JWSS - Journal of Water and Soil Science

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The present experiment evaluates the effects of some carbohydrate sources (corn, barley and millet) and the replacement of corn with different levels (0, 25, 50, 75, 100%) of barley and millet on the performance of common carp (Cyprinus carpio L.). In a completely randomized block design, 540 grower fish with an average body weight of 70 gr, were divided into 27 groups, 20 fish per group. Nine different diets were used and each diet was assigned to triplicate groups of fish for eight weeks.

Analyses of data showed that the replacement of corn by barley and millet resulted in a higher weight gain. The highest and lowest weight gains were observed with diets having 50 percent barley and 100 percent millet substitutions, respectively, although the differences with the control diet were not significant. Diets with 50 and 100 percent barley for corn substitutions showed a greater specific growth rate (SGR). As for the food conversion ratio (FCR), all the diets having barley and millet, irrespective of substitution levels, showed a better FCR relative to the control diet. However, the diet with 100 percent barley substitution had the best FCR, but no significant differences were observed (P>0.05) with the control diet. In general, the performance of barley was better than that of corn and millet, and millet was relatively better than corn. However, these results indicate that barley and millet can be suitable replacements for imported corn in diets used for common carp.

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The objectives of this study include the determination of the growth potential of Naeini lambs when fed with diets varying in energy and protein concentrations and also an investigation of the influence of level of energy and/or protein intake on carcass characteristics and composition. Ninety Naeini weather lambs (initial live weight 29.89 ± 2.9 kg) were used in a 92-day feeding experiment. Animals were blocked to each of nine dietary treatments. Diets contained either 2, 2.25 or 2.5 Mcal ME/Kg DM and 11.7, 13.2 or 14.7% CP diets were fed in a 3 × 3 factorial arrangement in randomized complete blocks.

Lambs fed with high energy diets consumed significantly more feed (P<0.05) than lambs given the medium (ME) or low energy (LE) diets. The average final body weight and daily weight gain for lambs fed with HE, ME and LE diets were 41.4, 38.3, 34.5 Kg and 162, 124, 74 g/d, respectively, which were significantly different (P<0.05). Feed conversion ratio in HE group was significantly lower (8.3) than ME (10.4) or LE (14.3) groups. Energetic efficiencies and protein efficiencies were better for HE than for ME and LE diets. Increasing dietary energy significantly (P<0.05) improved energy and protein efficiencies of the diets. Dressing percentage, lean meat and eye muscle depth were significantly (P<0.05) improved with increasing levels of energy in the diet, but also increased dissectible fat. No significant changes were observed in bone percentage and body ash due to any changes in dietary energy. As the protein level of rations increased, feed conversion ratio and carcass meat percentage increased, but carcass protein percentage decreased.

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The present experiment evaluated the effects of fat (Kilka fish oil) levels (0, 5, 10, 15 and 20%) in the diet (35% constant protein) on performance of rainbow trout. The experiment was performed in a completely randomized design, with 4 replicates, 200 grower fish with an average weight of 200±11 gr, each. They were randomly divided into 20 groups of 10 fish per group reared in separate pens. Fish were acclimated to the experimental conditions for 10 days before treatments began and then the experiment was performed over a period of 8 weeks. Measured criteria were weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), condition factor (CF) and flesh chemical composition (fat, protein, ash), and fat stored in liver. Results showed that the diet with 15 percent fat content had significantly (P<0.05) better WG and FCR than other diets, but no significant differences were observed for SGR and CF. Diets with 15 and 20 percent fat contents caused the highest fat content in meat and liver and showed significant differences (P<0.05) with the meat and liver fat content in fish fed fat-free diets. Diet with 15 percent fat content caused significantly (P<0.05) lowest protein content in meat. No significant differences were observed in the ash content of the flesh. From the results of the present study, the level of 15 percent Kilka fish oil is recommended for the rainbow trout diet.

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In order to study the effects of L-carnitine on performance and some blood biochemical parameters of rainbow trout, the present experiment was conducted with 144 fish (130±5 g) for 8 weeks. In a completely randomized design, the experimental fish were divided into 9 groups with 3 treatments and 3 replicates and 16 fish in each group. Levels of L-carnitine supplements were 0 (control), 1 and 2 g per kg of diet. Results indicated that specific growth rate (SGR), total body weight, weight gain and protein efficiency ratio (PER) were significantly increased by 1g/kg L-carnitine supplements (P<0.05). L-Carnitine also improved feed conversion ratio (FCR) of fish. Crude protein of fish fillet was increased, but its crude fat was reduced at 1g/kg L-carnitine treatment. Similarly, cholesterol, total protein, albumin and globulin of fish blood serum were significantly (P<0.05) increased by the same levels of L-carnitine in the diet, however, blood glucose level remained unchanged. L-Carnitine reduced visceral fat index and increased hepatosomatic index. In conclusion, the results of the present study indicated that the addition of 1g L-carnitine per kg of diet could improve the performance of rainbow trout at grower stage.