Programming sheep production on saltbush: adaptations of offspring from ewes that consumed high amounts of salt during pregnancy and early lactation

Abstract

We investigated if feeding a high salt diet (pellet containing 14% NaCl) or saltbush (Atriplex nummularia) to ewes between day 60 of gestation and day 21 of lactation would allow their offspring to gain more weight, and produce more wool, when grazing saltbush as adults compared to offspring from ewes that were fed a control diet (2% NaCl) or grazed pasture. At 10months of age, offspring grazed saltbush for 8 weeks then dry pasture for 2weeks. Throughout this time, liveweights, plasma renin activity and wool growth (g/day) were measured. Greasy and clean fleece weights, and fleece characteristics were measured at 14 months of age, and greasy fleece weight was measured again at 22 months after grazing pasture. Offspring from ewes that consumed the high salt pellet had an 8 and 10% increased fleece weight at 14 and 22 months of age, respectively (P _ 0.01). Offspring of ewes that consumed saltbush also showed an 8% increase in greasy fleece weight at 22 months of age (P _ 0.05). Offspring from ewes that consumed saltbush had lower plasma renin activity and gained tissue weight when grazing saltbush (P _ 0.05), whereas the other three treatment groups all lost weight (P > 0.05). Grazing pregnant ewes on saltbush induces important adaptations in plasma renin activity of their offspring, which allows them to gain weight when grazing saltbush as adults and may also increase the density of their wool follicles. Grazing pregnant ewes on saltbush can profit farmers in three main ways: (i) ability to utilise salt-affected land; (ii) increase weight gain of sheep when grazing saltbush; and (iii) increase fleece weight.