Lead poisoning in cattle and its implications for food safety

The lead poisoning incidents in cattle investigated by the Veterinary Laboratories Agency between 1990 and 2003 are reviewed. Lead poisoning was most commonly encountered in young calves, but cattle of all ages were affected. The lead was derived mainly from lead paint, lead accumulator batteries and lead in soil from old mine workings. Paint was responsible for the majority of cases of poisoning in young calves; yearling animals were most at risk from discarded batteries, and adult cows were most commonly poisoned by geochemical sources of lead. There was a marked seasonal incidence, with most cases occurring after turnout in the spring and early summer.     

Shedding routes of Coxiella burnetii in dairy cows: implications for detection and control

Reliable detection of Coxiella burnetii shedders is a critical point for the control of the spread of this bacterium among animals and from animals to humans. Coxiella burnetii is shed by ruminants mainly by birth products (placenta, birth fluids), but may also be shed by vaginal mucus, milk, and faeces, urine and semen. However, the informative value of these types of samples to identify shedders under field conditions is unknown. Our aim was then to describe the responses obtained using a real-time PCR technique applied to milk, vaginal mucus and faeces samples taken from 242 dairy cows in commercial dairy herds known to be naturally infected with Coxiella burnetii, and to assess their putative associations. Positive results were found in all types of tested samples even in faeces. No predominant shedding route was identified. Among the shedder cows, 65.4% were detected as shedders by only one route. By contrast, cows with positive results for all three samples were scarce (less than 7%). Testing a cow based on only one type of biological sample may lead to misclassify it with regards to its shedding of Coxiella burnetii and thereby underestimate the risk of bacterial spread within a herd.     

奶牛瘤胃发酵及调控

奶牛属于反刍动物,其与单胃动物相比,最主要的特点是能够利用纤维素和非蛋白氮来为人类生产食物,相对地不与人类竞争食物。奶牛瘤胃中栖居着大量的微生物。饲料中的营养成分在瘤胃中可被微生物降解发酵为挥发性脂肪酸、肽类、氨基酸及氨等成分;同时瘤胃微生物可以利用氮源、能源等发酵产物合成微生物蛋白质、B族维生素和维生素K等营养物质。在瘤胃发酵的过程中,有些过程对于奶牛是有利的,而有些则对奶牛是不利的。为了提高奶牛对饲料中营养物质的利用率或提高生奶质量．使奶牛发酵有利方面达到最佳,发酵损失降到最小,国内外动物营养学家、生物化学家和微生物学家对瘤胃发酵进行了研究,通过调控瘤胃发酵途径,使奶牛的健康、生产水平和饲料利用率得到了改善。本文就奶牛瘤胃发酵过程及调控技术进行了综述。     

Regulation of food intake in dairy cows in relation to milk production

The physiological state of the animal will influence the amount of energy it can utilize and this, in turn, will tend to affect its demand for food. Particularly when the energy concentration of the ration is not high, any effect of the physiological state on abdominal capacity will affect intake, e.g. young, fat or pregnant animals will have a reduced capacity compared to older, thin or non-pregnant animals, respectively. In general, intake of energy will increase with increasing concentration of digestible energy in the ration, but it becomes constant once the animal is able to meet its total requirement. When the energy concentration of the ration is not limiting, an increased output of energy will, in general, be matched by an increased intake. The response may not be immediate however, so that after parturition for example, peak food intake frequently occurs after peak milk yield. Correlations between intake and milk yield are generally low, whereas there is usually a marked relationship between body weight and intake in the lactating cow. Simple equations linking intake to body weight and milk yield are usually quite accurate in the general situation, but rarely of value to predict intake of an individual. More complex equations, though more accurate, are difficult to apply in the practical situation.The relationship between lactation and food intake is examined in some detail. It is concluded that efficiency of utilization of food energy for milk production could be improved by minimizing cyclic variations in liveweight of the cow during lactation. To permit this, methods are currently being examined for manipulating diet composition to enable the cow to consume enough food in early lactation to meet the requirement for milk production. If these methods are successful, it will be possible to feed the cow for constant liveweight by feeding to appetite at all times and altering the composition of the diet to match the energy demand of the cow. Allowance should be made for growth and pregnancy, but fatness should be avoided.     

牛生长激素(BST)对奶牛健康环境及食品安全的影响

随着人民生活水平不断提高，人们环保意识逐渐增强，百姓更加关注饲养畜禽对环境的影响以及餐桌上肉、蛋、奶等动物源性食品的安全。在养牛业，牛生长激素（BST）技术备受全世界人们注意，学术界、政府和奶牛场的１０００多名科学家在全球范围对它进行１５００多次试验，涉及３００００多头奶牛，这些结果惊人相似，又得到许多国家权威部门证实，本文将简述BST对奶牛健康、环境、奶业及食品安全的影响。自BST试验以来，所有试验表明BST对奶牛健康无不利影响，对酮病、脂肪肝、乳热、不孕、不耐热、跛行、呕吐、易患病、乳房炎、死亡等…     

奶牛氧化应激研究进展及其影响因素

<正>氧化应激由机体自由基的产生和清除失衡所造成,当机体产生的自由基超过机体防御能力时,过多的自由基可破坏蛋白质、核酸等生物大分子,使机体正常的代谢发生紊乱(Trevisan等,2001)。机体的各种生物膜(如红细胞膜)富含PUFA,产生的过多自由基易攻击细胞膜上的必需脂肪酸,造成细胞损害,影响     

Outbreak of botulism in a dairy herd in Turkey

In this study, the clinical findings and results of haematological and biochemical analyses of 26 cattle with botulism were evaluated. The most important clinical signs in the affected cattle included: decreased appetite, ataxia, difficulty to rise, loss of tongue tone, salivation and bradycardia. A definitive diagnosis of botulism was based on demonstration of the preformed toxin in ruminal and intestinal contents and feed materials including poultry litter, by mouse inoculation test. This study is the first confirmation, by direct toxin isolation, of Clostridium botulinum type C and Clostridium botulinum type D in cattle, in Turkey.     

The measuring frequency necessary for food intake and milk yield data in feeding studies in dairy cows]

An individual feeding experiment was carried out which comprised the daily milk analysis from Monday to Friday with proportional samples from the evening and morning milkings and the daily intake of the individual feed components being ascertained. For various measuring frequencies the following calculations were made: the mean values and their standard deviations, the absolute and relative control errors and their standard deviations, the standard deviations for the measuring error and the simple linear correlations and regressions between the various measuring frequencies for the individual parameters. From the results one can conclude that, in individual feeding experiments with dairy cows, five milk analyses per week do not bring about an essential improvement of accuracy in comparison with two analyses. If the composition of the ration remains the same and the same roughage is offered ad libitum, one can project the measuring of feed intake on five days per week for that of the whole week.     

Breeding dairy cows for the future in New Zealand

A brief history of the breeding of dairy cattle in New Zealand is provided. Dairy farming in New Zealand is unique compared with the majority of dairy systems in the developed world. New Zealand has a dependence on grass-based diets and a strict requirement for a 365-day calving interval. Four main areas are discussed: future traits to evaluate, advances in genetic evaluation technologies, impacts of crossbreeding, and future progeny testing schemes. These areas are not independent, e.g. the trend of increasing numbers of crossbred cattle in the national herd will have major impacts on the design of breeding schemes. It is foreseeable that in the future there will be improvements in the national breeding goal to better reflect on-farm profitability, and in the definition of traits and methods of data capture within the national breeding goal. Methods of selection and genetic evaluation that are currently feasible for a small population will become feasible for large populations as computing power improves. Genetic improvement of cows in New Zealand will continue to be a critical component of the increased economic efficiency achieved on dairy farms in this country.     

Pharmacokinetics of sulphanilamide and its three acetyl metabolites in dairy cows and calves

Summary

An intravenous low dosage of sulphanilamide (SAA) (14.0 mg/kg) to 6 pre‐ruminant calves revealed a biphasic SAA plasma disposition with a mean elimination half‐life of 4.1 h. The main metabolite in plasma was N₄‐acetylsulphanilamide (N₄), which 4 hours after injection exceeded the parent SAA plasma concentration. Urinary recovery of SAA was 10 to 16% of the dose; of N₄, it was at least 69%. Traces of the N₁‐acetyl (N₁) metabolite and the doubly acetylated derivative (N₁N₄) were present in urine. The renal clearances of the N₁ and N₄ metabolites showed a tubular secretion pattern, which was at least 2 to 6 times higher than that of SAA.

A single high oral SAA dose of 200 mg/kg to 3 dairy cows resulted in extensive metabolism of SAA into N₄ N₁, and N₁N₄ metabolites; their mean maximum plasma concentrations were 64, 48, 0.72 and 24 μg/ml, respectively. The mean disposition half‐life of SAA in plasma and milk was 10 h. In milk the metabolite concentrations exceeded those in plasma; the N₄ and N₁N₄ metabolite concentrations in milk exceeded that of SAA. The mean maximum concentrations of SAA, N₄, N₁, and N₁N₄ in milk were 52, 89, 2.3, and 98 pg/ml. respectively. For SAA and its metabolites, the binding to plasma and milk proteins was determined. No glucuronide or sulphate conjugates of SAA and its acetyl metabolites could be found in plasma, milk, or urine.

Based on the sensitivity of the bioassay (0.2 μg SAA/ml), a withholding time of 5 days was suggested for milk following single oral SAA dosage of 200 mg/kg.     

Pharmacokinetics of sulphanilamide and its three acetyl metabolites in dairy cows and calves

An intravenous low dosage of sulphanilamide (SAA) (14.0 mg/kg) to 6 pre-ruminant calves revealed a biphasic SAA plasma disposition with a mean elimination half-life of 4.1 h. The main metabolite in plasma was N4-acetylsulphanilamide (N4), which 4 hours after injection exceeded the parent SAA plasma concentration. Urinary recovery of SAA was 10 to 16% of the dose; of N4, it was at least 69%. Traces of the N1-acetyl (N1) metabolite and the doubly acetylated derivative (N1N4) were present in urine. The renal clearances of the N1 and N4 metabolites showed a tubular secretion pattern, which was at least 2 to 6 times higher than that of SAA. A single high oral SAA dose of 200 mg/kg to 3 dairy cows resulted in extensive metabolism of SAA into N4, N1, and N1N4 metabolites; their mean maximum plasma concentrations were 64, 48, 0.72 and 24 micrograms/ml, respectively. The mean disposition half-life of SAA in plasma and milk was 10 h. In milk the metabolite concentrations exceeded those in plasma; the N4 and N1N4 metabolite concentrations in milk exceeded that of SAA. The mean maximum concentrations of SAA, N4, N1, and N1N4 in milk were 52, 89, 2.3, and 98 micrograms/ml, respectively. For SAA and its metabolites, the binding to plasma and milk proteins was determined. No glucuronide or sulphate conjugates of SAA and its acetyl metabolites could be found in plasma, milk, or urine. Based on the sensitivity of the bioassay (0.2 micrograms SAA/ml), a withholding time of 5 days was suggested for milk following single oral SAA dosage of 200 mg/kg.     

硒的生物学特性与奶牛营养需要的研究进展

对硒的生物学特性,硒对奶牛健康的影响以及奶牛对硒的需要量作了比较全面的综述,为在奶牛饲养过程中提供科学的参考依据。     

Antipenicillinase in the serum of dairy cows

Serum from dairy cows was tested for inhibitory effect on penicillinase from a penicillin-resistant Staphylococcus aureus strain of mastitic origin. Among cows with subclinical mastitis caused by penicillin-resistant S. aureus there was a significantly higher frequency of individuals with penicillinajse-inhibiting serum than among healthy cows. Among the subclinical cases, a foregoing penicillin treatment of clinical mastitis appeared to increase the serum antipenicillinase activity.     

Nutrition and reproduction in dairy cows

Diagnosis of nutritional effects on herd fertility requires a systematic analysis of reproductive records in addition to quantifying the feeding program on the farm. Corroborative laboratory tests for specific deficiencies may be useful.     

Food safety implications of ochratoxin A in animal-derived food products

Ochratoxin A (OTA) is an important mycotoxin with potential to reach the human food chain through carry-over of contaminated, mostly cereal-based, feed into animal-derived products. Certain population groups, such as infants and children, are intensive and relatively restricted consumers of some animal-derived products, particularly milk and other dairy products, which may become contaminated with OTA. This review examines the literature on the occurrence of OTA in animal-derived products and discusses the public health and food safety implications of consumption of these products. The risk of OTA contamination of meat, milk, blood and derived products is discussed.     

引发奶牛乏情的疾病研究进展

奶牛乏情是指产后60～90 d没有发情表现的经产奶牛及14～18个月龄不发情的育成牛,机体不表现出任何明显的发情状态,导致卵泡发育不良,从而影响机体排卵,引起发情周期紊乱、妊娠推迟,这对奶牛业的发展产生重大的影响。本文主要综述奶牛出现乏情状态的繁殖性疾病的研究状况,为进一步研究奶牛产后乏情提供理论依据。