Australian Journal of Biological Sciences

Cutaneous myiasis in sheep arising from the activity of Lucilia cuprina larvae can result in significant physiological changes in susceptible animals. The stress imposed on the pituitary-adrenal axis of the sheep in response to myiasis and acute restraint is the subject of this investigation. Merino wethers were exposed to handling restraint, and blood sampling, during examination for blowfly strike; where necessary, they were treated for cutaneous myiasis. Significant changes in the plasma concentrations of immunoreactive beta-endorphin (beta-EP), ACTH and cortisol were found in sheep with extensive myiasis, as compared with unstruck sheep or those with only localized myiasis. In five susceptible sheep with extensive cutaneous myiasis, mean plasma levels of beta-EP, ACTH and cortisol were 307 +/- 71 pg ml-1, 953 +/- 58 pg ml-1 and 232 +/- 46 nmol l-1 respectively, compared with 818 +/- 89 pg ml-1, 641 +/- 41 pg ml-1 and 107 +/- 17 nmol l-1 in six unstruck sheep handled similarly. Whereas significant increases in plasma ACTH and cortisol can result from pituitary-adrenal responses to acute emotional or surgical stress, and are usually accompanied by a concomitant release of beta-EP from the pituitary, the present findings indicate a marked reduction in beta-EP levels and a significant increase in ACTH and cortisol in sheep following blowfly strike and acute handling restraint. This result suggests that cutaneous myiasis in susceptible sheep can alter the pituitary-adrenal response to acute restraint stress, and this could occur either by an alteration of precursor processing in the pituitary or by the selective release of ACTH.

DA Shutt

AI Smith

CA Wallace

R Connell

LR Fell

Effect of Myiasis and Acute Restraint Stress on Plasma Levels of Immunoreactive , ß-Endorphin, Adrenocorticotrophin (ACTH) and Cortisol in the Sheep

蝇蛆病和急性束缚应激对绵羊血浆中免疫反应性β-内啡肽、促肾上腺皮质激素(ACTH)和皮质醇水平的影响

The recorded behaviour of wild species of Ovis at the beginning of the breeding season supports the proposal that mating is synchronized by the 'ram effect', a phenomenon already described in domestic sheep. Animals separate into exclusive male flocks, and flocks of females and young animals for most of the year. They reunite just before the rutting season. At lambing there appear to be behavioural mechanisms that ensure that ewes lamb in close proximity to one another. It is hypothesized that these behavioural characteristics of wild sheep help protect the newborn and that much of the reproductive and maternal behaviour of domestic sheep may be traced to comparable behaviour in wild species.

DR Lindsay

Reproductive Behaviour in Survival: A Comparison between Wild and Domestic Sheep

生存中的繁殖行为：野生绵羊与家养绵羊的比较

Recent evidence suggests that changes in plasma zinc concentration may play a central role in the development of early lesions of zinc deficiency. The aim of the following work was to better understand events occurring in plasma during the onset of zinc deficiency, and to investigate biochemical mechanisms by which plasma zinc may exert its effects. Fifty male weanling rats of 90 g weight were allocated to five treatment groups of ten rats each. Treatments were: 1, zinc deficient, mixed diet (1-2 mg Zn per kg): 2, zinc deficient, self-select diet; 3, zinc repleted; 4, control, pair fed; 5, control, ad libitum fed. With the exception of treatment 1, which consisted of a 25% casein diet, all rats were offered protein as a separate component of the diet. Control rats received zinc in the drinking water (100 mg I-I). The sequence of events following initiation of zinc deficiency were: reduced plasma zinc concentration (2 days), reduced plasma angiotensin-converting enzyme and alkaline phosphatase activities (3-4 days), reduced feed intake and growth (5-6 days) and reduced percentage protein intake (12 days). Plasma zinc concentration in the deficient rats was inversely correlated with the growth rate of the rat over the previous 24 h. Zinc repletion resulted in marked overshoot in plasma zinc concentration (300%) and converting-enzyme activity (150%) within 24 h, but a return to normal within 72 )1. Alkaline phosphatase activity responded likewise, albeit more slowly. Protein self selection had no effect on the manifestations of zinc deficiency, although reduced protein intake was associated with lower plasma zinc concentration. The results provide evidence of a role for plasma zinc in the development of early clinical signs of zinc deficiency, possibly acting biochemically through reduced activity of zinc-dependent peptidases such as angiotensin-converting enzyme.

C L White

Relationship Between Plasma Zinc, Angiotensin-converting Enzyme, Alkaline Phosphatase and Onset of Symptoms of Zinc Deficiency in the Rat

血浆锌、血管紧张素转换酶、碱性磷酸酶与大鼠锌缺乏症状发作之间的关系

The effects of daily administration of 10 mg of highly purified ovine growth hormone (GH) for a period of 4 weeks on wool growth have been measured in 12 Merino ewes fed either a calculated maintenance energy intake or 1.6 times this amount (six on each ration). Concentrations of hormones, glucose, urea, alpha-amino N and amino acids in the blood were monitored and faeces and urine collected for measurement of nitrogen balance. Wool growth rate decreased by 20% during the 4 weeks of GH treatment in sheep fed the high energy diet, largely because of reduced wool fibre diameter. This was followed by restoration of normal growth and then an increase of up to 20% above control levels, a response which persisted for 12 weeks following cessation of GH administration, and which was due to increases in both fibre length and diameter. GH administration caused marked increases in plasma concentrations of GH, insulin and somatomedin C, glucose and free fatty acids, all of which returned to basal levels following cessation of GH administration. No consistent changes in plasma concentration of T3, T4, cortisol, prolactin or alpha amino N were detected. Plasma urea and methionine levels decreased during GH treatment and returned to, or were raised above, basal levels after the GH treatment period. GH injection also resulted in a net retention of N during treatment, followed by a transient period of net N loss. The GH-induced changes in wool growth may be caused by a change in the partitioning of amino acids between the muscle mass and the skin. No other contributing factor(s) were identified.

P C Wynn

A L Wallace

A C Kirby

E F Annison

Effects of Growth Hormone Administration on Wool Growth in Merino Sheep

生长激素对美利奴羊羊毛生长影响的研究

Two separate experiments were conducted with alloxan-induced, diabetic ewes. In one study it was found that the diabetes induced by alloxan could be stabilized with exogenous insulin (1 . 2-1' 3 U h -1). Feed intake and milk yield were maintained at normal levels even though a mild hyperglycaemia persisted. Despite this, milk fat content tended to increase, an observation that is consistent with insulin being a key factor in the aetiology of the low-milk-fat syndrome in the ruminant.

D Leenanuruksa

GH McDowell

Control of Glucose Homeostasis in Lactating Ewes: Use of the Alloxandiabetic/ Insulin-stabilized Ewe to Study Effects of Insulin and Growth Hormone

泌乳母羊血糖稳态的控制：利用四氧嘧啶糖尿病/胰岛素稳定母羊研究胰岛素和生长激素的影响

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Effect of Myiasis and Acute Restraint Stress on Plasma Levels of Immunoreactive , ß-Endorphin, Adrenocorticotrophin (ACTH) and Cortisol in the Sheep

Reproductive Behaviour in Survival: A Comparison between Wild and Domestic Sheep

Relationship Between Plasma Zinc, Angiotensin-converting Enzyme, Alkaline Phosphatase and Onset of Symptoms of Zinc Deficiency in the Rat

Effects of Growth Hormone Administration on Wool Growth in Merino Sheep

Control of Glucose Homeostasis in Lactating Ewes: Use of the Alloxandiabetic/ Insulin-stabilized Ewe to Study Effects of Insulin and Growth Hormone

Effect of Myiasis and Acute Restraint Stress on Plasma Levels of Immunoreactive , ß-Endorphin, Adrenocorticotrophin (ACTH) and Cortisol in the Sheep

Reproductive Behaviour in Survival: A Comparison between Wild and Domestic Sheep

Relationship Between Plasma Zinc, Angiotensin-converting Enzyme, Alkaline Phosphatase and Onset of Symptoms of Zinc Deficiency in the Rat

Effects of Growth Hormone Administration on Wool Growth in Merino Sheep

Control of Glucose Homeostasis in Lactating Ewes: Use of the Alloxandiabetic/ Insulin-stabilized Ewe to Study Effects of Insulin and Growth Hormone