Evaluation of Feed Quality and Supply to the Small-to-Medium-Scale Poultry Sector in Tanzania

Abstract

<p>Poultry performance is largely dependent on feed quality and supply. This thesis incorporated four studies, two based on survey instruments and two on feeding trials, conducted to evaluate feed quality and supply to the small-to-medium (SM) scale poultry sector in Tanzania. Trial interventions to improve the feed quality using Tanzanian replica diets were undertaken. A comprehensive literature review examined the role of poultry in Tanzanian society, the poultry production systems, broiler chicken nutritional requirements, common ingredients for commercial poultry feeds, common antinutritional factors affecting feed utilization and nutrient availability, and methods of improving feed quality and supply (Chapter 2). </p> <p>The findings of the survey carried out among SM-scale broiler farmers in Tanzania presented in Chapter 3 revealed the low production performance level of broiler chickens, attributable to poor feed quality and supply, high feed costs, the low market price of birds, and diseases. Chickens are sold at between five and six weeks, weighing about 1.6 kg, with an average profit margin of TZS 1 100.00 per bird. The analysis of the nutritive values of Tanzania-type chicken diets indicates that most of the diets from a variety of feed millers were low in crude protein, metabolizable energy (ME), and amino acids (Chapter 4). Eight diets were formulated at UNE, Australia, based on ingredients which are commonly used in Tanzania. The diets were formulated in pellet and mash forms, with or without microbial enzymes (Axtra XB and Quantum Blue), supplemented singly or in combination (Chapters 5 and 6). It was found that pelleted diets increased feed intake (FI) and body weight gain (BWG), and reduced feed conversion ratio (FCR). The addition of microbial enzymes, particularly in a combination of Axtra XB and Quantum Blue (phytase-containing product) also improved FI, BWG and FCR. The breasts, thighs, and drumsticks were heavier in birds fed the pelleted diets and were further improved with enzyme supplementation. Birds fed mash diets had heavier gizzard plus proventriculus, pancreas, and small intestine. </p> <p>Pelleted diets also increased the apparent metabolizable energy (AME), metabolizable energy intake (MEI), net energy of production (NEp), energy retained as protein (RE_p), and efficiency of ME use for energy and protein retention, while enzymes only improved the AME and RE_p (Chapter 6). Both pelleted diets and microbial enzyme supplementation increased the digestibility of gross energy, starch, protein, and fat. The digestibility of amino acids was higher in birds fed pellets, as well as with enzyme supplementation. In addition, the digestibility of minerals (Ca, P, K, S, Zn, and Fe) was higher in birds fed pelleted diets. The microbial enzyme, Quantum Blue (QB) increased the digestibility of P, K, and Zn while Ca and P digestibility was highest when a combination of Axtra XB+QB was added to diets. The ash content, weight, length, width, and breaking strength of the tibia bones were highest in birds fed pelleted diets. The microbial enzymes improved most bone traits, with the best results observed when a combination of QB and Axtra XB was added (Chapter 6). </p> <p>Cassava was evaluated as a substitute for maize in broiler diets (Chapter 7). Cassava meal was substituted for maize in four different proportions; namely, no cassava, low (25 %), medium (50 %) and high (75 %), supplemented with a cocktail of exogenous enzyme products, Rhonozyme (A and VP). High levels of cassava reduced BWG and increased FCR, which improved with the inclusion of enzymes. The dressing percentage (DP) and relative weight of drumsticks were reduced as the cassava level increased. Enzyme supplementation increased the DP, as well as absolute and relative breast, thigh and drumstick weight. The tibia ash content, weight, length, width, and bone strength decreased with higher levels of cassava but increased with the addition of the enzymes. The Ca, K, and Zn content of bones increased with higher levels of cassava, while P and Mg decreased. All mineral contents in the tibia bones improved with enzymes. Body fat and energy retained as fat (RE_f) decreased as the cassava level increased, while body protein and RE_p were unaffected by the cassava level. The inclusion of enzymes increased the body protein content and RE_p with a slight increase in body fat. In general, broiler performance was depressed by higher levels of cassava in the diets but was improved with microbial enzyme supplementation. </p> <p>The principal findings of this thesis confirm that the overall low performance of broiler chickens in Tanzania is linked to poor quality feeds and the high cost of ingredients. Most commercial feeds from Tanzanian producers exhibited low levels of the major nutrients and there was great variation in the feeds from different mills. Feed form also influenced the performance of broilers, with birds fed pelleted diets exhibiting superior performance to those on mash diets. Cassava meal can replace up to 50 % maize in broiler diets with no deleterious effects to bird performance. The application of the interventions tested in this study could benefit the Tanzanian poultry sector. </p>