JWSS - Journal of Water and Soil Science

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This experiment was conducted to determine the requirements of vitamin supplement and available phosphorus in broiler chickens from 42 to 56 days of age. In a completely randomized design, with a 3×3×3 factorial arrangement, 270 one-day-old commercial broiler chicks were divided into 27 groups (replicates) with 9 treatments, 3 replicates and 10 chicks in each group. Each of the nine diets was given to each treatment from 42 days of age. Levels of vitamin supplement were 0.5, 0.25, 0% and available phosphorus levels were 0.27, 0.22, 0.16%. Diets were isocaloric and isoprotein. Group weight and feed consumption of each replicate were determined after 42 and 56 days of age and daily gain, daily feed consumption and feed conversion were calculated. Percent of carcass components and tibia ash were determined.

Results indicated that removal of vitamin supplement from 42 to 56 days of age did not have any significant effects on daily gain, daily feed consumption, feed conversion, live weight, viscera, abdominal fat, carcass weight, wings, neck and back bone. Also, reduction of available phosphorus did not have any significant effect on daily feed consumption, feed conversion, live weight, viscera, abdominal fat, carcass weight, breast meat, femurs, wings, neck and tibia ash. Interaction between vitamin and phosphorus were significant for daily gain, daily feed consumption, live weight, wings, neck and tibia ash (P<0.005) and were highly significant for breast meat, femurs, and back bone (P<0.00l).

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Because of slight variation of the static head due to discharge fluctuations, the labyrinth weirs are considered to be economical structures for flood control and water level regulation in irrigation networks, as compared to other devices. Labyrinth weirs are composed of folded sections observed as trapezoidal and triangular in plan view. In this study, rectangular and U-shaped labyrinth weirs were investigated. Experiments were conducted on 15 labyrinth weir models. The models included eight rectangular labyrinth models and six U-shaped labyrinth models with different heights and lengths, and one linear model. All the experiments were performed in a horizontal rectangular flume, 7 m long, 0.32 m wide and 0.35 m high. The results indicated that for all the models, discharge coefficient increased sharply with an increase in Ht/P and attained a maximum value. This coefficient then decreased smoothly with a further increase in Ht/P. Increasing height of weirs increased the discharge coefficient for both rectangular and U-shaped weirs. The results also showed that increasing the length parallel to the flow direction decreased and increasing the length perpendicular to the flow direction increased the discharge coefficient. Generally, the discharge coefficient for rectangular weir was less than that of the U-shaped weir. The obtained results compared with those of Tullis et al. (1995) showed that discharge coefficient for U-shaped weir is more and for rectangular weir is less than that of the trapezoidal weir for angle of the side legs of 8 and 12 degrees.