Thesis (M.Sc. (Agriculture)) --University of Limpopo, 2010 / Ten experiments were conducted to determine the effect of dietary energy to protein ratio level on growth and productivity of indigenous Venda chickens raised in closed confinement from day-old up to thirteen weeks of age. The ten experiments were based on five different energy levels of 12.2, 13, 13.2, 13.4 and 14 MJ ME/kg DM. Each dietary energy level had five different levels of protein concentrations of 220, 190, 180, 170 and 160 g/kg DM, thus ending up with twenty five different dietary energy to protein ratio levels. Experiments 1 to 5 examined the effect of dietary energy to protein ratio on productivity of unsexed Venda chickens aged one to six weeks. Experiments 1 to 5 each commenced with 160 unsexed day-old indigenous Venda chicks with an initial weight of 25 ± 2 g per bird and each lasted for a period of six weeks. In each experiment, the chicks were randomly assigned to five treatments with four replications, each having eight birds. Thus, 20 floor pens (1.5 m2 /pen) were used in total for each experiment. All the five experiments were carried out around the same time. A complete randomized design was used for each experiment. A quadratic regression model was used to determine the ratios for optimum feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention in each experiment while a linear model was used to determine the relationship between optimal responses in the above variables and dietary energy to protein ratio levels. Dietary energy to protein ratio level for optimal response for any variable was relative and depended on the energy to protein ratio values of the diet. Energy to protein ratios of 63, 67, 70, 74 and 78 MJ ME/kg protein promoted optimal live weights of 415, 408, 370, 365 and 344 g at six weeks of age for diet energy levels of 12.2, 13, 13.2, 13.4 and 14 MJ ME/kg DM, respectively. However, optimal response trends for different variables were also influenced by the dietary energy to crude protein ratio. Optimal feed intake increased linearly with increasing dietary energy to protein ratio levels. Similarly, optimal metabolisable energy level increased linearly with increasing dietary energy to protein ratio levels without any increase in live weight. On the other hand, increasing dietary energy to protein ratio level decreased growth rate with a linear deteriorating feed conversion ratio,thus, negatively affecting live weight of the chickens at six weeks of age. However, increasing dietary energy to protein ratio levels improved efficiency of protein utilization with a linear deteriorating metabolisable energy utilization. In experiments 1 to 5, correlation analysis indicated that optimal feed intake, feed conversion ratio and metabolisable energy level were positively and strongly correlated with dietary energy to protein ratio levels while optimal live weight, growth rate and nitrogen retention were negatively and strongly correlated with dietary energy to protein ratio levels. The study indicated that a diet containing a crude protein content level of 178 g/kg DM and an energy level of 14 MJ ME/kg DM allowed for optimal utilization of absorbed protein and energy for growth in unsexed indigenous Venda chickens aged between one and six weeks. Experiments 6 to 10 examined the effect of dietary energy to protein ratio level on productivity of male Indigenous Venda chickens raised in closed confinement from seven up to 13 weeks of age. Each experiment commenced with 100 seven-week old male Venda chickens with an initial weight of 320 ± 2 g per bird. In each experiment, the chickens were randomly assigned to five treatments with four replications, each having five birds. Thus, 20 floor pens (1.5 m2/pen) were used in total for each experiment. All the five experiments were carried out around the same time and for a period of seven weeks. A complete randomized design wasused for each experiment. A quadratic regression model was used to determine energy to protein ratios for optimum feed intake, growth rate, feed conversion ratio,live weight, metabolisable energy, nitrogen retention, carcass yield, breast meatyield and fat pad deposition in each experiment while a linear model was used to determine the relationship between optimal responses of the above variables and dietary energy to protein ratio levels. Energy to protein ratios of 60, 71, 66, 72 and 71 MJ ME/kg protein promoted optimal live weights of 1167, 950, 983, 1235 and 1172 g at thirteen weeks of age for diet energy levels of 12.2, 13, 13.2, 13.4 and 14 MJ ME/kg DM, respectively. Optimal response trends in feed intake, growth rate, feed conversion ratio, nitrogen retention, and metabolisable energy intakes in male Venda chickens tended to increase with increase in dietary energy to protein ratio level. In contrast, optimal carcass and breast meat yield tended to decrease with increasing dietary energy to protein ratio level. However, optimal live weight and fat pad remained unchanged with increase in dietary energy to protein ratio value. Additionally, increasing dietary energy to protein ratio level improved efficiency of protein utilization with deteriorating metabolisable energy utilization.On the other hand, experiments 6 to 10 showed that optimal feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy level, nitrogen retention and fat pad were positively and poorly correlated with dietary energy to protein ratio levels while optimal carcass weight and breast meat yield were negatively and poorly correlated with dietary energy to protein ratio levels This study indicated that a diet containing 193 g CP/kg DM and an energy level of 14 MJ ME/kg DM allowed for optimal utilization of absorbed protein and energy for growth in male indigenous Venda chickens aged between seven and thirteen weeks.It is, therefore, concluded that optimal response trends for different variables in growing unsexed Venda chickens offered diets differing in optimal dietary energy to protein ratio levels are influenced by the diet crude protein content rather than the feed energy level per se. Diets containing decreased dietary energy to protein ratio levels may promote improved growth rate and efficient feed conversion ratio while naturally restricting feed intake. Diets containing increased dietary energy to protein ratio levels favoured efficient utilization of consumed dietary protein. However, with such diets, protein became limiting and birds increased their feed intake attempting thereby to obtain more of the limiting protein in order to meet their protein requirement regardless of the energy value of the diet.It is, also, concluded that growing male Venda chickens increased their feed intake with increase in dietary energy to protein ratio. This is contrary to what has been observed in broiler chickens which decrease their intake with increase in diet energy value. It is suggested that this might reflect the differences between indigenous and broiler chickens in terms of their genetic and physiological abilities to regulate their feed intakes according to dietary energy levels. / National Research Foundation (NRF)

Thesis (Ph. D. (Animal Production)) -- University of Limpopo, 2020 / A study was conducted to determine the effect of dietary crude (CF) levels of (3, 4, 5 and 7 %) on feed intake, digestibility, growth rate, feed conversion ratio (FCR) and live weight of male Ross 308 broiler and indigenous Venda chickens aged 1 to 42 days. The study, also, determined the effect of dietary CF level on the gastrointestinal morphology and digesta pH of gut organs of male Ross 308 broiler and indigenous Venda chickens aged 42 days. Dietary CF levels affected (P<0.05) feed intake, growth rate and live weight of male Ross 308 broiler and Venda chickens aged 1 to 21 days. A dietary CF level of 3.9 % optimized feed intake, while 4.5 % dietary CF optimized growth rate and live weight in male Ross 308 broiler chickens. However, dietary CF levels of 4.4, 4.8, 5.9 and 4.7 % optimized feed intake, growth rate, FCR and live weight, respectively, of male Venda chickens aged 1 to 21 days. Therefore, dietary CF level for optimal productivity depended on the breed of the chicken and production parameter of interest. Higher dietary CF levels decreased (P<0.05) crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF) digestibility values in male Ross 308 broiler chickens. Dietary CF levels of 3.8, 3.7 and 4.1 % optimized dry matter (DM) digestibility, metabolizable energy (ME) intake and nitrogen retention, respectively, in male Ross 308 broiler chickens aged 14 to 21 days. Increased dietary CF level, also, decreased (P<0.05) NDF and ADF digestibility values in male Venda chickens aged 14 to 21 days. Dry matter and CP digestibility values, ME intake and nitrogen retention of Venda chickens were optimized at dietary CF levels of 3.5, 3.7, 3.3 and 4.1 %, respectively. Feed intake of male Ross 308 broiler chickens aged 22 to 42 days were affected (P<0.05) by dietary CF level; and it was optimized at a dietary CF level of 6.4 %. Increased dietary CF level resulted in poorer growth rate, FCR and live weight of male Ross 308 broiler chickens. However, dietary CF levels of 4.5, 5.8, 6.4 and 5.7 %, optimized feed intake, growth rate, FCR and live weight, respectively, of male Venda chickens aged 22 to 42 days. Dietary CF levels of 3.4, 4.4, 3.7 and 4.4 %, optimized DM, CP and NDF digestibility values, and nitrogen retention, respectively, in male Ross 308 broiler chickens. However, dietary CF levels of 5.1, 5.3, 4.9, 10.1 and 5.1 % optimized DM, CP, NDF and ADF digestibility values, and nitrogen retention, respectively, of male Venda chickens. Therefore, dietary CF level for v optimal response in the chickens depended on breed, age and production variable of interest. The GIT weight of male Ross 308 broiler chickens was optimized at a dietary CF level of 4.1 %. In increased dietary CF level in male Ross 308 broiler chickens increased gizzard weights and decreased small intestine weights (P<0.05). Dietary CF levels of 6.3, 5.9 and 8.0 % optimized GIT, gizzard and caecum weights, respectively, in male Venda chickens. The small intestine weight of male Venda chickens was not affected (P<0.05) by dietary CF level. Caecum weight of male Venda chickens increased (P<0.05) with higher dietary CF level. However, caecum weights of male Ross 308 broiler chickens were not affected (P>0.05) by dietary CF level. The GIT and small intestine lengths were affected (P<0.05) by dietary CF level in male Ross 308 broiler chickens. Dietary CF levels of 5.6 and 5.5 % optimized GIT and small intestine lengths, respectively. However, in male Venda chickens, GIT and small intestine lengths were not affected (P>0.05) by dietary CF level. Digesta pH of the proventriculus and gizzard were affected (P<0.05) by dietary CF level in male Ross 308 broiler and Venda chickens. Different dietary CF levels of 5.5 and 7.4 % optimized the proventriculus and gizzard digesta pH in male Ross 308 broiler chickens, respectively. However, dietary CF levels of 4.2 and 4.3 % optimized the proventriculus and gizzard digesta pH values, respectively, in male Venda chickens. The two breeds of chickens had similar digesta pH values of the crop, proventriculus, gizzard and large intestines. However, male Venda chickens had higher (P<0.05) small intestine digesta pH values than male Ross 308 broiler chickens aged 42 days. Caecum digesta pH values of Ross 308 broiler chickens were higher (P<0.05) than those of Venda chickens aged 42 days. The second study was conducted to determine the effect of sodium bicarbonate supplementation level in the drinking water on feed intake, digestibility, FCR, growth rate, gut organ weight, length and digesta pH of male Ross 308 broiler and Venda chickens aged 22 to 42 days. The study, also, determined the effect of sodium bicarbonate supplementation level in drinking water on types of bacterial species in crop and gizzard digesta, as well as its effect on meat quality of male Ross 308 broiler and indigenous Venda chickens. Increased sodium bicarbonate vi supplementation level increased (P<0.05) water pH. Supplementation levels of 8.9, 2.04, 2.97 and 2.97 g of sodium bicarbonate per litre of drinking water optimized water intake, feed intake, growth rate and live weight of male Ross 308 broiler chickens, respectively. In male Venda chickens, there was a strong and positive relationship between sodium bicarbonate supplementation level and water intake of Venda chickens. A single supplementation level of 3.8 g of sodium bicarbonate per litre of drinking water optimized growth and live weight of male Venda chickens. There was a negative relationship between sodium bicarbonate supplementation level in the drinking water and NDF digestibility of male Ross 308 broiler chickens. Supplementation levels of 2.63, 6.67 and 7.0 g of sodium bicarbonate per litre of drinking water optimized DM and CP digestibility values, and nitrogen retention, respectively, in male Ross 308 broiler chickens. However, supplementation levels of 3.2 and 4.52 g of sodium bicarbonate per litre of drinking water optimized DM and NDF digestibility values, respectively, in male Venda chickens. There were negative relationships between sodium bicarbonate supplementation level in the drinking water and CP digestibility and nitrogen retention of male Venda chickens. Supplementation levels of 5.7, 2.2, 3.8, 7.6 and 7.2 g of sodium bicarbonate per litre of drinking water optimized proventriculus, gizzard and small intestinal weights, and GIT and small intestines lengths, respectively, in male Ross 308 broiler chickens. However, a sodium bicarbonate supplementation level of 2.8 % optimized proventriculus weights of male Venda chickens; the other digestive organ weights and lengths of Venda chickens were not affected (P>0.05) by sodium bicarbonate supplementation level. Sodium bicarbonate supplementation in the drinking water affected bacterial species found in the crops and gizzards of the chickens. There were different bacterial species found in the crop and gizzard digesta of male Ross 308 broiler and Venda chickens. Meat colour (L*, a* and b*) of the breasts and thighs of both breeds of chickens were not affected (P>0.05) by sodium bicarbonate supplementation. However, the redness (a*) values of the breast meat of male indigenous Venda chickens were higher (P<0.05) than those of breast meat from male Ross 308 broiler chickens. Sodium bicarbonate supplementation level did not affect (P>0.05) breast meat tenderness, juiciness, flavour and overall acceptability values and meat pH of Ross 308 broiler chickens. Supplementation levels of 3.6, 3.2 and 4.7 g of vii sodium bicarbonate per litre of drinking water optimized meat juiciness, flavour and shear force of male Venda chickens, respectively. It was concluded that sodium bicarbonate supplementation in the drinking water affected growth, NDF digestibility and bacterial species composition of male Ross and Venda chickens. Sodium bicarbonate supplementation level for optimal response in chickens depended on the breed and production variables of interest. / VLIROUS

(M.Sc. (Animal Production)) -- University of Limpopo, 2014 / Two experiments were conducted to determine the effect of dietary threonine level on productivity and carcass characteristics of indigenous Venda chickens. In each experiment the diets were isocaloric and isonitrogenous but with different dietary threonine levels. A complete randomized design was used in both experiments, the starter (1-7 weeks old unsexed chickens) and finisher (8-13 weeks old female chickens) experiments. The treatments were CT4 (4 g of threonine/kg DM), CT5 (5 g of threonine/kg DM), CT6 (6 g of threonine/kg DM), CT7 (7 g of threonine/kg DM) and CT8 (8 g of threonine/kg DM). A quadratic type of equation was used to determine dietary threonine levels for optimal feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy intake and nitrogen retention of unsexed Venda chickens aged one to seven weeks. Dietary threonine level affected (P<0.05) feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention. However, feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention of indigenous Venda chickens were optimized at different dietary threonine levels of 6.218, 6.437, 6.331, 6.655, 5.979 and 6.158 g/kg DM feed, respectively. Dietary threonine level did not affect (P>0.05) mortality rate of the chickens. The treatments for the second experiment were FT4 (4 g of threonine/kg DM), FT5 (5 g of threonine/kg DM), FT6 (6 g of threonine/kg DM), FT7 (7 g of threonine/kg DM) and FT8 (8 g of threonine/kg DM). Dietary threonine level had effect (P<0.05) on feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention of female Venda chickens aged eight to 13 weeks. Feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy intake and nitrogen retention of chickens were optimized at dietary threonine levels of 6.054, 6.142, 6.442, 6.201, 5.72 and 6.088 g/kg DM, respectively. However, dietary threonine level had no effect (P>0.05) on pH values of crop, proventriculus, gizzard, small intestine, large intestine and caecum of female Venda chickens aged 91 days. Carcass weights of female Venda chickens were affected (P<0.05) by dietary threonine level. Carcass, breast, drumstick, thigh, gizzard and liver weights of female Venda chickens aged 91 days were optimized at dietary threonine levels of 6.183, 6.201, 5.712, 5.847, 4.820 and 6.180 g/kg DM, respectively. Dietary threonine level v had effect (P<0.05) on crude protein and threonine contents of female Venda chicken meat. Meat crude protein and threonine contents of female Venda chickens aged 91 days were optimized at dietary threonine levels of 5.9 and 5.7 g/kg DM, respectively. Dietary threonine level had no effect (P>0.05) on meat flavour, tenderness and juiciness of female Venda chickens. However, meat flavour, tenderness and juiciness of female Venda chickens aged 91 days were optimized at dietary threonine levels of 5.977, 6.103 and 5.977 g/kg DM, respectively. No chicken deaths were observed. / National Research Foundation (NRF)