Efficacy of abamectin against natural infections of gastrointestinal nematodes and lungworm of cattle with special emphasis on inhibited, early fourth stage larvae of Ostertagia ostertagi.

The anthelmintic efficacy of abamectin (avermectin B1) was evaluated against gastrointestinal nematodes, including Ostertagia ostertagi inhibited larvae and lungworm, in yearling crossbred beef heifers during late spring. The calves were grazed on contaminated pasture for 10 weeks and then held under conditions free of nematode infection for 3 weeks prior to allotment and treatment on 5 June. Thirteen calves were randomly assigned to two groups of six by restricted randomization on body weights; the extra lightest calf was assigned to the non-treated control group. Group 1 calves were treated with abamectin at 200 micrograms kg-1 body weight by s.c. injection and Group 2 calves were not treated; all were killed at 14 days after treatment. Ostertagia ostertagi was present in all controls; arithmetic mean numbers of adults, developing fourth stage larvae (L4) and inhibited EL4 were 7683, 605 and 36,102, respectively. Other nematode genera present in controls in sufficient numbers for the experiment were Haemonchus placei adults, Trichostrongylus axei adults, Cooperia spp. adults, Oesophagostomum radiatum adults, Bunostomum phlebotomum adults, Dictyocaulus viviparus adults and E5 (immature adults). Abamectin was highly effective (consistently greater than 99% efficacy and P less than 0.05) in removing all nematodes present in treated calves as represented in non-treated controls, including the primary target of Ostertagia ostertagi inhibited EL4. The lowest efficacy was 93.8%, against D. viviparus E5.     

Vitamin deficiencies in cattle

Deficiencies of vitamins A, D, K, E and thiamin can cause severe limitations in beef production. In particular, vitamin A and E can be common causes of lost profit, secondary to limitations of reproductive and growth potential. Prolonged dry periods will reduce available A and E in pasture forage, as can ensiling and prolonged storage of harvested feedstuffs. Polioencephalomalacia is a thiamin responsive disorder, associated with high concentrate feeding and lush pastures. Antimetabolites, such as amprolium, will cause thiamine deficiency when fed in excess. Recent information has shown improved performance with supplemental beta carotene and niacin. The positive responses in reproductive performance, noted with cattle fed supplemental beta carotene, was independent of vitamin A. Supplementation of vitamins above National Research Council recommendations can be justified. However, proper evaluation of feed and animal status, and documentation of a response to supplementation is necessary before diagnosing deficiencies of specific nutrients.     

An invasive procedure for in utero fetal electrocardiology: recording of fetal electrocardiograms by applying electrodes through the uterus.

An in utero technique was developed that allows direct access to the canine fetus for experimentation. This procedure reduces the need for fetal manipulation and umbilical blood flow compromise and reduces fetal fluid loss. In pregnant bitches, uterine horns could be delivered through a ventral midline incision. By manipulating the fetal membranes, and positioning the fetuses through them, electrodes could be inserted subcutaneously in the fetuses. Electrocardiograms satisfactory for interpretation were obtained from as many as 4 fetuses in a bitch for periods up to postoperative week 3.     

The Prince Edward Islands: A sanctuary for seabirds in the Southern Ocean

This paper reviews the breeding distribution and numerical status of selected species of seabirds at 23 oceanic island groups in the Southern Ocean (between latitudes 35 and 70°S), based on census data and population estimates which have become available through increased scientific endeavour in the region during the last 15 years or so. The paper focuses on the avifauna of the Prince Edward islands, in the southern Indian Ocean, and points to the importance of these islands as a breeding station and sanctuary for seabirds. Only one oceanic island group, the Crozets, contains more species of breeding seabirds than the Prince Edward islands. Substantial segements (about 10% and greater) of the world breeding populations of the king and macaroni penguins, and the wandering, grey-headed, yellow-nosed and sooty albatrosses are based at the Prince Edward group. We recommend that Prince Edward Island (sensu stricto) should be a wilderness area, and that development at Marion Island should be kept to an absolute minimum.     

Studies on the ecology of actinomycetes in soil—VIII: Distribution and characteristics of acidophilic actinomycetes

Acidophilic actinomycetes, growing between pH 3.5 and 6.5, were isolated from 17 natural soils and mine wastes. Most isolates were Streptomyces spp. and selected ones were compared with some established neutrophilic species by assessment of overall similarity. Acidophilic and neutrophilic strains clustered separately, differing in a number of cultural and physiological characters, in addition to pH requirements. The possible importance of acidophilic actinomycetes in soil is discussed.     

ABSORPTION OF RADIO–ACTIVE PHOSPHORUS FROM TAP–AND NODAL ROOTS OF WHITE CLOVER (TRIFOLIUM REPENS L.)

Absorption by the tap-root and by different nodal roots of white clover S100 and translocation of ³²P were investigated to find to what extent nodal roots can compensate for the absence of a tap-root. ³²P absorbed from the tap-root was distributed evenly within the whole plant. When translocation from the 2nd and 7th nodal roots was studied, similar distribution was obtained only from the nodal root closer to the centre of the plant. The backward movement of ³²P absorbed from nodal roots at the base of the plant increased as the root size increased. Removal of tap-roots resulted in temporary depression of translocation; its effect disappeared within 3 weeks.
It is concluded that the ability of nodal roots to compensate for loss of the tap-root depends on their position and size.