The in vitro gas production technique was used to evaluate the fermentation kinetics of 125 whole citrus fruits samples (WCF). Six models were tested to describe the fermentation characteristics of this product characterized by high sugar and pectin and low protein content: 487, 195 and 64.7 g/ kg dry matter, respectively. The models were: exponential with and without lag (EXP 0 and EXP L , respectively); generalized Mitscherlich (GEXP L ); and one, dual and three pool logistic models (OLOG L, DLOG L and TLOG L , respectively). EXP 0 had the highest residual standard deviation (RSD=9.0 ml), the lowest being for the TLOG L (5.93 ml). TLOG L model obtained the best values fitting individual curves with a mean prediction error of 0.25 ml. Significant correlations were observed between the three different fractions of the TLOG L model and the chemical composition: quickly fermentable fraction with sugars (+0.43; P<0.001), high fermentable fraction with pectins (+0.23; P<0.05) and slow fermentable fraction with fibres (+0.38 and +0.34 for NDF and ADF, respectively; P<0.01), which could indicate the presence of three main fractions in WCF with different fermentation rates.

Seven diets were formulated in order to determine the nutritive value of whole maize plant at three stages of maturity by substitution of a control diet (C) with 20% and 40% whole maize plant at early dough, mid-dent and mature stages of grain. A digestibility trial was performed with 74 rabbits. Digestible protein and energy values of whole maize plant at different maturity stages were calculated by substitution and regression procedures. A fattening experiment was carried out with 200 rabbits from weaning (28 days of age) giving ad libitum either diet C or 20% mature whole maize plant. One hundred and forty-three rabbits were slaughtered at 63 days of age and some carcass traits were measured.The crude protein and fibre content of whole maize plant decreases as the kernel matures (CP: 8.3, 8.1 and 7.6% DM; CF: 15.8, 12.6 and 13.4% DM; NDF: 45.3, 38.0 and 38.0% DM; ADF: 19.1, 15.0 and 16.1% DM for early dough, mid-dent and mature stages, respectively). The digestible energy concentration, calculated by regression, of whole maize plant increased (P<0.01) with maturity stage (8.5, 9.5 and 10.4 MJ/kg DM, respectively) but the digestible protein value was higher (P<0.01) at the intermediate maturity stage (3.7, 4.5 and 3.2% DM). Rabbits given the diet with 20% plant maize at the maturity stage had similar feed intake (101 vs. 99 g DM/d) and live weight gain (44 vs. 45 g/d) but a worse feed conversion index than C rabbits (2.29 vs. 2.21, P=0.03). No differences were found at slaughter in live weight, carcass characteristics and dressing percentage of rabbits fed the two experimental diets.