Effect of dietary supplementation of Spirulina (Arthrospira platensis) and Thyme (Thymus vulgaris) on apparent digestibility and productive performance of growing rabbits

The aim of this study was to evaluate the effect of dietary supplementation with spirulina (Arthrospira platensis) or/and thyme (Thymus vulgaris) on total tract apparent digestibility of nutrients and the performance of growing rabbits. At weaning (5 wk of age) the rabbits were randomly allotted to 7 groups (42 rabbits/group, 3 rabbits/cage). Rabbits in the control group (C-C) received a control pelleted feed throughout the experiment (5-11 wk of age) without any supplementation (crude protein: 176 g CP/kg, neutral detergent fibre: 325 g NDF/kg). In the other groups, the control diet was supplemented with 5% spirulina (S, mainly in substitution of soybean meal), or 3% thyme (T, mainly in substitution of alfalfa meal) or by both 5% S and 3% T (ST) for the whole (5-11 wk of age; groups: S-S, T-T, ST-ST) or part of the growing period (8-11 wk of age; groups: C-S, C-T, C-ST). Supplementations had no effect on apparent digestibility of dry matter, organic matter, acid detergent fibre, gross energy and digestible energy. The CP TTAD was lowest in rabbits fed the S diet, whereas it was highest in C fed rabbits, the other 2 treatments being intermediate (P<0.001). The starch TTAD was lowest for S fed rabbits (98.3%) and highest for ST fed rabbits (99.4%), the other 2 dietary groups being intermediate (P<0.001). In contrast, the ether extract TTAD was higher in T than ST and C dietary groups (on av. 70.4 vs. 67.7% respectively; P<0.001), with S fed rabbits showing an intermediate value (69.1%). The NDF TTAD of the ST diet was lower than that of the other 3 groups (16.4 vs. 21.0% respectively; P<0.001). The TTAD of Ca reached the lowest value for the S diet (53.5%) compared with the other 3 diets (on av. 59.1%; P<0.001). The S diet also had the lowest digestibility (P<0.001) for K and P, but in this case the C group always showed the highest values (P<0.001), with T and ST rabbits exhibiting intermediate results. Spirulina and/or thyme dietary supplementation had no effect on feed intake (133 g/d), daily weight gain (38.3 g/d), morbidity (9.9 %) or mortality (1.8 %). Significant differences were only found for feed conversion ratio, which was lower for the C-T group (3.39) than for the C-C group (3.54; P<0.05). Based on these results, spirulina and thyme included separately or combined in growing rabbit diets did not exhibit substantial effects on growth performance or health status.