Impact of size disparity on growth performance, digestive metabolism, and antioxidant capacity of Macrobrachium rosenbergii under mixed culture conditions
摘要
In the aquaculture of Macrobrachium rosenbergii, size disparity among individuals is frequently observed, and these differences tend to become more pronounced as the culture cycle progresses. The present study aimed to investigate the effects of size disparity on the growth performance and physiological responses of M. rosenbergii. Prawns of differing initial sizes (4, 5, 6, and 7 cm) were cultured together under controlled mixed conditions for 30 days. The results demonstrated notable differences in the growth performance of mixed-cultured prawns of different sizes (P < 0.05). With increasing size disparity in the mixed culture, the growth rate of body length, body weight, specific growth rate, and survival rate of M. rosenbergii measuring 4 cm and 5 cm declined significantly (P < 0.05). Conversely, prawns measuring 6 cm and 7 cm exhibited a marked increase in these growth parameters under the same conditions. In the mixed-culture groups, prawns measuring 4 cm and 5 cm exhibited reduced levels of digestive enzymes (trypsin, amylase, and lipase), metabolic enzymes (lactate dehydrogenase), calcineurin, and acid phosphatase activities, as well as lower gene expression, compared to prawns in the monoculture groups (I4 and I5). In contrast, prawns measuring 6 cm and 7 cm in the mixed culture demonstrated higher enzyme activities and gene expression levels than those of the same size in the monoculture groups (I6 and I7). As the size disparity within the mixed culture increased, catalase activity and gene expression levels initially increased, then decreased. The results of this study indicate that as the size disparity in mixed cultures increases, the larger, dominant prawns negatively affect the growth, digestive processes, and immune system of the smaller prawns.