Effects of Free and Conjugated Methionine on Growth, Meat Quality, Mineral Profile, and Shell Strength in Garden Snails (Cornu aspersum)

The present study examined the impact of adding methionine (Met) and its conjugated form (Met-Met) on <i>Cornu aspersum</i> snails. The primary focus was on the animals' growth performance, the chemical composition of their carcass (whole body without the shell), the mineral profile, and the mechanical properties of their shells. In two experiments conducted under controlled laboratory conditions, diets supplemented with varying levels of Met addition (0.3, 0.6, 1.4 g/kg feed) were used, and the effects of free methionine, Met-Met and their mixture (1.4 g/kg feed) were compared. The study incorporated measurements of body weight, shell width, and mortality of snails. Analyses encompassing protein, fat, sulphur amino acids, glutathione levels, oxidative stress indices (DPPH, TAC, TBARS), and macro- and micronutrient content of carcass and shells were conducted. The findings demonstrated that adding 1.4 g Met/kg feed significantly enhanced the shells' weight gain (+56% vs. Control), shell weight (+56%) and crushing force (+135%). Furthermore, an increase in the Met content of the carcass was observed (+18%), along with elevated carcass Ca (+28%) and P (+30%) and higher shell Ca (+12%) and Zn (+87%), alongside reduced carcass Fe (-38%) and Cu (-19%). In Experiment II, the Met-Met group exhibited the highest carcass weight (+16% vs. Control), the greatest carcass-to-body weight ratio, and the highest proportion of mature individuals (+27%). Moreover, Met-Met supplementation improved Cu absorption and retention in the carcass (+19%). Also, the results suggest that the conjugated form of methionine may improve Cu absorption and storage in the carcass (+19%). The study's findings indicate that methionine addition, especially in Met-Met form, can substantially impact the efficiency of <i>C. aspersum</i> farming, enhancing both the productivity outcomes and the quality of the product. That is particularly important in increasing the shell's mechanical resistance and the carcass's nutritional value.