Prediction of the nutritive value of lucerne hay in diets for growing rabbits

Fifty-one New Zealand White × California rabbits were used to evaluate apparent in vivo dry matter (DM), organic matter (OM), energy, nitrogen (N), neutral detergent fibre (NDF) and amino acid digestibilities of five lucerne hays varying in chemical composition. Hays were ground and pelleted and given as sole feeds throughout the experiment. In vitro DM, OM, NDF and N digestibilities of feed samples were also determined. A ruminal incubation trial was performed to determine NDF disappearance of lucerne hays in nylon bags. The type of lucerne hay had a large effect on its nutritive value. The range of variation for digestible energy (DE) and digestible crude protein (CP) contents and for NDF digestibility was 6.4–9.2 kJ g−1, 114–164 g kg−1 and 0.204–0.276, respectively. The type of lucerne hay also affected lysine, methionine and threonine digestibilities. Stepwise regression analysis showed that the best single predictors for energy, CP, NDF and amino acid digestibilities were dietary NDF and non starch polysaccharide (NSP) contents, ruminal NDF degradability after 48 h of incubation and CP digestibility, respectively. Regressions using only chemical components as independent variables were also calculated. The results of this study showed that in vitro methods and prediction equations determined for mixed diets and concentrated ingredients need to be adjusted to estimate nutritive value of forages in rabbits.