Morphological and molecular changes in the kidney of offspring born to ewes exposed to a high-salt diet during pregnancy

[Truncated abstract] Native shrubs such as saltbush have been used to revegetate farmland affected by salinity. Apart from helping to limit the further spread of these saline areas, saltbush provides forage for grazing livestock. The high concentration of sodium in saltbush is associated with a decreased organic matter intake in sheep, which can lead to a decrease in weight gain if other feed sources are not provided to complement saltbush. However, with the provision of adequate digestible energy from other feeds or pastures, saltbush can be a valuable forage for pregnant ewes in the dry autumn period of southern Australia. It has been shown that a high-salt diet consumed by ewes during pregnancy can affect certain physiological traits in the offspring. The aim of this project was, therefore, to investigate how maternal high-salt intake during pregnancy would alter renal morphology and the regulation of some of the key hormones of the renin-angiotensin system in the offspring, and if these changes would persist into adulthood. Two experiments were conducted on Merino sheep; one on five-month-old lambs and the other on three-year-old adult sheep. Half of the sheep tested were born to ewes that were fed a diet containing a high amount of salt during pregnancy (10.3% - 13% NaCl; 'high-salt offspring'), whilst the remaining half were control animals whose mothers were fed a diet of standard salt content (0.5% - 1.5% NaCl; 'control offspring'). In the first experiment, the mothers' plasma aldosterone concentration was measured during the second half of pregnancy, whilst plasma renin activity and plasma aldosterone concentration were measured in the offspring at birth, two weeks of age, and at various times during a dietary 'salt challenge' in the post-weaned lambs at five months of age. In the 'salt challenge', weaned lambs were fed a high-salt (10.3% NaCl) diet over a 17-day period, and compared against counterparts fed a control diet (1.5% NaCl).