Native Grass Facilitates Mycorrhizal Colonisation and P Uptake of Tree Seedlings in Two Anthropogenic Substrates

Two microcosm experiments were conducted to study the role of extraradical mycelium (ERM) of arbuscular mycorrhizal fungi (AMF) in establishment and growth of tree species used for revegetation in anthropogenic substrates. Inoculated or non-inoculated Acer pseudoplatanus, Alnus glutinosa or Salix purpurea seedlings were grown with Calamagrostis epigejos (a grass spontaneously colonising degraded ecosystems) in two substrates (fly ash and coal mine spoil) either in direct root contact or in rhizoboxes with interaction only via ERM network. In both experiments, inoculation with AMF mostly had a positive effect on the growth of trees and increased the aggregation of fly ash. When plants grew in direct root-to-root contact, grass presence negatively affected tree growth, but it significantly improved mycorrhizal development (colonization of tree seedlings, spore number and ERM length). When grass and tree roots interacted via the ERM network, tree seedlings were successfully colonised by the ERM spreading from the C. epigejos roots. Mechanical disturbance of the ERM links between plants reduced AMF development and tree height in both substrates, but tree shoot biomass was not affected. In fly ash, inoculated, non-disturbed treatments showed significant transfer of ³²P from the grass to the tree seedlings. It can be concluded that roots of A. pseudoplatanus, A. glutinosa or S. purpurea seedlings can be colonised from the ERM network radiating from quickly growing grasses, which can act as important agents for AMF distribution and facilitate mycorrhization of planted trees. In particular for willow, grass seems to be an essential nurse plant to achieve successful root colonisation.     

A new method for bovine embryo production: a potential alternative to superovulation

Eight cows were used to study the feasibility of transvaginal ultrasound-guided puncture of follicles as a method for the collection of immature oocytes for embryo production in vitro. In six trials at intervals of seven days, 104 oocytes were collected. After in vitro maturation and fertilisation the 104 oocytes were transferred to the oviducts of sheep. Six days later, 75 oocytes were recovered by flushing the oviducts. Twenty-four per cent of the recovered oocytes/embryos had developed into transferable and viable morulae and, or, blastocysts. The data show that this non-surgical and repeated collection of immature oocytes can be used successfully for the in vitro production of bovine embryos. The procedure may produce yields of embryos comparable to those obtainable by conventional superovulation procedures.     

Increased tolerance to annual ryegrass toxicity in sheep given a supplement of cobalt

SUMMARY To determine whether oral cobalt supplements could modify the clinical onset of annual ryegrass toxicity, groups (n = 5) of sheep were dosed orally with 0, 4 or 16 mg cobalt/day. After 3 weeks on this treatment, toxic ryegrass seed was added to their feed to provide 0, 0.15 and 0.30 mg corynetoxins/kg body weight, daily. Sheep receiving cobalt ingested 30% more toxin than did unsupplemented sheep before clinical signs developed (P = 0.03). There was no significant difference between groups receiving 4 and 16 mg cobalt. The results showed that cobalt delayed, but did not prevent, the onset of clinical signs of annual ryegrass toxicity.     

Chemotherapy of Theileria parva lawrencei infections in cattle with halofuginone

Halofuginone lactate, given once orally at a dosage rate of 1,2 mg/kg body mass on the 1st, 3rd or 5th days of fever, resulted in the recovery of only 1 out of 5 splenectomized cattle. Three splenectomized animals, treated on the 1st as well as the 4th day of fever, recovered and were then carriers. Six untreated controls all died. The potential value of a chemotherapeutic agent for Theileria parva lawrencei infections in South Africa is discussed.     

Foot-and-mouth disease and the African buffalo (Syncerus caffer). 1. Carriers as a source of infection for cattle

Ten pregnant buffalo cows, six of which were subsequently shown to be carriers of SAT 1, 2 and 3 viruses, were captured in the Kruger National Park (KNP) and allowed to calve in captivity. The buffalo cows and calves were separated by a fence from 6 FMD susceptible cattle but the buffalo and cattle were obliged to use common drinking troughs and hay racks. Over a period of 15 months, during which the buffalo calves lost their maternally-derived immunity, neither the buffalo calves nor the susceptible cattle became infected with FMD virus. By the end of the observation period, however, only 1 buffalo cow still had detectable virus in its oesophageal/pharyngeal specimens.     

Effect of different methods of maintenance on the pathogenicity and infectivity of Babesia bigemina for the vector Boophilus microplus

Observations were made on the effects of five different methods of laboratory maintenance on the infectivity and virulence of Babesia bigemina for the tick Boophilus microplus. The original isolate was highly infective and virulent, causing premature death of engorged female ticks and reduced egg production. Maintenance of the strain by syringe passage in unsplenectomised calves at six to 10 week intervals reduced both its infectivity and virulence for ticks. When slow passages were preceded by a series of rapid passages in splenectomised calves, the changes to the strain were less pronounced. The other three procedures, rapid syringe passage in splenectomised calves and tick passage in either splenectomised or intact calves, had no statistically significant effect on the characteristics measured.     

Excretion of alcelaphine herpesvirus-1 by captive and free-living wildebeest (Connochaetes taurinus)

Excretion of alcelaphine herpesvirus-1 (AHV-1) is for all practical purposes limited to wildebeest calves under the age of 4 months. Sixty-one per cent of calves 1-2 months of age excreted virus with a mean titre of 9.8 X 10(4) cytopathic-forming foci/ml in their ocular fluid. The incidence declined sharply to less than 2% in wildebeest older than 6 months. No difference in age-related excretion of virus could be detected between free-living and captive wildebeest and no virus could be isolated from free-living pregnant wildebeest cows or from captive cows and their calves during the first 4 weeks after birth. The occurrence of wildebeest-derived malignant catarrhal fever (WD MCF) during spring, when wildebeest do not excrete virus, is a strong indication of the existence of an alternative host or an intermediate host capable of biological transfer of AHV-1.     

Failure of a recombinant Babesia bovis antigen to protect cattle against heterologous strain challenge

Groups of cattle were inoculated subcutaneously with (i) a recombinant DNA-derived Babesia bovis protein (KaBbl-GZ) fused to beta-galactosidase and combined with adjuvants, or (ii) native beta-galactosidase (GZ) plus adjuvant, or (iii) adjuvant only or (iv) a live, attenuated B bovis vaccine. KaBbl-GZ was produced in the lambda gt11-amp3 system as a 5-10 kD babesial polypeptide linked to GZ. KaBbl has previously been shown to be an immunodominant antigen of B bovis, localised at the apex of the parasite, and present in a range of B bovis strains. High levels of GZ antibodies were observed in KaBbl-GZ and GZ inoculated cattle, but specific KaBbl antibodies could not be detected by ELISA. Five months after primary inoculation, all cattle were blood challenged with a virulent heterologous B bovis strain. Despite four inoculations with KaBbl-GZ, significant protection against the challenge was not observed.