Abstract

The aim of this study was to determined nutritive value of five hybrids varying in maturity sown to plots of experimental site located in southern Slovakia. Nutrient contents and digestibility parameters were obtained from samples of herbage or silages to estimate net energy of lactation (NEL) contents and milk yield (MY) potential based on in vivo digestibility of organic matter (DOM), pepsin-cellulase in vitro digestibility of OM (IVOMD) using Ankom DaisyII Incubator (Ankom Technology Corp., NY, USA), cellulase digestibility of OM (CDOMD), neutral detergent fiber (CDNDF) or in vitro digestible non starch carbohydrates (IVDNSC). Genotype effect accounted for differences in carbohydrates content and crude protein (CP). Linear regression models increased coefficient of determination (R2) when CDOMD and IVOMD were included to predict in vivo apparent digestibility NDF (NDFD) but RMSE were higher compared to DOM. Structural carbohydrate contents had mostly precise estimates but limited R2 as the predictors of DOM, NDFD and NEL in combination with in vitro digestibility determinants. There was negative relationship of IVOMD and DOM (r = - 0.72; p < 0.01) but positive as it comes to CDOMD (r = 0.81; p < 0.01). Equations based on CDOMD (E7), IVDNSC and CP (E8) and CDNDF and Starch (E9) were selected to predict NEL. Residuals of NEL (observed – predicted) ranged from – 0.57 to 0.41 MJ/kg. Mid-late hybrids had higher MY kg/ha and MY kg/Mg than early (FAO 340). E7 and E9 were sensitive to ADL content while E8 favored hybrids rich in Starch.

Key words: sheep, carbohydrates, digestibility, energy, milk yield