PhD Theses

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Browsing PhD Theses by Subject "Food (chemical technology)"

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    Improvement of the nutritive value of maize cob using Sodium Hydroxide
    (University of Dar es Salaam, 1978) Kategile, Jackson Augusto
    The factors that influence the extent of in vivo digestibility and voluntary feed intake of NaOH treated maize cobs based diets were examined. The standard procedure of Na0H treatment was to mix the coarsely ground maize cob with Na0H solution and then allow it to react for 24 hours after which the maize cobs were dried in the sun or in the room. The dried maize cob was mixed with other ingredients prior to feeding caged sheep and the maize cob formed 50 to 85% of the rations. Na0H treatment is expressed as % to mean kg Na0H per 100 kg dry matter of maize cob. Na0H treatment rates ranged from 0 to 10% and resulted in significant increases in in vivo digestibility of dry matter (DM), organic matter (OM), cell wall constituents (CWC) and crude fibre (CF). The linear increases were obtained up to 5.0% NaOH treatment beyond which no further responses were obtained. A regression equation y =51 .57 + 2.28 x in which y = in vivo DM digestion of ration and x = % Na0H treatment rate (from 0 to 5%) was calculated with typical results. Similarly the voluntary feed intake followed the same trend and the values for g DM intake per W kg .75 were 60.5, 83.3, 95.7 and 96.0 for the control, 2.5 %, 5.0% and 7.5% in the order of increasing NaOH treatment rates in one experiment. The total digestible DM,OM, and energy was more correlated to voluntary feed intake than digestibility coefficients indicating the significance of improved feed intake by NaOH treatment. The volume of Na0H solution was varied from 25 to 200 1 per 100 kg DM of maize cob and the DM, OM, and CWC digestibilities were not affected by this factor, except the 25 1 volume which resulted in depressed digestion indicating the difficulty of getting effective mixing with small volumes. The incorporation of nitrogen in the form of urea at 0 0.5, 1.0 and 1.5% in the rations was beneficial in improving the digestion of DM, OM, and CWC and regression equations y1= 35•9 + 19.0 x, y2= 39.6 + 16.8 x and y3=24.8 + 21.6 x for y1 =DM digestion %, y2 = OM digestion % and y1= CWC digestion %, and x = urea incorporation in the diet. In one experiment molasses as a source of readily available carbohydrates was incorporated at 20% in maize cob based diet and in three other diets the molasses was completely replaced by cassava flour maize meal or maize bran. The replacement of molasses was detrimental on bath digestibility coefficients and voluntary feed intake, demonstrating the incompatibility of maize cob with high starch containing feedstuffs. The knowledge gained in the digestibility and voluntary feed intake experiments was used in formulating complete rations for a 63 days experiment involving 9 - 15 month old growing dairy heifers. Six animals per treatment group were assigned to a 0% NaOH or a 5% NaOH treated maize cob diet of sorghum silage. The voluntary feed intakes were 103 g and 119 g DM/ W kg .75 for the control and NaOH treated groups respectively. The growth rate was significantly (P < 0. 01) improved from 0. 412 to 0. 585 kg per day and the DM consumed per unit gain was reduced from 13.0 to 11.5 kg with NaOH treatment. In spite of the high concentration of sodium in the diet at 1.40 % on a DM basis in the treated group the animall were healthy. The sorghum silage group lost weight due to low quality characteristics of the silage and subsequent low feed intake. From this study it is evident that it is feasible to improve the nutritive value of maize cob by having the right conditions of NaOH treatment rate, volume of NaOH solution and feeding the treated maize together with molasses and adequate protein