Disturbances Impact on Longevity of Grass Seeds,Semi-Arid South African Rangeland

The effect of plant and soil disturbances on seed density, species richness, and seed longevity of the soil seed bank was quantified for a semi-arid rangeland, over a 5-yr period (2002/2003–2006/2007 growing seasons). The different soil and plant treatments included fire, tillage (intended as a trampling surrogate), and blocked seed rain (simulating heavy grazing). These three experimental factors were combined in a factorial arrangement. Seed responses were evaluated in the soil seed bank before the new seed set, after the first seed production event, and after the second seed production event. Before disturbance (physical impact on the plant and soil), soil seed bank was dominated by early successional species: conversely, aboveground vegetation was mainly dominated by perennial grasses. After only 4 yr of blocked seed rain, seedling emergence of Decreaser grass species ceased totally both in the field and seed bank, with lower effect on Increaser grass species. Emergence of both Decreaser and Increaser grass species decreased in the seed bank with tillage, whereas the opposite occurred in the field. By contrast, tillage increased the emergence of weeds in the seed bank. The decrease in emergence of Decreaser grass species in both seed bank and field was still evident 4 yr after the rangeland was burnt. The grass species Themeda triandra was the most sensitive to fire in terms of seedling emergence. Blocked seed rain treatment significantly decreased (P < 0.05) species richness. Regardless of treatments applied, there was poor similarity between aboveground vegetation and the associated seed bank. Differences in the soil seed bank are likely to reflect manifested properties rather than short-term changes. Several characteristics of seed banks (species composition, seed abundance, and longevity) must be considered in order to understand the dynamics of plant communities following disturbances.     

Larval development of Gilchristella aestuaria (Gilchrist, 1914) (Pisces: Clupeidae) from southern Africa

The larval development ol the southern African endemic clupeid Gilchristella aestuaria is described and illustrated from specimens collected in the Swartvlei and Sundays estuarine systems of the Cape Province. Free embryos have no visible gut, unpigmented eyes and bodies, and are dependent on the yolk sac contents for nutrition. This stage lasts until about 4 mm body length (BL) when the eyes become pigmented and a gut becomes visible. Between 4 mm and 7 mm BL melanophores on the ventral aspect of the body form, and the dorsal and caudal lin anlagen develop. Between 7 mm and 8 mm BL the swimbladder lorms, flexion occurs and the anal fin anlage develops. By the 10 mm BL stage most of the skeletal elements have begun to differentiate, with the vertebral centra already showing signs of ossification. General ossification commences between 12 mm and 13 mm BL. All unpaired fins have the adult complement of rays by 15 mm BL. Scalation starts between 16 mm and 17 mm BL and is complete by 20 mm BL. Body depth increases gradually, from about 5% of BL in the early larval stages to >14% of BL in the juveniles. The pre-anal length decreases from about 87% of BL in the larvae to approximately 69% of BL in the juveniles. Head length increases from approximately 11% of BL in the larvae to 24-29% of BL in the juveniles. The larval snoui is initially 2% of BL, increasing to 7% of BL in the juvenile stages owing to the development of jaw elements.     

Intermittent Stress in Pigs: Behavioural and Pituitary-Adrenocortical Reactivity

Abstract

Ninetysix pigs, half females and half castrated males from 12 litters, were housed in 24 groups of 4 litter mates (2 females, 2 castrates). The pigs were weaned at 4 weeks of age and from the age of 115 days half of the groups were subjected to a schedule of unpredictable, inescapable electroshocks for 33 days, and half served as control. The adrenocortical reactivity to ACTH stimulation and to an emotional stressor (the procedure associated with initiation of blood collection) was measured in females, whereas the behavioural and pituitary-adrenocortical reactivity to an open field test was measured in castrates, as was the behavioural reactivity in a social test. Intermittent stress increased adrenocortical reactivity to ACTH stimulation significantly. This effect was present within the first week of intermittent stress (p < 0.06), but no difference was found after 4–5 weeks of stress. In contrast, the adrenocortical reactivity to additional emotional stressors was unaffected by stress after one week of intermittent stress, but increased after 4–5 weeks. In the open field test, centre location increased after one week of intermittent stress, whereas exploration decreased and walking and ambulation increased after 4–5 weeks of stress. In addition, 4–5 weeks of intermittent stress decreased aggressiveness in a social test. In conclusion, the change in reactivity to an additional acute stressor during intermittent stress appeared in different variables and contexts at different times during the course of intermittent stress. Thus, assessment of stress based on changed reactivity has to include several distinct measures of behavioural and hormonal reactivity.     

Animal health in organic agriculture: new guidelines and perspectives for food animal practitioners

In the last decade, the organic agriculture in Switzerland has been substantially increased due to the interest of consumer and financial incentives of the federation. Ruminants take directly or indirectly the largest part from grassland used within the organic managed surfaces. As the contacts between veterinary practice and organic agriculture has increased, the potential for veterinary activity in this area has developed considerably. The organic agriculture guidelines stipulate that all the preventive measures should be taken in feeding, keeping and breeding to insure animal health safety. This requires veterinary services for herd management. The organic status of a farm affects veterinary practice also in the form of alternative therapy/drugs administration and measures like dehorning and tail-docking. An important point in organic managed herds requests that treatment of animals should depend on alternative medical preparations or procedures based on veterinarian's experience and also on the therapeutic effect on the animal species concerned as well as on the disease. However, there are no restrictions on the veterinarian to use registered drugs as long as no alternative therapy, according to experience and possible success, is available to treat the animals. The prophylactic administration of allopathic veterinary drugs is not permissible. Further features in organic farms regarding the use of drugs are the keeping of withholding/withdrawal time, the documentation and the treatment frequency tolerated by organic marketing. Despite the above measures, the animal health has a priority regardless of its organic status. Although management of organic farms represent a unique responsibility, there are still obvious deficits in the education of veterinary practitioners for this new situation. However, in the future the extension of veterinary activity to include the alternative medical therapy should be regarded for the practitioner as a challenge and an opportunity at the same time.     

Estimation of the proportion of body fat in mice from the proportion of body water

We compared the proportion of body fat in mice as measured by chemical analysis with that estimated from the proportion of body water. First, we measured the proportion of fat by chemical analysis in 78 mice that had a proportion of body fat in the range from approximately 5 to 20%. Then, we constructed a regression line that described the relationship between the proportion of body water and the proportion of body fat by using data from several other published studies in mice (% body fat = -1.20 x % body water + 88.07, r = 0.9597, sy.x = 2.75, p < 0.001). With this regression line, we estimated the proportion of body fat from the proportion of body water that was measured by drying the carcasses at 60 degrees C for 3 days. Body fat data obtained from this regression line were similar to those obtained by chemical analysis. Thus, these results suggest that reliable values for the proportion of body fat can be derived from the proportion of body water and this method provides a tool to rapidly measure the proportion of body fat in mice.     

Abnormal ocular pigment deposition and glaucoma in the dog

The combined occurrence of ocular pigment deposition and glaucoma has been described in Cairn Terriers. Recently, this condition was also observed in two other breeds: the Boxer (two cases) and the Labrador Retriever (one case). Six dogs were referred to the Ophthalmology section of the Department of Clinical Sciences of Companion Animals and to a private referral clinic because of glaucoma or blindness in one or both eyes. In five cases ophthalmic examination showed pigment depositions in the sclera around the entire circumference of the perilimbal zone. Eight enucleated eyes (four eyes of two Cairn Terriers, three eyes of two Boxers and one eye of a Labrador Retriever) were examined microscopically. All eyes showed the same findings: an extensive infiltration of large melanin-containing cells with an eccentric nucleus, located in the iris, ciliary body, retina, choroids and sclera. Transmission electron microscopy of two of the examined eyes revealed that the morphology of most of these cells was consistent with melanophages. While reports in the veterinary literature concerning this condition are limited the cells concerned have been described to be melanocytes. Further research is needed to conclusively identify the cell type. As described in the present report, the histologic and transmission electron microscopic findings suggest a different etiology of the ocular pigment deposition and glaucoma compared with the pigment dispersal syndrome in humans.     

California National Animal Health Monitoring System for meat-turkey flocks, 1988-1989: diagnostic testing results.

Six hundred fourteen meat turkeys were submitted for necropsy from 24 California ranches as part of the National Animal Health Monitoring System (NAHMS). Enteritis was the most frequent pathologic diagnosis in birds 18 days old or younger and the second most frequent diagnosis in birds 19-70 days old. Hemorrhagic enteritis was the most frequent diagnosis in birds aged 19-70 days. Tibial dyschondroplasia, bronchopneumonia, and ascaridiasis were ranked one through three in frequency of diagnoses in birds over 70 days of age. Salmonella was isolated from 71% of flocks tested, and Mycoplasma meleagridis was isolated from 33% of tested flocks over 70 days of age. Antibodies to several disease agents were detected, including hemorrhagic enteritis (100% of flocks over 70 days old) and Newcastle disease (63% of flocks over 70 days old).     

Une nouvelle voie d'abord du ventricule latéral du cerveau chez la brebis (Ovis aries).

The proposed technique consists of placing a catheter in the olfactory recess of the lateral ventricle of the brain of a sheep. Twenty adult ewes were used in the study. The olfactory recess is in the frontal region 25 +/- 3 mm below the skin, just caudal to the line joining the supraorbital foramen and approximately 8-10 mm from the median plane. The approach is relatively easy under normal experimental conditions. The wall of the olfactory bulb, however, is fragile, and the animals must not have been injured by Oestrus ovis.     

Influence of passage model, sampling site, and marker dosing time on passage of rare earth-labeled grain through Holstein cows

Three duodenally cannulated, lactating Holstein cows were dosed with rare earth-labeled grain to evaluate effects of passage model, sampling site, and marker dosing time on digesta passage parameters. Cows were given ad libitum access to feed twice daily. Rare earth-labeled grain (applied by the 24-h immersion technique) was fed immediately before (Dy) or 2 h after (Yb) the morning feeding, and duodenal digesta and feces were sampled. Marker excretion curves were fit to a two-compartment, biexponential model, using curve peeling or to a series of two-compartment models, with one to six orders of gamma time-dependency in the fast compartment, using nonlinear regression. Passage estimates from the curve-peeled, biexponential model were similar to those from the best fit of the nonlinear models, which had three orders of gamma time-dependency. Ruminal passage rate of grain, averaged across models, sampling site, and dosing time, was .077/h. Estimates of time to first appearance of marker at the sampling site and mean retention times were longer (8 vs 1 h and 25 vs 17 h, respectively), but passage rates were similar, when determined from fecal compared with duodenal samples (P less than .05). Marker dosing time did not influence any of the parameters. It is concluded that both curve-peeling (linear regression) and nonlinear regression methods can be equally useful for evaluating passage kinetics of grain in dairy cows and that sampling site and time of marker dosing have little effect on passage parameter estimates.