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1.
This study was carried out to evaluate the effects of water temperature (WT) and dietary protein levels on growth, body composition and blood biochemistry of GIFT tilapia (Oreochromis niloticus; initial average body weight: 38.75 ± 0.61g, n = 20). The fish were fed with six diets contained graded levels of protein (209.6, 251.0, 302.4, 354.3, 401.9 and 456.8 g/kg) and raised in each of WT (22°C, 28°C and 34°C) for 8 weeks. Results showed that the growth, feed utilization and protein efficiency were significantly increased with the increase of dietary protein level and followed by the latter platform at each WT. The fish raised at 28 and 34°C showed similar growth performance, and their values were significantly higher than the fish raised at 22°C (p < 0.05). The lipid contents in whole body were decreases with the increase of dietary protein level at each WT. However, the whole‐body protein, ash and moisture contents were not affected by dietary protein level or WT (p > 0.05). The values of serum biochemical indices (ALP, ALT, AST and TCHO) were all decreased with the increase of dietary protein. The optimal dietary protein requirement for GIFT tilapia to achieve maximal growth performance is 374.4, 301.7 and 304.9 g protein/kg diet at 22, 28 and 34°C, respectively.  相似文献   
2.
深入了解西瓜核心种质资源的群体结构及遗传多样性,可以准确指导亲本间杂交组合的有效配置,避免具有相似遗传背景材料的组合,以便提高育种效率。据此,本研究通过采用45对具有多态性的SSR标记对不同来源的78份西瓜核心种质进行了多元统计分析。结果表明,45个SSR标记共检测出175个位点,其中具有多态性位点数为165个,多态性比率达95.41%,且每对引物平均检测到等位基因位点3.67个,PIC大小范围在0.049~0.781之间,平均值为0.415,其有效等位基因数(Ne)、期望杂合度(He)、观测杂合度(Ho)、多样性指数(I)及Nei's基因多样性指数(H)在该群体水平上分别为2.258、0.479、0.521、0.850和0.476,同时筛选出了28对多态性高、带型稳定、易于统计的核心引物,构建了78份西瓜核心种质的SSR指纹图谱。群体结构分析表明,78份西瓜核心种质资源划分为2大类群和4个亚群,其中来自不同地域的美国材料和日本材料分别独立趋于2大类群中,而中国种质材料普遍交叉分布于2大类群中,且各亚群之间存在着明显的基因交流,分子方差分析表明种质间遗传多样性主要存在于品种间和居群间。  相似文献   
3.
[目的]研究桉树趋嫩性害虫综合防治技术。[方法]对桉树芽木虱、蓟马、蚜虫、叶蝉、叶螨等桉树趋嫩性害虫进行调查与分析。[结果]潮间带蟹+森林鼠妇乙醇液对桉树趋嫩性害虫具有比较明显的防治效果,控制效果达到93.1%。[结论]结果在林业生产中有一定意义。  相似文献   
4.
5.
Although pork producers typically aim to optimize growth rates, occasionally it is necessary to slow growth, such as when harvest facility capacity is limited. In finishing pigs, numerous dietary strategies can be used to slow growth so pigs are at optimal slaughter body weights when harvest facility capacity and/or access is restored. However, the impact of these diets on pork carcass quality is largely unknown. Thus, this study aimed to evaluate the efficacy of dietary strategies to slow growth in late finishing pigs and evaluate their effects on carcass composition and pork quality. Mixed-sex pigs (n = 897; 125 ± 2 kg BW) were randomly allotted across 48 pens and assigned to 1 of 6 dietary treatments (n = 8 pens/treatment): (1) Control diet representative of a typical finisher diet (CON); (2) diet containing 3% calcium chloride (CaCl2); (3) diet containing 97% corn and no soybean meal (Corn); (4) diet deficient in isoleucine (LowIle); (5) diet containing 15% neutral detergent fiber (NDF) from soybean hulls (15% NDF); and (6) diet containing 20% NDF from soybean hulls (20% NDF). Over 42 d, pen body weights and feed disappearance were collected. Pigs were harvested in 3 groups (14, 28, and 42 d on feed) and carcass data collected. From the harvest group, 1 loin was collected from 120 randomly selected carcasses (20 loins/treatment) to evaluate pork quality traits. Overall, ADG was reduced in CaCl2, Corn, and 20% NDF pigs compared with CON pigs (P < 0.001). However, ADFI was only reduced in CaCl2 and 20% NDF pigs compared with CON (P < 0.001). Feed efficiency was reduced in CaCl2 and Corn pigs compared with CON (P < 0.001). Hot carcass weights were reduced in CaCl2 pigs at all harvest dates (P < 0.001) and were reduced in Corn and 20% NDF pigs at days 28 and 42 compared with CON pigs (P < 0.001). In general, CaCl2 and 20% NDF diets resulted in leaner carcasses, whereas the Corn diet increased backfat by 42 d on test (P < 0.05). Loin pH was reduced and star probe increased in CaCl2 pigs compared with CON pigs (P < 0.05); no treatments differed from CON pigs regarding drip loss, cook loss, color, firmness, or marbling (P ≥ 0.117). Overall, these data indicate that several dietary strategies can slow finishing pig growth without evidence of behavioral vices. However, changes to carcass composition and quality were also observed, indicating quality should be taken into consideration when choosing diets to slow growth.  相似文献   
6.
为探明杂交鲌“先锋1号”与其母本翘嘴鲌(Erythroculter ilishaeformis)(♀)和父本黑尾近红鲌(Ancherythroculter nigrocauda)(♂)的营养品质差异,对三种鲌肌肉营养品质进行了测定和评价。结果显示:杂交鲌水分含量显著高于父本,粗脂肪含量显著低于父本,灰分含量显著低于母本。杂交鲌肌肉的胱氨酸(Cys)含量显著高于母本,必需氨基酸指数(EAAI)高于父本。杂交鲌肌肉中十五碳烷酸(C15∶0)、α-亚麻酸(C18∶3)的相对含量显著高于翘嘴鲌和黑尾近红鲌。杂交鲌肌肉硬度显著高于母本,肌肉弹性显著低于父本;铁含量与父本无显著差异,但显著高于母本。结果表明,杂交鲌“先锋1号”肌肉营养成分兼具双亲的优良性状,表现出一定的杂交优势,是一种优质的营养资源。  相似文献   
7.
中国粮食安全百年变化历程   总被引:4,自引:1,他引:3       下载免费PDF全文
以人粮关系为主线、以中国社会经济发展为辅线,重点回顾了近百余年中国粮食安全变化历程及其社会经济背景。提出粮食安全问题分析的4个纬度,即农民生计、土地制度、农业科技、政策管理。认为重粮重农不轻工商、控制人口过快增长、完善土地使用制度、发展农业科技、维护国家长治久安是保障粮食安全的5个要素。最后指出应树立包括数量安全、结构安全、生态安全、质量安全在内的广义粮食安全观,系统地构建粮食安全保障体系。  相似文献   
8.
A 12‐week feeding trial was conducted to evaluate the effects of replacing fishmeal (FM) with soybean meal (SBM), rapeseed meal (RM) and cottonseed meal (CSM) on growth, feed utilization and body composition of juvenile hybrid sturgeon Acipenser baerii ♀ × Acipenser schrenckii ♂ (initial body weight, 8.63 ± 0.24 g). Five isonitrogenous and isoenergetic diets were formulated as follows: a control diet (FM60) containing 600 g/kg FM and four other diets (FM45, FM30, FM15 and FM0 containing 450, 300, 150 and 0 g/kg FM, respectively) where protein from FM was substituted by a mixture of SBM, RM and CSM. Fish fed FM0 and FM15 had poorer growth performance, feed utilization, apparent digestibility coefficients of dry matter, protein, lipid and gross energy, and fed FM0 had poorer hepatosomatic index and survival compared with the fish fed FM60. The whole body lipid in fish fed FM0 was significantly higher than that in fish fed FM60 and FM15. This study indicates that 300 g/kg of FM can be replaced with a mixture of SBM, RM and CSM in the diet of juvenile hybrid sturgeon without compromising growth performance, feed utilization and body composition.  相似文献   
9.
城市半自然森林具有独特的群落结构和生物多样性特征,研究城市化影响的半自然森林更新特征,可以为城市生物多样性保育与地带性植被恢复重建提供借鉴。文章以上海辰山残存半自然森林1 hm^2固定监测样地为对象,调查分析半自然森林更新苗的物种组成特征。结果表明:1 hm^2样地更新苗共5 937株,分属22科32属37种,其中上海自然分布的乡土种占57.89%,明显高于城市人工林的乡土树种比例;香樟、构树、天竺桂、朴树和小蜡等5种更新苗占总数的57.2%,聚集性分布格局明显;在11个植被群落类型中,各类型更新苗的丰富度普遍较高,不同树种的更新苗存活和发育潜力存在差异。  相似文献   
10.
以白梭梭荒漠和盐生假木贼荒漠为对象,采用野外调查取样法,通过对两类不同类型荒漠草地土壤营养成分的测定分析,探讨不同类型荒漠草地土壤营养成分对短期封育的响应规律,为荒漠草地的管理和保护提供科学依据。结果表明:1)盐生假木贼荒漠草地的土壤营养成分含量显著高于白梭梭荒漠草地;2)短期封育对盐生假木贼荒漠草地土壤系统的碳密度、全氮、全磷和全钾含量的影响较小(P>0.05);3)短期封育下,白梭梭荒漠草地土壤碳密度增加了43.46%(P>0.05),但全磷和全钾分别降低了33.53%(P<0.05)和60.30%(P<0.05)。综上所述,短期封育对盐生假木贼荒漠影响较小,而对白梭梭荒漠草地土壤碳密度的积累有利;同时,导致白梭梭荒漠草地土壤全磷和全钾含量有下降趋势,表明封育效果与荒漠植被类型和土壤类型之间存在密切的关系。  相似文献   
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