An option to increase the productivity of saline land is to graze sheep on salt-tolerant plants, which, during the summer/ autumn period, can contain 20% to 25% of their dry matter as salt. This study assessed the impact of coping with high dietary salt loads on the reproductive performance of grazing ewes. From the time of artificial insemination until parturition, 2-year-old maiden Merino ewes were fed either a high-salt diet (NaCl 13% of dry matter) or control diet (NaCl 0.5% of dry matter). Pregnancy rates, lamb birth weights, milk composition and the plasma concentrations of hormones related to salt and water balance, and energy metabolism were measured. Leptin and insulin concentrations were lower (1.4 6 0.09 v. 1.5 6 0.12 ng/ml; (P , 0.05) and 7.2 6 0.55 v. 8.2 6 0.83 ng/ml; P , 0.02) in response to high-salt ingestion as was aldosterone concentration (27 6 2.7 v. 49 6 5.4 pg/ml; P , 0.05), presumably to achieve salt and water homeostasis. Arginine vasopressin concentration was not significantly affected by the diets, but plasma concentration of T 3 differed during gestation (P , 0.02), resulting in lower concentrations in the high-salt group in the first third of gestation (1.2 6 0.18 v. 1.3 6 0.14 pmol/ml) and higher concentrations in the final third of gestation (0.8 6 0.16 v. 0.6 6 0.06 pmol/ml). T 4 concentration was lower in ewes ingesting high salt for the first two-thirds of pregnancy (162 6 8.6 v. 212 6 13 ng/ml; P , 0.001). No substantial effects of high salt ingestion on pregnancy rates, lamb birth weights or milk composition were detected.Keywords: aldosterone, high salt, insulin, leptin, reproduction IntroductionSalinity is an increasing problem in agriculture worldwide (Ghassemi et al., 1995) and the use of halophytic plants such as saltbush represents one of the few options available to revegetate salinised landscapes and re-establish grazing systems . Some landholders in Australia are grazing sheep on saltbush to fill a summer/ autumn feed gap (Masters et al., 2006), a period that coincides with the greater demands of late pregnancy for autumn-or winter-lambing ewes. However, feeding saltbush may possibly have a negative impact on reproductive performance of the ewes as high salt intake may reduce intake and cause physiological changes associated with adaptation to the salt load.High salt intake has been shown to reduce voluntary feed intake (Masters et al., 2005;Blache et al., 2007) as well as the efficiency of energy use for production (Arieli et al., 1989) in sheep. A decrease either in voluntary feed intake or in fat reserves is usually associated with a decrease in the concentration of metabolic hormones such as insulin and leptin (Chilliard et al., 2005) and recently a high salt ingestion has been shown by Blache et al. (2007) to affect energy metabolism through changes in insulin concentrations in sheep fed high salt (20% NaCl) diets. Thus, the ingestion of large amount of salt may impact energy availability and consequently reproductive performance.There are also physiological 'con...

The relative importance of amino acids, carbohydrates, minerals and vitamins for wool production and the maintenance of quality wool is presented. The chapter outlines the nutritional processes involved in fibre production within the wool follicle, as well as the relationship between nutrient supply from the gastrointestinal tract and fibre growth rate, fibre diameter, fibre length, staple length, clean fibre yield and wool colour. The wool growth response to nutrition is a reflection of changes in the nutrient supply to the wool follicle, which responds by altering the rate, extent and pattern of its primary processes of cell division, gene expression, and protein synthesis. Protein, energy, minerals and vitamins influence these processes, but the precise nature of the wool growth response to these nutrients is influenced by the genotype of the animal and its reproductive status.

The aim of the experiments reported was to evaluate the protection from microbial breakdown of two methionine formulations (Lactet and Mepron) and to measure responses in wool production, liveweight, amino acids and glutathione in blood and tissues when one of these forms of methionine (Lactet) was supplied to merino wethers fed at maintenance. Lactet was well protected against microbial breakdown in the rumen. Peak values for concentrations of methionine in plasma, following administration of the different forms of methionine into the rumen, were 574, 148 and 143pmol L-1 for Lactet, DL-methionine and Mepron. Production responses to dosed levels of Lactet (0, 1, 2, 3, 5, 8 g methionine dayw1) were measured over 63 days in the animal house. Significant linear responses were obtained for wool growth (4-38%), fibre diameter (0.5-2 8m) and liveweight gain (30-1 15%). Concentrations of reduced glutathione in blood, liver and skin were increased, at some times during the experiment, by provision of Lactet. However, responses were inconsistent and highly variable among sheep, Glutathione was of limited use as an indicator of sulfur amino acid intake or status. Sulfate in plasma increased markedly at all levels of Lactet intake, and there was a linear relationship between Lactet intake and the concentration of sulfur in wool. Plasma free methionine and the ratio of methionine to total essential amino acids showed significant linear responses to the supplements. It was concluded that Lactet was an effective method of supplying rumen-protected methionine to ruminants.

The safety and effectiveness of a loose mineral lick containing all known essential elements was investigated in an experiment in which 96 Merino weaner wethers grazed subterranean clover/grass pastures during summer and autumn. The treatments were no supplement or mineral mix ad libitum; there were four plots of 12 sheep per treatment. The mean intake was 29 � 1 g/head per day of the mix and those offered the minerals had blood concentrations of P, S, Se and vitamin BIZ in the normal range. Unsupplemented Control sheep had blood concentrations of P, S and Se in the deficient range for all or part of the experimental period. There was an estimated 1.6-fold range in mineral intake between sheep, and none refused the mix. Concentrations of Cu, Cd and F in tissues and bone of sheep offered the mineral mix were within accepted safety margins. The mineral lick increased live weights by 4.5 kg during summer (P < 0 - 05), increased clean fleece weight by 240 g (9%), (P < 0.01), and increased wool staple strength by 15 N/kt (40%), (P < 0.01). The pasture concentrations of most macro elements decreased between November and March, respective concentrations being (g/kg DM): K, 17- 7 and 1.9; Na, 4-0 and 0.31; S, 1.6 and 0.9; N, 12.9 and 10; P, 1-95 and 1-08; Ca, 7-86 and 9-75; Mg, 2.29 and 1-38. Changes in trace element concentrations were small, the respective values being (mg/kg): Cu, 9.7 and 10-3; Mn, 47 and 67; Fe, 56 and 323; Zn, 20 and 20; Mo, 0-2 and 0.35; and Se, 0.015 and 0.032. The loose mineral lick was a safe and effective means of supplying macro and trace elements to grazing sheep during summer.