Effect of dietary supplementation of Spirulina (Arthrospira platensis) and Thyme (Thymus vulgaris) on growth performance, apparent digestibility and health status of companion dwarf rabbits

Raising and caring rabbits for purposes of companionship has become more popular within households. This has recently created attention in formulating balanced diets that include raw materials with nutritional characteristics capable of improving animal health status. The aim of this study was to compare, in balanced diets formulated for growing dwarf rabbits, the effect of the dietary inclusion of 3% microalga Spirulina (Arthrospira platensis, S) and/or 2.5% Thyme (Thymus vulgaris, T) leaves on the dietary fatty acid (FA) profile, the coefficients of total tract apparent digestibility (CTTAD), and the nutritive value of such diets on animal growth performance and health status. Four isonitrogenous (161±4 g/kg) and iso-energetic (16.8± 0.1 MJ/kg) diets for growing pet rabbits were formulated: a control diet (C), a diet with 2.5% Thyme (T diet), a diet containing 3% Spirulina (S diet), and a diet with both 2.5% T and 3% S supplementations (TS diet). Diets were fed for 14 weeks to 120 dwarf rabbits (divided in 4 groups of 30 each) initially aged 7 weeks with a mean body weight of 643±4.7 g. Supplementing T and S resulted in diets richer in polyunsaturated FA (PUFA), notably in C18:2n-6 in S, T and TS diets and in C18:3n-3 in S diets, although formulating diets with different proportions of raw materials to obtain equal energy contents may have played a role in the differences in the FA profile. The GLA (C18:3n-6) level was ten-fold higher in the S-enriched diets. The n-6/n-3 ratio was favourably low in all diets (on average 2.6), and the lowest ratio was observed in the S and TS diets (2.12 and 2.53, respectively). At the end of the study females reached a higher body weight (P<0.05) probably due to the higher feed intake during the experimental period. Dietary treatments did not negatively affect the animal growth performance. A decrease (P<0.01) of the CTTAD of ether extract (0.87 vs 0.85 vs 0.85 vs 0.84, in C, T, S, TS, respectively) was observed, which was probably due to the slight decrease of dietary EE content and the increase of PUFA proportion in the diets. The CTTAD of ADF and cellulose increased with TS addition compared to the C diet (0.22 vs 0.17 and 0.28 vs 0.22 for TS and C diets, respectively; P<0.05). Morbidity and mortality were unaffected by the dietary treatment. We conclude that S and/or T can be included at a rate of 3% and 2.5% respectively in the diet of growing dwarf rabbits with no substantial effects on growth performance and energy or nutrients digestibility. At these rates of inclusion, S and T did not prevent animals from getting sick or dying during the 14 weeks of study period. A longer follow-up is necessary in companion dwarf rabbits to investigate whether S and T confer beneficial effects in healthy mature, elderly and debilitated animals.