Evaluation of two N cycle models for the prediction of N mineralization from grassland soils in the UK

Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.     

Theileria parva: the immune status of calves born of dams immunised against East Coast fever

Eight Friesian cross cows three months pregnant to a single Friesian bull were immunised against East Coast fever by infection with Theileria parva (Muguga) sporozoite stabilate and treatment with pyrrolidino-methyl tetracycline. They were challenged with the homologous stock four times before calving and a fifth time after calving, and resisted all five challenges which killed all of the five groups of five susceptible controls. Calves born to these hyperimmunised dams were fully susceptible on challenge with the same stabilate, as were susceptible cows from the same farm and their calves. In both instances the calves died three to seven days earlier than the cows which were approximately 10 times heavier. These results show that one- to two-month-old taurine calves from artificially immunised dams are not protected from experimental T parva sporozoite challenge and that there is no inherent calfhood resistance to East Coast fever.     

The Effect of Diet on the Biochemical Composition of Juvenile Artemia: Potential Formulations for Rock Lobster Aquaculture

The lipid class and fatty acid (FA) composition of juvenile Artemia fed continuously on four diets—the microalga Tetraselmis suecica , a mix of oat bran-wheat germ-lecithin (OWL), OwL-eicosapentaenoic acid (EPA), and OWL-EPA-arachidonic acid (AA)—were examined over a 9-d experiment in an attempt to approximate the FA profile of phyllosoma larvae of wild southern rock lobster Jasus edwardrii . The main difference in lipid class composition of Artemia fed the four diets was the relative level of polar lipid (PL) and triacylglycerol (TAG). By day 9, the algal-fed Artemia were highest in PL (95% of total lipid) and lowest in TAG (2%), whereas the remaining diets resulted in Artemia with 16–30% PL and 41–82% TAG. After 2 d, the relative FA composition of all Artemia treatments closely reflected those of the diets, with no marked change after further feeding (to day 9). In terms of the content of essential polyunsaturated fatty acids (PUFA), by day 5 Artemia fed: 1) with the algal diet contained 7 mg/g FA dry mass (0.3% DHA, 6.3% EPA, 3.4% AA of total FA); 2) with the OWL diet contained 3 mg/g (0.3% DHA, 0.9% EPA, 0.7% AA); 3) with the OWL-EPA diet contained 55 mg/g (6.2% DHA, 11.6% EPA, 1.1% AA); and 4) with the OWL-EPA-AA contained 83 mg/g (3.8% DHA, 7.5% EPA, 17.4% AA). The PUFA profiles of Artemia using the OWL-oil diets were similar to wild rock lobster phyllmmata, although levels of doco-sahexaenoic acid (DHA) were lower (10% DHA) than in J. edwardsii larvae. On the basis of PUFA composition data alone, the results suggest the suitability of the OWL-oil mixed diets for consideration for feeding to Artemia used in the culture of southern rock lobster larvae, particularly if the level of DHA can be further enhanced.     

Common and stage-specific antigens of Theileria annulata.

Western blot analysis of Theileria annulata antigens was carried out using sera collected from cattle which had been immunised and challenged with either T. annulata sporozoites or schizont-infected cells. Three antigens between 71 and 73 kDa proved to be common to the three stages of parasite studied: sporozoites, schizonts and piroplasms. An antigen was found at 32 kDa which was specific to T. annulata piroplasms. Results were reproducible using sera from Morocco and the UK. At least one of the proteins at 71-73 kDa, but not that at 32 kDa were also recognised by sera from animals infected with Babesia species.     

Cliff swallow colonies as information centers

Colonies of cliff swallows (Aves: Hirundo pyrrhonota) appear to be information centers in which colony residents acquire information on the location of food sources. Individuals that have been unsuccessful on a foraging trip return to the colony, locate a successful forager, and follow that individual to a food source. Individuals often follow, and are followed by, their neighbors within the colony, possibly because neighbors can observe foraging success through food brought back to nestlings. All individuals are equally likely to follow others or be followed, and thus all individuals benefit from opportunities to receive information.     

Pathogenicity of various isolates of Alcaligenes faecalis for broilers

Day-old broilers or specific-pathogen-free chickens were inoculated intranasally with approximately 1 X 10(8) organisms of eight different field isolates of Alcaligenes faecalis. Major differences in the pathogenicity of isolates and their ability to colonize the trachea were found. Only two isolates (Wilson and Lockamy) produced mild clinical signs of respiratory disease ("snicking," dyspnea). The same two also colonized the respiratory tract, especially the trachea, in large numbers; they persisted for 31 days. Of the remaining six isolates, five were also able to colonize the respiratory tract but did so to a lesser degree and less persistently, without causing clinical signs. Only one isolate (CS) was incapable of becoming established in the respiratory tract of chicks after intranasal inoculation.     

Mortality in near‐term ostrich embryos during artificial incubation

1. The ostrich industry in South Africa (and elsewhere) experiences a high rate of embryo mortality during artificial incubation of eggs. Most of this mortality takes place in the last 10–14 d of incubation.

2. We carried out post‐mortem examinations on 111 embryos that died within this period to assess the causes of this mortality.

3. Malpositioning and severe oedema were the predominant symptoms of dead‐in‐shell embryos with 55% being malpositioned and 41% showing severe oedema. Of these, 22 embryos (24%) showed both symptoms. Malpositioning generally results from incorrect setting of the eggs or inadequate turning and oedema was significantly correlated with the amount of water lost from the eggs which in turn was correlated with egg size.

4. Myopathy, gross lesions of internal organs, haemorrhage, bacterial infections and congenital deformities were found in less than 10% of chicks examined for these symptoms.     

Isoenzyme variation in piroplasms isolated from bovine blood infected with Theileria annulata and T parva.

Blood from calves infected with Theileria annulata and T parva was freed from host cell elements and the piroplasms liberated from the red cells by ammonium chloride lysis. Lysates of the purified piroplasms and control host cell material were examined electrophoretically for several enzymes. Zymograms stained for glucose phosphate isomerase showed distinct differences between the host cell enzyme pattern and parasite enzyme patterns. The isoenzyme pattern of T annulata piroplasms differed from the isoenzyme pattern of T parva piroplasms.