不同时间断乳对母牦牛发情影响的观察

对带犊牦牛分别在8月1日、8月27日和10月12日进行断乳,结果Ⅰ组母牛共发情104头,发情率为69.33%,Ⅱ组母牛发情54头,发情率为36.00%,Ⅰ组比Ⅱ组多发情50头,高48.01%,差异性极显著(P<0.01)。Ⅲ组母牛发情4头,发情率4%。Ⅱ组比三组Ⅲ组多发情36头,高90%,差异性极显著(P<0.01)。Ⅰ组母牦牛发情率最高,持续时间长,Ⅱ组母牦牛只有一个发情高峰,持续比较短,Ⅲ组母牦牛发情率低,持续时间也短。     

近54a中国北方严寒期时空变化特征及其影响因素

利用中国北方269个气象站点1960—2014年逐日平均气温数据,以候均温为统计数据,采用线性倾向估计、Mann-Kendall(M-K)检验、累积距平、Morlet小波功率谱及相关分析等方法,探讨了中国北方严寒期的时空变化特征及其影响因素。结果表明:近54 a来,中国北方各区域严寒期起始候推迟,终止候提前,候数缩短,其中,西北地区起始候推迟最显著,华北地区终止候提前最突出,华北地区候数缩短最长。严寒期空间差异显著,表现为:自南向北,起始候提前、终止候推迟、严寒期延长的趋势更突出;且严寒期变短地区多于变长地区。突变和小波分析表明,北方严寒期在1980s末到1990s初发生了突变,东北、华北和西北地区的严寒期分别存在4.00 a、7.09 a和3.19 a的优势周期。此外,纬度每增大1°,严寒期延长1.30 p;北半球极涡面积指数和亚洲区极涡面积指数是中国北方严寒期变化的重要因素。     

蛋鸡生产过程中两个关键的过渡时期

蛋鸡生产过程中，从育雏期到育成期，随着蛋鸡自身生理特点的变化，饲养管理条件和技术措施需随之改变，这种改变一定要逐步稳妥进行。蛋鸡从育成结束到产蛋开始，各方面也有一个过渡的过程，这一过程中要做的工作较多，是一个比较特殊的时期，有人将17～22周龄称为蛋鸡的预产期，能否平稳度过预产期，有关以后产蛋性能的发挥和蛋鸡的有效利用，实践中应予以重视。     

新时期农村群体性事件的成因与对策——基于经济学的分析视角

介绍了新时期农村群体性事件的特征,运用经济学的相关理论,从经济学的角度探求群体利益受损的原因,以及群体为何采取这种极端的利益诉求方式,并在此基础上提出农村群体性事件的预防与应对建议。     

Effects of Harvest Period on the Production of White River Crayfish,Procambarus acutus acutus

Abstract

Crayfish harvest was initiated at a cool water temperature (15°C) and warm water temperature (20°C) from culture ponds (0.1 ha) with a resident population of white river crayfish, Procambarus acutus acutus.Crayfish were harvested for 24 days for a total of 1,977 trap-days/ha (March 9-May 12, 2000 from the cool-harvest treatment and May 5-June 15, 2000 from the warm-harvest treatment). The mean total length (TL) and production of harvested white river crayfish (WRC) was similar between treatments. The population structures of WRC from the cool and warm periods of harvest were substantially different; large WRC (≤100 mm TL) from the cool-harvest period were 3.1 times more abundant than large WRC during the warm-harvest period. A similar number of small WRC were harvested from the two treatments; however, those small WRC harvested during the warm period was significantly longer than the small WRC during the cool-harvest period. The estimated large WRC biomass contribution to the total harvest from the cool-harvest period was 37% in comparison to 15% during the warm-harvest period. The estimated dollar value of the production during the cool-harvest period was 40% more than that from the warm-harvest period.     

预防围产期奶牛酮病的营养策略

本文综述了围产期奶牛的脂肪代谢变化特点,对处在围产期奶牛酮病预防的营养调控策略进行了总结,以期为奶牛生产提供理论基础和实践参考.     

施磷量与磷肥基追比对弱筋小麦产量和品质的影响

以扬麦15为试验材料，研究不同施磷量和磷肥基追比对弱筋小麦产量和品质的调控效应。结果表明：施磷量0～108kg／hm2范围内，随着施磷量的增加，两种磷肥基追比处理的产量及其构成因素都相应增加，继续增加施磷量，各项指标有所下降；磷肥基追比以基肥：拔节肥=0．5：0．5处理各项指标都高于基肥：拔节肥=1；0处理。在适宜的施磷量范围内，随着施磷量的增加，籽粒的蛋白质含量、直链淀粉含量、支链淀粉含量、总淀粉含量、湿面筋含量均呈下降趋势，继续增加施磷量，又有所回升，籽粒中的醇溶蛋白和谷蛋白含量则呈先上升后下降的趋势。     

播种时期和浸种对君迁子出苗的影响

对君迁子(Diospyros lotus.l.)种子播前浸种和浇底水处理,于不同时期播种试验。结果表明:自然条件下,君迁子在1月底之前播种出苗较好;土壤持水量低时,播前应浸种,播种时应浇底水,可保证出苗率。君迁子种子休眠不明显,只要水分充足,4月初以前播种均可获得理想的育苗效果。     

Sensory quality and chemical composition in carrots: A multivariate study

Carrots from designed trials and organic and conventional farms were analysed for sensory quality and chemical composition. The data were combined in principal component analyses and partial least squares regression for exploration of the main factors responsible for the variation in quality. One of the most important factors was fertilization. Carrots grown with no fertilizer and carrots fertilized with 40–80 kg nitrogen ha^?1 as mineral fertilizer or 20–72 tons ha^?1of organic fertilizer contained more total sugars and total flavour strength, less crispness, crude protein, true protein and carotene, and had a lower pH, compared with carrots fertilized with 100–192 kg nitrogen ha^?1 as mineral fertilizer. Location site was also very important in the explanation of the total variation and was a composite factor of precipitation, temperature in June, growth system and length of growth period. Soil type, amount of organic fertilizer, use of pesticides and temperatures in July and August seemed to be of less importance.