Herbage intake of dairy cows in mixed sequential grazing with breeding ewes as followers

This study aimed to evaluate the hypothesis that mixed sequential grazing of dairy cows and breeding ewes is beneficial. During the seasons of spring–summer 2013 and autumn–winter 2013–2014, 12 (spring–summer) and 16 (autumn–winter) Holstein Friesian cows and 24 gestating (spring–summer) and lactating (autumn–winter) Pelibuey ewes grazed on six (spring–summer) and nine (autumn–winter) paddocks of alfalfa and orchard grass mixed pastures. The treatments “single species cow grazing” (CowG) and “mixed sequential grazing with ewes as followers of cows” (MixG) were evaluated, under a completely randomized design with two replicates per paddock. Herbage mass on offer (HO) and residual herbage mass (RH) were estimated by cutting samples. The estimate of herbage intake (HI) of cows was based on the use of internal and external markers; the apparent HI of ewes was calculated as the difference between HO (RH of cows) and RH. Even though HO was higher in CowG, the HI of cows was higher in MixG during spring–summer and similar in both treatments during autumn–winter, implying that in MixG the effects on the cows HI of higher alfalfa proportion and herbage accumulation rate evolving from lower residual herbage mass in the previous cycle counteracted that of a higher HO in CowG. The HI of ewes was sufficient to enable satisfactory performance as breeding ewes. Thus, the benefits of mixed sequential grazing arose from higher herbage accumulation, positive changes in botanical composition, and the achievement of sheep production without negative effects on the herbage intake of cows.     

Virulence traits of avian pathogenic (APEC) and fecal (AFEC) <Emphasis Type="Italic">E. coli</Emphasis> isolated from broiler chickens in Algeria

Avian pathogenic E. coli (APEC) is the etiologic agent of avian colibacillosis, the most common disease responsible for chicken morbidity in the world. Although multiple virulence-associated factors were identified, their prevalence in Algeria is still poorly known. In the present research, 92 avian pathogenic E. coli (APEC) isolates were recovered from broilers with clinical signs and lesions of colibacillosis. In addition, 32 E. coli isolates collected from feces of healthy birds (AFEC) were included for comparison. All isolates were investigated by PCR for the presence of a total of 11 virulence-associated genes described for avian pathogenic (iroN, ompT, hlyF, iss, iutA, and fimC) and diarrheagenic E. coli (eae, stx, elt/est, ipaH, and aggR). The sensitivity of 39 APEC isolates to 16 antibiotics was also determined using antimicrobial pretreated microplates. Here, we report that 98% of the examined isolates host at least one of the tested virulence factors. The most prevalent genes in APEC were iutA (90.6%), ompT (86.9%), and iss (85.8%); whereas, iutA (78.1%), fimC (78.1%), and iroN (68.7%) were the highest prevalent genes in AFEC. Our data showed that none of the AFEC isolates harbor any of the tested diarrheagenic genes. Moreover, only elt/est (5.4%), stx (2.1%), and ipaH (2.1%) genes were carried by APEC isolates. We further established that ceftazodime, ceftiofur, mequindox, amoxicillin/clavulanic acid, and meropenem were the most efficient antibiotics against the analyzed APEC isolates. Overall, our findings provide more insights about APEC and AFEC virulence potential in Algeria which could participate in the fight against colibacillosis.     

Feeding behavior of feedlot lambs fed diets containing levels of cassava wastewater

In this study, we evaluated the effects of including cassava wastewater in the diet on the feeding behavior of feedlot lambs in 35 male uncastrated Santa Inês × Dorper crossbred lambs at an approximate age of 3 months, with an average live weight of 20.0?±?3.4 kg. Diets were formulated with hay of cassava shoots (roughage) and a concentrate based on corn and soybean, with a roughage:concentrate ratio of 50:50, plus inclusion of cassava wastewater at the levels of 0, 12, 24, 36, or 48 g/kg of the total diet. Feeding behavior was evaluated between the 46th and 52nd days of the experiment. Increasing cassava wastewater levels in the diet reduced (P?<?0.05) the intakes (kg/day) of dry matter and neutral detergent fiber as well as the efficiency of rumination (g/cud and g/h) of dry matter and neutral detergent fiber. The other behavioral parameters were not affected by wastewater inclusion in the diet. Therefore, the inclusion of up to 48 g/kg of cassava wastewater on fresh matter of diets is not recommended for feedlot lambs.     

Prevalence and risk factors of mycobacterial infections in farm and trade cattle in southwestern Nigeria

We evaluated the prevalence of mycobacterial infections (i.e., Mycobacterium bovis and non-tuberculous mycobacteria [NTM]) and their associated risk factors among cattle herds and trade cattle in southwestern Nigeria. Through cross-sectional study design, cattle herds from three locations were screened using the single intradermal comparative cervical tuberculin test based on two diagnostic standards; more than 4 mm (? 4 mm) and more than 2 mm (? 2 mm) cut-off points. Abattoir study involved screening trade cattle for tuberculous lesions. Overall, 515 cattle from 45 herds were screened. Using >?4 mm, animal level and herd prevalence of 11.7 and 46.7% were recorded, respectively. Applying the ? 2 mm cut-off, animal level and herd prevalence increased to 31.1 and 60.0%, respectively. Significantly, using the ? 2 mm cut-off, cattle in medium size herds/extensive management system (OR?=?1.6; 95% CI 1.1–2.5) and Sokoto Gudali (OR?=?2.3; 95% CI 1.4–3.8) were more at risk of being positive reactors, while Rahaji (OR?=?0.3; 95% CI 0.1–0.7) breeds of cattle and cows in the peri-urban area (OR?=?0.4; 95% CI 0.2–0.9) were less at risk of being positive reactors. Again, M. avium reactor of 21.7% was observed. In the abattoir, 1797 cattle were examined with 126 lesions suggestive of tuberculosis (TB). Culture/molecular analyses confirmed 2.2% M. bovis and 0.9% NTM infections. Risk factors associated with bovine TB among trade cattle were sex (OR?=?4.0; 95% CI 1.2–13.5) and age (OR?=?0.3; 95% CI 0.1–0.9). We confirm 11.7% prevalence of mycobacterial infections among populations of cattle screened with breed and herd size being major risk factors.     

不同年限封育对黄土高原典型草原地上植被的影响

为了揭示自然恢复过程中植被动态变化规律,以黄土高原典型草原为研究对象,采用野外调查与室内分析相结合的方法,分析不同年限封育(0、5、15、23和32年)对草地植被特征、物种多样性和群落演替动态变化的影响。结果表明,随着封育年限的增加,枯落物量和厚度呈递增趋势,群落盖度呈先增加后降低趋势,群落密度呈递减趋势,地上生物量和禾草地上生物量均呈先增加后降低的趋势,且均在封育23年草地达到了峰值。不同年限的封育对Simpson多样性指数和Pielou均匀度指数影响不显著(P0.05)。地上植被的物种丰富度呈先增加后降低趋势,且在封育15年达到峰值。地上植被群落封育演替的一般模式为杂类草生长阶段→本氏针茅(Stipa bungeana)逐渐占优势阶段→本氏针茅稳定发展阶段。     

桑沟湾养殖海带生长的模型预测

海带(Saccharinajaponica)是一种常见的大型经济褐藻,是海洋生态系统重要的初级生产者,也是我国北方沿海主要的养殖藻类。本研究旨在建立海带个体生长数值模型,并以此预测中国北方近海大规模筏式养殖条件下海带的生长情况。本研究以桑沟湾养殖海带为例,利用可视化模型软件STELLA描述海带生长的关键过程及其与环境参数的关系,以净生长量(N_(growth))=总生长量(G_(growth))–呼吸作用(resp)–枯烂(E_(kelp))为基本框架,模拟和预测海带的生物量和叶片长度变化。海带的总生长用光照、温度、盐度、海带体内营养盐(包括N和P)等强制函数定义,其中,光照参数来自桑沟湾气象记录,盐度、温度和营养盐为现场调查实测值。模型模拟桑沟湾养殖海带的长度与干重结果与实测值的拟合度R~2值分别为0.936、0.963,说明该模型能够很好反映海带的真实生长情况。可靠的个体生长模型是评估海带养殖容量的基础,并可为水产养殖区的空间规划提供决策依据。     

基于DEB理论的皱纹盘鲍个体生长模型参数的测定

为获取皱纹盘鲍(Haliotis discus hannai)个体生长模型所需的6个关键参数,设计了饥饿耗能、温度对耗氧的影响等相关生理实验,计算得到各项参数值。单位体积维持耗能率的值 、形成单位体积结构物质所需的能量值 、单位体积最大储存能量 和储备能量值 4个参数,通过连续测定皱纹盘鲍饥饿过程中呼吸耗氧率和软组织干重不断下降直至保持稳定时的能量值计算;温度函数中Arrhenius温度 的数值根据皱纹盘鲍在不同温度梯度下的单位干重耗氧率测定、计算;形状系数δm值通过统计测量的壳长、软组织湿重等生物学参数拟合回归得到。结果显示,皱纹盘鲍在饥饿后,呼吸耗氧率和软组织干重分别降低了26.3%和70.0%,呼吸耗氧率由2.69 mg/(ind.?h)逐渐降低并稳定在0.8 mg/(ind.?h),软组织干重由(5.21±0.89) g降低至(3.84±0.22) g;根据公式计算得 和 的值分别为20.18 J/(cm3?d)和8120 J/cm;皱纹盘鲍饥饿前后有机物含量分别为80%和58%,经过换算, 和 的值分别为2726 J/cm3和32583 J/g。不同规格的皱纹盘鲍在水温为5℃~20℃范围内,温度与单位干重耗氧率呈正比;当水温超过20℃之后,温度与单位干重耗氧率呈反比。在转折点20℃之前,单位干重耗氧率的ln值与温度(热力学温度,K)的倒数呈线性关系,线性回归方程斜率的绝对值为Arrhenius温度 值( =7196 K)。生物学统计分析鲍壳长(L)与体积(V)呈三次函数关系：V=0.0639 L3.1621(R²=0.9852),根据公式对软组织湿重的立方根与壳长进行线性回归,所得的斜率即为形状系数δm值(δm=0.43)。本研究对建立以DEB理论为指导的皱纹盘鲍个体生长模型提供了数据支撑。     

东北宿根花卉在花海建设中的应用——以莲花山花海项目为例

本文以莲花山南北向花海的东北宿根花卉种植为例,介绍了东北宿根花卉在花海及园林绿化工程中的应用,并总结了在施工过程中遇到的问题,为今后花海的景观设计及施工提供思路和方向.     

不同覆盖处理对元宝枫叶生物活性物质含量的影响

以2年生元宝枫苗为试材,对其进行不同覆盖处理,测定叶内黄酮、绿原酸、叶绿素、SOD活性酶和丙二醛的含量,并进行方差分析和多重比较.结果表明:不同覆盖处理对元宝枫叶中生物活性物质含量的影响十分明显,黄酮含量在白膜覆盖下最高,绿原酸和叶绿素含量在绿膜覆盖下最高,SOD酶活性和丙二醛含量在红膜覆盖下最高,黄酮、叶绿素、丙二醛含量在不同覆盖处理下均以α=0.01水平上差异极显著,SOD酶活性和绿原酸含量以α=0.05水平上差异显著.     

抗生素对泡桐丛枝病植原体和发病相关蛋白质的影响

泡桐(Paulownia sp.)是我国重要的速生用材和绿化树种;然而,丛枝病的发生给我国的泡桐生产带来了巨大的损失.