Oestrous behaviour in a herd of dairy cows.

A group of 60 housed Friesian cows were observed continuously for a period of 25 days, during which time all cows were recorded for incidence of mounting activity and 18 selected cows were recorded for various aspects of maintenance activity. All 60 cows were judged as showing oestrus. Average duration of oestrus (+/-SD) in 33 cows was 14-9 +/- 4-7 hours, and the cows were mounted 56-3 +/- 34-8 times. The greatest mounting activity was associated with the night hours. There was no diurnal pattern of onset of oestrus. The majority of mounting activity (79 per cent) occurred in the cubicle area of the building. Comparison of maintenance activities showed that oestrous cows spent, on average, less time standing in a cubicle (P less than 0-01), lying in a cubicle (P less than 0-001) and more time standing elsewhere (P less than 0-001) than non-oestrous cows. The results are discussed in relation to oestrus detection.     

Anthelmintic action—A metabolic approach (a review)

The effects of anthelmintic drugs on intermediary metabolism of parasites can be examined using techniques developed for the investigation of metabolic regulation. Most attention has been paid to the pathways of respiratory metabolism in parasites, since maintenance of high energy levels is essential to an organism's survival. Respiratory metabolism is thus a prime target for anthelmintic attack. Parasites differ from their hosts in a number of pathways of respiratory metabolism and they produce incompletely-oxidised organic acids as end products.A variety of anthelmintic drugs have been shown to inhibit some enzymes of these pathways, including phosphoenolpyruvate carboxykinase, malate dehydrogenase, and the fumarate reductase, ‘succinoxidase’ and succinate decarboxylase systems. Energy synthesis in mitochondria from parasites is also inhibited by many anthelmintics: this target is a particularly important one since its properties differ significantly from those of the host. This process requires considerable study and it may not necessarily be valid to equate ‘uncoupling’ in mammalian tissues with that in parasite tissues. Changes in ATP levels affect flux through the respiratory pathways; a complete assessment of effects of anthelminstics on the respiratory pathways of parasites would include measurement of the uptake and utilization of carbon sources (e.g., glucose and glycogen), of metabolic intermediates, including adenine nucleotides, and of excreted end products. Sites of change can then be identified and studied in greater detail.Comparison of the effect of mebendazole in vivo and in vitro on unrelated species, Moniezia expansa and Fasciola hepatica adults, sheds some light on the mechanism of its anthelmintic effects. This drug elicits similar changes in proportions and totals of adenine nucleotides in the two species, but it differs in the rapidly of its effect, its effect on glucose uptake and glycogen depletion, and in changes in respiratory end product. Consequently mebendazole may not act in the same way against these two species. It also affects a number of other systems in other parasites: the suggestion of a single ‘mode of action’ may be inappropriate for this compound.Respiratory metabolism is not the only system affected by anthelmintics: other parasite systems are also attacked, but the final effect of lethal anthelmintic is observed as changes in the respiratory metabolic pathways. Some anthelmintics, for example, levamisole, affect the respiratory pathway directly, but also affect other systems (the nervous system in the case of levamisole) and may be effective in vitro but not in vivo. In these cases it is necessary to distinguish between effects that may be subordinate to a primary effect, and to take host and permeability factors into account.     

Genetic variation among American seed sources of Ailanthus altissima (Mill.) Swingle

Variability among and within seed sources of naturalized Ailanthus altissima (Mill.) Swingle in seed and height growth characteristics indicated that significant differences exist both at the seed source and between individual trees. Genetic variance was distributed in an approx. 1 : 2 ratio among seed sources and individual mother trees respectively. Results of the study suggest that artificial selection of ailanthus for breeding purposes would be most efficient if primary selection were directed toward individual trees.     

Synergistic action of mebendazole and levamisole in the treatment of a benzimidazole-resistant Haemonchus contortus in sheep

One-year old worm free, merino wethers, were each infected with 5000 H. contortus larvae of a strain resistant to mebendazole at a rate of 52 mg/kg body weight of sheep. After 21 days, they were assigned to two trials. The preliminary trial showed that mebendazole and levamisole acted synergistically on the H. contortus infection. In the second trial, sheep were treated with 0.35 mg/kg levamisole (one seventh the minimum effective dose against susceptible worms) or 40 mg/kg mebendazole (40 times the minimum effective dose against susceptible worms). In each case the anthelmintics did not reduce worm burdens, although mebendazole depressed egg production. However, when mebendazole and levamisole, at the above dose rates, were administered simultaneously, total worm counts in sheep were reduced by almost 60%. Similar results were obtained when the levamisole was administered 8 h or 14 h after mebendazole treatment. The implications of these observations for the treatment of benzimidazole-resistant haemonchiasis in sheep are discussed.