Evaluation of rice milling by-products from Mwea irrigation Scheme in layer chicken diets

Abstract

Lack of affordable high quality feeds is one of the major constraints to the development of a vibrant poultry sub-sector in Kenya. Maize and its by-products have traditionally been used as the main energy sources in poultry feeds. Maize, however, is expensive because it is also staple food in diets of most Kenyan communities. It is therefore necessary to investigate new sources of energy as replacement for maize in poultry diets. Two experiments were done to determine the feeding value of rice milling by-products found at the Mwea Irrigation Scheme (MIS) in Kirinyaga district. The by-products evaluated were special coarse bran (SCB), fine bran (FB) and broken rice (BR). Specific objectives were to determine the nutrient composition of the by-products, assess the effect of feeding graded levels of the byproducts on layer chicken performance, and determine the optimal level of inclusion. A total of three hundred and eighty Isa-brown layer chicks were used for the two experiments: one hundred and sixty eight for the first and two hundred and twelve for the second. They were housed in battery cages located at the Poultry Unit in the University of Nairobi from the onset of lay to the end of the experimental period. In the first experiment, five diets containing graded levels of special coarse bran (SCB) (0 - 20% of diet) were formulated, while fine bran was fixed at 20 %. They were fed for sixteen weeks (21st to 36th weeks of age) during which performance data was collected and evaluated. Results of proximate analysis of the by-products showed that fine bran had higher levels of ether extract and crude protein than those of maize grain. Special coarse bran had high levels of crude fibre, while broken rice had a composition similar to that of maize. Over the sixteen- week experimental period, layer performance data showed that birds fed on diet containing 20% SCB had the highest feed intake (14.18 kg per bird) while those fed on the diet with no SCB, had the lowest (9.12 kg per bird). Feed intake hence increased with increasing levels of SCB in the diet. Trends in egg mass production closely followed those of feed consumption. Layers fed on the diet containing 20 % SCB produced 3.85 Kg egg mass per bird, which was significantly (P<0.05) higher than those produced by birds on maize soya bean meal control and diets with 15, 10, 5 and 0 % SCB (3.74, 3.75, 3.47, 3.19 and 3.18 Kg egg mass per bird respectively). The best feed conversion ratio (feed: egg mass) was observed in the layers fed on the maize soya bean meal control diet (2.81) while those on the diet containing 20% SCB had the poorest (3.68). Feed conversion ratio declined with increase in the level of SCB (2.86, 3.20, 3.46 and 3.57 for diets with 0, 5, 10 and 15 % SCB respectively) In Experiment 2, all three by-products were evaluated in an on-station and on-farm experiment. They were compared to a commercial layers mash diet and a formulated maize-soya bean control diet. Results showed that overall feed intake values for birds fed on diets containing 5 and 10% SCB (7.12 and 7.20 Kg/ bird respectively) were significantly (P < 0.05) higher than those of birds on the commercial layers mash and maize-soya bean diets. The higher feed intake for layers on rice- based diets positively influenced all the performance parameters up to 5 % SCB inclusion level, in the same manner explained in experiment 1. The economic analysis of the study showed that birds on the 20 % FB and 20 % SCB diet had a gross margin per bird that was higher by Ksh. 2 / bird than for those on the control diet. Gross margins for 5 and 10 % SCB diets were similar, but higher by more than Ksh. 39/ bird compared to the control diets. Overall, the rice based diets were well utilized and gave higher gross margins than the maize based control diets demonstrating good potential and affordability. The MIS rice by-products could therefore substitute for maize and its by- products in layer chicken diets up to 40 % when using FB and SCB and up to 65 % if additionally including BR