Effects of α2-adrenergic drugs on blood platelets in sheep

Xylazine (0.2 mg/kg, iv) alone or preceded by atipame-zole (0.125 μg/kg, iv) or by aspirin (10 μg/kg, iv) was administered to 18 sheep. Medetomidine (60 μg/kg, iv) was also administered to 12 sheep. Xylazine, but not medetomidine, significantly reduced the number of platelets. Both atipamezole and aspirin prevented this reduction. It was concluded that α₂-agonists would seem to produce platelet aggregation that may contribute to the development of the respiratory changes that follow the administration of α₂-agonists in sheep, but probably not always to a degree that could result in a significant decrease in the number of circulating platelets.     

Measurement of nitrate leaching losses from arable plots under different nitrogen input regimes

Abstract. Leaching losses of nitrate-nitrogen were measured from a set of eight hydrologically isolated plots on a clay loam soil over the period from September 1987 to February 1990. Variable drainflow recovery from the plots hampered accurate estimation of nitrate loading, but results suggest that, when inorganic nitrogen fertilizer is applied up to the recommended amount, there is little influence of the amount applied on the amount leached. We did, however, observe the following effects on nitrate leaching: leguminous green manure incorporated in autumn increased leaching of nitrate-nitrogen by 10–15 kg per hectare during the winter; autumn cultivation caused some increase in leaching compared with no cultivation in one year; some systematic variations in nitrate leaching occurred between years and between plots, but were unrelated to treatments.
From the results we conclude that green manuring does not provide sufficient nitrogen for organically grown crops on this soil but contributes significantly to nitrate leaching, and that growing spring cereals, with the land remaining in stubble as long as possible in autumn, may be the best strategy to minimize nitrate leaching.     

Mangroves as indicators of coastal change

In view of the unique biological characteristics of mangroves, it is interesting to assess the extent to which these ecosystems can be used as indicators of coastal change or sea-level rise. From recent studies of mangrove mortality at several locations (including Guiana, Gambia, Côte d'Ivoire, Kenya, India and Bangladesh), it appears that these coastal ecosystems are so specialized that any minor variation in their hydrological or tidal regimes causes noticeable mortality. Each species of mangrove (but particularly those belonging to the genera Rhizophora, Bruguiera, Sonneratia, Heritiera and Nypa) occurs in ecological conditions that approach its limit of tolerance with regard to salinity of the water and soil, as well as the inundation regime. If the duration of daily immersion were to be modified by tectonic, sedimentological or hydrological events, the species either readjusts to the new conditions or succumbs to unsuitable conditions. Consequently, the use of remote sensing data for mangrove ecosystems offers excellent potential as a tool for monitoring coastal change.     

Land use, rainfall and erosion risk on the South Downs

Abstract. In 1989–90 over 80% of the erosion on agricultural land in the South Downs was on ploughed or cultivated surfaces prepared for spring planting of cereals. This was in contrast to the pattern in previous years when most erosion was in winter cereal fields. An unusual late winter rainfall peak was the primary cause. Periods of erosion risk associated with other land uses on the South Downs are also discussed.     

Histopathology of Experimental Schistosoma bovis Infection in Goats

The inflammatory host response to Schistosoma bovis in young goats was studied at necropsy by light microscopy 34 weeks after primary exposure to 3,000 cercariae (group B, n=6), 34 weeks after primary exposure to 3,000 cercariae followed by challenge with 2,500 cercariae at week 17 (group C, n=5), and 17 weeks after primary exposure to 2,500 cercariae, given on week 17 of the experiment (group D, n=6). Three goats served as uninfected controls. The faecal egg output had been minimal for 17 weeks prior to necropsy in groups B and C and only for the last 2 weeks in group D.Histological studies were carried out on the small intestine, liver, lung and spleen, and tissue egg counts were performed. In sections of the small intestine and liver, a panel of histopathological variables were quantitated to characterize the host response and differences between groups of animals were evaluated with one way analysis of variance. The mean tissue egg count in the small intestine was slightly but not significantly higher in group C than group B and about twice as high in group D (D vs B or C p<0.01). Group means of numbers of inflammatory foci per section of gut wall corresponded well with those of tissue egg counts, suggesting that the rate of inflammatory destruction of eggs did not differ markedly between the groups. Egg material was less commonly seen in granulomas of the small intestine in group B than in group D (p<0.01), suggesting lower passage of eggs through the gut wall during the later than during the earlier phase of patent primary infection. The frequency of eosinophil-rich hepatic inflammatory foci was much higher in group D than in the other groups (D vs B p<0.05, D vs C p< 0.01), and coincided with a high degree of blood eosinophilia in this group at the time of sacrifice. Challenged goats showed a significantly higher frequency of markedly fibrotic inflammatory foci in the liver and of liver granulomas with a marked giant cell component than goats of the other groups. Hepatic portal fibrosis was least prominent in animals with 17- week- old primary infections, implying a possible relation between this change and duration of infection.     

Attempts at Preventing Further Spread of Bovine Virus Diarrhoea Virus (BVDV) Infection in 5 Danish Dairy Herds in which BVDV had been Isolated

In 5 herds in which bovine virus diarrhoea virus (BVDV) had been isolated, all animals were bled for virological and serological examination. After the herd blood test, follow up blood tests were made on calves born up to 6 months later in 1 herd, 9 months later in 1 herd and up to 12 months later in 3 herds. Persistently infected animals (PI animals) were removed and after a time period a small herd sample of 10 animals that were born after removal of the PI animals were examined for BVDV antibodies.At the herd blood test a total of 21 PI animals were detected. During the follow up period another 25 PI animals were born.Among animals in the small herd samples collected after removal of the PI animals, antibody positive animals were found in the 2 herds with the shortest follow up period. In the 3 herds with a 1 year follow up period there were no antibody carriers in the herd sample.It seems possible to prevent further spread of infection with BVDV if all animals in the herds as well as animals born during the following year are examined and PI animals removed.     

Peripartal Excretion of Eimeria Oocyst by Cows on Swedish Dairy Farms and the Age of Calves at First Excretion

Faecal samples were collected 3 times a week for 6 weeks from 22 peripartal cows and for up to 15 weeks after birth from 27 calves in 3 herds, to determine the numbers of Eimeria oocysts excreted and the age at which the calves first excreted oocysts. Only low numbers of oocysts were excreted by the cows and no oocysts were detected in 93% of the samples. However, half the cows excreted oocysts at least once. The age at which the calves first excreted oocysts ranged from 2.5 to at least 15 weeks, and there was a significant difference between the herds in their mean age at first excretion. Oocysts of Eimeria alabamensis, E. auburnensis, E. bovis and E. ellipsoidalis were found in numbers ranging from 7 to 8450 oocysts per gram faeces. About 50% of the calves excreted oocysts before they were transferred to group pens. The primary source of infection of the calves was probably their penmates or the previous occupants of the pens, and the cows probably played a subsidiary role.     

Investigations on the Occurrence of Hereditary Diseases in the Danish Cattle Population 1989-1991

Agerholm, J.S., A. Basse and K. Christensen: Investigations on the occurrence of hereditary diseases in the Danish cattle population 1989-1991. Acta vet. scand. 1993, 34, 245-253.– The methods of the Danish Bovine Genetic Disease Programme are outlined, and the results obtained during the first 3 years in function are described. The most common disease reported was spinal muscular atrophy in calves of the Red Danish Dairy breed with 312 reports. Necropsy was performed on 162 cases, and spinal muscular atrophy was diagnosed in 82 of these. Bovine progressive degenerative mye-loencephalopathy, rectovaginal constriction, syndrome of arthrogryposis and palatoschisis, hereditary chondrodysplasia (2 different types), syndactylism, epitheliogenesis imperfecta, and osteogenesis imperfecta was diagnosed with 1 case each. Lethal trait A46 was diagnosed in 4 calves. Some of these diseases have not previously been described in Denmark, and epitheliogenesis imperfecta was for the first time diagnosed in the Hereford breed. Chromosome translocation 1/29 was detected in the Blonde d’Aquitaine (BAQ), Limousine, and Red Danish Dairy breed. The aberration occurred frequently in BAQ. Furthermore, a complex chromosome translocation t(l;8;9)(q45;ql3;q26) was detected in the Red Danish Dairy breed.     

Insemination with Stallion Semen Frozen in 0,5 ml Straws

Contents: An insemination trial using frozen semen is described. The freezing procedure was slightly modified from the Hannover method. The insemination dose consisted of 7 medium straws containing approx 1 10⁹ spermatozoa. A total of 28 mares of the Norwegian Trotter breed were inseminated during the 1991 season. During oestrus the mares were examined at 12 hour intervals, and the insemination was carried out after detection of ovulation. The pregnancy rate was 43% after the first insemination, increased to 68% after second and further to 75% after the third and last insemination. The foaling rate was 61.5%.