Animal-derived feedstuffs as possible vectors for bovine encephalopathy (BSE) in Germany. Part 2: Assessment of vector risk for compounded feed

Specific conditions and practices of cattle feeding in Germany have to be taken into account for assessing the risk of feed born transmission of bovine spongiform encephalopathy, especially regarding the situation before the year 2000 when specific directives were introduced for feed production. The present retrospective epidemiological study includes data on feed production and the estimated amount of animal derived feedstuffs for the production of compounded feed for cattle. Risk assessment was performed based on the 'reproduction rate' (R0), that is defined as the estimated number of infections resulting from the processing of brain and spinal cord of BSE affected cattle that is recycled to bovines via feed. Under the conditions as given in Germany until the year 2000 the reproduction rate of BSE via the inclusion of animal derived feedstuffs in compounded feed production for cattle was estimated to be 1.1. Thus, it can be expected that BSE could be reproduced in the system, but with comparatively low efficiency. The expected incidence of BSE should be considerably lower compared to the situation during the 90th in the UK, due to the markedly lower recycling rate of animal protein in cattle feeding. Animal fat could have been a significant factor for BSE transmission due to contamination by proteinaceous brain and spinal cord material during the production process. The relative significance of fat containing feedstuffs for BSE transmission could have been higher in Germany compared to the situation in the UK where meat and bone meal was produced under different conditions and frequently used in higher proportions as an ingredient for compounded feed for ruminants.     

Animal feeding and feed legislation after the detection of the first indigenous BSE cases in Germany

In Great Britain, even the earliest tangible signs indicating the epidemiologic significance of meat and bone meal in the spreading of BSE soon gave rise to increasingly rigorous legislative measures regulating animal feedstuffs. In 1994 a ban on the feeding of animal proteins to ruminants was implemented throughout the entire EU. But until the first BSE cases were actually confirmed in locally raised cattle (November 2000), feeding practice and legislation more or less in Germany remained unaffected by the efforts undertaken in Great Britain. This situation was suddenly changed on 1 December, 2000, when the so-called "Verfütterungsverbot" was put into effect, a law which drastically extended bans regarding the feedstuffs (including fishmeal and animal fats) as well as the species concerned (all animals used in food production). In 2001 the "contamination" phenomenon (ingredients of animal origin were detected in mixed feeds) became a vital issue for the feed industry; through the media, the subject "feedstuff safety" gained a previously unseen level of public awareness. Those circles concerned with mixed feed production and animal husbandry were increasingly confronted with the consequences of the "Verfütterungsverbot" (availability and pricing of substitute ingredients; the demand for amino acids and inorganic sources of phosphorus; problems finding adequate substitutes for animal fats; poor digestibility of alternative components such as indigenous legumes or vegetable fats in calf diets; lower utilization rate of original phosphorus in mixed feeds with negative consequences for skeletal development). With the conditional approval of fishmeal (except in feeds for ruminants) the situation has eased again to a certain degree; on the EU level there are increasing signals pointing toward a political intention to reinstate the utilization of by-products of slaughtered animals qualified for human consumption (with the exception of fallen/dead animals and specific risk material) in poultry and swine feeding. In Germany, at least, the question of animal fat utilization for food-producing animals is still unsolved.     

Case-control study on feed risk factors for BSE cases born after the feed ban in France

In France, after the ban on meat and bone meal (MBM) in cattle feeding in June 1990, cases of Bovine Spongiform Encephalopathy (BSE) have continued to be detected in bovines born after that ban (called BAB cases). A case-control study was therefore carried out to determine the way these cases were contaminated. A multivariate conditional model was built adjusting for the production type of the animals and taking into account the herd size. The results confirmed that feeding cattle with proprietary concentrates was at risk for BSE, with an adjusted odds ratio of 6.8 (2.5; 18.7) for the consumption of less or three different proprietary concentrates and 17.6 (5.7; 54.8) for more than three, when comparing with no consumption of proprietary concentrates, considering feeding of bovines before the age of two. The results suggest that cross-contaminations by MBM in bovine concentrates have occurred after 1990. To a lesser extent, on-farm cross-contaminations, i.e. consumption by cattle of feedstuffs initially dedicated to other animals and which could legally contain MBM, have probably also existed, since the presence on farms of poultry fed purchased feed involved an increased risk of BSE with an odds ratio of 1.8 (1.1; 3.0). The use of milk replacers, which often incorporates animal fats, was also at risk with an odds ratio of 1.8 (1.0; 3.1).     

Area-level risks for BSE in British cattle before and after the July 1988 meat and bone meal feed ban

In this paper we investigate area-level risk factors for BSE for the cattle population present in Great Britain between 1986 and 1997. By dividing this population into two birth cohorts, those born before the July 1988 ban on feeding ruminant-derived meat and bone meal to ruminants and those born after, second-order regional influences are distinguished from the strong first-order south-to-north gradient of area-level BSE risk using Bayesian hierarchical models that account for structured (spatially correlated) and unstructured heterogeneity in the data. For both cohorts area-level risk of BSE was increased by a more southerly location and greater numbers of dairy cattle, relative to non-dairy cattle. For the cohort of cattle born after the July 1988 ban on feeding ruminant-derived meat and bone meal area-level BSE risk was additionally associated with greater numbers of pigs, relative to cattle. These findings support the role of low level cross-contamination of cattle feed by pig feed as an influence on BSE incidence risk as the epidemic evolved. Prior to the 1988 meat and bone meal ban unexplained BSE risk was relatively uniformly distributed across the country whereas after the ban there were spatially aggregated areas of unexplained risk in the northern and eastern regions of England suggesting that local influences allowed BSE control measures to be less-successfully applied in these areas, compared with the rest of the country. We conclude that spatially localised influences were operating in divergent ways during the two phases of the epidemic.     

Evaluation of the effectiveness of selected measures against bovine spongiform encephalopathy (BSE) in Switzerland by use of the basic reproduction ratio R0

The effectiveness of two measures against Bovine Spongiform Encephalopathy (BSE), the compulsory processing of animal by products to meat and bone meal (MBM) at 133 degrees C under 3 bars of pressure for 20 minutes in February 1993 and the exclusion of fallen stock, heads with eyes and spinal cord of cattle older than 30 month from MBM production in April 1996, was evaluated in a process model. The transmission of BSE by calculation of the basic reproduction ratio R0 was modelled.The results were verified by use of a cohort model, based on observed surveillance data. Prior to 1990, before the ban of feeding MBM to ruminants, R0, as calculated in the process model, was above 1, coherent with a slowly progressing BSE epidemic. Since 1991, values of R0 were low at 0.06.The corresponding R0 values derived from the cohort model were higher, the lowest value 0.13 calculated for 1996. Given such low R0 values, the epidemic should have died out. Additionally, no influence of the two measures was obvious at that time given the low level of R0. The discrepancy between the results of the two models is evidence for a dependency of the BSE epidemic from an infection source not considered in the process model. This infection source is most likely importation of feed ingredients and MBM.     

动物源性饲料检测技术研究进展

饲料安全与动物生产、环境污染和人类健康密切相关。动物废弃物进入饲料行业曾经弥补了蛋白质饲料不足的缺口,但却带来了新的问题。自1986年第1例BSE出现后,世界许多国家和地区相继出台相关饲料法规以规范饲料行业,普遍禁止动物源性饲料在反刍动物生产中应用。因此,需要切实可行的检测技术为保障饲料安全提供技术支持。作者以组织学特征为基础的显微镜分析方法、以蛋白质和DNA为基础的免疫学和PCR分析方法、高效液相色谱法和近红外光谱法在动物源性饲料组分中的研究应用进展等方面做了综合评述。     

Characterization of antibiotic-resistant bacteria in rendered animal products.

Antibiotics are used in food animal production to treat diseases and also to improve performance. Antibiotics are not used on all farms, and antibiotic resistance is occasionally found on farms that do not use antibiotics. Rendered animal protein products are often included in poultry feeds and could potentially serve as a source of antibiotic-resistant bacteria. One hundred sixty-five rendered animal protein products from cattle, poultry, and fish were aseptically collected from poultry feed mills. Fifty-five percent of the poultry meal samples had detectable levels of gram-negative bacteria ranging from 40 to 10,440 colony-forming units/g of sample. Poultry meal and meat and bone meal had the greatest number of samples with bacteria resistant to five or more antibiotics. A high percentage of feed samples (85%) contained bacteria resistant to amoxicillin, ampicillin, clavulanic acid, or cephalothin, whereas few samples contained bacteria resistant to ciprofloxacin, kanamycin, or trimethoprim/sulfamethoxazole. Acinetobacter calcoaceticus, Citrobacter freundii, and Enterobacter cloacae were the most commonly isolated antibiotic-resistant bacteria. Isolation for Salmonella was also performed, with 14% of the meat and bone meal samples containing Salmonella sp. Only one of the meat and bone meal isolates, Salmonella livingstone, was resistant to five or more antibiotics. Many of the antibiotic-resistant bacteria contained integrons, genetic elements that mediate multiple drug resistance.     

A Case of Bovine Spongiform Encephalopathy in Denmark

Bovine spongiform encephalopathy (BSE), a transmissible spongiform encephalopathy in cattle, was first described in England by Wells et al. (1987). The infection occurs mainly due to digestion of feedstuffs containing ruminant derived protein in form of meat and bone meal contaminated with a scrapie-like agent (Wilesmith et al. 1991). Later, cases of BSE were diagnosed in the Republic of Ireland, Oman, France, and Switzerland (Marinovic & Senn 1991). This report describes the first case of BSE in Denmark.     

A case of spongiform encephalopathy ("cattle madness") in a cow in Switzerland

Spongiform encephalopathies occur in humans and several domestic animal species. Among them, the bovine spongiform encephalopathy (BSE) has aroused considerable interest because of a massive outbreak of this disease in Great Britain, which is thought to result from feeding meat and bone meal contaminated with the spongiform encephalopathy agent. We observed the first case of BSE in Switzerland, which is also the first case on the European continent. A 6 year old cow suffered from progressive neurological disease. On neuropathological examination typical spongiform changes and neuronal vacuolation were found. The origin of the infection remains unknown. It cannot be excluded that the animal was exposed to cattle feed derived from Great Britain. It is possible that additional sporadic cases may occur in Switzerland, an outbreak such as in England is unlikely to happen.     

A quantitative assessment of the risk of exposure to bovine spongiform encephalopathy via meat-and-bone meal in Japan

The feeding of meat-and-bone meal (MBM) derived from cattle infected with bovine spongiform encephalopathy (BSE) is a major source of BSE infection. The risks of BSE infection via MBM in Japan were examined quantitatively to estimate infectivity to cattle via MBM derived from a single clinically infected animal being rendered. Three routes of exposure were modeled: (i) feeding cattle concentrates containing MBM as an ingredient, (ii) feeding cattle concentrates contaminated with MBM from non-ruminant feed at feed plants and (iii) directly feeding MBM in supplemental form to cattle on farms. The effectiveness of measures designed to restrict the feeding of ruminants with ruminant MBM (feed restriction) as well as differences in the risk of exposure among regions were examined using the model.

The model revealed that the median total infectivity fed to dairy cattle via MBM derived from one infected animal was approximately 0.49 cattle oral ID₅₀ (5th percentile = 0.43 ID₅₀, 95th percentile = 0.54 ID₅₀). This value was reduced by 55% after the addition of MBM to cattle concentrates was restricted in 1996. The risk of exposure in dairy cattle was twice that in beef cattle. Comparisons of regional differences in exposure risk indicated that the risk was highest in a region where 14 of the 20 BSE cases reported to date were born. Our model suggested that the routes of exposure via MBM were unlikely to result in increased propagation of BSE in Japan. Furthermore, despite some regional variation, the risk of exposure declined further after the feed restriction was imposed in 1996.     

Creatine and creatinine contents in different diet types for dogs – effects of source and processing

The concentrations of creatine and its degradation product creatinine were determined in a variety of unprocessed as well as processed feedstuffs suitable for dogs. Unprocessed feedstuffs were categorised as single feedstuffs, bone and raw food diets (BARF), and small vertebrates, for example prey animals. Processed feedstuffs were categorised as meat/meat and bone meals, complete wet diets and complete dry diets. The feedstuffs were chosen to cover a broad range of each of the three defined processed and unprocessed feed categories available on the market without further subclustering. The creatine content of the samples was compared on a dry matter, protein and energy basis. The relation of creatine to crude protein permitted a rating of the meat quality in terms of muscle tissue. Results: We found no difference in creatine concentrations between the three categories of unprocessed feedstuffs (raw single feedstuffs, prey and BARF diets), neither on a dry matter basis nor when expressed relative to crude protein and metabolisable energy respectively. Significantly lower levels were determined in meat/meat and bone meal and commercial dry diets (e.g. 303 mg creatine/MJ ME in unprocessed vs. 6 mg/MJ ME in processed feedstuffs; p < 0.001). We conclude that in relation to ME, the exclusive use of conventionally processed diets for dogs, especially dry diets, leads to considerably lower intake of creatine which is a natural compound of the diet of this carnivorous and omnivorous species.     

Salmonella serotypes encountered in animal feed additives in Lebanon.

Animal feed-additive samples (n = 300) were examined for the presence of salmonellae, using the selenite-F broth-enrichment method followed by subculturing on Salmonella-Shigella and brilliant green agar with sulfadiazine selective agar plates. Samples consisted of a variety of feed additives: 119 bone meal samples, 77 meat meal samples, 40 fish meal samples, and 64 miscellaneous meal samples. Results of examination found 49 (41.2%) of the bone meal samples, 6 (7.8%) of the meat meal samples and 2 (5%) of the fish meal samples contained salmonellae. Of 57 isolates representing 24 serotypes, 4 most frequently isolated serotypes were Salmonella meleagridis (35.1%), Salmonella tennessee (7%), Salmonella chester (5.2%), and Salmonella senftenberg (5.2%). This study shows a high Salmonella-contamination rate of bone meal compared with meat meal and fish meal samples. Of 12 known positive bone meal samples that were examined, 100% of 25-g samples, compared with 70% to 100% of 2.5-g samples and 30% to 90% of 0.25-g samples and 30% to 90% of 0.25-g samples, were positive for salmonellae.     

Bovine spongiform encephalopathy: epidemiological studies on the origin.

The results of further epidemiological studies of bovine spongiform encephalopathy (BSE) support the previous findings that the onset of exposure of the cattle population to a scrapie-like agent, sufficient to result in clinical disease, occurred in 1981/82. The onset of this exposure was related to the cessation, in all but two rendering plants, of the hydrocarbon solvent extraction of fat from meat and bone meal. A further possible explanation, related to the geographical variation in the reprocessing of greaves to produce meat and bone meal, was identified for the geographical variation in the incidence of BSE.     

Reducing the proportion of animal protein in feed for rainbow trout (Salmo gairdneri). 2. Supplementation of methionine and lysine

Continuing previous investigations, two test feedstuffs whose fishmeal content had been reduced to 5% and which were supplemented with 4.5 g methionine and 5.0 g lysine per kg resp. 6 g methionine and 6 g lysine per kg were proofed in comparison with a fattening feed for trout as customary in trade and with a fish meal content of 35%. The content of animal protein in the control feed was at least 75% (crude protein content 41%), in test feed I at most 35% (crude protein content 35.4%), in test feed II at most 17% (crude protein content 33.9%). All feedstuffs had the same energy content. The tests were made with rainbow trout (Salmo gairdneri) of 80...100 g at the beginning and at water temperatures of 11...12 degrees C. They were conducted over a period of 112 days. After giving the same amount of feed, growth of and feed expenditure for the fish feed with the test feedstuffs were less suitable than of those fish which had received the control feed. Concerning the protein efficiency ratio, the productive protein value and the energetic expenditure too, the best results were achieved with the control feed.     

肉骨粉类饲料在畜牧业上的应用与研究

肉骨粉类饲料营养价值较高,营养成分的变异性很大,其养分的利用率属于中等水平,存在一定的安全性问题。本文就肉骨粉类饲料的营养特点、饲用安全性和肉骨粉的可利用性及其在畜牧业上的应用作一简要综述。     

Bovine spongiform encephalopathy: case-control studies of calf feeding practices and meat and bonemeal inclusion in proprietary concentrates

Following the identification of meat and bonemeal as the most likely source of exposure for the occurrence of bovine spongiform encephalopathy (BSE) in Great Britain case-control studies were initiated to investigate this hypothesis. These involved a comparison of the consumption of specific proprietary calf feedstuffs, and whether or not meat and bonemeal had been included, between animals born in 1983-84 in BSE-unaffected herds and confirmed cases of BSE also born in 1983-84. The feeding of proprietary concentrates containing meat and bonemeal was found to be a statistically significant risk factor for the occurrence of BSE. These studies therefore support the initial hypothesis that BSE occurred as a result of exposure to a scrapie-like agent via meat and bonemeal.     

BSE, feed and cattle in Switzerland: is there a spatial relation?

Cross-contamination of cattle feed with meat and bone meal (MBM) allowed in feed for other species is regarded as the current hypothesis for the infection pathway of Bovine Spongiform Encephalopathy (BSE) cases occurring after the implementation of a ban on feeding MBM to cattle. This study was aimed at establishing a spatial relation between BSE cases in Switzerland and the findings of MBM in cattle feed. A cluster analysis and a cohort study were performed. Two hundred sixteen BSE cases born after December 1990 and detected until August 1st 2005, screening data of 504 feed producers between 1996 and 2001 and population data from the Swiss 2001 cattle census were included. The cluster analysis showed feed producer, positive for MBM contaminations in cattle feed, as possible cluster centres for BSE cases. In the cohort study, farms within a radius of 2 and 10 km around positive feed producers showed significantly higher odds to have a BSE case than the control group. The odds ratio and its 95% confidence interval were 2.23 (1.26-3.93) for the 2 km radius and 1.38 (1-1.9) for the 10 km radius. The results provide evidence for a spatial relation between cross-contamination and BSE occurrence. These findings support the hypothesis of cross-contamination to be an important route for BSE transmission after a feed ban.     

动物产品中牛、羊源性成分多重PCR检测方法的建立

以肉骨粉、鱼粉、猪肉干和鱼肉干为研究对象,异硫氰酸胍法提取总DNA,18S rDNA片段的扩增结果表明提取到的DNA中不存在抑制PCR的物质。应用梯度PCR技术对牛、羊源性成分检测的退火温度进行了优化,在单一PCR检测技术的基础上分别进行了18S rDNA片段和牛、羊源性成分的多重PCR分析,得到了预期的结果。试验表明,本文建立的多重PCR方法具有快速、简便、准确等特点,对动物产品牛、羊源性成分检测具有重要意义。     

动物蛋白饲料中动物源性成分的鉴别1.同一PCR鉴别动物蛋白饲料中牛羊成分

为了防止牛海绵状脑病(俗称疯牛病)和羊痒病传入我国,对来自疫区国家的动物源性饲料进行动物种类鉴别非常必要.本研究根据牛羊特异性卫星DNA建立了同一PCR体系同时检测羊、牛源性物质的方法.应用DNA提取液制备模板,不但有效地缩短了试验时间,还大大降低了成本,有利于在生产实际中推广应用.