Changes in the population of germinated seed in a hill pasture during and after a pastoral fallow

A pastoral fallow, which involves no defoliation of pasture for a period, generally from spring to autumn, is a management tool that can be used either to reduce plant population density through self-thinning prior to oversowing improved plant germplasm or to encourage natural reseeding in order to increase sward persistence and productivity. Two field experiments were carried out in a hill pasture in New Zealand to quantify the response of the seed population, germinated from soil plugs under glasshouse conditions for over 7 months, to pastoral fallow, as influenced by the timing and duration of the fallow, fertilizer application and aspect, and to identify the germination patterns of different plant species in fallowed and grazed swards. A spring–autumn pastoral fallow increased the germinated seed population of grasses, legumes and weeds by 161%, 51% and 59%, respectively, compared with the grazed control. The variation in germinated seed population during the pastoral fallow showed that seed quantity can be controlled by manipulating the timing and duration of a pastoral fallow. Short duration (2–3 month) pastoral fallows resulted in a significantly lower germinated grass seed population than the full (spring–autumn) fallows. Fertilizer application reduced the germinated grass seed population by 26%. The germinated legume seed population was higher with a shady than a sunny aspect. Regression analysis revealed that the germination patterns of all plant species followed a negative exponential function. Partial differentiation of this function derived a germination rate curve on which a two-pool (ephemeral pool and base pool) model was developed to describe quantitatively the dynamics of germinable seed reserves in the soil.     

Efficacy of a single dose of oral antibiotic given within two hours of birth in preventing watery mouth disease and illthrift in colostrum-deficient lambs.

An antibiotic with a product licence limited to the treatment and control of infectious bacterial enteritis associated with Escherichia coli in piglets was tested for its ability to control watery mouth disease in neonatal lambs. Three groups of lambs were kept in conditions commonly encountered in intensive lambing systems, where high levels of environmental bacterial contamination may be expected. They were allocated at birth to: a control group (group 1) consisting of 18 colostrum-deprived lambs; group 2, consisting of 17 lambs given one feed of colostrum when they were two hours old; and group 3, consisting of 18 colostrum-deprived lambs given spectinomycin orally when they were two hours old. Nine group 1 lambs became diseased and were killed for humane reasons. Blood biochemical changes included hyperglycaemia followed by hypoglycaemia, lactacidaemia, hypoproteinaemia and metabolic acidosis, and postmortem examination of the diseased lambs showed signs consistent with endotoxaemia and a clinical diagnosis of watery mouth disease. Coliforms were isolated from the blood of all group 1 lambs and from half the lambs in groups 2 and 3, but endotoxaemia and watery mouth disease occurred only in group 1 lambs. The results for groups 2 and 3 showed that neither colostrum nor antibiotic at the rates and frequency used prevented bacteraemia, although consecutive samples were positive only on three occasions. Group 3 lambs consistently grew more rapidly than the surviving group 1 lambs and as rapidly as group 2 lambs. There was no evidence that male lambs were more prone to watery mouth disease than female lambs. The results indicated that the antibiotic spectinomycin did not induce endotoxaemia during low-grade bacteraemia and that a single oral dose given within two hours of birth protected colostrum-deprived lambs delivered into a contaminated indoor environment against watery mouth disease.     

Blood lactate disappearance after maximal exercise in trained and detrained horses

The influence of training on blood lactate concentrations during treadmill exercise and a 40-minute inactive recovery period was examined in seven trained and seven detrained thorough-bred horses. Lactate concentrations were measured in venous blood collected at the end of each exercise state, and at intervals for 40 minutes afterwards. Measurements were made of maximum oxygen uptake (V̇O_2max, ml kg⁻¹ min⁻¹), VLA4 (velocity at which blood lactate concentration was 4 mmol litre⁻¹); LA8 (lactate concentration [mmol litre⁻¹] during exercise at 8 m sec⁻¹), peak lactate (highest lactate concentration after exercise), LA40 (lactate concentration 40 minutes after exercise), the time of peak lactate concentration (minutes after exercise) and the rate of disappearance of blood lactate (Rt_d). The trained horses had a significantly lower LA8 (2·1 ± 0·1 vs 6·5 ± 1 mmol litre⁻¹, P<0·01), higher VLA4 (9·8 ± 0·2 vs 5·8 ± 0·6 m sec⁻¹, P<0·01) and higher V̇0_2max (156·3 ± 3·8 vs 107·1 ± 3·9 ml kg⁻¹ min⁻¹, P<0·001). The value of Rt_d and the time of peak lactate concentration were not significantly different.     

Mixed function oxidase and glutathione transferase activity in last instar Heliothis virescens larvae

Methyl parathion-resistant and -susceptible strains of Heliothis virescens were assayed for mixed function oxidase and glutathione transferase activity at four time periods within the last instar. No significant differences were found between the mixed function oxidase or glutathione transferase activities of the resistant and susceptible strains. However, significant differences did appear among time periods within the last instar. Larvae assayed during the postfeeding time period (60–80 hr) had the highest mixed function oxidase activity, which was 28 times that of last instar larvae assayed during the first time period (0–19 hr). Glutathione transferase activity appeared to be highest during the 20- to 39-hr and 40- to 59-hr time periods, but the differences among time periods were small. The importance of these findings to studies of insecticide resistance and plant herbivore interactions is discussed.     

Endogenous inhibitors of glutathione S-transferases in house flies

The inhibition of glutathione S-transferase by endogenous compounds present in the soluble fraction of house fly homogenates was investigated. The highest inhibition was found with the female abdomen and increased with incubation time and with an increase in the tissue concentration. The correlation of increased inhibition with a parallel increase in the darkening of the soluble fraction indicated a possible association with melanization, thereby suggesting quinones as the possible endogenous inhibitiors of glutathione transferase. In vitro experiments demonstrated that quinones produced by mushroom tyrosinase did indeed inhibit glutathione S-transferase. Inhibition by quinones can be prevented by including glutathione or bovine serum albumin in the homogenization buffer. The inhibitory activity of a variety of quinones and related compounds on purified glutathione S-transferase was investigated. Oxygenated aromatics with hydroxy groups in the 1,2- or 1,4-position or ketonic carbonyls in the 1,4-position are good inhibitors of glutathione S-transferase.     

Sodium monofluoroacetate (Compound 1080) poisoning in dogs

Sodium monofluoroacetate (Compound 1080) is a widely used pesticide for control of feral animals such as the fox. Accidental poisoning of domestic animals occurs despite strict regulations on 1080 usage. Dogs are particularly susceptible to the toxin. The mechanism of 1080 toxicity, susceptibility of target and non-target species, persistence of 1080 in the environment and risk of accidental poisoning are discussed. Particular emphasis is placed on 1080 toxicity in the dog. Early recognition of intoxication is most important for prognosis and relies upon characteristic clinical signs and diagnostic findings. The treatment of 1080 intoxication remains a challenge with no proven antidotes. However, there are possible benefits from monoacetin, acetamide, calcium salts, colestipol, activated charcoal, peritoneal dialysis, sodium bicarbonate, neurotransmitter modulators and four-methylpyrazole. A recommended treatment protocol for 1080 toxicosis in dogs is included. Safety measures such as the use of wire dog muzzles and investigating alternatives to 1080 in pest control programs may be the key to reducing the incidence of future accidental poisonings.     

Management of equine sarcoids: 1975-93

Treatment options for equine sarcoids are briefly reviewed and the results of a retrospective study of 63 cases of equine sarcoid (66 lesions) treated by clinicians from the Rural Veterinary Centre, Camden, Australia from 1975 to 1993 presented. Five different treatments were employed in the management of these 66 lesions, including surgical excision alone or in combination with cryotherapy, radiotherapy, immunotherapy and tumour transfer to a subcutaneous site on the neck. The majority of cases were treated with surgical excision alone (18/66), excision followed by cryotherapy (31/66) and immunotherapy (16/66), with success rates of 28%, 42% and 81% respectively. Success was defined as no sign of recurrence of the lesion at the time of follow-up, at least 6 months later.