Effect of total replacement of the soya bean meal by lupine seeds (L. albus and L. luteus) on performance and digestion characteristics of growing rabbits

Abstract

This study aimed to evaluate whole lupin seeds (Lupinus. albus and Lupinus luteus) as an alternative crude protein (CP) source to soybean meal (SBM) in diets for growing rabbits. Diets contained 150 g/kg of SBM (control; CTD), white lupin seeds (LAD) or yellow lupin seeds (LLD) as the main protein source were used. The diets were similar in the level of digestible crude protein (CP), and digestible energy and limiting amino acids. Sixty hybrid rabbits (New Zealand x Californian; 20 rabbits per diet; 1025 ± 72 g of live weight (LW)), weaned at 35 days of age, were used for growth performance evaluation from 35 to 69 days of age. A feed restriction (80 %) was performed during the first 14 days of the experiment (from 35 to 49 days). At the end of the growth trial, 30 rabbits (10 rabbits per treatment) were slaughtered without fasting. The caecum was weighted and its content was collected, the pH was measure and samples were taken and frozen for laboratorial analysis. Forty eight rabbits (24 cages and 16 rabbits per diet; 60 days of age; 2115.0 ± 211.6 g LW) were selected from the growth trial and used in the digestibility assay. No significant (P > 0.05) effects was observed on the LW and feed intake between diets in all ages studied. Considering the total growing period (35−69 days), weight gain was higher (P < 0.05) in rabbits fed the CTD (47.7 g/day) than rabbits fed lupine diets (42.8, and 42.1 g/day in rabbits fed the LAD and LLD, respectively). Similarly, feed conversion rate was lower (P < 0.05) in rabbits fed CTD (3.1, 3.5 and 3.6 g/g in rabbits fed the CTD, LAD and LLD, respectively). There were differences in digestibility of organic matter with CTD presenting the highest value (0.622; P < 0.05). Regarding de digestibility of CP, the highest value was found for LLD (0.738; P < 0.05). Digestibility of fibre fractions was not affected by diet (P > 0.05). The caecal parameters were not affected by the replacement of SBM by lupine, except the pH values that were higher in lupine diets (5.74 and 5.77 LAD and LLD, respectively; P < 0.05). In conclusion white and yellow lupin seeds are a suitable dietary protein source for growing rabbits although a slightly worsened of the growth performance of rabbits fed LAD or LLD was observed. Future trials must be conducted using lower levels of lupine seeds in diets and including also an economic evaluation of the results.