Serologic and virologic investigations on the presence of BLV infection in a dairy herd in Syria

237 cattle of a dairy herd in Syria were tested for anti-BLV antibody by the ELISA. 194 animals were additionally examined by the agar gel immunodiffusions test (AGID) on BLV antibodies and 100 by polymerase chain reaction (PCR) for BLV provirus. BLV specific antibodies were determined by means of AGID and ELISA at 62.9% and 69.2% of the examined animals, respectively. Using the PCR method the BLV provirus was detected in 89% of the investigated cattle. Only one ELISA seropositive animal was negative for BLV provirus. The results show the high BLV contamination of this herd and lead to the presumption of wide spread enzootic bovine leukosis in Syria. In the case of the diagnosis of BLV-infection, the PCR-technique compared to the serological tests proved to be much more sensitive. By the detection of BLV antibody, the ELISA showed a higher sensitivity than the AGID and in this way, is advisable as a method of choice for screening investigations. Restriction enzyme and sequence analysis of PCR-amplificates demonstrate that different BLV provirus variants (A, B and C) in the examined herd occur, where the variant C which a high similarity to an Australian BLV provirus isolates showed, occurred most frequently at 92.5%.     

Importance of water for the health and productivity of the dairy cow

Four lactating Friesian cows (average weight 485 kg, milk yield 22 kg d-1) were maintained in completely controlled circumstances and deprived of water for 72 hours. During this period they were carefully monitored and lost 100 kg in bodyweight, principally accounted for by cumulative losses of water in milk, urine, faeces and respired air. The mean rates of respiration and rumen contraction decreased by approximately 50 per cent. Mean body temperature increased by 0.5 degrees C, but pulse rate did not change significantly. Dry matter intake, particularly of hay, decreased rapidly to less than 10 per cent of normal on the third day. Milk yield decreased only slightly during the first 24 hours but on the third day the average yield was only 28 per cent of normal; the composition of the milk did not change significantly. There were significant progressive increases in serum sodium concentration (after four hours water deprivation), osmolality (after 24 hours), urea (after 38 hours), copper (after 48 hours) and magnesium and total protein concentration (after 62 hours); packed cell volume (measured with a Coulter Counter) increased after 38 hours but packed cell volume (determined in a microhaematocrit centrifuge) increased only after 62 hours. In spite of the dehydration the cows showed no signs of distress. Within 48 hours of the cows being given free access to water, bodyweight, appetite, milk yield and blood composition had returned almost completely to normal.     

Mechanisms linking metabolic status and disease with reproductive outcome in the dairy cow

Culling for infertility remains the main reason for disposal of dairy cows, limiting productive lifespan. In extreme cases, ovulation is inhibited, preventing the possibility of conception. More often cows do conceive, but fail to remain pregnant owing to intrinsic problems in the embryo and/or to a poor-quality reproductive tract environment. Both aspects have a genetic component and are also influenced by management practices affecting nutrition and health. The relative importance of these factors varies among heifers, first-lactation and older cows. A common theme, however, is that an internal signalling system exists which reduces fertility when the cow is in an unsuitable metabolic state to sustain a pregnancy. This may be directly related to nutrient shortage caused by inadequate feed intake, or because available nutrients are being prioritized towards growth or milk production, away from reproduction. Evidence is presented for the involvement of the somatotrophic axis (GH, IGF1, insulin, IGFBP2) and leptin as key metabolic signalling molecules. Another emerging theme is the interaction between metabolism and disease that affects the fertility. Common examples include (i) calf diseases causing inadequate heifer growth and increased age at first calving; (ii) poor peripartum energy status reducing the capacity of the uterus to involute and mount an effective immune response, thereby increasing the likelihood of endometritis; and (iii) development of mastitis after conception, a contributory factor to both early and late embryo mortality. Finally, recent evidence suggests that times of metabolic stress cause mitochondrial damage that also contributes to a reduction in longevity.     

The influence of Borna disease viral infection on dairy cow reproduction

We investigated the influence of Borna disease virus (BDV) infection on the clinical state of dairy cows. Sera from 149 cows were examined using enzyme-linked immunosorbent assay and western blotting detect antibodies to the BDV-nucleoprotein antigen. Among 149 investigated cows, 25 (16.8%) showed a positive reaction to BDV antigen. No significant difference existed in milk production or medical history between seropositive and seronegative cows. Although the estrus cycle appeared normal even in the seropositive cows, the frequency of artificial insemination and calving-to-conception intervals significantly increased in seropositive cows. Therefore, fertilization failure was recognized in the BDV-antibody positive cows.     

The effect of intra-ruminal selenium pellets on growth rate,lactation and reproductive efficiency in dairy cattle

In each of two dairy herds (A and B), rising yearling heifers (Trial 1) and adult cows (Trial 2) were assigned to three treatment groups. Untreated animals were compared to animals treated with either two or four intra-ruminal pellets containing 3 g of elemental selenium. The administration of pellets at the recommended dose (two pellets per animal) was effective in elevating whole blood glutathione peroxidase activity and selenium concentration to over 10 times those of control animals.

In Trial 1, a 15% response in liveweight gain (p<0.001) occurred in yearling heifers in the herd with the lowest pre-treatment selenium status. In Trial 2, cows receiving two pellets produced a greater milk volume (p=0.06) and more milk solids (p=0.02) than untreated controls; an increase in volume of 5.4% and 8%, and in milk solids of 6.5% and 6.4%) were noted in herds A and B respectively. There was a trend toyards decreasing somatic cell counts in milk from the treated cows when compared to controls, the four-pellet group in Herd A and the two-pellet group in Herd B being significantly different from their respective control group. No between-group differences were noted in calving-first service or calving-conception intervals, nor in the proportion of animals pregnant to first or all services. The administration of selenium at twice the recommended dose rate yielded no additional response above that noted after the administration of the recommended dose. The results of this study support the use of currently recommended Ministry of Agriculture and Fisheries selenium reference ranges in cattle for the prediction of a response to supplementation.     

奶牛产乳热的预防

文章介绍了产乳热和亚临床低血钙的发病机理,强调调整奶牛产犊前后钙磷代谢是降低代谢紊乱的关键环节.在几种传统的解决方案基础上着重介绍了阴离子盐在预防产乳热方面的作用和在生产上的应用.     

Associations between farm management practices, productivity, and bovine leukemia virus infection in Ontario dairy herds

The objective of this study was to investigate the associations between herd-level bovine leukemia virus (BLV) status and herd-level management and production variables. The study population consisted of 1330 cows sampled from 102 Ontario dairy herds. The individual-cow prevalence of BLV infection in the population (based on AGID testing) was 23%, with 69.6% of herds having one or more positive animals. The herd-level explanatory variables were divided into two datasets containing winter housing variables and all non-seasonal variables, and summer housing variables and all non-seasonal variables. In both datasets, multivariable analyses found a negative association between herd-level milk production and BLV status, and positive associations between weaning age and purchasing animals from outside sources, and BLV status. Housing pre-weaned calves in hutches or separate calf buildings in either season was associated with an increased risk of BLV. The model containing winter housing variables also included positive associations between contact with older animals and BLV status, and between BLV status and the facilities used to house dry cows in the winter.     

Ovulation rate, lambing rate, litter size and embryo survival of Rambouillet sheep selected for high and low reproductive rate

Ewes from lines selected for high and low reproductive rate and a control line bred and selected randomly were endoscopically examined 3 to 5 d after breeding to determine ovulation rates in the fall of 1985, 1986 and 1987. Fertility (ewes lambing per ewe exposed), lambing rate (lambs born per ewe exposed) and litter size (lambs born per ewe lambing) were evaluated at lambing in the spring of each year. Embryonic survival was estimated as the number of lambs born per corpora lutea. Ovulation rates were 1.28, 1.73 and 1.46 for low, high and control lines, respectively. More (P less than .01) single ovulations occurred in low-line ewes than in the other two lines; high-line ewes had more (P less than .01) twin ovulations than did low- or control-line ewes. Fertility did not differ among lines. Selection line affected (P less than .01) lambing rate at first and all services. Control-line ewes had mean lambing rates at first and all services that were intermediate between those of the low and high lines, which were different from each other. Line x age of ewe interactions existed (P less than .01) for lambing rate at all services and litter size at first and all services. High-line ewes had lower lambing rates and litter sizes as 2-yr-olds than other lines, but their performance increased steadily to 6-yr-olds, whereas the low and control lines remained relatively constant. Embryo survival differed (P less than .10) between lines, being 74%, 63% and 67% for low, high and control lines, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

纤维在奶牛生产中的营养作用

纤维是奶牛的一种必需营养素,它在奶牛的泌乳、繁殖等生理活动中都起到了非常重要的作用。搞清楚纤维在奶牛生产中的作用原理、生产中的添加量以及怎样高效率的利用纤维等问题将对提高奶牛单产、提高经济效益有重要意义,此文就这些问题作了综述,供奶牛养殖者参考。     

奶牛热应激及其调控措施

奶牛热应激是奶牛对不利于生理活动的高温环境产生的一种非特异性应答反应,其影响奶牛的生产性能和生理功能。本文综述了热应激对奶牛的影响及其调控措施。     

奶牛低血钙症与其他疾病的关系

随机选取分娩当天(0d,31头)、围产后期(产后14~21d,25头)、泌乳早期(产后50~60d,39头)、泌乳中期(产后120~150d,40头)和泌乳后期(产后200~220d,40头)的奶牛为试验动物,调查和记录临床各类资料并检测血钙浓度。结果显示,5个时期奶牛的低血钙症发生率分别为90%,64%,41%,25%和43%,分娩当天发病率最高;分娩当天患低血钙症奶牛随后易患繁殖疾病、乳房炎、肢蹄病、消化系统疾病和酮病,发病率分别为33.33%,22.22%,20.37%,9.26%和14.81%,淘汰率为41%。表明该牛场低血钙症较为多发,并易引发其他疾病,淘汰率较高。     

菌糠饲料在奶牛养殖中的应用研究

<正>我国奶牛养殖业的发展现状与发展趋势已发生巨大变化,随着人们物质生活水平的不断提高,对鲜奶及奶制品的需求量不断增加,奶牛养殖业规模化成为我国畜牧业发展必然趋势。近年来,我国奶牛业发展较快,奶牛是草食家畜,其生长、生产需要大量优质     

金华市发展奶牛业的新举措

金华市奶牛乳品行业通过多年来的不懈努力,目前,已有存栏奶牛2.57万头、乳制品加工企业35家,日加工能力1100吨,是金华市的支柱产业、特色产业,有力地促进了农村产业结构的调整。但也充分认识到存在的问题和与国内外先进奶业之间存在的差距:原料奶质量差、饲养管理粗放、奶牛单产不高、现代设施应用低、奶牛日粮结构单一,制约乳制品质量的提高。为此,以提高原料奶质量和奶牛单产为重点,做大做强奶牛乳品业为目的,市委市府提出战略性调整和奋斗目标:2005年奶牛饲养量5万头、2010年10万头,具体发展新举措如下:1实施“东扩西移”,调整养殖区域布…     

The role of conserved forages in the nutrition of the dairy cow

Forages are universally popular ingredients in dairy rations because of (1) their agronomic properties, (2) their economy as sources of energy and essential nutrients, and (3) their physiological role in digestion. The contribution that forages make in support of milk production is limited by the cow's capacity for feed intake, especially in early lactation. While varying greatly from cow to cow, feed intake is more highly correlated to daily milk yield in mid-lactation than earlier. Factors affecting intake of forage are discussed. Early harvesting in combination with proper conservation are shown to maximize the potential of forage for supporting milk production.The effects of forage quality and quantity in mixed diets are discussed in relation to rumen fermentation and milk yield response. It is emphasized that although liberal grain feeding is needed to attain high milk yield, restricted forage allowance may seriously affect milk yield and milk composition. It is concluded that the importance of forages generally declines compared to concentrates with increased milk production but that liberal feeding of high quality forages is needed to maintain normal digestion and high milk yield under practical farm conditions.     

Treatment of lacerated flexor tendons in a dairy cow, using specialized farriery

A heel extension shoe was used as an adjunct to primary tendon repair in a dairy cow. A shoe was placed on the foot for 6 weeks after the foot had been immobilized for 6 weeks in a cast. The shoe was continuous across the toes to provide even support for both claws and was nailed and clinched in the same way a shoe is applied to a horse's hoof. Special adaptations included drilling nail holes closer to the rim of the shoe to accommodate the narrower bovine hoof wall. The cow was permitted controlled exercise for gradual remodeling and strengthening of the tendon repair. When the shoe was removed 12 weeks after surgery, the metatarsophalangeal and distal interphalangeal joints were in normal posture. We consider application of a therapeutic shoe to be an important adjunct to surgical repair of major tendon injuries in adult cattle.     

奶牛酮病的诊疗体会

奶牛酮病是碳水化合物和脂肪代谢紊乱所引起的一种全身功能失调的代谢性疾病。该病的特征是酮血、酮尿、酮乳、低血糖,消化机能紊乱、产奶量下降、时有神经症状。主要发生于产后泌乳第一个月的高产奶牛和营养状况良好的奶牛,也发生于其他能量摄入不足的各个泌乳阶段。在各奶牛场临床酮病的发病率为20％～25％不等,发病奶牛不仅产奶量显著下降,发情延迟,配种不孕且易引起所产犊牛发病率和死亡率增高,给奶牛场的经济效益造成很大的损失。