Nutritive value and evaluation of appropriate feeding strategies of grain sorghum varieties for poultry in Tanzania

PhD Thesis

In Tanzania, maize scarcity, high cost and competitiveness between humans and other livestock has necessitated the search for alternative energy sources for poultry. In view of this, four studies on the assessment of the suitability of commercially available Tanzanian grain sorghum varieties (GSV) for poultry and evaluation of appropriate feeding strategies of diets containing GSV were conducted. In the first study, a cross section survey was conducted in selected food markets of Singida, Dodoma and Morogoro regions to identify types of available commercial GSV whereas in the second study, assessment of nutritive values of identified GSV was carried out. In the third and fourth study, two feeding experiments to evaluate the effectiveness of using final sugar molasses (SCM) and Moringa oleifera leaf meal (MOLM) as additive in GSV based diets on performance of growing chicks and layer chickens and egg quality characteristics and consumers’ preferences were carried out. Semi-structured questionnaire and personal observation guided by checklist were used to collect information on type, identity and source of GSV. The identified GSV were analyzed for proximate and anti-nutritional components, minerals, some amino acids, metabolizable energy (MEn) and starch using standard procedures in the second study. GSV collected from local food markets, were ground and packed in nylon bags for use in the feeding experiments. Fresh Moringa leaves were harvested dried under the shed, ground through hammer mill to make MOLM. Molasses was obtained from Mtibwa Sugar Company. Other feed ingredients were obtained from local livestock feed dealers. 2x3 factorial experiment in which two GSV for high tannin sorghum (HTS) and low tannin sorghum (LTS); three supplementary strategies for non-supplemented GSV based diets (CTL) and 10% DM- SCM andiii 10% DM-MOLM (MOL) supplemented GSV based diets to make six dietary treatments for the feeding experiments. The data of the second study was analyzed using descriptive statistics whereas for the third and fourth study the General Linear Model Procedure was used. The results showed that out of the twelve Tanzanian commercial GSV identified, 75% were predominately landraces with local identity.58% of GSV had white coat colour and were sourced from Singida and Dodoma region. The overall chemical composition for GSV was found to be dry matter (DM) (88.3% ± 0.44), metabolizable energy (MEn) (13.8MJ/KgDM±0.39), ether extract (EE) (3.2%DM±0.46) and crude protein (CP) (1 l.l%±0.63). In addition, GSV contained a range of high crude fiber (CF) (1.8-6.8%DM), ash (1.8- 6.9%DM) and condensed tannins (2.1-5.8%DM) as leucocynidin equivalent and low macro/micro minerals and essential amino acids., The results did not show any significant correlation between coat colour and amount of condensed tannins in GSV. The results of the present study showed that use of FITS as a main source of energy led to poor dry matter intake (DMI), lymphocyte, and oesinophils and monocyte ratios for growing chicks whereas poor DMI, feed conversion and egg production were observed in layer chickens but produced more desirable eggs in terms of aroma, flavour and yolk colour after being stored for long time. The LTS diets had better DMI, lymphocyte, oesinophils and monocyte ratios and feed conversion for growing chicks whereas better feed conversion and egg production were observed in layer chickens but relatively produced undesirable eggs in terms of aroma, flavour and yolk colour after being stored for long time. The results further showed that supplementation of GSV based diets with final SCM led to increased leg abnormality incidences (LAI), paleness of the bird’s body parts and decreasediv lymphocyte and oesinophils ratios for growing chicks. In layer chickens decrease in egg production and impairment of feed conversion, egg aroma, flavor and yolk colour when final sugar cane molasses was added to GSV based diets were noted. Addition of MOLM to GSV based diets, prevented occurrence of LAI and improved colour of the bird’s body parts; monocyte, lymphocyte and oesinophils ratios and feed conversion for growing chicks. Egg production, feed conversion, Roche egg yolk color scores (RYS) and consumers’ yolk colour score index (YSI) were improved by the addition MOLM in GSV based diets for layer chickens. It can be concluded that Tanzanian commercial GSV have high feed component and energy content showing their potential in poultry feeding but their utilization could be limited by presence of high anti-nutritional factors and low content minerals and amino acids. Moreover, FITS has relatively lower feeding values than LTS in poultry feeding may be due to the negative effects of tannins which impair the utilization of nutrients though they may produce relatively more desirable egg in terms aroma and flavour qualities when stored for long time. However, LTS has higher feeding value for poultry due to nutrition adequacy although may cause to leg abnormalities in chicks if it contains high phytates and may lead to unpleasant egg aroma, flavour and yolk colour when stored for long time. It can further be concluded that utilization of MOLM additive to GSV based diet for poultry improve feeding value of HTS and LTS in layer chickens due to its ability to compensate deficient minerals, pigments, energy, amino acids and proteins. But, use of SCM additive to GSV based diet for poultry worsens HTS and LTS feeding values due to the negative its effects in utilization of nutrients associated with its ability to increase rate of passage in gastro­ intestinal tract. Following findings of this study, partial utilization of Tanzania GSVV as a source of energy in poultry feeding is recommended but it’s fully use should be accompanied by supplementation of synthetic minerals, pigments and amino acids or strategic feeding options. Moderate use of HTS in layer chickens’ diets is suggested but fully utilization should require supplementation of synthetic pigments, minerals and amino acids and energy sources or strategic feeding options for health chicks and production of desirable eggs. Fully utilization of LTS in layer chickens’ diet is highly recommended but requires supplementation of synthetic pigments and minerals for production health chicks and desirable eggs. Addition of up to 10%DM- MOLM level for improving HTS and LTS feeding value for layer chickens is recommended whereas the use of 10%DM- final SCM level is not suggested. Further research is recommended to evaluate economics of using MOLM additive to GSV based diet for layer chickens and nutritive value of different GSV in Tanzania rural.