The pharmacokinetics of chloramphenicol in plasma and saliva of dairy cows

In the present study the pharmacokinetics of chloramphenicol were investigated in bovine plasma and saliva. The method of detection of chloramphenicol, a radio-immunoassay, requires only small sample volumes, no further clean-up, and a large number of samples can be processed simultaneously. This enabled the collection of a larger number of samples over a longer period of time than in previous studies. The intention was to obtain a complete pharmacokinetic profile of chloramphenicol, to evaluate it according to common open-compartment models, and to compare it with the results of previous studies. The radio-immunoassay results were confirmed by analysing a number of samples distributed over the concentration range of interest by a gas-chromatographic method with electron-capture detection. The suitability of saliva was evaluated as a possible means of monitoring compliance with the ban on chloramphenicol in the Federal Republic of Germany in milk-producing animals.     

Apical fracture of the proximal sesamoid bone in standardbred horses: 43 cases (1990-1996).

OBJECTIVE: To determine whether fracture fragment dimensions, suspensory ligament damage, and racing status at the time of injury were associated with outcome in Standardbred horses with apical fracture of the proximal sesamoid bone. DESIGN: Retrospective study. ANIMALS: 43 Standardbred racehorses. PROCEDURE: Medical records, racing records, and radiographs were reviewed, and ultrasonographic findings were scored. Measurements of the fractured portion of the proximal sesamoid bone were made. RESULTS: Seventy-four percent (32/43) of horses were pacers, and 26% (11/43) were trotters. Statistical differences between trotters and pacers regarding ability to start, number of starts, or amount of money earned after injury were not detected. Females earned significantly more money per start after injury than males. Eighty-six percent (37/43) of fractures involved hind limbs and 14% (6/43) involved forelimbs. Horses with forelimb injuries earned less money per start. Severity of suspensory ligament damage did not affect postinjury racing performance. A higher proportion of horses that had raced before injury returned to racing after surgery than horses that had not raced before injury, although a significant difference between these groups was not detected. Eighty-eight percent of horses that raced before injury raced after injury. Fifty-six percent of horses that did not race before injury raced after injury. Fracture fragment dimensions did not affect outcome. CLINICAL IMPLICATIONS: Dimensions of the apical fracture fragment of the proximal sesamoid bone in Standardbred horses and degree of suspensory ligament damage did not affect outcome. Prognosis for return to racing soundness is good in horses that had raced before injury and fair in horses that had not raced before injury.     

The humoral and cellular immune response of sheep against Borna disease virus in endemic and non-endemic areas

Borna Disease (BD) is a mostly fatal disease of horses and sheep endemic in central Europe. Antibodies to Borna disease virus (BDV) have been described in sheep and other species living in BD non-endemic areas. Meaningful clinical BDV serology is hampered by difficulties in defining serological cut-offs, which require the investigation of populations from endemic areas. Here we studied BD serology in sheep from endemic and non-endemic areas of similar geography in Switzerland. Antibodies to BDV antigens were detected by ELISA and indirect immunofluorescence analysis (IFA) only in sera from 3 of 6 sheep with autopsy confirmed BD. One serum was positive by IFA but not by ELISA, while 2 sera were negative in both assays, indicating that not all diseased animals develop BDV specific antibodies. Six % of clinically healthy animals (6/106) from an endemic area and 2% from a non-endemic area (4/192) had serum antibody to either BDV p40 or p24 as detected by ELISA. None of the animals showed a cellular immune response to BDV p40. In some healthy sheep from the endemic area, serum antibody titers to BDV p24 antigen remained elevated over several months without onset of disease symptoms. Infections with either BDV or related viruses may thus occur at low frequency in sheep from non-endemic areas leading to the production of antibodies to BDV antigens. We further propose viral strain differences or environmental factor(s) may determine the clinical outcome.     

Doubled-haploid versus single-seed descent and S1-family variation for testcross performance in a maize population

Progress made in the in situ gynogenesis technique since 1990 now allows production of a high number of maize (Zea mays L.) doubled-haploid (DH) lines. The aim of the study was to compare DH lines versus selfing lines for testcross performance. DH and single-seed descent (SSD) lines were produced from random S₁ progenies of a broad-base population. For grain yield, kernel moisture, plant height, ear height and leaf length, the three population means were similar. Except for kernel moisture, the genetic variance of DH lines was nearly twice as high as the genetic variance of S₁ families, as expected. On the other hand, genetic variance among SSD lines was only 1.5 times higher than the genetic variance of S₁ families. This lower variance could be due to a selection bias in the method of production of SSD lines. However, for all traits, heritability of SSD or DH lines was higher than heritability of S₁ families. Epistasis effects in DH progenies were not significant. The consequence was a high correlation between S₁ testcross progenies and DH or SSD testcross progenies, meaning that the S₁ testcross value can be used to select the best families from which DH lines will be extracted. As a whole, the observed variation in DH lines appeared to be more in accordance with the observed variation among S₁ families than with the observed variation among SSD lines.     

外源脱落酸对抗寒性狗牙根抗氧化酶活性的影响

以寒敏感的普通狗牙根、海岸狗牙根和抗寒的新农1号狗牙根、喀什狗牙根为供试材料,研究外源脱落酸（0 mg•L^-1、5 mg•L^-1、15 mg•L^-1、25 mg•L^-1）在4 ℃低温处理下（处理时间24 h、72 h）对叶片相对电导率（EC）、丙二醛（MDA）含量、超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性、过氧化物酶（POD）活性的影响。结果表明：与CK2（喷水、常温培养）相比,4 ℃低温处理24 h、72 h,无论是否喷施外源脱落酸,狗牙根均表现为[WTBX]EC[WTBZ]增大,MDA含量增加;但与CK1（喷水、4 ℃低温处理）相比,喷施外源脱落酸可以诱导狗牙根细胞EC、MDA含量降低,促进SOD活性、POD活性、CAT活性的进一步增加,保护膜系统的完整性,增强其对低温的适应。综合分析认为,抗寒狗牙根的适宜外源脱落酸喷施浓度为15 mg•L-1,寒敏感狗牙根为5 mg•L^-1更有利于其对低温的适应。随着低温处理时间的延长,抗寒狗牙根SOD活性增加率、MDA含量降低率明显高于寒敏感狗牙根,说明SOD酶活性不同可能是狗牙根抗寒性差异的原因之一。     

Risk Factors for the Development of Hypokalemia in Neonatal Diarrheic Calves

Background

Neonatal diarrheic calves have a clear negative potassium balance because of intestinal losses and decreased milk intake but in the presence of acidemia, they usually show normokalemic or hyperkalemic plasma concentrations.

Objectives

To assess whether marked hypokalemia occurs in response to the correction of acidemia and dehydration and to identify factors that are associated with this condition.

Animals

Eighty‐three calves with a clinical diagnosis of neonatal diarrhea.

Methods

Prospective cohort study. Calves were treated according to a clinical protocol using an oral electrolyte solution and commercially available packages of 8.4% sodium bicarbonate, 0.9% saline and 40% dextrose infusion solutions.

Results

The proportion of hypokalemic calves after 24 hours of treatment (19.3%) was twice as great as it was on admission to the hospital. Plasma K⁺ after 24 hours of treatment was not significantly correlated to venous blood pH values at the same time but positively correlated to venous blood pH values on admission (r = 0.51, P < .001). Base excess on admission (Odds ratio [OR] = 0.81, 95% confidence interval [CI] = 0.70–0.94), duration of diarrhea (OR = 1.37, 95% CI = 1.05–1.80), milk intake during hospitalization (OR = 0.54, 95% CI = 0.37–0.79) and plasma sodium concentrations after 24 hours (OR = 1.12, 95% CI = 1.01–1.25) were identified to be independently associated (P < .05) with a hypokalemic state after 24 hours of treatment.

Conclusions and Clinical Importance

Findings of this study suggest that marked depletion of body potassium stores is evident in diarrheic calves that suffered from marked metabolic acidosis, have a low milk intake and a long history of diarrhea.     

Variations in parameters of liver function and plasma progesterone related to underfeeding and ketosis in a dairy herd

Twenty-eight Norwegian Red Cattle dairy cows were fed silage ad libitum and restricted amounts of concentrates. Blood samples were collected before morning feeding, once or twice weekly, from 2 weeks before to 12 weeks after calving. Parameters of liver function, carbohydrate status and fertility were recorded in order to assess their interrelationships. Eight cows were treated for clinical ketosis. Four of these had to be treated 2 or 3 times. Aspartate aminotransferase and bilirubin showed the highest within-animal coefficients of correlation with acetoacetate. Analysis of variance revealed a significant effect of carbohydrate status (indicated by plasma acetoacetate levels) on the levels of aspartate aminotransferase, glutamate dehydrogenase and sorbitol dehydrogenase, though only a small part of the total variation was explained by this factor. The estimated volume density of liver fat in the 4th week of lactation averaged 6.0 +/- 6.4% (+/- SD) ranging from 0.1-25.1%. Liver fat content at this stage of lactation was not significantly correlated with other indicators of liver function or carbohydrate status. Cows treated for clinical ketosis had significantly lower plasma progesterone values at the time of first ketosis treatment than untreated multiparous cows. The frequency of high progesterone values (greater than 3 ng/ml) being significantly lower in treated than in untreated cows during the period from 3-5 weeks post partum, though not at later stages. In conclusion, the results revealed a significant relationship between carbohydrate status and liver function, and also between clinical ketosis and luteal function.