Valor nutritivo de pastagens de regadio. Suplementação de ovelhas “Serra da Estrela” em pastoreio, produtividade e interpretação metabólica dos resultados

The study reports the productivity and nutritive value of an irrigated pasture grazed by sheep of the Serra da Estrela breed between September and February. The value of the pasture was evaluated by the production of milk and meat, during two consecutive lambing seasons in September. Grazing was conducted rotationally. The pasture’s botanical composition, dry matter (DM) and nutritive value were evaluated before sheep entered each plot. The ewes were supplemented with corn or corn gluten feed (CGF). Lambs suckled their dams up to 21 days of age. Between 21 and 42 days the ewes were milked once a day and at 42 days the lambs were weaned and milking was twice a day. Body live weight (BLW) and average daily gain of lambs, as well as BLW, body condition score, production and composition of the milk of the sheep were evaluated. The nutritive value of the pasture was higher at the beginning of the 1st year, with values of 321.5±19.45; 263.0±15.45 and 749.3±23.69 g/kg DM respectively for NDF, PB and OM digestibility, and decreased over the grazing periods. The ewes’ performance was higher in the first year and for those supplemented with CGF: higher lamb weaning weights, milk production in both milking periods and milk constituents. The evaluation of the “non-esterified fatty acids”, “insulin” and “urea” serum indicators were important in interpreting the production results. Dairy ewes’ supplementation should consider the mobilization of body reserves and be limited to the onset of lactation and its composition should include rumen-undegradable protein in addition to soluble carbohydrates.