## 4 Discussion  
The data demonstrate that PRSE had a positive effect on growth, survival, and feed conversion efficiency in juvenile black tiger shrimp. This effect on growth appeared to begin from a very early stage of the trial (from 0 to 35 days of feeding, 58 to 93 post-larvae (PL) shrimp), with shrimp mass differences between treatments decreasing over the following 35 days of feeding (35-70 days of feeding, 94 to 128 PL). However, the overall shrimp weight and length remained larger in all treatments with PRSE included. This suggests that shrimp fed the PRSE diets would be likely to reach their harvest weight quicker, improving the turnover of shrimp receiving dietary PRSE in a production scenario. One of the most significant findings of the trial was the improvement of FCR. This dose-dependent trend was observable at both the 35- and 70-day marks of the trial. In addition, improvements from the control diet were also observed at every dose of PRSE studied at both of these time points, with the most pronounced difference observed with the 6 g/kg dosage. Due to the FCR continuing to show a linear regression alongside the increasing inclusion of PRSE, it is possible that the optimal dosage for FCR improvement has not been reached in this trial. However, the improvement in FCR following a relatively  
Figure 3: (**a**) The expression of dcr1 and (**b**) the viral loads (viral copies/uL pleopod extract) of hepatopancreas parvovirus (HPV) and (**c**) gill-associated virus (GAV) in juvenile black tiger prawns fed diets with increasing levels of a polyphenol-rich extract derived from sugarcane (PPE) for 70 days. Horizontal lines indicate no relationship was present. The other prawn pathogens tested for—infectious hypodermal and hematopoietic necrosis virus (IHHNV), yellow head virus genotype 7 (YHV7) and genotype one (YHV1), white spot syndrome virus (WSSV), whenzhou uncharacterised prawn virus (When-2), and Vibrio parahaemolyticus (Pir-A)—were not detected. Data are mean \(\pm\) SEM, \(n=4\) (or 3 for the control group, as one replicate was lost), where the results for all animals were pooled for each tank. minor change in the feed formulation is a result that justifies further examination of the potential mechanisms contributing to this finding. The effect of PRSE on survival was one of the key findings of this trial. Over the first 35 days, there was no clear trend in survival due to amount of PRSE included in the diet. This may be due to interference derived from cannibalism and aggression between individuals in the early moulting phases. However, over the entire 70-day timeframe of the trial, there was a positive relationship between the levels of PRSE included in the diet and the increased rate of survival across the population. As a result of these significant differences in survival correlated with the intake of extract, it is expected that the total biomass yield would be further increased beyond the improvements to FCR and growth rate already discussed. It should be noted, however, that the test conditions of this study placed the animals in close proximity, which could have caused undue stress and likely impacted survival throughout the study. In fact, shrimp on a non-PRSE diet had a lower survival than seen in many feed additive trials (e.g., [37], although survival in experimental tank systems for feed trials can vary dramatically from study to study [38]. For a more substantial representation of the impact of PRSE on survival, this study should be replicated in a commercial rearing environment. This trial demonstrates that the inclusion of the PRSE sugarcane extract has a range of benefits, but it is difficult to hypothesise the exact mechanism that has produced these results and the molecular mechanisms need to be examined further. One of the main polyphenols identified in the sugarcane extract is chlorogenic acid. This phenolic acid has been included in shrimp diet formulations previously, with significant improvements to survival and FCR analogous to what was observed in the present trial [39].