Water quality
The results revealed that water quality parameters w.r.t water temperature (33.23 to 33.48oC) ; DO (10.61 to 10.96 mg l
-1); pH (7.07 to 7.15); TA (151 to 155 CaCO
3 mg l
-1); NH
3-N (0.05-0.06 mg l
-1), NO
3--N (0.39 to 0.53 mg l
-1), NO
2--N (0.04 to 0.06 mg l
-1) and O-PO
43- (0.05-0.07 mg l
-1) did not vary significantly (Table 3) among treatments and control and were well within the acceptable levels required for normal growth and physiological activities of fish. Consistency and uniformity of water quality parameters among treatments revealed that the presence of acid in silage supplemented diets did not have any detrimental effect on water quality especially with respect to alkalinity and pH, which remained in optimum range for pangas catfish culture as described by Santhosh and Singh (2007) and Abedin
et al. (2017).
Fish survival and growth
Survival (%) of fish was significantly higher (p£0.05) in all the treatments as compared to control (93.33, 96.66 and 98.33% in D1, D2, D3; 100% in D4 and D5 and 96.66% in D6, respectively). Results revealed 100% fish survival in D4 and D5
i.e diets having no FM, but having combination of FS and plant protein sources. According to Kamei
et al (2018) survival of pangas varied from 93.33 to 96.19%, when fed with diets, in which FM was replaced with blended protein source consisting of one third each of FS, groundnut oil cake and soybean meal @ 25%, 50%, 75% and 100% level. Maximum survival of 96.19% was observed in diet, where 75% of FM was replaced with blended protein source. Datta
et al. (2018) reported poultry waste, FM, FS and soybean meal equally effective in terms of pangas survival (100% after 120 days of experiment). Significantly higher (p£0.05) fish growth in terms of FBW, NWG, SGR and PER was observed in D3 (21.33g, 19.00, 2.47 and 0.51). The differences for K and FCR were insignificant in all the treatments and control, however minimum value for FCR was observed in D3 (2.02) and maximum (3.08) in control D1 (Table 4). The findings of the present study are in line with results of previous study by Salah al-Din (1995), where inclusion of FS improved growth performance of catfish (
Clarias lazera). Fagbenro and Jauncey (1994), also reported fermented fish-silage co-dried with protein feedstuffs as suitable protein supplement in case of juvenile catfish (
C. gariepinus), which can provide up to 50% of dietary protein without affecting feed efficiency, fish growth or health. Better growth rate of fish fed with acid silage may be due to the presence of comparatively higher amount of free amino acids and active hydrolytic enzymes, released by the action of acid.
Soltan and Tharwat (2006) in their study found that dried fish by-products silage can successfully replace up to 25 and 50% of fishmeal (FM) in tilapia and catfish diets without any negative effects on BW, WG and SGR, while the higher incorporation levels (50, 75 or 100%) significantly reduced the final BW for both the species. Fagbenro and Bello-Olusoji (1997) and
Plascencia-Jatomea et al., (2002) also revealed best FCR and PER in Nile tilapia fry fed with diets containing 0, 10 and 15% of shrimp head silage as a replacement to FM and higher FCR was obtained by the higher replacing levels (20, 25 and 30%). On the other hand,
Wassef et al., (2003) found that, partial or total replacement of FM by fermented FS alone or mixed with soybean meal did not significantly affected FCR and PER. Similarly, no significant differences in the weight gain, SGR, % survival and FCR were observed in
L. rohita fingerlings by the dietary intake of acid ensilage @ 2.5, 5 and 10%
(Tanuja et al., 2017).
Haematological parameters
Significantly higher (P£0.05) Hb (g %) and Ht (%) were recorded in all treatments as compared to control with maximum values of Hb and Ht (Fig 1) in D4 (8.00 and 20.00). Hb and Ht are important indicators of fish health. Hb is the protein contained in the red blood cells and is responsible for supplying oxygen to the tissue and for continuous supply of oxygen, sufficient Hb level should be maintained. An appropriate quantity and quality of protein is to be maintained for keeping these parameters at a level required for optimized fish growth (Datta
et al. 2018 and Khan
et al. 2018). The results of the present study depict positive impact of FS supplementation on fish in terms of higher Hb and Ht may be due to its ability to stimulate blood formation (Habte-Tsion
et al 2013, Yones and Metwalli 2015). Further, according to Hedayati and Tarkhani (2014), 7.17 g % of Hb indicate good health of
P. hypophthalmus and the values for Hb remained above 6.0 g % in all the treatments during the present study.
Biochemical parameters and lipid profile
Results obtained from the present study showed that the fish fed on experimental diets had significantly (P£0.05) higher total protein, albumin and globulin (g dl
-1) as compared to control fed fish (D1) with highest values in D4 (4.32, 1.20 and 3.33) and lowest in D6 (2.47, 0.68 and 1.79). Alb/Glb ratio was significantly higher in D3 (0.58), however, the differences were insignificant among other treatments and control, except D5 (Fig 2). The results in terms of serum biochemical parameters improved in all silage treatments and remained at par or deteriorated as compared to control and are in line with hematological parameters showing maximum values in D4 (Fig 2). The increase in serum protein, albumin, globulin and Alb/glb ratio are considered to be associated with a strong immune response of fish
(Wiegertjes et al., 1996) coupled with improved haematological parameters resulting from enhanced nutritional status of fish. Similar observations were recorded by Salah
et al (2014), who reported a significant (P£0.05) increase in total protein and albumin levels in common carp,
Cyprinus carpio where FM was replaced with fish bio silage at different levels (0, 25, 50 or 75%). The concentration of serum biochemical constituents (total protein, albumen, globulin, cholesterol, triglyceride, alkaline phosphatase, urea and creatinine concentration) did not vary significantly with dietary inclusion of acid ensiled fish waste silage @ 3,6 and 12% by replacing FM in Japanese quail
(Tanuja et al., 2018).
Lipid profile in terms of Cholesterol (mg dl
-1) and Triglycerides (mg dl
-1) showed an increase an all the experimental diets (Fig 3) as compared to control with highest values in D3 (366.53 and 56.00) and lowest in D1 (16.00) and D6 (193.20) respectively. Whereas, HDL (mg dl
-1) were found to be significantly higher in D1 (53.00) as compared to all the experimental diets with minimum values in D6 (10.30), whereas LDL and VLDL were found to be higher in all the treatments as compared to control with maximum values in D3 (110.00 and 11.32 mg dl-1). Improved triglycerides and cholesterol can be co-related with better health status of fish resulting in improved survival and growth. Low concentration of plasma triglycerides usually corresponds to poor lipid reserves (Wagner and Congleton, 2004), while elevated triglycerides may be due to an imbalanced diet
(Lemaire et al., 1991). Goda et al., (2007) too reported higher body lipid content for African catfish,
C. gariepinus, fed with diets containing either poultry by-product meal (75%) or soybean meal (100%), as observed in present study. These results are also in agreement with the results of Gouveia (1992), who reported an increase of body lipid with the inclusion of poultry by-product in diets of rainbow trout,
O. mykiss. Likewise, the serum triglyceride concentration increased significantly (P£0.05) with 10% inclusion level of fish silage in broiler chicken
(Boitai et al., 2018).
Antioxidant parameters
SOD (U mgl
-1 Hb) and LPO (nmol MDAg Hb
-1) was found to be significantly higher (P£0.05) in D1 (0.74 and 1.38), with minimum values of SOD in D6 (0.10) and LPO in D2 and D5 (0.44) (Fig 4). SOD and LPO are considered as indicators of immune status of any organism. The findings of the present study are in line with Lin and Lou (2011), who studied effects of inclusion of soybean meal at 0, 25, 50, 75 and 100% levels in replacement for FM in practical diets for juvenile tilapia,
O. niloticus ×
O. aureus. Results indicated that SOD activity decreased as compared to control, when the substitution level was more than 50%. Similar observations were recorded by
Gui et al., (2010) who reported a decreased antioxidant activity in crucian carp (
Carassius auratus gibelio), when fed with different dietary levels (0, 10, 50 and 100g kg
-1) of cottonseed meal protein. Qi-you
et al. (2008) too reported similar observations while studying effects of partial replacement of FM with soy protein isolated and meat bone meal (30%, 20% and 10%) on growth and non-specific immunity in rainbow trout (
O. mykiss).