沙地柏人工林和天然林风沙土特性研究

为了深入了解固沙植被恢复对土壤理化性质的影响,以毛乌素沙地东南缘沙地柏人工林和天然林为研究对象,通过收集灌丛下5个土层(0-100 cm)的土壤样品,分析其土壤颗粒组成及8个理化指标,探讨了沙地柏生长对风沙土特性的影响。结果表明:研究区土壤粒度组成以砂粒(体积分数97.09%)为主,其次是粉粒和黏粒,并形成以中砂(50.26%)为主的单峰,土壤弱碱性,其养分含量整体水平低,且具有明显表层聚集现象。土壤养分含量与土壤粒度之间存在良好的相关性,表现为土壤有机质、速效钾和盐分含量与细沙物质(粒径<100μm)含量呈线性正相关,与粗砂物质(100~500μm)呈线性负相关。沙地柏生长对风沙土改良效果呈现出人工林16 a树龄优于7 a树龄,天然林地迎风坡优于背风坡。整体上,造林时间增加土壤颗粒的粗细分配趋于良好态势发展,土壤结构优化,土地荒漠化进程减缓。因此,沙地柏可作为毛乌素沙地生态恢复工程的优良灌木。     

绵羊放牧方式及强度对围封恢复草场牧草细胞壁成分及营养价值的影响

选取内蒙古自治区典型草原区封育恢复中天然放牧草场,进行毛肉兼用细毛羊的暖季放牧试验.采用2×5完全随机试验设计,设定不同放牧方式（不放牧,连续放牧,四区、五区、六区轮牧）及2种放牧强度（1.0,1.4 hm2/un.sh）,运用酶分析方法分析比较了围封过程中放牧绵羊对封育草场牧草细胞壁成分月动态变化及营养价值的影响.结果表明,整个暖季放牧期内,不同放牧区牧草营养物质含量主要受到放牧方式的显著影响（P＜0.05）.具体表现为,不放牧处理牧草细胞壁有机物（OCW）含量始终显著低于各放牧处理,不同放牧处理间没有明显差异;划区轮牧处理牧草始终保持着较高的消化性部分且显著高于连续放牧处理;不放牧处理牧草始终保持着较高的Oa和较低的Ob,而连续放牧处理与其相反,各轮牧处理间没有显著差异;轮牧处理总可消化养分（TDN）和代谢能（ME）含量较高,尤其在牧草生长旺盛期（八月份）,六区轮牧放牧场牧草可利用营养物质含量最高,营养价值最高.     

三维模式下培养时间对奶牛乳腺上皮细胞酪蛋白基因表达的影响

本试验旨在研究三维模式下培养时间对奶牛乳腺上皮细胞(BMECs)酪蛋白基因表达的影响。采用3头健康的3～5岁泌乳黑白花奶牛的乳腺组织,将BMECs经1代纯化后进行三维培养,在三维模式下分别培养3、5、7、9 d,测定BMECs中αs1-酪蛋白、β-酪蛋白、κ-酪蛋白的基因表达量。结果表明,利用三维模式培养5 d的BMECsαs1-酪蛋白和κ-酪蛋白基因表达量极显著高于培养3、7、9 d(P<0.01);利用三维模式培养5 d的BMECsβ-酪蛋白的基因表达量极显著高于培养3、7 d(P<0.01),高于培养9 d,但差异不显著(P>0.05)。结果显示,三维模式下培养时间影响BMECs中αs1-酪蛋白、β-酪蛋白、κ-酪蛋白的基因表达量,本试验条件下最佳培养时间为5 d。     

The effect of ivermectin treatment of late pregnant dairy cows in south-west Victoria on subsequent milk production and reproductive performance

SUMMARY A total of 498 dairy cows in 5 predominantly pasture-fed herds were allocated to pairs. One cow in each pair was treated with a single dose of ivermectin during the dry period. Treated and untreated cows were managed as a single group throughout the trial. Most cows calved between 45 and 115 days after treatment. When data from all herds were pooled, treated cows produced an extra 74 L of milk over the first 100 days of the subsequent lactation (95% confidence interval 20 to 128). Means were greater among treated groups relative to untreated groups in all 5 herds. However, when analysed individually, differences were statistically significant (P < 0.05) in 1 herd only. Over the complete lactation, mean milk volume for treated cows was 86 L greater than for untreated cows (95% confidence interval of difference -57 to 229; P = 0.24). Untreated cows produced 2473 L and 5883 L for the first 100 days of lactation and for the complete lactation, respectively. Milk production responses to treatment did not vary significantly with parity, body condition score, previous production index, calving date category or with plasma pepsinogen concentration or faecal egg count at the time of treatment. Faecal egg counts and plasma pepsinogen concentrations were low at the start of the study. The interval from calving to conception was 4.8 days less in treated cows (95% confidence interval 1.2 to 8.2) relative to untreated cows when data from all 5 herds were pooled. Differences within individual herds were not statistically significant.     

Concentrations of luteinising hormone and progesterone in pregnant and non-pregnant heifers

An experiment was conducted to determine if concentrations of luteinising hormone or progesterone were different in pregnant or non-pregnant heifers for seven days before and 20 days after a successful or non-successful insemination. Heifers with an oestrous cycle length of 18 to 24 days only were used and they were bled at 08.00, 16.00 and 24.00 each day for seven days before and for 20 days after insemination with thawed semen (treatment 1) or semen diluent (treatment 2). Animals allocated to treatment 3 had the embryo nonsurgically flushed from the uterus at days 10 to 12 while animals allocated to treatment 4 were inseminated with semen diluent and then had a viable embryo transferred to the uterus between days 10 and 12. All animals were slaughtered between 19 and 21 days after insemination and pregnancy rate determined. There were no differences in basal luteinising hormone levels between treatments. Blood concentrations of progesterone were not different before insemination and for 16 days after insemination for pregnant (11 out of 15) and non-pregnant heifers (14) allocated to treatments 1 and 2. Between days 17 and 20, progesterone concentrations declined in non-pregnant heifers. Transfer of an embryo to non-pregnant heifers on day 10 to 12, did not affect progesterone concentrations, but non-surgical flushing of the embryo caused a decline in blood concentrations of progesterone. It was concluded that basal blood concentrations of luteinising hormone and progesterone, in samples taken three times daily were not different in pregnant or non-pregnant heifers before and for 16 days after insemination.     

Herd and within-herd BoHV-1 prevalence among Irish beef herds submitting bulls for entry to a performance testing station

Infectious bovine rhinotracheitis (IBR), caused by bovine herpes virus 1 (BoHV-1), may result in various clinical consequences, including severe respiratory disease and conjunctivitis, venereal disease and reduced reproductive performance and abortion. This paper presents the serosurveillance findings from an intake of bulls into a performance testing station in Ireland during November 2007. The herd and within-herd BoHV-1 prevalence in 53 Irish beef herds and the risk factors for infection in these herds were determined, among bulls entering a beef performance testing station in Ireland. BoHV-1 status was determined for 41 herds, of which 30 (73.2%) herds were infected and the mean within-herd BoHV-1 prevalence was 28 (± 20)%. Multivariate exact logistic modelling revealed increasing numbers of contiguous herds and decreasing percentage of males within the herd as significant risk factors associated with infected herds. These findings highlight the high prevalence of BoHV-1 infection in those Irish beef herds that submitted bulls to this performance testing station, and raise concerns regarding IBR control nationally.     

Photonic band gap guidance in optical fibers

A fundamentally different type of optical waveguide structure is demonstrated, in which light is confined to the vicinity of a low-index region by a two-dimensional photonic band gap crystal. The waveguide consists of an extra air hole in an otherwise regular honeycomb pattern of holes running down the length of a fine silica glass fiber. Optical fibers based on this waveguide mechanism support guided modes with extraordinary properties.     

不同时期滴灌氮量对冀西北坝上地区洋葱产量和品质的影响

以洋葱品种"红贝特"为试材,设4个施氮水平处理N0、N1、N_2、N3,以CK为对照,测定了膜下滴灌洋葱的植株性状、鳞茎性状、品质和产量等指标,以探讨冀西北坝上地区地膜覆盖洋葱适宜的滴灌氮量,给当地洋葱施肥提供合理施肥依据。结果表明:处理N1的植株性状、鳞茎性状均显著高于CK,产量较CK提高12.26%;处理N1可溶性蛋白质、可溶性固形物、可溶性糖和维生素C含量较CK分别增加27.13%、8.16%、19.15%和60.71%,而硝酸盐含量CK较N1提高85.67%;在该试验条件下,洋葱获得最佳效益时的氮肥施用量和时期分别为苗期追N 31.5kg·hm~(-2),茎叶生长期追N 47.25kg·hm~(-2),鳞茎膨大初期追N 47.25kg·hm~(-2),鳞茎膨大中期追N 31.5kg·hm~(-2),并在整个生长时期配施P_2O_575kg·hm~(-2),配施K_2O 255kg·hm~(-2)。