鼻气管鸟杆菌对鸡的感染及其防制

鼻气管鸟杆菌发现于 1 990年 ,自那时以来已在世界范围内被公认为一种呼吸道病原菌 ,可在肉用鸡引起原发感染或继发感染。对种鸡进行免疫接种是减轻鼻气管鸟杆菌所致经济损失的有效方法。     

Infectious bronchitis serology in broilers and broiler breeders: correlations between antibody titers and performance in vaccinated flocks

In this study, a follow-up was made between 1993 and 1997 from broiler breeders at birth down to offspring broilers at processing, through vertically integrated registration of infectious bronchitis virus (IBV) antibody titers and performance data. All measurements were used two by two in a simple correlation study to calculate the degree to which they were linearly correlated. The antibody patterns in the broiler breeders indicated frequent field infections breaking through vaccinal immunity. Significant correlations measured between antibody titers and production parameters within and between the generations strongly suggested negative effects of IBV infections on laying percentage in the breeders and on mortality and daily weight gain in the broilers. Economic losses associated with IBV infections in the broilers occurred predominantly in flocks hatched with low and erratic maternal antibody titers. We concluded that IBV vaccination strategies should aim at high and uniform antibody titers in the broiler breeders.     

Epidemiology and significance of chicken infectious anemia virus infections in broilers and broiler parents under nonvaccinated European circumstances

A serologic survey in unvaccinated broiler parent and broiler progeny flocks demonstrated seroconversion against chicken infecrious anemia virus (CIAV) in all parent flocks before or around point of lay and in 38% of the broiler flocks examined at slaughter age. The presence of CIAV antibodies at slaughter of broilers was positively correlated with slaughterhouse condemnation rates. Results indicate that CIAV infections are highly prevalent in both broiler parent and broiler flocks and that CIAV infections in broilers are associated with increased slaughterhouse condemnation.     

Lipid nutrition

Cows in early lactation or producing more than 80 lb of milk per day need supplemental fat and can benefit from it. Fat should be added to the diet over a period of several weeks to allow the cows to become accustomed to it. Feed intake should be monitored because additional fat may decrease feed intake and offset the benefit of the fat. Supplemental fat should not exceed 4 to 5% of the dry matter intake. The first 2% of added fat should be supplied by oilseeds under most circumstances. The next 1 or 2% can come from commodity fat if availability and handling ability permits its use. If the last increment of fat is needed, it should be supplied by specialty fats that have been processed to improve ruminal inertness. Extra calcium, magnesium, and ruminally undegraded protein should be added to the diet when fat is added. Fat is a more expensive source of energy than feed grains in most of the world and should not be used beyond needs.     

Has bovine somatotropin (BST) an effect upon drug disposition? Comparative studies in goats and cattle with sulphadimidine and antipyrine after parenteral administration of BST,zeranol and proligestone

Daily subcutaneous BST injection in lactating cows, bulls and castrated male dwarf goats did not induce significant changes in the pharmacokinetic parameters of antipyrine (AP) and sulphadimidine (SDD). Similarly, no changes were obtained after injection of slow-release BST formulations in lactating cows and non-lactating female goats. In contrast to androgenic hormones, both zeranol and proligestone had no effect upon the disposition of AP and SDD, although both synthetic hormones did induce enhanced plasma somatotropin concentrations. In goats, metabolic effects induced by zeranol and BST included significant reductions in plasma urea values, whereas plasma creatinine levels were somewhat lower after daily BST administration.     

Significance of infectious bursal disease serology in an integrated quality control program under European epidemiologic conditions

In this study performed between 1993 and 1997, infectious bursal disease virus (IBDV) antibody titers and performance data were recorded in a vertically integrated monitoring scheme in order to make a follow-up from day-old parents down to the broilers at slaughter. All measured data were used two by two in a simple correlation study to calculate the degree to which they were linearly correlated. It appeared that high and/or uniform antibody titers in the parents were correlated with increased daily weight gain and decreased mortality and slaughterhouse condemnation in the broilers. Antibody titers and their CVs were negatively correlated in broiler parents and their offspring at day-old and even at slaughter. Results indicate that high and uniform antibody titers against IBDV in broiler parents are important for good performance of the broiler offspring, at least under the epidemiologic conditions of this study, which included the presence of very virulent IBDV strains in the field and the sole use of live intermediate vaccines in broilers as well as broiler parents.     

Self-trapping of dark incoherent light beams

"Dark beams" are nonuniform optical beams that contain either a one-dimensional (1D) dark stripe or a two-dimensional (2D) dark hole resulting from a phase singularity or an amplitude depression in their optical field. Thus far, self-trapped dark beams (dark solitons) have been observed using coherent light only. Here, self-trapped dark incoherent light beams (self-trapped dark incoherent wavepackets) were observed. Both dark stripes and dark holes nested in a broad partially spatially incoherent wavefront were self-trapped to form dark solitons in a host photorefractive medium. These self-trapped 1D and 2D dark beams induced refractive-index changes akin to planar and circular dielectric waveguides. The experiments introduce the possibility of controlling high-power coherent laser beams with low-power incoherent light sources such as light emitting diodes.     

Relationship of hepatic lipidosis to health and performance in dairy cattle

In a field study of 80 cows in 9 dairy herds, serial liver biopsies were performed over the peripartum period to determine degree of hepatic lipidosis. Cattle were separated into categories of mild, moderate, and severe hepatic lipidosis on the basis of maximal amounts of hepatic triglyceride that accumulated during this period. Number of cattle with mild, moderate, and severe hepatic lipidosis were 52, 16, and 12, respectively. Cattle with severe hepatic lipidosis had greater concentrations of hepatic triglyceride before calving and after parturition, and greater serum nonesterified fatty acid concentrations and body condition loss after parturition than cattle with mild hepatic lipidosis. Rate of disease and culling and death rate because of disease were greater in cattle with severe hepatic lipidosis. Cattle with severe hepatic lipidosis had reproductive performance equal to clinically normal cattle; however, cattle with moderate hepatic lipidosis had increased days to conception, possibly related to greater milk production.     

Congenital porto-systemic shunts in sixteen dogs and three cats

Congenital porto-systemic shunts in sixteen dogs and three cats are described. A major symptom was hepato-encephalopathy. In most cases diagnosis was based on elevated venous ammonia levels, abnormal ammonia tolerance and results of operative mesenteric portography. Clinical signs, laboratory findings, results of portography, and pathologic findings in the liver and the central nervous system are described. A diagnostic schedule is proposed to aid in recognition of this syndrome.