Graduation date: 1993

The objectives of this research were (1) to study the relative ability of genetically different types of domestic chickens to digest and absorb fat of different types, and (2) to relate fat absorbability coefficients to dietary apparent M. E. values obtained with genetically different types of chickens feeding on diets containing the different types of fat, (3) to search for a possible cause of poultry genetic difference in fat absorbability by examining some of the factors most likely to influence fat digestion and absorption in the genetically different types of chickens. Using New Hampshire, White Leghorn and broiler-type birds, it was found that until 6 weeks of age the New Hampshires were significantly (P≤0.05) superior to the others in their ability to utilize animal tallow. Differences among birds in the absorbability of corn oil were small. Differences in dietary M.E. estimates were closely associated with differences in fat absorbability values and on a 12% tallow diet, the R² values computed on a within age between breeds basis, were 0.67, 0.36 and 0.022 at 3, 5, and 9 weeks of age respectively. This general decline in R² values was a reflection of the narrowing of the range of fat absorbability differences among different types of birds as they grew older. The overall conclusion based on these results, is that breed and/or age differences in M.E. estimates are to a large extent attributable to breed and/or age differences in the absorbability of dietary lipid materials. The search for potential causes of the observed breed differences in fat absorbability was therefore the main theme of the subsequent experiments. A study of the feed passage time in birds of different genetic backgrounds failed to provide any conclusive evidence on whether or not breed differences in ingesta transit time are in measureable terms responsible for fat absorbability differences. It was found, however, that with diets containing 12% of animal tallow or corn oil, feed passage time was significantly longer regardless of the type of birds. On the basis of the results of an experiment in which in vitro pancreatic lipase activity was measured, the New Hampshires ranked first followed by Broilers and White Leghorns in that order. However, the magnitude of differences among them was small. Supplementation of the 12% tallow diet with the bile salt, sodium taurocholate, improved fat utilization significantly by the broiler-type and White Leghorn chicks to the extent of 8.6% and 7.2% respectively. The improvement in fat absorbability was associated with a significant reduction in the amount of fecal soap fatty cacids. The effect of the sodium taurocholate suggested that in the Broilers and White Leghorn chicks, the supply of bile salts was below the critical micellar concentration required for efficient tallow fat absorption. Results from a general study on intestinal fatty acid binding protein (FABP) revealed that a fatty acid binding protein in the same molecular weight range as that one demonstrated in the rat, exists in the intestinal mucosa of the adult chickens and in the mesenteric intestine of day-old chicks prior to the ingestion of any feed. / Land and Food Systems, Faculty of / Graduate

Thesis (MSc. (Animal Production)) -- University of Limpopo, 2016 / This study was conducted to determine the effect of supplementing diets with antimicrobials and effective microorganisms on productivity and carcass characteristics of Ross 308 broiler chickens. The study consisted of two parts. The first part determined the effect of antimicrobial and effective microorganism (EM) supplementations on growth performance of unsexed Ross 308 broiler chickens aged one to 21 days. A complete randomized design was used and 150 unsexed day-old chicks with an initial weight of 42 ± 2g were randomly assigned to five different treatments which were replicated 3 times with each replicate having 10 chicks. The five grower diets had the same nutrients (20% CP and 12MJ/kg) but different supplementation levels of 0g oxytetracycline and 0ml EMs/l of water (UAM0EM0), 0.01g oxytetracycline (UAM0.01EM0), 30ml EMs/l of water (UAM0EM30), 50ml EMs/l of water (UAM0EM50) and 100ml EMs/l of water (UAM0EM100). A quadratic regression model was used to determine dietary effective microorganism supplementation levels for optimal feed intake and live weight of Ross 308 broiler chickens. A linear model was used to determine the relationship between dietary effective microorganism supplementation levels and metabolisable energy intakes. Antimicrobial and effective microorganism supplementations did not have any effect (P>0.05) on growth rate, feed conversion ratio and mortality. Antimicrobial supplementation improved (P<0.05) feed intake and live weight of the chickens. Supplementation with 50ml of EMs/l of water improved (P<0.05) feed intake. Supplementation with 50 or 100ml of EMs per litre of water increased (P<0.05) ME intake of the chickens. Effective microorganism supplementation levels of 72.25 and 48.29ml of drinking water optimized feed intake and live weight, respectively. The second part of the experiment determined the effect of antimicrobials and effective microorganisms on productivity, blood, carcass characteristics and meat quality of male Ross 308 broiler chickens aged 22 to 42 days. The chickens were randomly allocated to five treatments with three replications, each having six chickens. A total of 90 male chickens, with the initial live weight of 452 ± 3g were allocated to the treatments in a complete randomized design. The chickens were fed a grower diet supplemented with 0g oxytetracycline and 0ml EMs/l of water (MAM0EM0), 0.01g oxytetracycline (MAM0.01EM0), 30ml EMs/l of water (MAM0EM30), v 50ml EMs/l of water (MAM0EM50) and 100ml EMs/l of water (MAM0EM100). Antimicrobial and effective microorganism supplementation did not have effect (P>0.05) on feed intake, growth rate, live weight, ME intake, blood glucose and mortality. Poorer (P<0.05) feed conversion ratio was observed with the supplementation of antimicrobial. Blood glucose levels were optimized at an effective microorganism supplementation level of 29.00ml of EM/l of drinking water (Figure 4.05). Supplementing diets with antimicrobials and effective microorganisms did not have effect (P>0.05) on crop, gizzard, proventriculus and large intestine pH values of male chickens. However, supplementation with of 100ml of EMs per litre of drinking water reduced (P<.0.05) the pH of ileum. Effective microorganism supplementation level of 85.00ml per litre of drinking water optimized the crop pH value. Antimicrobial and effective microorganism supplementations did not have influence (P>0.05) on gizzard, proventriculus, small intestine, caecum, large intestine, liver and heart weights of male chickens at 42 days. Effective microorganism supplementation level of 50ml per litre of drinking water reduced (P<.0.05) crop weight. Antimicrobial and effective microorganism supplementations did not have effect (P>0.05) on whole gastro-intestinal tract (GIT), small intestine and caecum length of the chickens. Antimicrobial supplementation reduced (P<0.05) the length of large intestine. Effective microorganism supplementation levels of 41.00, 45.50 and 85.00ml per litre of drinking water optimized crop weights and caecum and large intestine lengths, respectively. Antimicrobial and effective microorganism supplementations did not have any influence (P>0.05) on live weight, carcass weight, breast weight, drumstick weight ad thigh weight. Similarly, antimicrobial and effective microorganism supplementations did not have influence on meat tenderness, juiciness and flavour. There were no antibiotic and effective microbe residues in the meat. It is, therefore, concluded that effective microorganism supplementation did not have much effect on production parameters, carcass characteristics and meat quality of Ross 308 broiler chickens.

With the narrow margin of profit in the broiler enterprise, how can producers increase profit potential? It is not an easy task to answer this question since the net financial return depends on many factors; some are related to the animal, some to the feed, some to the environment and others are outside the production system, like availability and cost of labour and capital. Many researchers have attempted to improve the efficiency of the system using alternative management strategies and to develop a unified theory that could simultaneously evaluate all the relevant factors and the interactions between them. Simulation models are seen as the most promising means of moving this subject forward. Geneticists are continually improving the potential growth rate of broilers, yet there has been little change in feed specifications for these birds over the past few decades. Only recently has it been possible to make use of simulation models to optimise the feeds and feeding programs of modern broiler strains at a commercial level, but little testing of these programs has been carried out. What is needed is a thorough investigation of these models, which at present are based on an individual, as opposed to a population response. Modelling plays an increasingly important part in animal science and research as a way of organizing and evaluating the large body of existing knowledge. With the use of an accurate description of the potential growth rates of broiler genotypes, it is possible to make more efficient use of growth models which are becoming more abundant in the industry and which, in turn, enable the nutritionist or producer to predict the performance of animals when subjected to a given feed or feeding programme. The predictions made by most of the growth models now available are based on individual animals, and the results obtained may be inadequate in optimising the nutrient requirements of a broiler population because of the variation that exists in these populations. Variation in performance traits in broilers may be the result of variation in the genotype, in the environmental conditions within the house, and in the composition of the feed offered to the birds, and these sources of variation cannot all be accommodated in a model that simulates the food intake and growth of just one bird. But if variation is to be incorporated into growth models, it is necessary to ascertain the effects of variation in the various genetic parameters on the mean response of the population. A sensitivity analysis is useful in accomplishing this objective. Similarly, it is important to know what the optimum size of a simulated population should be, that takes account both of the accuracy of the simulation and the time taken to complete the exercise. This is especially important when optimisation routines are followed, as such calculations are time consuming. As a means of addressing these issues, simulation exercises were conducted using EFG Broiler Growth Model version 6 and EFG Broiler Optimiser Model version 1 (EFG Software, 2006) to determine: (a) whether it is worth generating a population when optimising feeds and feeding programs for broilers, rather than using the average individual, (b) the size of the population required to obtain an accurate estimate of the population response when optimising the feeding program for different objective functions, (c) the effect of changing the value of genetic parameters such as mature protein weight, rate of maturing, feathering rate and the maximum lipid:protein ratio in the gain on the optimum amino acid contents and nutrient densities of broiler feeds, and (d) the effect of variation in nutrient composition of different batches of feed, which have the same nutrient profile but different qualities of the main protein source, on broiler performance. A review of sources of variation in the nutrient content of poultry feed was conducted, and simulation exercises were carried out to determine to what extent broiler performance is affected by the segregation or breakage of pellets into small pieces at the time of delivery and along the feed conveyor within the broiler house, by the change in nutrient quality that might occur along the conveyor, and by the microclimates that develop in a longitudinally ventilated broiler house. The tendency in broiler marketing in most parts of the world is to sell broilers cut up, as portions or deboned after evisceration, rather than selling whole birds. Estimation of the growth rates of carcass parts is therefore of considerable importance if simulation models are to be useful in optimising the feeds and feeding programmes of broilers under different conditions. Allometric equations are used in the EFG broiler growth model to predict the weights of these carcass parts from the weight of body protein at the time. These equations are based on data collected many years ago, and it would be useful to determine whether they are still relevant in the face of announcements by the major broiler breeding companies that tremendous strides have been made in improving breast meat yield, for example, by judicious selection. For the purpose of this investigation it was important to determine to what extent the weights of the physical parts varied at the same body protein weight, thereby enabling a more accurate estimation of the variation that could be expected in these weights when developing a population response model. Towards this end, experiments were conducted to determine the effect of dietary protein content on the performance of Cobb and Ross broilers, including mortality and uniformity, and on the allometric relationships between the physical and chemical components of the body and body protein. The overall objective of these exercises was to address issues relating to the use of simulation models in predicting food intake and growth of broilers, in optimising the amino acid contents and nutrient densities of feeds for broilers, and in representing a population of broilers when the performance of only one bird is simulated at a time. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

With the worldwide increase in consumption of poultry meat in recent years, the production of hatchable eggs from broiler breeding stock has become a critically important component of the poultry industry. Surprisingly, a perusal of the literature pertaining to broiler breeder nutrition leads to the conclusion that research nutritionists have neglected these birds. It has been assumed in many cases that the research on laying hens is applicable to broiler breeders. However, fundamental differences are apparent between the two strains that should be investigated more comprehensively if the potential of broiler breeder hens is to be achieved. Commercial laying hens have been selected predominantly for increased egg production whereas broilers have been selected for early rapid growth rate. By selecting for improved growth rate, both food consumption and mature weight of these birds has increased (Reddy, 1996), but because of the negative genetic correlation between body weight and egg production (Robinson et al, 1993) reproductive performance has not been improved. Broiler breeder hens differ from commercial laying hens, by their non-normal frequency distribution of egg outputs, their considerable lipid reserves, and by the fact that many do not lay in closed cycle. The practice of restricting feed intake during both the rearing and laying periods has become a standard management procedure in commercial broiler breeder operations and this differs from the manner in which commercial hens are fed. This raises important issues regarding the requirements of these birds for energy, amino acids and other essential nutrients, as the birds do not have the opportunity of meeting their nutrient requirements by adjusting food intake upwards when one or more of these nutrients is deficient in the feed. It is the duty of the nutritionist to provide the correct daily allowance of each nutrient in order to achieve maximum egg output by the flock, but given the variation between hens within a flock, such decisions need to be made on both biological and economic grounds. Improved strains are continually being produced by breeder companies, which exhibit better growth, feed efficiency and productivity. The way in which broiler breeder hens were fed in the past might not be the most effective way to feed the latest strains. Getting the right amount of feed with the right nutrient levels at the right time is the most important part of feeding broiler breeders, and to succeed their daily nutrient requirements need to be known. Information concerning the nutritional requirements of broiler breeder hens is limited in comparison to other types of domesticated poultry. However, enough information is available concerning energy and amino acid nutrition of this type of poultry to enable one to develop models useful for constructing accurate feeding programmes. The most appropriate way of estimating the nutrient requirement of broiler breeder hens during the laying period, or of optimising a feeding strategy, is by the use of simulation models. Emmans and Fisher (1986) suggested that a better approach to the problem of describing requirements and of expressing them quantitatively can be achieved by considering: firstly, the bird’s characteristics, secondly by defining resource scales carefully and thirdly by considering the quantities of each resource needed per unit of function. This approach has a greater chance of success than attempting to measure requirements by direct experimentation. Energy and amino acids are required for growth of tissues, egg production, maintaining normal body temperature, vital life functions and activity. For development of feeding programmes, we are most concerned with the three primary components, maintenance, growth and egg output. There are a number of factors that impact on the total nutrient requirement of the breeder. The maintenance component is affected by body size, environmental temperature, level of activity (housed in floor pens vs. cages) and possibly breed. Regarding the growth component, in the case of broiler breeders during lay the composition of growth needs to be addressed: whether this is only lipid gain or also includes protein gain. Lastly, the egg component is influenced by egg mass and hen age. In order to calculate energy and amino acid requirements, one must have knowledge of the requirements per unit of body protein weight, growth rate and egg mass. By continually monitoring the environmental conditions in the broiler breeder house, as well as body weight, egg weight and egg number, it is possible to estimate the state of the hens at any time and hence the optimum nutrient concentrations that should be fed the next day of the laying period by using the Breeder Model presented in this thesis. Optimising the feeding of broiler breeders during the laying period is made difficult because of the many interacting factors influencing their performance All the hens are not the same, they are not housed in the same environments, and the costs of feeding and the revenue derived from the sale of the product differs from one locality to another. The solution to this problem lies in the use of simulation models to describe the causal relationship between inputs and the predicted responses. This thesis explored new concepts and components for a simulation model to predict the nutrient requirement and performance of broiler breeders after sexual maturity. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

The objective of the study was to evaluate the effect of an exogenous multi-blend enzyme ( -glucanase and xylanase) on the performance of the broiler chickens and laying hens fed diets based on wheat and barley. Experiments were conducted on a flock of broilers and two flocks of laying hens. In both cases feed and water were provided ad libitum. The enzyme effect of enzyme addition on the broiler performance involved 2080 day-old male and female chicks in 48 pens, allocated one of four dietary treatments (0, 50, 100 or 200g/ton enzyme supplementation), to 35 days of age. On day 35, ten birds from each treatment were sacrificed for the analysis of the digestive organs weight (gizzards and livers). The trial was divided into two phases: a starter (1 to 21 d) and grower (22 to 35 d). Feed consumption was measured weekly and birds were also weighed weekly. The investigation of enzyme effect in laying hen diets involved 896 birds for each specific period. Each replicate consisted of four cages (four birds per cage) with a common feeder; 16 hens/pen of 56 pens. Eggs were weighed three times a week, feed consumption weekly and birds every weeks. The addition of a multi-blend enzyme significantly improve body weight, body weight gain, food intake, and feed conversion ratio for both sexes (P<0.05) in broiler chickens. There was a significant improvement in egg production in laying hens (P<0.05). Egg weight and egg mass were not significantly improved. Wheat and barley have cell wall components (arabinoxylans and -glucans respectively) which have a negative effect on the nutritive value of these feeds and therefore performance in poultry fed diets based on these ingredients. Addition of an exogenous multi-blend enzyme( -glucanase and xylanase) could help reduce these effects and improve performance and digestibility values in poultry. The null hypothesis was there will be no difference between supplemented and un-supplemented diets based on wheat and barley in performance of poultry. The results of this study suggest that the inclusion of 50 g/ton enzyme helps improve poultry performance, especially in young birds. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Breeding companies advertise their chickens as having been selected for heavier breast meat. However, when comparisons are made between strains, these are normally made at a common age, and under these conditions the heaviest birds will have the heaviest breast meat yield. More meaningful comparisons would be made by relating breast weight to body protein weight, as these are allometrically related. Two experiments were conducted to test the hypothesis that the allometric relationship for each body part is the same irrespective of strain, sex and feed protein content, i.e. that geneticists have not been successful in changing the allometric relationship between breast meat weight and body protein weight. In the first trial, three strains, two sexes and four feed protein levels were used to 6 weeks of age, and in the second, four strains, two sexes and three feed protein levels were used to 12 weeks. Birds were sampled weekly, and the weights of breast meat (no skin or bone) and the meat and skin of the thigh, drum and wing were recorded before determining the body protein content of each of 1526 broilers. The hypothesis could not be corroborated when the data from the two trials were combined so a further trial was conducted to determine the amount of lipid that is deposited in the meat and skin of each of the commercially important parts of the broiler, on the assumption that differences in lipid deposition between strains, sexes and feed protein levels in the various physical parts would assist in explaining the anomalies in the analyses. It was confirmed in the third trial that the small differences between the observed and predicted weights of the physical parts may be accounted for through varying amounts of lipid deposition in these parts, depending on strain, sex and feed protein level, which must be accounted for when using allometry to predict the weights of the physical parts of the broiler at different stages of growth. The data collected in this series of trials may be used to predict the weights of these physical parts more accurately than has been the case to date. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

This study was designed to devise a method by which the optimum combination of dietary energy and protein could be found that maximises the margin over feeding cost in an egg production enterprise. It was necessary to be able to predict feeding costs and revenue associated with the use of a wide range of feeds varying in protein and energy. To this end, two experiments were conducted using 256 Lohmann (128 White and 128 Brown) in the first, and 1296 Hy-line Brown laying birds in the second trial, that were 33 and 38 weeks old at the beginning of the two trials. Using the WinFeed 1.1 (1996) feed formulation programme, four basal (corner) feeds were formulated in both experiments, from which four protein and four energy contents (16 feeds) were produced in the first experiment, and six protein and three energy contents ( 18 feeds) were used in the second. Each feed was given to three replicates of 16 birds in the first trial, and to three replicates of 24 birds in the second. The trials each lasted ten weeks, and the data collected included food intake, change in body weight, egg weight and rate of laying. Using the results from these two experiments and from previously published research, the effects of dietary protein and energy on food intake were predicted independently, and these predictions were then used to determine the cost of feeding. Similarly, egg weight and rate of lay were predicted independently for changes in dietary protein and energy, from which the revenue could be calculated over the range of energy and protein contents. It is understood that a more integrated approach would be more accurate for this purpose, but such an approach was beyond the scope of this investigation. The use of contour plots based on regression analyses of the estimated income-minus-feeding cost on changes in dietary protein and energy enabled evaluations to be made of the effect on profitability of changes in egg price and maize price. And it was deduced that under conditions in which the maize price is high, maximum profitability is achieved with high energy and high protein content, irrespective of the price paid for eggs. When the maize price is reduced, the combination of protein and energy that yields the highest return over feed cost changes to low protein and low energy feeds. This change is defensible on the grounds that the price of high-density feeds does not change as much as that of low-density feeds when the maize price is lowered, whereas production, and hence returns, remains the same, hence the low density feeds yield higher returns under such circumstances. The method applied in this study appears to be a useful tool for decision-making by egg producers and nutritionists. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

The increased demand for breast meat of broiler chickens has challenged researchers to investigate management techniques that could be used to increase the production of this valuable commodity. Two experiments were conducted in this study; the first investigated the effect of early feeding of newly hatched broilers on breast meat yield (BMY) at market weight, and the second focused on improving BMY of broilers exposed to short daylengths by feeding higher than conventional levels of dietary protein. In the first experiment, of the 528 eggs set in the incubator, half were placed, at day 18, in hatching trays containing a commercial broiler starter feed whilst the others (the held group) were hatched conventionally. Six chicks from both fed and held groups were sampled at nine-hour intervals from the time that the first chicks hatched for a subsequent period of 36 h. After measuring their body weight these chicks were euthanised and dissected in order to measure their breast and yolk weights. Body protein, lipid and water contents were measured on each chick. At day 21, six birds from the fed and held groups were sampled, and body weight, breast weight and body protein content were measured. The yolk sac weight for fed birds was significantly reduced compared to that of held birds (P < 0.001). Both fed and held birds had the same breast weight at hatch, but at day 21 the mean breast weight of the fed birds was significantly heavier than of held birds (P < 0.05). The birds that were removed first from the hatcher had a reduced breast muscle weight compared to those that were removed last. In the second experiment, a total of 3200 day-old broiler chicks were reared in eight light-tight rooms. Four lighting regimens (12L: 12D, 16L: 8D, 20L: 4D and 24L: 0D) were randomised between rooms, with each light treatment being replicated twice. Each room was divided into four pens and 100 chicks in each pen received one of four dietary protein treatments. At day 35, three birds from each pen were sacrificed so that measurements could be made of breast, thigh, drum and wing weight, and carcass chemical composition. Breast weight increased as daylengths increased except in birds that were fed low protein diet (143 g protein/kg feed). High levels of dietary protein increased breast weight in birds on all other daylengths except for those on 12 h which showed a reduced breast muscle weight when dietary protein content was increased. The results of the first trial suggests that breast meat yield could be improved if newly hatched chicks are offered feed immediately after hatch, however the hypothesis that this increment was due to an overall increase in body protein content in the first few days after hatching could not be corroborated. The results further showed that held birds do not withdraw nutrients from breast muscle to maintain growth at hatch, this is because birds that stayed longer in the hatchery without feed showed increased breast muscle weight compared to those that were removed first. The second trial could not identify a suitable feeding programme to overcome the problem of a lower breast muscle weight that results from the use of 12 h of lighting compared to that when long daylengths are used. Highest breast weight was obtained when birds were fed high protein diet at 20 h. More research is required to further investigate the combined effect of early feeding and daylength on breast meat yield in broiler chickens. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Department of Animal Science / BSCAGR