Sheep fed only silage or silage supplemented with concentrates. 1. Effects on ewe performance and blood metabolites

In Scandinavia, winter diets for sheep are forage-based, with concentrates commonly being added in the latter part of pregnancy and during lactation. In organic production, however, the level of concentrates is restricted and rations are sometimes purely forage-based. It is uncertain if feeding only forage fulfils the nutritional requirements of high producing ewes. The aim of this project was to compare the performance and nutrient status of ewes fed only silage from mid-pregnancy until the end of lactation (SIL), or silage and a maximum of 40% concentrates before lambing, and 50% afterwards (CON). The study was conducted during two consecutive indoor feeding seasons (Y1 and Y2), with 41 and 51 ewes, respectively. In Y1, the silage was of high nutrient quality, whereas the silage used in Y2 had a lower content of energy and protein and more fibres. The general level of feed intake was lower in Y2 than Y1. There were significant differences in body condition between SIL and CON ewes in both years. Blood samples from the ewes were analyzed for betahydroxybutyrate (BHB), non-esterified fatty acids (NEFA) and urea. In both years, SIL ewes had higher NEFA and BHB than CON ewes two weeks after lambing, In Y2, urea was lower in SIL ewes than in CON ewes after lambing. Litter size also had a significant impact on the blood metabolites. In conclusion, feeding only silage is not recommended for ewes with more than one lamb, unless the silage is of a very high nutritional quality.