Effectiveness in learning complex problem solving and salivary ion indices of psychological stress and activation

The physiological and metabolic impacts on sheep and cattle of feed and water deprivation before and during transport

“…Individually confined cattle, which are known to be stressed because of isolation 40 – 42 , have increased Na appetite 43 due to the natriorexigenic effect of heightened pituitary–adrenal secretion. During stress, Na concentration of saliva declines to restrict losses 44 . Although the glucocorticoids do not themselves induce a Na hunger, they do so in conjunction with the mineralocorticoid aldosterone 45 , which is released in response to stress and is responsible for increasing Na appetite during Na depletion 46 .…”

“…The rate at which Na is extracted from ECF into saliva is affected by the animal's chewing activities. Saliva production at rest is appreciably lower than during eating, particularly forages, or rumination 57 , and is affected by stress levels 44 . Data from a 40 kg sheep with an oesophageal fistula, examined six times over 7 months, indicated rates of salivation that varied from approximately 7 ml/min at rest to 30 ml/min when vigorously eating chopped lucerne hay (JP Hogan, unpublished results).…”

“…Assuming that the Na content of mixed saliva in sheep is similar to that in cattle, 105 mEq/l 63 , saliva production at the rate of 2 litres/h during eating would extract in 1 h about one-tenth of the Na in ECF. However, it is not known whether in response to aldosterone 64 the concentration of salivary Na might have been reduced 44 and that of K increased. This would help to explain the decrease in Na levels in the rumen when sheep were re-fed after an 18 h fast 33 .…”