The influence of rapid growth in broilers on florfenicol pharmacokinetics – allometric modelling of the pharmacokinetic and haemodynamic parameters

1. The aim of this study was to determine if the pharmacokinetics (PK) of florfenicol (FF) undergo age-dependent changes in broilers. Since drug elimination depends on cardiovascular functions, a haemodynamic study was performed in parallel.

2. Broilers of 0.68, 1.27, 2.45 and 5.13 kg were administered FF in a single intravenous dose of 30 mg/kg body weight. Plasma drug concentrations were determined using high-performance liquid chromatography and PK parameters were calculated using a non-compartmental model. Echocardiography was used to measure haemodynamic functions.

3. During growth, the area under the drug concentration-time curve (AUC_inf) increased from 25.7 ± 2.9 to 39.0 ± 8.0 mg h/l. Total body clearance (Cl_B) gradually decreased from 1.19 ± 0.14 to 0.80 ± 0.15 l/h/kg. Elimination half-life increased from 0.73 ± 0.08 to 1.07 ± 0.07 h, whereas volume of distribution (V_ss) remained unchanged. Haemodynamic measurements revealed an increase in cardiac output, from 495 ± 65 to 1303 ± 306 ml/min, in the respective body weight groups.

4. Allometric models for PK and haemodynamic parameters were developed and validated. All models proved to be statistically significant; however, only models for Cl_B and V_ss met stringent validation criteria. Model for Cl_B was used to calculate an optimal dose for a given age group that provides uniform AUC_inf.

5. Age-dependent change in FF kinetics may cause variability in therapeutic response under clinical conditions. A novel approach to the dosing protocol was proposed as a means of optimising therapeutic efficacy.     

Collection and short-term preservation of semen from free-ranging eastern grey kangaroos (Macropus giganteus: Macropodidae)

Objectives To evaluate electro-ejaculation of free-range eastern grey kangaroos in the field and assess the efficacy of four diluents to preserve sperm motility over a 48-h period at 5°C.
Procedure and design Under gaseous anaesthesia, 25 free-range kangaroos were electro-ejaculated and characteristics of the ejaculate noted. Spermatozoa obtained from eight ejaculates were diluted in phosphate buffered saline containing various combinations of egg yolk and glucose and refrigerated at 5°C for 48 h.
Results Spermatozoa were recovered from 24 of 28 ejaculates. Mean (± SEM) semen volume (mL) and pH were 25.0 ± 1.9 and 7.1 ± 0.1 respectively. The forward motility (%), rate of movement of sperm (0 to 5) and sperm concentration (x 10⁶/mL) were 77.4 ± 1.5, 3.8 ± 0.9 and 31.2 ± 7.3 respectively. There was no significant difference between the four diluents in their ability to maintain forward motility of spermatozoa over 48 h. However, rate of movement over the same period was significantly (P < 0.01) improved when sperm were diluted in phosphate buffered saline containing 10% egg yolk.
Conclusions Electro-ejaculation is a safe and reliable method for collecting semen from free-ranging eastern grey kangaroos. Preliminary attempts at short-term preservation showed that the motility of kangaroo spermatozoa could be adequately stored for 24 h and that the addition of egg yolk to the semen diluent was beneficial for improving the rate of sperm movement.     

Epidemic of blindness in kangaroos - evidence of a viral aetiology

OBJECTIVE: To determine the cause of an epidemic of blindness in kangaroos. DESIGN AND PROCEDURES: Laboratory examinations were made of eyes and brains of a large number of kangaroos using serological, virological, histopathological, electron microscopical, immunohistochemical methods, and PCR with cDNA sequencing. In addition, potential insect viral vectors identified during the disease outbreak were examined for specific viral genomic sequences. SAMPLE POPULATION: For histopathological analysis, 55 apparently blind and 18 apparently normal wild kangaroos and wallabies were obtained from New South Wales, Victoria, South Australia, and Western Australia. A total of 437 wild kangaroos and wallabies (including 23 animals with apparent blindness) were examined serologically. RESULTS: Orbiviruses of the Wallal and Warrego serogroups were isolated from kangaroos affected with blindness in a major epidemic in south-eastern Australia in 1994 and 1995 and extending to Western Australia in 1995/96. Histopathological examinations showed severe degeneration and inflammation in the eyes, and mild inflammation in the brains. In affected retinas, Wallal virus antigen was detected by immunohistochemical analysis and orbiviruses were seen in electron microscopy. There was serological variation in the newly isolated Wallal virus from archival Wallal virus that had been isolated in northern Australia. There were also variations of up to 20% in genotype sequence from the reference archival virus. Polymerase chain reactions showed that Wallal virus was present during the epidemic in three species of midges, Culicoides austropalpalis, C dycei and C marksi. Wallal virus nucleic acid was also detected by PCR in a paraffin-embedded retina taken from a blind kangaroo in 1975. CONCLUSION: Wallal virus and perhaps also Warrego virus are the cause of the outbreak of blindness in kangaroos. Other viruses may also be involved, but the evidence in this paper indicates a variant of Wallal virus, an orbivirus transmitted by midges, has the strongest aetiological association, and immunohistochemical analysis implicates it as the most damaging factor in the affected eyes.     

Short-term and long-term PQ, QT and R-R intervals' variability at the resting condition and after exercise testing in healthy Anglo-Arabian horses

The duration of electrocardiographic (ECG) parameters: PQ, QT and R-R intervals change during long-term and short-term observation as the consequence of the fluctuations in autonomic nervous system activity among others dependent on the exercise and resting. There is no data of horse breed influence on these parameters. The aim of the study was to assess the duration and the variability of the PQ, QT and R-R intervals in the resting conditions and after exercise testing in Anglo-Arabian horses. Material and Methods: 27 healthy Anglo-Arabian horses aged 3.4 +/- 1.0 years (15 male, 12 female) had ECG examination in the standing position using Einthoven system of leads. The longest and the shortest PQ, QT and R-R intervals were measured after night rest and after exercise testing and the means were calculated. Conclusions: 1) In Anglo-Arabian horses the difference between the longest and the shortest PQ interval at rest vs. after exercise is 0.06 +/- 0.05 vs. 0.03 +/- 0.02, QT interval is 0.04 +/- 0.03 vs. 0.04 +/- 0.04, R-R interval 0.19 +/- 0.15 vs. 0.08 +/- 0.11. 2) The PQ and R-R intervals reveal high short-term variability either at the resting conditions or after exercise testing. 3) After exercise testing PQ, QT and R-R intervals are shorter than at the resting conditions. The delta PQ and R-R are 2 times smaller in contrast to delta QT which is constant. 4) The PQ and R-R interval variability was greater at the baseline condition than after exercise testing. The QT variability was similar at baseline condition to that after exercise testing.     

Contributions to an animal trait ontology

Improved understanding of the biology of traits of livestock species necessitates the use and combination of information that is stored in a variety of different sources such as databases and literature. The ability to effectively combine information from different sources, however, depends on a high level of standardization within and between various resources, at least with respect to the used terminology. Ontologies represent a set of concepts that facilitate standardization of terminology within specific domains of interest. The biological mechanisms underlying quantitative traits of farm animal species related to reproduction and host pathogen interactions are complex and not well understood. This knowledge could be improved through the availability of domain-specific ontologies that provide enhanced possibilities for data annotation, data retrieval, data integration, data exchange, data analysis, and ontology-based searches. Here we describe a framework for domain-specific ontologies and the development of 2 first-generation ontologies: Reproductive Trait and Phenotype Ontology (REPO) and Host Pathogen Interactions Ontology . In these first-generation ontologies, we focused on "female fertility in cattle" and "interactions between pigs and Salmonella". Through this, we contribute to the global initiative toward the development of an Animal Trait Ontology for livestock species. To demonstrate its usefulness, we show how REPO can be used to select candidate genes for fertility.     

Influences of myogenin genotypes on birth weight, growth rate, carcass weight, backfat thickness, and lean weight of pigs.

Lean weight is related to muscle fiber number. Muscle fiber formation (myogenesis) occurs only during embryonic development when it is under the control of the MyoD gene family consisting of myogenin, MyoD1, myf-5, and myf-6. Myogenin has a central position within the MyoD gene family because myogenin expression abrogates myoblast proliferation potential and regulates the differentiation of single nucleated myoblasts into multinucleated myofibers. Thus, myogenin genotype could be related to variation in the number of muscle fibers formed, leading to variation in muscle mass and, thus, lean weight. A polymorphism at the porcine myogenin locus was associated with birth weight, growth rate, lean weight at 200 d, and backfat thickness. Yorkshire pigs from two commercial lines were genotyped, and crosses between heterozygous pigs and heterozygous and homozygous pigs were made. Resulting litters were genotyped, and phenotypic data were collected. Significant differences were found between the two homozygous myogenin genotypes for birth weight, growth rate, and lean weight, but not for backfat thickness. Variation at the myogenin locus explained 4% of the total phenotypic variation in birth weight, growth rate, and carcass weight, and 5.8% of the total variation in lean weight. We conclude that myogenin genotype influences porcine growth rate and muscle mass.