Assessment of the Long-Term Viability of the Myxospores of Myxobolus cerebralis as Determined by Production of the Actinospores by Tubifex tubifex

While whirling disease was first observed in Rainbow Trout Oncorhynchus mykiss in 1893, the complete life cycle of Myxobolus cerebralis (Mc), the causative agent of the disease, was not understood until 1984, when it was shown to involve two obligate hosts, a salmonid fish and the aquatic oligochaete Tubifex tubifex (Tt). The viability of the triactinomyxon (TAM) actinospores produced by Tt has been well studied, and is known to be temperature dependent and measured in days and weeks. Assertions that Mc myxospores produced by infected fish remain viable for years or even decades were made during the mid-20th century, decades before the Mc life cycle was described. Moreover, the duration of myxospore viability has not been well studied since the life cycle was elucidated. In a series of time-delay treatments, we assessed the long-term viability of Mc myxospores by exposure to Mc-susceptible Tt oligochaetes and quantified TAM production. As the time delay between inoculation and incubation of Mc myxospores in sand and water and exposure to Tt oligochaetes increased, TAM production decreased exponentially. Production among the 15-d time-delay replicates was reduced 74.7% compared with the 0-d treatment. Likewise, total TAM production was reduced 94.5, 99.4, and 99.9%, respectively, in the 90-, 120-, and 180-d time-delay treatments. Linear regression analysis of our data and the absence of TAM production among replicates of Mc myxospores held at 5°C for 365 d prior to exposure to Mc-susceptible Tt oligochaetes indicate that the long-term viability of Mc myxospores is less than 1 year under the conditions of this study.

Received May 14, 2014; accepted September 27, 2014     

Comparison of the stressfulness of harvesting broiler chickens by machine and by hand

The procedures of manual and machine catching acted as short-term stressors, and induced a state of fear in 8-week-old broiler chickens. The heart rate of birds caught by both methods rose to similar high values but that of birds caught by machine returned to near normal rates more quickly, suggesting that they were less stressed. The duration of tonic immobility, a response which increases with fearfulness, was much longer in manually-caught birds. These results suggest that stress could be reduced and welfare improved by catching and picking up broiler chickens by a carefully designed machine, rather than by hand.     

利用正交试验设计研究葡萄糖处理豆粕对奶牛过瘤胃蛋白的影响

以3头装有永久性瘤胃瘘管的中国荷斯坦牛为试验动物,采用尼龙袋法研究在不同因素下葡萄糖处理豆粕,在奶牛瘤胃内不同时间点DM、CP消失率及其有效降解率的作用效果。结果表明:在不同时间点,提高葡萄糖添加量可使DM、CP消失率逐渐降低,所有试验组与未处理组差异均显著(P0.05),葡萄糖添加量、加热温度、加热时间、含水量四个因素均对蛋白质降解率影响显著,四个因素的影响顺序为:加热温度加热时间葡萄糖添加量含水量;随着加热温度升高、加热时间的延长、葡萄糖添加量的增加,豆粕DM降解率与瘤胃蛋白降解率都逐渐下降。     

通过营养调控降低畜禽排泄物对环境的污染

随着畜牧业生产规模的不断扩大和集约化程度的不断提高,畜禽排泄物对环境的污染已受到普遍重视。为获得高生产性能而给畜禽提供过量营养是造成环境污染的主要原因之一,通过营养调控来最大限度地提高动物对营养物质的利用率是解决问题的重要手段。     

耐高温酵母菌对啤酒糟发酵效果的影响

用出发菌、耐高温酵母菌发酵啤酒糟进行试验,结果表明:在32℃的恒温箱中发酵,出发菌组和耐高温酵母菌组对啤酒糟的营养价值有较大提高,较未处理组CP分别提高1.43、1.87个百分点,TP分别提高1.43、2.71个百分点,差异显著(P<0.05);耐高温酵母菌组CP和TP较出发菌组提高0.44、1.28个百分点,差异显著(P<0.05),而TP/CP值没有显著差异,但有增高趋势。     

Factors affecting the retention of calcium by the chick

The addition of 5 or 10% tallow to a broiler diet containing 0.9% calcium reduced the retention of that element, although not sufficiently to cause a deficiency. Supplementation of the diets with vitamin D₃ above the minimum requirement level did not improve the retention of calcium in the added fat diets.     

黄曲霉毒素的生物学去除方法

黄曲霉毒素(AFT)是一类有毒致癌物,污染粮食、饲料等,对人体及生物危害较大。该毒素的解毒与去毒一直是研究的热点。本文综述了黄曲霉毒素的生物学解毒方面的研究成果。     

Inhibition of Dermatophilus congolensis by substances produced by bacteria found on the skin

Bacteria, isolated from the skins of clinically normal sheep, were tested for inhibitory activity against Dermatophilus congolensis grown in vitro. Out of 85 bacterial isolates, 19, mainly Bacillus spp., showed zones of inhibition when grown together with D. congolensis. The inhibitory activity was shown to be due to the metabolites released by the bacteria.     

消炎痛抑制山羊黄体溶解

在山羊发情周期第１６～２１天，每天给４只山羊按每公斤体重注射消炎痛１２ｍｇ；另４只山羊注射相应体积的玉米油作为对照，用血浆孕酮水平来监视黄体溶解过程。将血浆孕酮水平降到每毫升１ｎｇ以下的时刻定为黄体完全溶解的时间。对照组山羊的黄体在周期的１９．７ｄ完全溶解；处理组山羊的血浆孕酮水平到周期的第２２天时仍无明显的下降趋势。每天按每公斤体重注射１２ｍｇ消炎痛完全阻止了山羊的黄体溶解。