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The feeding value of Kenyan sorghum, sunflower seed cake and sesame seed cake for poultry Jacob, Jacqueline P.

Abstract

The availability of affordable, quality feed has been a limiting factor in the development of the Kenyan poultry industry. Kenya already has an established feed industry, but feed production has been limited by the availability of suitable feedstuffs. The potential of Kenyan sorghum, sunflower seed cake (SFC) and sesame seedcake (SSC) as feed ingredients in poultry diets was evaluated at the University of Nairobi, Kenya. A survey of Kenyan sorghum revealed a large variation in the composition of the grains grown. Local sorghum varieties tended to have very high tannin content (up to 13.8% of dry matter) and would most likely be unsuitable for inclusion at high levels in poultry diets. Two of the improved sorghum varieties (Serena and Seredo) had tannin levels of less than 5% and may be suitable energy sources in poultry feeds. Serena was the improved sorghum variety most readily available for purchase in large quantities and was the brown sorghum variety used in all feed trials. A survey of locally produced SFC revealed a large variation in the composition of the cakes available. The main factor limiting the use of SFC in poultry diets is its high fibre content. The crude fibre content of the SFC samples analyzed varied from 24.1 to 40.2% of dry matter. The average composition of the SFC samples, on a dry matter basis, was 29.8% crude protein, 12.5% ether extract, 30.8% crude fibre, 7.2% ash and 19.7% nitrogen-free extract but, because of the wide variation in composition of the cakes, the use of average values for diet formulation could lead to substandard feeds. Locally produced SSC appeared to have less variation in its composition than the locally produced SFC. Excluding one sample which had a very high ether extract and crude fibre content, the average composition of the SSC samples, on a dry matter basis, was 49.8% crude protein, 11.1% ether extract, 9.8% crude fibre, 14.2% ash, and 21.8% nitrogen-free extract. From the results of this study it was concluded that the composition of Kenyan sorghum, SFC and SSC is very different from that of similar products produced in North America or Europe. The use of North American or European tables of composition for diet formulation, therefore, is not recommended. A preliminary study involving two four-week feeding trials investigated the possibility of overcoming any detrimental effects of sorghum tannin on growth or feed efficiency by supplementing the diet with intact protein or with D,L-methionine. In both trials, however, Serena sorghum (tannin content of 2.0-2.2% catechin equivalents) was substituted for white maize with no effect on final body weight or feed conversion ratio (FCR). The feeding values of Kenyan Serena sorghum, SFC and SSC were studied in an eight week broiler trial and a twenty-four week layer trial. Substituting Serena sorghum for white maize in the diets reduced growth for broilers and egg production for layers. The reduction in feed costs associated with the Serena sorghum diets was not sufficient to compensate for the reduction in body weight or egg production so that, based on December 1992prices, it was not economical to substitute Serena sorghum for maize in broiler or layer diets. Serena sorghum would be an economical substitute for white maize in broiler diets if the price of sorghum was reduced 16.7-26.8%.A 6.3-21.6% reduction in the price of sorghum is required to make it an economical substitute for white maize inlayer diets. The level of the price reduction required is dependent upon the main protein source of the diet. Substituting a portion of the imported soybean meal (SBM) in the diet with locally produced SFC had no effect on final body weight for broilers, but resulted in significantly lower egg production for layers. Based on December 1992 prices, the SFC/SBM broiler diets were more economical than the SBM broiler diets. A 300%increase in the price of SFC is required before it would no longer be economical to replace 30% of the imported SBM of broiler diets with local SFC. The reduction in feed costs associated with the SFC/SBM layer diets was not sufficient to compensate for the reduction in egg production. The price of SFC would have to be almost zero before the SFC/SBM maize diets would be economically competitive with the SBM maize diets. Even if SFC was available at no charge, the SFC/SBM sorghum diets would not be economically competitive with the SBM sorghum diets. Substituting locally produced SSC for imported SBM in the diet resulted in a significantly higher final bodyweight for broilers, but significantly lower egg production for layers. Based on December 1992 prices, SSC was an economical substitute for imported SBM in the broiler, but not the layer, diets. A 240-250% increase in the price of SSC, is required before SSC would no longer be an economical substitute for imported SBM in broiler diets. A slight reduction in the price of SSC or an increase in the price of SBM would make SSC an economical substitute for imported SBM in layer diets. Based on the results of this study Kenyan Serena sorghum appears to be a suitable substitute for maize in both broiler and layer diets but further research is required to determine the maximum concentration of sorghum tannin that can be included in the diet without adversely affecting production. Locally produced SFC and SSC appear to be suitable substitutes for imported SBM in broiler but not layer diets. Further research is required into the cause of the depressed egg production for the SFC/SBM and SSC layer diets.

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