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991.
《Animal : an international journal of animal bioscience》2018,12(5):1102-1110
The aim of this study was to evaluate the effect of using different floor types to accommodate growing and finishing beef cattle on their performance, cleanliness, carcass characteristics and meat quality. In total, 80 dairy origin young bulls (mean initial live weight 224 kg (SD=28.4 kg)) were divided into 20 blocks with four animals each according to live weight. The total duration of the experimental period was 204 days. The first 101 days was defined as the growing period, with the remainder of the study defined as the finishing period. Cattle were randomly assigned within blocks to one of four floor type treatments, which included fully slatted flooring throughout the entire experimental period (CS); fully slatted flooring covered with rubber strips throughout the entire experimental period (RS); fully slatted flooring during the growing period and moved to a solid floor covered with straw bedding during the finishing period (CS-S) and fully slatted flooring during the growing period and moved to fully slatted flooring covered with rubber strips during the finishing period (CS-RS). Bulls were offered ad libitum grass silage supplemented with concentrates during the growing period. During the finishing period, bulls were offered concentrates supplemented with chopped barley straw. There was no significant effect of floor type on total dry matter intake (DMI), feed conversion ratio, daily live weight gain or back fat depth during the growing and finishing periods. Compared with bulls accommodated on CS, RS and CS-RS, bulls accommodated on CS-S had a significantly lower straw DMI (P<0.01). Although bulls accommodated on CS and CS-S were significantly dirtier compared with those accommodated on RS and CS-RS on days 50 (P<0.05) and 151 (P<0.01), there was no effect of floor type on the cleanliness of bulls at the end of the growing and finishing periods. There was also no significant effect of floor type on carcass characteristics or meat quality. However, bulls accommodated on CS-S had a tendency for less channel, cod and kidney fat (P=0.084) compared with those accommodated on CS, RS and CS-RS. Overall, floor type had no effect on the performance, cleanliness, carcass characteristics or meat quality of growing or finishing beef cattle. 相似文献
992.
993.
庙台槭(Acer miaotaiense Tsoong)为我国三级保护植物,是秦岭特有的濒危树种,具有重要的经济价值和观赏价值。通过对庙台槭主要分布区野生资源进行调查,研究其种群的年龄结构、静态生命表、存活曲线和死亡曲线,用动态指数(Vpi、Vpi')和时间序列模型预测其种群发展趋势。结果显示,庙台槭种群幼龄个体多,中龄和老龄个体少,其生存曲线呈Deevey-Ⅲ型;静态生命表及相关曲线分析显示,庙台槭种群的存活率与径级表现出显著负相关,而种群死亡率曲线总体呈先下降后增加的趋势;种群数量动态分析显示,庙台槭种群整体结构处于增长型,在缺乏成年个体的情况下,种群对外部环境的抗干扰能力下降;时间序列预测发现,经过幼苗、幼树阶段,同一时间曲线的庙台槭种群数量在高径级所占比例略有增加,但高龄级个体相对较少;庙台槭分布地区的主要植被类型为落叶阔叶林和常绿阔叶林,但庙台槭个体受保护较少,人为活动及病虫害影响较大,天然更新困难,生存和保护状况不容乐观。 相似文献
994.
简述措勤地区双壳类的地层分布及组合特征,描述双壳类化石20属20种,其中有6新种。非海相双壳类(Isodomella,Costocyrena)的发现具有重要意义。 相似文献
995.
广西珍稀濒危植物区系的基本特征 总被引:5,自引:0,他引:5
本文在简述广西珍稀濒危植物生态环境和区系组成的同时,重点分析了其植物区系的基本特征。这些特征主要有:区系成分复杂,热带性质明显,特有成分突出,古老成分较多,喜酸成分占优势,绝大部分种类分布在海拔1000m以下。 相似文献
996.
997.
香瓜梨对温度响应的生理特性研究 总被引:2,自引:1,他引:1
置于不同温度(5-35℃)下的香瓜梨幼苗,在15-30℃时叶片的光合速度较高。20℃时的标株叶片具有最高的光合速率,光事电子传递活性,PSII的光化效率和电子传递的量子效率,叶绿素含量,但细胞膜透性最低。5-10℃的低温和35℃的高温明显降低生理参数,且随处理时间的长,其降低程度越明显,解除5℃的低温处理后转自然温度环境(15-20℃)中6d,叶片细胞的电解质渗漏降低。 相似文献
998.
F344/N-Smu-D大鼠生长发育若干生物学特性的检测 总被引:1,自引:0,他引:1
Fischer344大鼠在国外广泛应用于肿瘤研究与慢性毒性试验,八十年代中期引入我国。我们对F344/N-Smu-D大鼠的生长发育的若干生物学特性进行了检测。结果表明,该品系大鼠体型较SD大鼠与Wistar大鼠小,除睾丸、垂体、肾上腺、乳腺外的大部分器官与组织的自发性肿瘤的发生率相对较低,将F344/N-Smu-D大鼠种群与F344/DuCrj种群比较,在体重、耗食量,血液学与生化学等方面的若干特性差异较大,肿瘤发生率与死亡差别不大。 相似文献
999.
广州白云山风景名胜区的植被特点及其林分改造 总被引:5,自引:1,他引:4
论述了广州白云山风景名胜区的自然环境和植被演变历史,分析了植被特点和植被演替趋势,提出了林分改造建议。 相似文献
1000.
Greenhouse mesocosms of freshwater marsh vegetation were exposed to a simulated saltwater intrusion event followed by a recovery period during which water levels and interstitial water salinity were adjusted over a range of conditions. Virtually all above-ground vegetation, including the three dominant species, Sagittaria lancifolia L., Leersia oryzoides (L.) Swartz, and Panicum hemitomon Schultes, was killed by the initial saltwater intrusion event. P. hemitomon did not recover, but S. lancifolia and L. oryzoides, as well as many of the other species initially present, exhibited some ability to recover depending on post-saltwater intrusion conditions. Increasingly harsh recovery conditions (for freshwater marsh vegetation), including more reduced soil conditions, higher interstitial salinities, and higher interstitial sulfide concentrations were associated with decreased live above-ground biomass and species richness. The effect of elevated salinity on vegetative recovery became more pronounced under flooded conditions. This experiment illustrates that the response of a freshwater marsh community to the long-term disturbance effect of a transient saltwater intrusion event will be strongly influenced by post-intrusion salinity and water levels. 相似文献