Impact of low-cost diets on maturation of the red claw crayfish Cherax quadricarinatus: An integrative approach during a long-term study

The onset of sexual maturity represents a complex step in animal life involving morphological, physiological, and behavioral changes. From this point onward, the energy income from food will be involved in three energetic-demanding-competing processes: metabolism-homeostasis, growth, and reproduction. Hence, in cultured species formulated feeds need to cover all nutritional requirements of the growing phase and the additional cost demanded by reproduction. Two low-cost diets, AD1: 0.56 and 2 CE: 0.64 U$S kg−1 manufactured with local supplies specifically formulated for Cherax quadricarinatus, were evaluated in a prolonged assay with females at the transition from juvenile to mature. Protein content was 440,2 and 380 g kg−1 and lipid content was 134,8 and 114,9 g kg−1 for AD1 and AD2, respectively. Females were obtained in the laboratory from our reproductive stock and were fed daily at 1.5% of their weight/day. The female mean initial total length was 6.5 ± 0.6 cm and mean body mass was 6.8 ± 0.7 g, which represents juveniles at the beginning of vitellogenesis. The experiment ended after three molting events when females achieved the full mature condition (⁓16–20 g). Somatic indices, growth, feed efficiency, biochemical composition of the ovary and hepatopancreas, ovarian growth, and histological alterations in hepatopancreas were analyzed. Both diets demonstrated that the high demands of both somatic and ovarian growth in maturating females were not covered, contrasting with previous results in early juveniles. This highlights the enormous energetic cost of vitellogenesis at the start of sexual maturity and the differential nutrients demand during crayfish growth. Biochemical analysis demonstrated a lower oocyte quality due to the experimental diets, as well as decreased reserves both of lipids and carbohydrates and a possible impact on carotenoids content. The hepatopancreas also showed partial histological damage and differences in its biochemical content. Although further analysis is required, lower embryo survival, hatching rate, and early performance of juveniles are expected in progeny from females fed with both diets. The low-cost diets tested are useful as a baseline from which modified formulations can be considered to achieve a more adequate composition enhancing somatic and gonad growth as well as feed efficiency in maturing females