hr). Five different algorithms were applied for the analysis of reference gene stability: BestKeeper, geNorm, NormFinder, the comparative ΔCt method, and a novel approach using multivariate linear mixed‐effects modelling for stable reference gene selection. TBP and POLR2B were identified as the two most suitable and B2M and RN18S as the two least stable reference genes for normalization. Despite our review, the current literature showing that RN18S is one of the most commonly used reference gene in chicken gene expression studies, its applicability for normalization should be evaluated before each qPCR experiment.     

A note on cloning and analysis of the osteopontin gene with egg quality traits in two Chinese domestic ducks

ABSTRACT

1. Osteopontin (OPN) is a highly phosphorylated acidic glycoprotein that plays a crucial role in eggshell formation. In this study, an 893-bp cDNA sequence of the OPN gene, which encodes 180 amino acids, was obtained.

2. Polymorphisms of the OPN gene were analysed with DNA sequencing and polymerase chain reaction-single-strand conformation polymorphism methods in two Chinese domestic laying ducks (Jingding n = 100, Youxian n = 478, respectively).

3. One polymorphism was identified in exon 7 (NM_ 004676534.1:c.267T>C) of the OPN gene, with three genotypes: TT (both T allels weren’t mutated (wild type)), TC (one T allel was mutated to C (heterozygote genotype)) and CC. (both T allels were mutated to C (homozygote 20 genotype)) Association analysis with egg quality traits in the two Chinese domestic laying ducks showed that the ducks with the CC genotype had significantly greater eggshell strength and eggshell thickness (p < 0.05). Hence, the exon 7 267T>C polymorphism of the OPN gene is a potentially valuable genetic marker for laying duck breeding programmes.     

Effect of supplemental dietary slow‐release urea on growth performance and physiological status of dairy heifers

We examined the effect of supplemental dietary slow‐release urea on the growth performance and physiological status of 16 dairy Holstein heifers (10 months of age, 322 ± 10 kg). The heifers were offered a formulated isocaloric and isonitrogenous 70:30 roughage : concentrate ration and were assigned randomly to one of four levels of slow‐release urea supplementation (0% [U₀], 1% [U₁], 1.5% [U_1.5] and 2% [U₂] dry matter [DM]). The total study lasted 95 days, which included a 20 days adaptation period. Dry matter intake (DMI) of U₂ was lower than the intakes of U₀ and U₁ (p < .05), while average daily gains (ADG) of U₁ and U_1.5 were higher than U₀ and U₂ (p < .05). Rumen volatile fatty acids concentration did not differ among the four treatments, while ammonia nitrogen concentration increased with an increase in urea level (p < .05). Serum blood urea nitrogen concentration was lower in U_1.5 than in U₀ and U₂ while serum free fatty acids concentration in U₂ was higher than in the other three treatments (p < .05). We concluded that the addition of urea at a level of 1.5 to 2.0% DM resulted in a reduction in DMI but the addition of 1.0%–1.5% urea resulted in the highest ADG, with no negative effects on rumen fermentation and health status of the calves.     

燕麦幼苗对低温胁迫的响应

在0、12、36、60 h不同时间梯度下,对7个燕麦(Avena sativa)品种(青引1号、青引2号、青引3号莜麦、青海甜燕麦、青海444、青燕1号和林纳)进行连续低温(5℃)胁迫,比较其抗寒能力。结果表明,与低温胁迫前(0 h)相比,低温处理后(12、36和60 h)7个燕麦品种幼苗叶片丙二醛、脯氨酸含量和超氧化物歧化酶、过氧化物酶活性均显著增加(P0.05);各燕麦品种幼苗叶片丙二醛、脯氨酸含量和过氧化物酶、超氧化物歧化酶活性在低温胁迫初期(0-12 h)显著增加(P0.05)并达到最大值;随着低温胁迫时间延长,其含量开始下降。7个燕麦品种抗寒能力依次表现为青引3号莜麦青海甜燕麦青引2号林纳青燕1号青海444青引1号。