Growth hormone transgenesis and feed composition influence growth and protein and amino acid content in transgenic G3 mutiara catfish (Clarias gariepinus)

Clarias gariepinus growth hormone (CgGH) transgenesis was previously used to develop a population of second-generation (G(2)) transgenic mutiara catfish (C. gariepinus). The third generation of these fish (1-month old fingerlings) had 2-3 times improvement in growth compared to non-transgenic fish in the commercial feed test for 6 weeks of rearing. We assessed the impact of CgGH transgene expression on growth and protein and amino acid content of the G(3) generation of these transgenic mutiara catfish relative to non-transgenic catfish. Since variation in composition of feed mixes can affect protein and amino acid content of fish, we tested three mixtures of commercial feed and boiled tuna (Euthynnus affinis): feed A (50:50 feed to tuna), B (65:35), and C (80:20) to transgenic catfish. Feed A* (50:50) was fed as a control to non-transgenic catfish. Feed efficiency, including feed conversion ratio and protein use efficiency (i.e., protein retention and protein productive value), was assessed. Feed efficiency, protein content, and essential amino acid content in G(3) transgenic catfish (feed A and B) were higher than in non-transgenic fish (feed A*). The latter were deficient in lysine and methionine. Transgenic catfish fed with feed C (80:20) showed lysine deficiency and lower growth than fish fed feeds A and B. Feed B (65:35) was the optimal feed mixture utilized; it increased growth, protein levels, and feed conversion efficiency in G(3) catfish. The growth of transgenic fish was higher than non-transgenic fish when supported by feeding with balanced nutrients.