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Availability of nutrients in vegetable protein supplements for the chick Nwokolo, Emmanuel R. N.

Abstract

Content and availability of nutrients in four vegetable protein supplements (palm kernel, soybean, cottonseed and rapeseed meals) were determined using growing chicks. Average availability of sixteen amino acids in these feedstuffs ranged from 84.5% (palm kernel meal) to 97.3% (soybean meal). Palm kernel meal was lowest and soybean meal highest in content of essential amino acids. Results of mineral availability (calcium, phosphorus, magnesium, manganese, zinc and copper) indicated high content and availability of calcium, phosphorus and magnesium; low content and availability of zinc and copper. Average availability of minerals varied from 50.0% (palm kernel meal) to 74.3% (soybean meal). Among mineral elements tested, phosphorus (78.0%) and calcium (72.6%) showed the highest availability while zinc (44.0%) was least available. Crude fibre and phytic acid were implicated as factors depressing availability of minerals tested. Crude fibre content was inversely related to availability of all six minerals tested while phytic acid content significantly (P^O.01) affected availability of phosphorus, calcium, zinc and magnesium. Metabolizable energy (ME) of the feedstuffs determined using three week old broiler chicks, ranged from 1957 kcal/kg dry matter (rapeseed meal) to 2796 kcal/kg dry matter (palm kernel meal). Chemical constituents, available carbohydrate and metabolizable energy content of seven different rapeseed meals were determined. Metabolizable energy values ranged from 1492 kcal/kg (Span A) to 1957 kcal/kg (commercial RSM). Of all chemical constituents tested, ether extract, sugar and starch content were most significantly (P«%0.01) related to metabolizable energy and were incorporated into equations to predict ME of rapeseed meal from their chemical constituents. Content and availability of six minerals (Ca, P, Mg, Mn, Zn, Cu) were determined using the test rapeseed meals. Samples were high in calcium, phosphorus and magnesium and low in copper in comparison to other vegetable protein supplements. Average availability of minerals ranged from 52.2% (Span A) to 64.0% (commercial RSM). Among minerals tested, phosphorus (75.3%), copper (74.3%) and calcium (68.0%) showed the highest availabilities. Zinc was least available (44.1%). Treatment of palm kernel meal with 3%, 5% or 7% NaOH in an attempt to delignify the material and improve its nutritive value, caused a reduction in protein, acid detergent fibre and acid detergent lignin content of the meal. There was considerable amino acid destruction, the extent being directly related to the severity of the alkali treatment. Incorporation of alkali-treated meal -at 30% level into broiler starter rations depressed growth rate and feed efficiency of chicks. Inclusion of palm kernel meal at 10%, 20% or 30% into a standard broiler starter diet significantly (P«»0.05) increased average daily gain of chicks over controls. Highest growth rate and feed efficiency were observed in chicks on the 10% PKM ration. Increased level of PKM incorporation slightly depressed feed efficiency but not growth rate of chicks. The need for increased utilization of vegetable protein supplements in chick rations especially in the developing countries was discussed.

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