Parturition is a natural event that involves stress and pain for the mother. We thus hypothesized that levels of stress hormones measured during parturition could reflect levels reached in response to severe discomfort and pain of other kinds as well. The aim of this study was therefore to determine whether plasma concentrations of cortisol, adrenaline, noradrenaline, -endorphin, met-enkephalin, vasopressin and oxytocin vary depending on the phase and severity of labour in dairy heifers (ten) and dairy goats (six), and how these hormones interact with each other. Blood samples were taken once a day for 3 days before labour and for 3 days afterwards and at predetermined phases during labour. All heifers delivered one calf and five of them needed obstetrical assistance. Two of the goats delivered one kid, and four had twins; all kidded without help. The cortisol concentration peaked when the calf and the first kid were born. In the heifers, plasma adrenaline increased after delivery, while the noradrenaline concentration did not change significantly in heifers that needed assistance, but increased during expulsion in heifers calving without help. In the goats, adrenaline and noradrenaline concentrations increased in association with expulsion of the first kid. The -endorphin concentration increased during labour in goats. In heifers that needed assistance, -endorphin concentration increased 1 h after labour but there was no change in heifers that did not need assistance. The met-enkephalin concentration was elevated during expulsion in heifers and fluctuated in the goats. Both oxytocin and vasopressin increased during expulsion in both groups of heifers, but vasopressin increased four times more in heifers needing assistance. In the goats, oxytocin reached its highest levels just as the feet of the first kid became visible, and vasopressin peaked as the head emerged. Parturition took longer in heifers that needed assistance than in those that did not. It is concluded that, even though the pattern of change differed between hormones during labour, the changes were related to the phases of labour. A longer labour therefore meant that the hormone concentrations stayed elevated for longer. Vasopressin reached high levels in goats and was the only hormone for which plasma concentrations were higher in heifers that needed assistance than in those that did not, indicating that this hormone is released in order to deal with the painrelated stress associated with labour.

Pregnancy challenges the homeostatic mechanisms of the mammalian body, especially these controlling the cardiovascular system. In the dairy ruminant the lactation period places the same or even greater demands on that system, but the adaptations that help dairy goats to deal with its demanding lactation period have received comparatively little attention. In goats, the blood volume expands in parallel with the body weight increase during pregnancy and with an increase in cardiac output and a decrease in total peripheral resistance. In a study by Linzell (1974), the cardiac output remained at the same level or became greater after parturition, and Chaiyabutr et al. (1980 a,b) have reported that lactating goats with low milk production had a smaller cardiac output.The blood flow to the mammary gland is directly related to milk production (Linzell, 1974;Davis & Collier, 1985), and with the increasing efficiency of milk production in dairy goats and cows it appeared of interest to study the effect on cardiac dimensions and function in the dairy goat. For cardiovascular studies during different reproductive periods it is preferable to use the same animals, but no serial studies on heart dimensions and function have previously been done in goats. Echocardiography is a non-invasive method for measuring stroke volume and cardiac output from cardiac dimensions and heart rate. It has been claimed to be the method of choice for serial measurements in pregnant women (Duvekot & Peeters, 1994). It has also been evaluated in clinically normal cows (Pipers et al. 1978) and is used routinely for cardiac diagnosis in many species, including goats (Yamaga & Too, 1984;Gardner et al. 1992). We studied cardiac dimensions and function during late pregnancy, peak lactation, and the non-pregnant, non-lactating (dry) period in dairy goats. Chronically implanted telemetric devices were used for measurements of arterial blood pressure (Hydbring et al. 1997) in order to calculate changes in total peripheral resistance (TPR) and to investigate if the echocardiographic procedure affected the goats.A serial study of heart function during pregnancy, lactation and the dry period in dairy goats using echocardiography Echocardiography and Doppler measurements were performed to investigate changes in heart dimensions and function during pregnancy, lactation and the non-pregnant, non-lactating (dry) period in dairy goats. Eight Swedish domestic goats (Capra hircus) were studied with two-dimensional (2DE), M-mode and continuous wave Doppler measurements. Cardiac dimensions did not differ between periods. The mean cardiac outputs were 35 and 28 % greater during pregnancy and lactation, respectively, vs. the dry period. Arterial blood pressure (measured by telemetry) did not differ between reproductive periods before echocardiographic measurements, but became elevated during the measurements, with the smallest rise during lactation. Heart rate was elevated during pregnancy and increased further during echocardiographic measurements, but was not elevat...

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The aim of this study was to investigate the extent of sympathetic nervous system activation during parturition in four unrestrained goats. Chronically implanted radiotelemetry devices registered heart rate and arterial blood pressure around the clock and blood was sampled for determination of plasma adrenaline and noradrenaline concentrations before, during and after labour. Two goats delivered two kids after moderately intensive abdominal contractions. A third goat had dystocia, and was treated with prostaglandin F2 alpha. One normal kid and one mummified foetus were delivered manually. After milking, a third kid was born spontaneously. The fourth goat experienced severe abdominal contractions and delivered one kid. Mean blood pressure was 69 +/- 2 mmHg the day before parturition, increased gradually during the labour pains, and reached a maximal value of 120 +/- 7 mmHg when the head of the first kid was visible (P < or = 0.05). Heart rate was 134 +/- 4 beats min-1 the day before parturition and peaked when the first kid was born (159 +/- 6 beats min-1, P < or = 0.05), as did plasma adrenaline concentration (from 0.4 +/- 0.2 nmol L-1 to 2.7 +/- 1.2 nmol L-1, P < or = 0.05). The concentration of noradrenaline increased from 4.8 +/- 2.3 nmol L-1 to 12.2 +/- 8.4 nmol L-1 (P < or = 0.05), when the head of the first kid was visible. Expulsion of the second and third kids caused relatively smaller increases in blood pressure, heart rate and catecholamines than those seen with the first born kid. It is concluded that changes in pressure, heart rate and catecholamines during parturition are related to the different phases of labour and not to its duration or severity.

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