Doctoral Degrees (DAPAE)

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    Nutrient content and the effects of feeding four Namibian encroacher bush species on growth, methane production and carcass characteristics of Damara sheep
    (University of Namibia, 2022) Shiningavamwe, Katrina L.
    The aim of this study was to evaluate the nutritional and feeding value of four Namibian encroacher species on the intake, digestibility, growth performance and carcass characteristics of Damara sheep. In the first experiment, the nutritional quality of four encroacher bush species (Senegalia mellifera, Dichrostachys cinerea, Terminalia sericea and Rhigozum trichotomum) was evaluated. Leaves and twigs (< 20mm stem diameter) harvested during the late dry, early rainy and late rainy seasons were analysed for proximate content, minerals, amino acids, fatty acids and anti nutrient composition. In the second experiment, in vitro dry matter digestibility, in sacco neutral detergent fibre digestibility and methane production on the same samples above were evaluated. In the third experiment, milled bush biomass was evaluated as alternative roughage source in total mixed rations fed to five castrated 13 month old Damara sheep, with an average initial body weight of 37.2 ± 2.4 kg at 40% inclusion rate in diets, with the main focus on the nutrient intake, in vivo dry matter digestibility and nitrogen retention. In the fourth and fifth experiments, the feed intake, growth performance, slaughter weights and carcass characteristics of Damara sheep lambs (15 males and 15 females) with an average initial weight of 16.7 ± 1.9 kg fed bush-based diets were evaluated. The results of the study indicated that most nutrients analysed were influenced (P < 0.0001) by season x species interaction. The crude protein (CP) contents was moderate (70 to 111 g/kg dry matter (DM)) except for T. sericea which was below 50 g/kg DM. The ash-free neutral detergent fibre (NDFom) and ash-free acid detergent fibre (ADFom) contents were high for all species (594 to 734 g/kg DM and 463 to 580g/kg DM, respectively), across all seasons. The concentration of acid detergent lignin of species ranged from 138 g/kg DM (R. trichotomum) to 223 g/kg DM (D. cinerea) but varied across seasons within species. A moderate proportion (50.9-56.7g/100g CP) of protein in R. trichotomum and S. mellifera was soluble, while the other species had a high proportion (> 70 g/100g CP) of their CP bound to ADF. The levels of condensed tannins (CT) was relatively low (< 55 g CT/kg DM) in all species and within the safe limits. All the bush species had low to moderate concentrations of minerals, while concentration of total amino acids and fatty acids was in the range of 39.4 to 77.7 g/kg DM and 1.17 to 2.84 g/kg DM, vii respectively. In vitro methane gas production of all fourspecies was higher (P < 0.001) during the late dry season compared to the early rainy season (147.6 versus 92.0 mL/g 138 DM). The in vitro organic matter digestibility of the species decreased (P < .001) from late dry to early rainy season, except for S. mellifera. Increase of indigestible neutral detergent fiber (P < .001) was observed from late dry to early rainy season for other species, except for S. mellifera which decreased. Dry matter and CP intakes of the control diet was higher than the bush-based diets. Digestibility coefficients of ≥ 0.70 were obtained on bush-based diets for all nutrients except for NDFom and ADFom which ranged from 0.40 to 0.60. Positive nitrogen retention of 45-58% of N intake was also achieved across diets. The bush-based diets supported average daily gains of up to 156 g/day, feed conversion ratio of 7.6 to 9.6 kg feed/kg weight gain, carcass weights of 11.4 to 12 kg and their carcasses characteristics were similar (P > 0.05) to the control diet. In conclusion, milled bush species could be considered of intermediate nutritional quality, despite their high fibre fraction, high proportion of their CP bound to ADF and indigestible NDF. Milled bush can replace traditional roughage sources such as grass and lucerne hay at 40% inclusion rate in properly formulated and balanced ruminant diets without adverse effects on the dry matter intake, digestibility, growth performance and carcass characteristics of growing lambs. However, there is still a need for further research to improve the utilisation of these bush species
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    Effects of pelleting millet-based diets on the performance of broiler chickens
    (University of Namibia, 2019) Hafeni-Shihepo, Sesilia
    This study evaluated the effects of pelleting and replacing maize with pearl millet (PM) cultivar (Okashana 2) on the production performance and cost efficiency of broilers. The experimental design used in this study was a Completely Randomized Design with a 2 x 3 factorial arrangement of treatments (i.e. two processing methods (grinding and pelleting) and three replacement levels (50%, 75% and 100%). A commercial finisher pelleted diet was used as a positive control. The first experiment investigated the effects of pelleting on nutritional composition of broiler diets when maize was replaced with PM at 50%, 75%, and 100% levels. The second experiment examined the influence of pelleting on the growth performance of broiler chickens. In this study, the effects of pelleting and replacing maize with PM on the carcass characteristics, gizzard and proventriculus as well as the cost efficiency of broiler production were determined. Results from this study revealed that PM grains had higher (P<0.05) CP, fat and essential amino acids content compared to maize grains. Pelleted diets had higher (P<0.05) CP contents compared to their respective mash diets. Pelleting reduced (P<0.05) crude fibre, calcium and fat contents of broiler diets at all replacement levels. A combined effect of grinding and pelleting indicated that pearl millet based broiler diets contains high CP, fat and calcium contents compared to maize based diets. Pelleting had no significant effects (P>0.05) on the feed intake, live weights, weight gain, feed conversion ratio (FCR) and mortality rate of broiler chickens. Pelleting increased carcass weight significantly when maize is replaced with PM at 50%. Replacing maize with PM had no significant influence (P>0.05) on the feed intake, live weights, weight gain and FCR of broiler chickens. Replacing maize with PM grains had no significant effect (P>0.05) on the carcass characteristics of broiler chickens. Replacing maize with PM had no significant effect (P>0.05) on the development of the gizzard and proventriculus. Replacing maize with PM had no significant (P>0.05) effect on feed production costs of broiler diets. Pelleting had no significant effects (P>0.05) on the cost of feeds required per 1 kg of weight gain. Due to similar gross margins observed for mash and pelleted diets, when feeding broilers, producers may choose to use either of them based on their own preferences. This study revealed that PM based diets can successfully be pelleted and replace maize up to 100 % without any adverse effects on growth performance, carcass characteristics and feeding costs. The optimal replacement level in this study was found to be 50 % PM, which yielded high weight gain, carcass weight and better FCR.
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    Cultivation and use of Moringa as a nutritional and medicinal supplement for goats in central Namibia
    (University of Namibia, 2018) Korsor, Morlu
    Goats (Capra aegarus hircus) are small ruminants found in almost all parts of the world reared by both rural subsistence and commercial farmers as a sustainable source of household income and protein-food supply. About 480 million goats exist across the world, about 75% of which are found in developing countries (Boer Goat Breeder‘s Society of Namibia, 2008). Goats can be classified in a number of ways, but the simplest classification is by animal products. The three major classifications are (1) dairy, (2) fibre and (3) meat. The two other major classifications include pets or companions and goatskin breeds. Furthermore, some breeds are dual-purpose from which two products can be obtained, such as meat and milk (Flanders & Gillespie, 2015). Much of southern and western Namibia is used for small-stock farming in which goats predominate in many communal farming districts. Among the 2.5 million goats in Namibia, about 40% are Boer goats and 60% belong to indigenous breeds, and, over 65% of all goats are found in communal areas (Mendelsohn, 2006; Kruger & Lammerts-Imbuwa, 2008). Although goats are predominantly browsers that do not seem to compete with cattle and sheep when roaming freely in the natural veld (Rothauge & Engelbrecht, 2000), it is critical to feed and supplement their rations, especially during lactation, for improved production. Lactating Boer goats need 400 g of lucerne, 150 g maize and 150 g broiler litter per day, or 100 g of brewer grains supplement daily during winter (Smith, 2006). In Namibia, goats are mostly reared for meat, when the owner is too poor to own cattle. Goats, which are more popular than sheep, are milked for domestic purposes, slaughtered for household consumption and sold in times of cash needs (Schneider, 1994).