## 1 Introduction  
The giant river prawn (_Macrobrachium rosenbergii_) is among the most important freshwater crustaceans in global aquaculture due to its high commercial value and favorable production performance [1]. Its appeal lies in several biological and zootechnical advantages, including high fertility, adaptability to a wide range of environmental conditions, tolerance to fluctuations in water quality, and rapid growth rates [2,3]. In 2020, the global production of _M. rosenbergii_ reached approximately 294,000 tons, making a significant contribution to total crustacean aquaculture output [4]. This tropical species has gained increasing attention not only for its market demand but also for its potential role in developing more sustainable aquaculture systems [5].  
In recent years, considerable research efforts have been devoted to improving productivity and profitability in _M. rosenbergii_ farming. Strategies have included the use of growth enhancers, dietary immunostimulants [6,7], and the dietary inclusion of alternative protein sources to reduce reliance on fishmeal, a limited and costly marine-derived resource [8,9]. Among these alternatives, hydrolyzed animal proteins have shown encouraging results across multiple crustacean species. For example, in Pacific white shrimp (_Peneus vannamei_), dietary replacement of fishmeal with poultry by-products and swine liver hydrolyses (up to 25%) improved growth performance, feed conversion ratio, and nutrient retention [10], while also modulating the intestinal microbiota by decreasing the relative abundance of Vibrionaceae [11]. Furthermore, the inclusion of protein hydrolyses--such as hydrolyzed feather meal--at 6% maintained growth, digestive enzyme activity, health status, and body composition in _P. vannamei_ during both nursery and grow-out phases [12,13].  
Hydrolyzed feather meal (HFM) has emerged as a promising candidate among animal protein hydrolyses due to its high protein content and potential to support circular economy principles. For instance, the current global market of feather meal is USD 619.1 million [14], and the European annual production of feather meal is approximately 175,000 tons [15]. In terms of current market price, HFM trades for USD 661.8 metric ton\({}^{-1}\), which is substantially cheaper than fishmeal (USD 1788.4 metric ton\({}^{-1}\)) [16].  
Derived from poultry industry by-products, HFM offers a sustainable mean of reducing aquaculture dependence on marine protein sources. Prior studies have demonstrated the feasibility of partially replacing fishmeal with HFM in diets for _P. vannamei_[17,18] and _Penaeus mondon_[19] without compromising growth performance. However, HFM digestibility can be lower than that of fishmeal, potentially due to the presence of disulfide keratin structures [20,21]. Then, HFM may present low methionine content and the potential accumulation of undesirable residues if not properly processed [20,22].  
The use of HFM in freshwater crustacean diets remains underexplored. While limited work has been conducted on juvenile white shrimp [13,23] and juvenile longer river prawn [24], no studies to date have evaluated the use of HFM in _M. rosenbergii_, particularly during early developmental stages. Therefore, the present study aims to investigate the effects of increasing dietary inclusion levels (0 to 6%) of hydrolyzed feather meal as a partial replacement for fishmeal on the growth performance, digestive enzyme activity, and antioxidant status of _M. rosenbergii_ post-larvae during the nursery phase.