鸡肉和鸡蛋中金刚烷胺与金刚乙胺残留检测UPLC-MS/MS法研究

建立了鸡肉和鸡蛋中金刚烷胺与金刚乙胺残留检测的超高效液相色谱-串联质谱方法（UPLC-MS／MS）。样品在酸性条件下乙腈提取后,用正己烷去除脂肪,高速离心去除蛋白质等杂质,上机测试。液相色谱条件：色谱柱为BEHC18（50×2．1mm,1．7μm）,流动相为0．1％甲酸乙腈溶液＋0．1％甲酸水溶液,流速0．3mL／min,柱温30cI二,进样量10μL。质谱条件：电喷雾离子源（ESI^＋）,多反应监测（MRM）方式进行采集。结果表明：金刚烷胺与金刚乙胺在2～100ng／mL浓度范围内均呈现良好的线性关系,相关系数（R。）分别为=0．9977和0．9988;鸡蛋和鸡肉中金刚烷胺与金刚乙胺残留检测方法检测限均为1ng／g,定量限均为2ng／g。从鸡肉组织在2、5和10ng／g三个添加浓度检测结果可以看出,金刚烷胺与金刚乙胺的平均回收率分别为79．6％～107．5％和78．4％～101．2％,批内和批间RSD均小于15％。从鸡蛋在2、5和10ng／g三个添加浓度检测结果可以看出,金刚烷胺与金刚乙胺的平均回收率分别为90．8％～111．1％和75．4％～87．4％,批内和批间RSD均小于15％。该方法具有简便快捷、灵敏度高、定性准确等特点。     

Production, disinfection and evaluation for aquaculture applications of rotifer resting eggs from Bohai Bay, P.R. of China

The dynamics of resting egg production of the rotifer Brachionus plicatilis originating from a wild population in the Tanggu Saltworks (P.R. China) was investigated. In the natural environment as well as in semi-controlled rearing conditions an increased resting egg production was noticed with declining food availability. Processed resting eggs had a hatching efficiency of 3 x 10 6 rotifers per gramme irrespective of their origin. Hatching started 22 h after the initiation of incubation and was completed after 36 h. Rotifers obtained from resting eggs could be further cultured on Culture Selco® and enriched with Super Selco®. The fatty acid profile of these rotifers were not divergent from reference rotifers (originating from the Laboratory of Aquaculture and Artemia Reference Centre) demonstrating that this strain was not catabolizing essential fatty acids and could be used for enrichment purposes. Storage of resting eggs at 4°C resulted in a 50% lower hatching after 1 year but remained stable during the next 2 years. The resting eggs used for storage could easily be disinfected without affecting their hatching characteristics. These results indicate that this material could be used as inocula for mass cultures of live food for commercial hatcheries.     

Efficiency of presence-absence sampling used to estimate the mean abundance of fish eggs

ABSTRACT:   Statistical properties of estimators relating to the mean abundance of fish eggs were investigated using the data from the presence-absence sampling (PAS) and counting sampling (CS). PAS, which focuses on the presence-absence of eggs in a sample, is more cost-effective yet is unlikely to give more precise estimates than CS, which counts the number of eggs. But when limitations are given on the sampling cost and number of sampling stations, PAS may have advantages. This study shows that the mean square error (MSE) of the maximum likelihood estimator (MLE) based on PAS may become smaller than the MSE of the MLE based on counting data when the number of observations for PAS becomes larger. The observation number for PAS is determined, which minimizes the MSE of a combined estimator from the two MLE under a restriction of the total cost of observation. A dual problem is also solved. It is shown that MSE of the MLE in PAS is a monotone increasing function of the oversight probability. PAS becomes more informative as the distribution of the number of eggs is more aggregated.     

Economic effects of proposed changes in living conditions for laying hens under the National Organic Program

In this paper, we estimate the costs and benefits of implementing the proposed National Organic Program for laying hens compared with alternatives. For the regulatory proposals under option 2, the regulatory cost will be zero because most producers are already in compliance with the proposed regulation. The anticipated benefits of this regulation will be zero as well, because the current market prices already reflect consumers’ willingness to pay for the existing animal welfare conditions. For the regulatory proposals under option 3, before market adjustments, the average regulatory burden for the entire organic egg industry will amount to $0.09 per dozen eggs, with extreme variations between $0 for small operations and $2.30 per dozen for large operations. If we rely on the average price of organic eggs, $2.69 per dozen, and assume a maximum estimated benefit associated with improved animal welfare conditions, that consumers would be willing to pay of about 30% above the current market price, the estimated benefit of regulation amounts to $0.81 per dozen eggs. Based on the findings, we conclude that option 2 is welfare neutral and could be easily adopted because it already has been adopted by representative producers. For option 3, the benefit-cost ratio is larger than 1, which indicates that the proposal passes the benefit-cost ratio test. The obtained result, however, has to be interpreted with serious reservation because of the differential effect that the proposed regulation would have on different industry participants. Under option 3, the effect of the proposed changes on small organic egg producers is negligible because most small producers are operating under conditions similar to the proposed living standards. However, costs will increase substantially for large organic egg producers and likely cause a substantial number of producers to exit organic production and switch to conventional production, which would cause a substantial decline in the prices of conventional eggs and organic feed in the short run.     

Efficacy for a New Live Attenuated Salmonella Enteritidis Vaccine Candidate to Reduce Internal Egg Contamination

To evaluate the efficacy of a novel attenuated Salmonella Enteritidis (△lon△cpxR) vaccine candidate (JOL919), chickens were immunized through oral and intramuscular routes to reduce egg contamination against S. Enteritidis challenge. Birds were orally immunized with JOL919 on the first day of life and were subsequently boosted in the 6th and 16th weeks through oral (group B) or intramuscular (group C) route, while control birds were unimmunized (group A). The chickens of all groups were challenged intravenously with the virulent S. Enteritidis strain in the 24th week. The immunized groups B and C showed significantly higher plasma IgG and intestinal secretory IgA levels as compared to those of the control group. The lymphocyte proliferation response and CD45⁺CD3⁺ T‐cell number in the peripheral blood of the groups B and C were significantly increased. In addition, the egg contamination rates were significantly lower in the group B (0%, 10.7% and 0%) and the group C (3.6%, 14.3% and 3.6%) as compared to the group A (28.6%, 42.8% and 28.6%) in the 1st, 2nd and 3rd weeks post‐challenge. All animals in the groups B and C showed lower organ lesion scores in the liver and spleen and lower bacterial counts in the liver, spleen and ovary at the 3rd week post‐challenge. These results indicate that this vaccine candidate can be an efficient tool for prevention of Salmonella infections by inducing protective humoral and cellular immune responses. In addition, this vaccine did not prevent egg contamination, but did appear to reduce incidence. Booster immunizations, especially via oral administration route, showed an efficient protection against internal egg contamination with S. Enteritidis.     

Seasonal shift in spawning of Atlantic cod (Gadus morhua L.) by photoperiod manipulation: egg quality in relation to temperature and intensive larval rearing

Commercial intensive fry production of Atlantic cod will be dependent on production of viable eggs independent of season. This can only be done by manipulation of maturation by photoperiod, but little is known about potential effects on egg characteristics and larval viability. In two cod broodstocks, maturation was successfully advanced or delayed 6 months compared with normal spawning season (March–April) by manipulation of photoperiod. The advanced broodstock spawned both in spring and autumn the same year. In two of the spawning tanks during autumn, ambient temperature was reduced after reaching 13.7°C during the first half of the spawning period. Egg quality and viability were monitored, and several egg batches were incubated, hatched and start‐fed for examination of growth and survival. Temperatures above 9.6°C resulted in significant reductions in fertilization and normal egg development. Concurrently, fractions of dead and unfertilized eggs increased with elevated temperature. Actual relative fecundity was not affected by temperature. Egg characteristics improved when temperature was controlled and lowered below 9.6°C. Occurrence of irregular spawners suggests that handling of broodstock fish should be avoided during maturation and spawning. Cod larvae originating from eggs of the advanced or delayed broodstocks were successfully reared beyond metamorphosis. Survival was 9.0–46.6% and 29.3% in green and clear water respectively. Survival correlated with both initial and average feeding conditions, but growth rate did not correlate with either of survival and feeding conditions. Specific growth rates (8.3–13.6% day⁻¹) is comparable with other intensive rearing trials with cod, but were lower than reported from nature‐like systems.     

Possible mechanisms underlying fluctuations in the Far Eastern sardine population inferred from time series of two biological traits

A cycle of fluctuation in the Far Eastern sardine, Sardinops sagax, population is accompanied by an abrupt drop and recovery of fish size and lipid content of parent fish, which may reflect a phase variation from coastal to oceanic and its reverse. The cycle begins with the survival success of a smaller number of eggs produced by high-quality parents, which is triggered by a global climate change (density-independent process), and finally ends in the survival failure resulting from an overexpansion of an enormous number of fish produced by low-quality parents (density-dependent process).