Variability in the performance of juvenile Chinook salmon is explained primarily by when and where they resided in estuarine habitats

Estuarine habitats provide rearing opportunities for the juvenile life stage of anadromous fishes. Because survival is positively correlated with juvenile performance, these estuarine habitats play an important role in population abundance and productivity. To provide information for the recovery of several depressed stocks of Chinook salmon in the Columbia River Basin, we sought to identify the factors that explain variability in performance. Using otolith‐derived estimates of juvenile somatic growth rate as an index of recent performance, we observed a negative nonlinear relationship between growth rate and day of year, and a decreasing and increasing trend of growth rate over the 8 years of this study and distance from the river mouth respectively. Using a generalised linear modelling approach, we found that variability in juvenile somatic growth rate was best explained by where and when individuals were collected, their body size, contaminant loads, stock of origin, and whether a fish was hatchery produced or unmarked. Lastly, we argue that a considerable improvement to the growth rate of juveniles in estuarine habitats is physiologically possible. The results of this 8‐year study provide a baseline of the performance of juvenile Chinook salmon to evaluate habitat restoration programs and to compare against future anthropogenic conditions.     

A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants

AIM: To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.

METHODS: Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000?cells/mL at the first herd test after calving.

RESULTS: Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000?cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000?cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40–1.30).

CONCLUSIONS AND CLINICAL RELEVANCE: In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.     

德国核桃‘No.120'幼胚胚轴与子叶体细胞胚胎发生及其植株再生

核桃 (Juglansregia)‘No . 12 0’品系授粉 7～ 8周的幼胚胚轴与子叶在含不同植物生长调节剂组合的诱导培养基上培养 4周后转移至无植物生长调节剂的继代培养基上培养 ,不同发育时期的体细胞胚直接形成于胚轴与子叶表面。子叶与胚轴分别在KT 2mg/L BA1mg/L IBA 0 .0 1mg/L与 2 ,4 D 2mg/L KT 1mg/L的组合的诱导下体细胞胚胎发生频率最高。体细胞胚经 3～ 5℃低温处理 2个月 ,31.6%的体细胞胚能发育成正常生长的植株     

草地早熟禾种间原生质体电融合条件的研究

为改良培育草地早熟禾(Poa pratensis)新品种,拟建立草地早熟禾商用品种与具有优良性状的野生早地早熟禾种间原生质体融合体系。采用电融合法,研究了电融合仪的电场条件和原生质体密度对草地早熟禾种间原生质体融合的影响。结果表明:在交流电场强度和频率分别为20 V/cm和2000k Hz时,原生质体可在较短的时间内形成2~4个原生质体串;最适于草地早熟禾种间原生质体融合的直流脉冲强度为200 V/cm、DC幅宽为40μs、直流脉冲次数为3次,原生质体密度为3×105个/m L,在此条件下,草地早熟禾种间原生质体总融合率和一对一融合率可分别达到25.39%和12.27%。     

谷氨酰胺对延边黄牛卵母细胞成熟及重组胚发育的影响

为了提高卵母细胞的成熟率及重组胚胎的发育率,在体外成熟液中添加了不同浓度的谷氨酰胺,研究谷氨酰胺对延边黄牛卵母细胞成熟的影响,并观察它对重组胚胎后续发育的影响,从中筛选出最佳的体外培养条件。结果表明,1.0 mmol/L的谷氨酰胺能够显著提高卵母细胞的成熟率,同时也能提高囊胚发育率。说明谷氨酰胺能够提高延边黄牛卵母细胞的体外成熟率,并能促进囊胚发育。     

不同水平复合益生菌制剂添加对奶牛生产性能、乳品质及体细胞数量的影响

为分析不同水平复合益生菌制剂添加对奶牛生产性能、乳品质及体细胞数量的影响,试验选择胎次、产奶量、泌乳天数相近的荷斯坦奶牛160头随机分成4个组,每个组4个重复,每个重复10头,1组饲喂基础日粮为对照组,试验2、3、4组每头奶牛分别在基础日粮中添加20、40、60 g/d复合益生菌制剂,预试验7 d,试验期为60 d。结果表明:(1)试验后的30、60 d,试验3、4组的平均产奶量较1相比分别提高16.0%、14.9%、25.6%、24.1%(P<0.05);(2)试验2、3、4组的4%乳脂校正、乳蛋白率、总固形物均高于1组(P>0.05);试验2、3、4组的尿素氮均低于1组(P>0.05);试验3、4组的乳糖率、乳脂率较1组分别提高14.6%、13.4%、5.0%、4.2%(P<0.05);(3)试验后的60 d,试验3、4组乳中体细胞数量较1组相比降低9.3%、7.1%(P<0.05)。综上,每头牛每天添加40 g复合益生菌制剂可以提高奶牛的生产性能、乳品质,减少体细胞数量。     

绵羊去透明带卵母细胞体细胞核移植研究

为探索简化的核移植程序,本研究分析不同成熟培养时间、去核过程中紫外光照时间、融合电压强度、激活剂种类、不同培养方法对绵羊去透明带卵母细胞核移植的影响。结果表明:卵母细胞成熟培养18～19 h后去除透明带,其极体排出和附着效果最佳。采用1.9 kV/cm直流电压融合去核卵母细胞与颗粒细胞,融合率为88.2%,效果最好。离子霉素对重构胚具有较好的激活效果,卵裂率为82.1%,囊胚率为10.4%;压制WOW(s孔中孔)发育组卵裂率和囊胚发育率与四孔板培养组相比无显著差异,但卵裂率和囊胚发育率并不高;去除透明带的绵羊卵母细胞采用衰减1/4的UV照射10 s辅助去核后,卵裂率为35.6%,但重构胚未能发育至囊胚。结果显示,通过去透明带辅助显微操作去核的方法进行的绵羊体细胞克隆程序较易掌握。