Dietary Formic Acid and Vitamin D3 as Growth Effective Supplement for Grass Carp Fingerlings

The study was carried out at Fisheries Research Farm, University of Agriculture, Faisalabad. Four earthen ponds, each having dimensions 19m×6m×1.5 m were selected and fixed with fine mesh to avoid any unwanted animals to enter the ponds. The ponds were filled with tube well water. Ctenopharyngodon idella (grass carp) (n=25) were stocked after measuring their weight and length in each experimental pond on 1st May 2016. Mixture of inorganic fertilizers that is urea and single superphosphate (1:1), was added in each pond on weekly basis for one month prior to fish stocking. The fish were fed with the fish feed 2% body weight of fishes twice a day. The water level of ponds was maintained throughout the study period. The sampling was done on fortnightly basis and feed ratio was adjusted accordingly. The fish were finally harvested and measured after 90 days feeding period of 1st August 2016.

For feed formulation four experimental diets (FD1, FD2, FD3 and FD4) were prepared that contained formic acid (%) and vitamin D3 (IU/Kg) at following proportion 0, 0; 2, 0; 0, 5000 and 2, 5000, respectively. The duration of experiment was three months. For experimental diet formulations, cereal grinding machine (FFC-45, JIMO, China) was used for grinding and sieving of (0.05 mm) the diet ingredients. The minerals mixed fish oil and vitamins were added after grinding of ingredients. Approperiate amount of water was used for pellet formation. Experimental extruder (Model SYSLG30-IV) was used for the prepration of pellets (3.5 mm), which were dried upto 10% moisture and packed in plastic bags and stored at 20°C during the entire feeding experiment.

Growth performance was assessed on fortnightly basis from each pond in terms of weight gain by the fish. At the end of feeding trial eight fish were starved for a day and dipped in clove oil (3000 mg/L) for 40-60sec to anesthetise (Khajepour et al., 2012). Fish was sacrificed by a sharp blow on head. For proximate analysis standard method of AOAC (1995) were followed to determined moisture at 105oC for 12 h in micro Kjeldahl apparatus used for the determination of crude protein (N x 6.25), Crude fat was estimated by petroleum ether extraction method (Soxtec system HT2 1045) and ash content were measured in electric furnace (Eyela-TMF 3100) by ignition at 650oC for 12 h to constant weight.

The data was analyzed by Two-way ANOVA under RCBD was applied on resulted data (Steel et al., 1996). For the comparison of means Student-Newman-Keuls test was used, when significant differences occurred (Snedecor and Cochran, 1991). For analyzing statistical data CoStat computer package (Version 6.303, PMB320 Monterey, CA 93940, USA) was used.

Weight gain and specific growth rate (SGR) were calculated as:

Table I shows growth performance of fish. All growth parameters were significantly improved by feeding formic acid and vitamin D3 supplemented diet. Muscle proximate analysis is given in Table II. Result showed that C. idella fed with vitamin D3 increased the crude protein (18.30±0.01), ash (2.43±0.02) and decreased the fat (3.84±0.02) contents while same results were observed by supplementation of formic acid for crude protein (18.20±0.02) and ash (2.18±0.02) contents.

The growth rate increased with acidification, because acids increase the mineral availability and their utilization in body. The Organic acids reduce the gastic pH, which improves the activity of many metabolic enzymes leading to improve growth rate (DeWet, 2005; Park et al., 2009). Similarly, Hossain et al. (2007) reported the higher growth rate of pagrus major with the supplementation of citric acid which results in the higher mineral dissociation and forms chelated mineral complexes that are easily absorbed in body. Moreover, organic acid lowers the gastric emptying rate. Present research work showed that supplementation vitamin D3 significantly increased growth rate which may owe to increase utilization of phosphorous. Because of phosphorous utilization Ling-Hong et al. (2015). Similar results were also reported by Ling-Hong et al. (2015) that supplementation of vitamin D increased the growth rate in Wuchang bream. A similar increase in weight gain % of rain bow trout was observed by feeding vitamin D (Coloso et al., 2001).

Values sharing similar letters in a column are non-significant at P<0.05. FA, formic acid; VD3, Vitamin D3, FD, FA+VD3; WG, weight gain; SGR, specific growth rate.

Values sharing similar letters in a column are non-significant at P<0.05. For aabbreviations, see Table 1.

In present study crude protein, crude fat and ash content of muscle were affected by supplementation of vitamin D3 and formic acid. A similar decrease in the lipid content in the muscle of fish were observed by citric acid supplementation, however the yet action is unknown Khajepour et al. (2012). In present research work the effect of vitamin D3 supplementation showed not significant effect on moisture content in muscle of Ctenopharyngodon idella. Similar results were observed by Ling-Hong et al. (2015) who said that addition of vitamin D3 did not affect the moisture content in the muscle of fish while lipid contents, crude protein and ash contents were significantly affected. Moisture is not sensitive indices of dietary vitamin D3. Supplementation of vitamin D in fish diet had non-significant effects on crude lipid in grass carp. This indicated that deficiency of vitamin D in fish body and also decreases the bioavailability of lipids (Jiang et al., 2009).

In conclusion, dietary formic acid and vitamin D3 improves the growth performance and muscle proximate analysis in the Ctenopharyngodon idella fingerlings.

The authors declare no conflict of interest.