White lupin seeds
As for the whole plant, the Lupinus albus seeds (beans) are recommended for rabbit feeding since a long time (Benoit et al., 1948). The common recommended level of incorporation in balanced diets for growing rabbits varies from 10 to 20% according to the experiments for growing rabbits (Battaglini et al., 1991; Mesini, 1997; Sarhan, 1999; Seroux, 1984; Volek et al., 2008; Volek et al., 2009). But it should be noticed that higher incorporation levels such as 40% or 50% were experimentally used without alteration of growth performance (Fekete et al., 1986; Kelly et al., 1990). White lupin seeds could also be used successfully in the diet of lactating rabbit does. Compared to a soybean-sunflower meal control diet, a diet with 25% white lupin seeds increases the 1-31 d. milk production of the rabbit does by 11%, most probably in relation with the higher lipids content of the lupin diet: 4.1% vs. 2.3% (Volek et al., 2014). Despite the variations of seed composition of the different cultivated varieties of Lupinus albus, their is no intrinsic great difference in nutritive value between cultivars, since no difference between varieties in rabbit growth performance was observed in a comparison of 6 white lupin seeds cultivars made in France (Lebas, 1986).
For other species such as poultry and particularly pigs, the presence of alkaloid and some other antinutritional factors in lupin seeds makes a pre-treatment (washing, heating...) or the addition of enzymes very useful for the optimization of their utilisation in animal feeding (Cheeke et al., 1989; Brenes et al., 1993). On the contrary, rabbit is poorly sensitive to lupin's alkaloids (Cheeke et al., 1989), and seeds washing or the addition of an enzymes cocktail failed to improve the white lupin nutritive value for growing rabbits (Falcao-e-Cunha et al., 2008). Nevertheless extrusion of imported Australian white lupin seeds (16% of the diet) improved rabbit's growth rate by 10% above the control diet without lupin in an Italian study (Battaglini et al., 1991).
In practical conditions, white lupin seeds could be considered as an interesting source of proteins (~35% DM) with a high level of digestible energy: 13.5 to 16.0 MJ/kg DM (Fekete et al., 1986; Lebas, 1986; Maertens et al., 2002). The high level of energy is the consequence of the relatively low level of fibre, NDF 17.5% of DM, and more, of the high content of lipids, 9-10% DM, despite the very low starch content (Petterson, 2000). These lipids are relatively rich in alpha-linolenic acid C18:3, that represents 9-10% of total fatty acids (Chiofalo et al., 2012). This is able to improve the quality of rabbit meat for human consumption through a better omega 6 to omega 3 ratio (Volek et al., 2011), and can also explain partly the improvement of the sanitary situation of rabbits during production observed with white lupin seeds when compared to soybean meal (Colin et al., 2012; Uhlířová et al., 2016). However, the proteins of white lupin seed are not very rich in lysine for proteins of a legume seed (~ 4.9g /16 g N), just covering the growing rabbit needs. But as for other leguminous seeds, the proteins of white lupin seeds are strongly deficient in sulphur-containing amino acids, covering only 65% of rabbit needs (Lebas, 2013), a situation which makes necessary the complementation of this source of proteins with other raw materials such as cereals or cereal byproducts (wheat bran...), or with synthetic methionine.
Whole plant Forage
Lupinus albus whole plant is a forage know in Europe to be useful in rabbit feeding since a long time. Used as only feed, its nutritive value was estimated similar to that of green alfalfa (Brüggemann, 1939 cited by Voris et al., 1940). Effectively dried lupin forage used as the main source of fibre in a rabbit diet induced growth rate and feed efficiency similarly or even better than alfalfa meal used in the same conditions (Harries et al., 1999).
Green lupin used as forage distributed ad libitum may replace 20% of a concentrate complete feed without alteration of growth rate of fattening rabbits But if the daily allowance of concentrate represents only 60% of the spontaneous intake of the ad libitum control, the spontaneous intake of the additional green lupin forage is not sufficient to permit the same growth rate (El-Gendy, 1999).
White lupin hulls
Lupin seed external coat, generally named hulls after removal, represents 22% of the whole grain (Petterson, 2000). In a study were in the diet 10% wheat bran were replaced by 5% white lupin hulls + 5% barley, rabbits showed normal figures for growth rate (52.4 g/d on average), feed intake (155.1 g/d on average) and feed conversion ratio (2.97 on average). For the 2 diets, digestibility coefficients were similar for energy, crude proteins or NDF. As a consequence white lupin hulls could be considered as a suitable source of fibre for rabbits with 86.9% NDF and 7.2% ADL, but with a very low content of proteins i.e about 4.5%, as for cereal straw (Volek et al., 2013).