Evaluation of the effects of different diets on the welfare of Gilthead seabream (Sparus aurata) broodstock

Gilthead seabream is one of the most important aquaculture species both at European and world level. Its characteristics and qualities make it an excellent source of protein and, due to continuous increase in protein demand, the production is expected to grow further, as it has in the last decades. Reproduction is one of the most important factors that must be taken into consideration to improve aquaculture field, along with the other reproductive factors that have an impact, such as broodstock management and, in particular, nutrition. The nutritional components of the diet, the intake level and the duration of the feeding period are just some of the aspects that directly affect the quality of the offspring. Being the gilthead seabream mainly a carnivorous species, it requires an important protein component in the diet. In aquaculture, fishmeal and fish oil are the main high-quality protein sources used in commercial feeds formulation, however alternative and affordable protein sources exist. Considering that expenses related to feeding in intensive-reared marine species contribute significantly in terms of percentage of total production costs, it is fundamental to identify alternative cost-effective raw materials. These materials should optimize not only economic and nutritional aspects but also reproduction efficiency while maintaining welfare. The present study evaluates the effects of three different diets on some welfare indicators. A gilthead seabream broodstock (N. 66) divided into three tanks, each containing 7 females and 15 males, were fed three diets containing a mix of four alternative ingredients, in partial substitution of the regular formulation. Each tank was administrated a different diet, with inclusion levels of 0%, 5% and 10%, of respectively. The welfare indicators analysed in this thesis are those associated with the stress response e.g. cortisol levels in serum, muscle, fins, scales and eggs, determined by means of radioimmunoassay, alongside oxidative stress and glucose-lactate levels in serum. The results obtained in this study suggest that the different diets did not negatively affect the welfare of the gilthead seabream in breeding, however they are not sufficient to conclusively demonstrate the influence of novel alternative diets on gilthead seabream broodstock, requiring further investigation.