Plasma beta-endorphin and adrenocorticotrophin in young horses in training

A controlled period of submaximal exercise on a treadmill was used as a standardised stress test in 6 young horses to monitor the effects of training. Circulating plasma concentrations of immunoreactive beta-endorphin (IR beta-EP) were measured before, during and after the exercise period. The stress test was conducted on 3 occasions during an intensive training program lasting 14 weeks. In week 3 a marked increase in plasma IR beta-EP (P = 0.003) was demonstrated as a result of training, but by the last exercise test performed in week 9 no significant increase in plasma IR beta-EP concentrations could be detected. During the training period the basal concentrations of plasma IR beta-EP significantly decreased (P = 0.0059). Plasma adrenocorticotrophin (ACTH) did not increase during exercise, although there was a trend of decreasing basal plasma ACTH by the end of the training period. It was concluded that a standardised work test acted as a mild stress to unfit horses, but as the horses' fitness increased the hormonal response to exercise diminished. Basal plasma beta-EP concentrations were decreased with increasing fitness.     

Effects of antibiotic therapy at drying off on mastitis in the dry period and early lactation

Four strategies for selecting cows for intramammary therapy with benzathine cloxacillin at drying off were compared in 12 Victorian dairy herds. The bacteriological status of all quarters of all (1044) cows was determined just before drying off, within 2 d of calving, and again 3 to 5 months after calving. All cases of clinical mastitis (from calving to mid-lactation) were recorded. Cows not infected at drying off were allocated randomly to 2 subgroups of approximately 350 cows each: not infected, not treated (NI-NT), or not infected, all quarters treated (NI-AT). New infection rates in the dry period (3.8% for NI-NT vs 2.1% for NI-AT) and in early lactation (4.1% for NI-NT vs 3.9% for NI-AT) were low and these differences were not significant. Incidence of clinical mastitis in early lactation was almost 50% higher for the treated group of uninfected cows compared with the untreated group (0.05 less than p less than 0.1). Cows infected in one or more quarters at drying off were split randomly into 2 subgroups of approximately 170 cows each: infected, all quarters treated (I-AT), or infected quarters treated only (I-QT). The new infection rate during the dry period was nearly 4 times higher for I-QT (15.3%) due to significantly more new infections by Staphylococcus aureus and Streptococcus uberis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pesticide residues in the total diet in Canada. IV. 1972 and 1973

Foods, representing an average Canadian diet, were prepared for eating, made into homogenised composites, each containing one type of produce, and analysed for pesticide residues and arsenic. The amounts found were at a consistently low level which could contribute approximately 20 μg total pesticide residues and 35 μg arsenic/person/day.     

Eclogitic diamond formation at jwaneng: No room for a recycled component

Eclogitic diamonds have a large range of delta13C values, whereas peridotitic diamonds do not. Paired delta15N-delta13C-N variations in 40 eclogitic diamonds from the Jwaneng kimberlite in Botswana show that neither the influence of recycled biogenic carbon nor the global and primordial heterogeneity of mantle carbon are likely for the origin of the large delta13C range; the data instead support a fractionation process. It is proposed that carbonatitic mantle melts from which diamonds crystallize undergo different evolutions before diamond precipitation, when percolating through either a peridotite or an eclogite. These different evolutions, reflecting the presence or absence of olivine, can account for their respective delta13C distributions.     

Response to Chemical Alarm Cues under Weakly Acidic Conditions: A Graded Loss of Antipredator Behaviour in Juvenile Rainbow Trout

A wide variety of aquatic organisms, including juvenile salmonids, assess local predation risks using chemosensory cues. Such chemical cues are typically released from injured conspecifics and their detection may lead to species-typical antipredator behaviour, increasing the probability of prey to survive during predator encounters. Studies have demonstrated however, that under weak acidification (pH ~6.0), the response towards these chemical alarm cues is impaired. However, it remains unknown if the loss of response is graded (i.e., the behavioural response decreases with a reduction in pH) or if there is a threshold pH at which prey can no longer detect the alarm cues. We conducted two laboratory experiments to examine the effects of a graded reduction in pH on the behavioural response of juvenile rainbow trout to conspecific chemical alarm cues. The results of our first experiment suggest that at pH 6.6 and above, the alarm cues elicited a strong antipredator response, while alarm cues buffered to pH 6.2 did not (i.e. not different from distilled water). However, alarm cues buffered to pH 6.4 elicited a weak response, suggesting a graded response. We directly tested this in our second experiment using a repeated measures design. The response to alarm cues at varying pH levels did indeed follow a graded loss of function. Together, our results suggest that juvenile rainbow trout exhibit a reduction in the response to conspecific alarm cues proportional to ambient acidity and that the response to these critically important cues is lost at pH below 6.4. As the detection and response to these chemical alarm cues have been shown to confer direct survival benefit to individuals, these results are therefore presented in relation to possible sub-lethal effects of anthropogenic acidification to freshwater fish.     

Congenital biliary atresia and jaundice in lambs and calves

An outbreak of congenital biliary atresia and jaundice is described, in which approximately 300 crossbred lambs and 9 crossbred calves died. The affected animals failed to thrive, developed jaundice and white scours and died within 4 weeks of birth. A common feature of this outbreak and a similar occurrence 24 years previously was the grazing of plants growing on the exposed silt foreshores of Burrinjuck Dam by ewes and cows in the early stages of pregnancy. Epidemiological and pathological findings suggested that a toxic insult to the foetus in early gestation caused choledysgenesis and biliary atresia, leading to diffuse, subacute to chronic cholangiohepatopathy and cirrhosis.     

Strategies for mastitis control: dry cow therapy and culling

SUMMARY The effects of three selection strategies for dry cow therapy on prevention of new infections and rate of antibiotic usage were compared. Quarter infection status of 1044 cows in 12 herds was determined by bacteriological methods at drying off, calving and three to five months into the following lactation. Cows that were uninfected at drying off were randomly allocated to treatment (whole udder, dry cow therapy) and non-treatment groups. Infected cows were randomly allocated to whole udder or infected quarter only treatments. The strategies compared were blanket treatment (treat all quarters of all cows), selective cow treatment (treat all quarters of any cow infected in one or more quarters) and selective quarter treatment (treat infected quarters only). Selective cow treatment was identified as the preferred strategy. Blanket treatment resulted in increased antibiotic usage (15.5 vs 6.4 tubes per infection eliminated) with no additional benefit, and selective quarter treatment resulted in a higher new infection rate (6.4%vs 3.9% quarters) in the dry period. The prevalence of infection within a herd at drying off had no influence on new infection rates in the dry period or early lactation. The cure rate after dry cow treatment (mean of 66%) decreased significantly with increasing age (P < 0.001). Cows infected in the previous lactation contributed over 76% of infections at calving and nearly 70% at mid-lactation. To lower the incidence of mastitis in a herd, a greater emphasis on culling of older infected cows and prevention of new infections during lactation is needed.