Differential Effects of Exogenous Progesterone Administration at Different Stages of the Luteal Phase on Endogenous Oestradiol Concentration in Cows

We have investigated the effects administering exogenous progesterone, via insertion of a controlled internal drug release (CIDR) for 4 days, from either day 5 or day 12 of the oestrous cycle on plasma oestradiol concentrations. In study 1, in which progesterone was administered from day 5, measurement of plasma oestradiol in daily samples revealed a significant (p < 0.001) decrease in peripheral oestradiol concentration. In contrast, in study 2, similar administration of progesterone from day 12 had no effect on plasma oestradiol concentration. In study 3, collection of hourly samples following progesterone treatment on day 5 revealed peak progesterone concentrations within 1 h of CIDR insertion and nadir oestradiol concentrations within 4 h. The results demonstrate that treatment with progesterone early in the luteal phase causes a rapid inhibition of oestradiol secretion, while later treatment does not. While improvements in pregnancy rate following progesterone treatment at this time have traditionally been attributed to increases in progesterone, the potential involvement of decreased oestradiol secretion has often been overlooked.     

Electrode scalp impedance differences between electroencephalography machines in healthy dogs

Scalp electrode impedance measurements recorded by wired and wireless electroencephalography (EEG) machines in 7 healthy dogs were compared. Eight recordings resulted in 80 impedance readings from subdermal wire electrodes (locations F7/F8, F3/F4, T3/T4, C3/C4, Fz, and Cz). Impedance values were measured first from the wired and then the wireless EEG machine. Wireless impedance measurements were higher than the wired EEG machine in 79/80 readings (P ≤ 0.05), being on average 2.83 kΩ [P ≤ 0.05, 95% confidence interval (CI): 2.51 to 3.14, SD = 1.42] higher. Impedances from the wired machine ranged between < 0.5 and 9 kΩ (mean = 3.09, median = 2.00, SD = 2.15), whereas impedances from the wireless machine ranged between 2.69 and 6.07 kΩ (mean = 5.92, median = 5.05, SD = 2.59). Despite these differences in impedance measurements, both machines measured similar impedance patterns. The wireless EEG machine’s impedance measurements, therefore, should be acceptable for veterinary clinical settings.     

The ecology and conservation of Llyn Idwal and Llyn Cwellyn (Snowdonia National Park,North Wales,UK)—two lakes proposed as special areas of conservation in Europe

1. This paper gives a comprehensive account of the ecology of Llyn Idwal and Llyn Cwellyn, two nationally well known and internationally important conservation lakes in Snowdonia National Park, North Wales. Idwal has a small but precipitous catchment with relatively large areas of heathland and base rich bare rock. Cwellyn has a larger catchment with a substantial proportion of woodland, including coniferous plantations, and a long history of human activity. 2. The chemistry of the waters in both lakes is indicative of nutrient-poor conditions but Idwal exhibits relatively high alkalinity and pH values. 3. The diatom floras are typical of nutrient-poor upland waters, with species composition reflecting the alkalinity differences. Isoetids form a dominant component of the macrophyte floras, with the most diverse assemblage recorded at Idwal. 4. The zooplankton communities are distinctive, with only a small number of species occurring in both lakes. The macroinvertebrate faunas are dominated by insect taxa typical of stony shores. Supplementary stocking of the Idwal trout population has been reported. 5. The conservation importance of the sites lies primarily in their representation of nutrient-poor mountain lake systems and the macrophyte assemblages which include a number of rare species. In addition, a genetically unique arctic charr population is present in Cwellyn. 6. Impoundment, water abstraction, acidification, eutrophication and the recreational use of the sites are identified as potential environmental impacts. The conservation management of the sites is related to the extent of the reserve boundaries and catchment activities. Aspects of the future management and environmental monitoring of Idwal and Cwellyn as Special Areas of Conservation under the European Community Council Directive on the conservation of natural habitats and of wild fauna and flora are discussed. © 1998 John Wiley & Sons, Ltd.     

Growth response to increasing doses of microencapsulated vitamin B12 and related changes in tissue vitamin B12 concentrations in cobalt-de cient lambs

AIM: To investigate growth responses of cobalt-deficient lambs to increasing doses of microencapsulated vitamin B₁₂, and to measure associated changes in serum and liver vitamin B₁₂ concentrations over 243 days.

METHODS: From a flock grazing pastures that had low cobalt (Co) levels (about 0.06 mg Co/kg dry matter), 4-6-week-old lambs (n=137) were assigned to four groups and received either no treatment or a subcutaneous injection of 3.0, 4.5 or 6.0 mg of microencapsulated vitamin B₁₂ on Day 1. At approximately monthly intervals, all lambs were weighed and blood samples were collected from a selection (n=10) of monitor animals, up to Day 243. Liver biopsies were also carried out on the monitor lambs (n=8) on Days 1, 124 and 215.

RESULTS: The vitamin B₁₂-treated lambs grew significantly faster (p<0.001) than untreated animals. Liveweights after 243 days were 28, 45, 45 and 47 kg for the untreated, 3.0, 4.5 and 6.0 mg vitamin B₁₂-treated lambs, respectively. Of the initial group of untreated lambs, 68% had to be removed before the end of the trial because of substantial weight loss, but none of the treated animals were similarly afflicted. Serum vitamin B₁₂ concentrations increased in all vitamin B₁₂-treated lambs, reaching a peak at Day 25, and those of the 4.5 and 6.0 mg vitamin B₁₂-treated lambs remained significantly higher (except at Day 124) than the untreated lambs to Day 187. However, at Day 124, but not Day 215, the liver vitamin B₁₂ concentrations of treated lambs were two to three times higher than those of controls.

CONCLUSIONS: The growth rates of Co-deficient lambs were markedly improved by injection of 3.0, 4.5 or 6.0 mg of microencapsulated vitamin B₁₂, and liveweights were maintained for at least 243 days. Serum vitamin B₁₂ concentrations were related to this growth response; concentrations of <220 pmol vitamin B₁₂/l were associated with a 95% probability that lambs were Co-deficient and would thus respond to Co/vitamin B₁₂ supplementation. Based on these data, the current New Zealand reference criteria for Co deficiency should be reviewed.

CLINICAL SIGNIFICANCE: An injection of 3 mg microencapsulated vitamin B₁₂2 given to lambs at tailing will treat Co deficiency and will increase and maintain liveweights in a flock for up to 8 months.     

The UK Environmental Change Network: Emerging trends in the composition of plant and animal communities and the physical environment

This review identifies the major trends in physical, chemical and biological data between 1993 and 2007 at the 12 terrestrial sites in the United Kingdom Environmental Change Network (ECN) and assesses the effectiveness of the programme.Temperature and precipitation increased and sulphur (S) deposition decreased across the network. There were also significant local trends in nitrogen (N) deposition. The decreasing S deposition was associated with increasing pH of rainfall and soils and there was widespread evidence of soil pH showing recovery from acidification.Warm-adapted butterfly species tended to increase at northern, upland sites, consistent with an effect of increasing temperatures. In contrast, carabid beetle species associated with cooler northern and upland areas showed declining populations. The increasing trend in precipitation may account for a decline in ruderal plant species in the lowlands, reversing an increase associated with drought in the early part of the time series.There was no general shift in the composition of plant communities which might reflect rising soil pH. This may reflect the slow dynamics of plant community processes or a distinction between pH trends at the surface and lower soil horizons.The ECN is effective in detecting trends in a range of different variables at contrasting sites. Its strength is the ability to monitor causes and consequences of environmental change in the same programme, improving the ability to attribute causes of change, which is essential to developing conservation policy and management in the 21st century.     

Correlation of motor evoked potentials with magnetic resonance imaging and neurologic findings in Doberman Pinschers with and without signs of cervical spondylomyelopathy

OBJECTIVE: To establish the reference ranges for motor evoked potential (MEP) latency and amplitude in clinically normal Doberman Pinschers, compare the MEPs of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy (CSM; wobbler syndrome), and determine whether MEP data correlate with neurologic or magnetic resonance imaging (MRI) findings. ANIMALS: 16 clinically normal and 16 CSM-affected Doberman Pinschers. PROCEDURES: Dogs were classified according to their neurologic deficits. After sedation with acepromazine and hydromorphone, transcranial magnetic MEPs were assessed in each dog; latencies and amplitudes were recorded from the extensor carpi radialis and cranial tibial muscles. Magnetic resonance imaging was performed to evaluate the presence and severity of spinal cord compression. RESULTS: Significant differences in cranial tibial muscle MEP latencies and amplitudes were detected between clinically normal and CSM-affected dogs. No differences in the extensor carpi radialis MEP were detected between groups. There was a significant correlation (r = 0.776) between the cranial tibial muscle MEP latencies and neurologic findings. Significant correlations were also found between MRI findings and the cranial tibial muscle MEP latencies (r = 0.757) and amplitudes (r = -0.453). CONCLUSIONS AND CLINICAL RELEVANCE: Results provided a reference range for MEPs in clinically normal Doberman Pinschers and indicated that cranial tibial muscle MEP latencies correlated well with both MRI and neurologic findings. Because of the high correlation between cranial tibial muscle MEP data and neurologic and MRI findings, MEP assessment could be considered as a screening tool in the management of dogs with spinal cord disease.     

In extruded feline diets,thiamine degraded at a similar rate when stored at −20°C,compared to room temperature

Thiamine is an essential dietary nutrient in cats; however, studies on the stability of thiamine in pet food are limited. The objective of this study was to analyze thiamine concentrations in commercial feline extruded diets over time at room and freezing temperatures. Twelve diets were split in half and thiamine concentrations were assessed using fluorometry. One half of each diet was then stored at room temperature (24°C) and the other half was frozen (−20°C). Subsamples were analyzed at 2 other time points at 6-month intervals up to 1 year. Data were assessed using a mixed procedure (2-factor factorial model with factors time and treatment). Based on F-tests, thiamine concentrations decreased over time (P = 0.001), with no treatment*time interaction (P = 0.9534). In conclusion, regardless of treatment, thiamine degraded at a similar rate over time.     

Reproductive Parameters of Mangalarga Marchador Mares in a Commercial Embryo Transfer Programme

The objective of this study is to evaluate the reproductive efficiency in donors and recipient Mangalarga Marchador mares in commercial programmes of embryo transfer (ET) and the effects of some reproductive characteristics and ET methodology on conception rates in the recipient mares. A total of 1140 flushing procedures were performed and 830 embryos (72.8%) were recovered. There were no differences between the rates of embryonic recovery in the different breeding seasons (p > 0.05) and 92.8% of the recovered embryos were 8–9 days old. There was no difference in the embryonic recovery regarding the collection order from the first to the ninth embryo collection along the breeding season, as well as among mares inseminated during the foal heat or subsequent cycles (p > 0.05). Pregnancy rates observed in the total period of all reproductive seasons at 15, 30, 45 and 60 days of pregnancy were 73.4, 69.9, 66.7 and 64.5%, respectively. Differences in pregnancy rate and early embryonic loss rates were not observed between embryos transferred immediately after collection (66.8% and 13.5%) and embryos transported at room temperature for periods of <1 h (62.9% and 14.4%; p > 0.05). Pregnancy rates were higher when the interval between ovulations of donor and recipient mares remained between ?3 and ?2 days (p < 0.05), and the lowest rates were observed for intervals of ?6 days (p < 0.05) with intermediary values for intervals of ?1, 0 and +1 (p > 0.05). Embryonic loss rates, however, did not differ between intervals of ovulation’s synchronism between donor and recipient mares (p > 0.05). This flexibilization in the ovulatory synchronism between donor and recipient mares optimizes the use of recipient mares, thus reducing costs and facilitating management of horse breeding farms.