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    Small-scale poultry production systems in Botswana and evaluation of a natural zeolite in broiler diets : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutritional Science at Massey University
    (Massey University, 2001) Badubi, Slumber
    Two entirely separate research issues form the two parts of this thesis. A survey of small-scale poultry production systems in Botswana is presented in Part A and an evaluation of a natural zeolite in broiler diets in Part B. Part A examined the aspects of management, productivity parameters, farm inputs, housing, feeding, diseases and marketing in small-scale poultry farms in Botswana. In both small-scale layer and broiler farms, only a small percentage of producers were below the age of 30 years, probably reflecting the high costs associated with these systems. Clearly young people would not have the necessary capital to start the projects and the finding emphasises lack of credit being a major constraint to the growth of poultry industry in Botswana. In the two production systems, female producers showed a higher percentage of ownership of poultry projects showing that the government policies have achieved the objective of encouraging involvement of women in business. The average hen day production in small-scale layer farms was 71.7% and the average feed intake was 108. lg per hen per day. Correlation analysis showed that the feed intake was positively related (P = 0.03; R2 = 0.92) to egg production. It was observed that hen day egg production was low in farms where feed intake was low, highlighting the importance of providing sufficient amounts of feed. An average of 1 740g of feed was required to produce one dozen of eggs. This feed efficiency level was better than those recorded in some countries, but poorer than the breeder's recommendation (1 580g feed/dozen eggs). Hens were culled after 52 weeks in production (around 78 weeks of age). During this period, a hen produced an average of 245 eggs; this was lower than 300 or more eggs for modern layers under optimum conditions. Factors responsible for the poor layer performance under small farm conditions in Botswana are clearly complex, but poor managerial skills and, poor quality of feed and pullets are major contributing reasons. The lower production levels, however, show that there is room for improvements and also highlight the need for better record keeping. The average mortality from 18 weeks of age to culling was 8.46%. Diseases or conditions reportedly associated with these deaths included Newcastle Disease, prolapse of the uterus and diarrhoea, but none of the producers vaccinated their flocks. The small-scale broiler farms in Botswana grow an average of 4-5 batches per year. The number of production cycles is determined by the number of sheds in a farm, the interval between broiler batches and the availability of the market in a given location. Most broiler farms adhered to the extension advice of two weeks interval to prevent any disease transmission between batches. The average slaughter age was 48.3 days at an average carcass weight of 1.46 kg. The average amount of feed required to produce a broiler bird was 4.6 kg. The feed conversion ratio for small-scale broiler birds in Botswana was 2.72 kg feed/kg gain, considerably higher when compared to Cobb standards (1.60 kg feed/kg gain). The high feed conversion ratio values in small-scale farms are due probably reflective of, among others, the poor quality feeds, management conditions, length of the production cycle and feed wastage. Correlation analysis showed that when the age at slaughter increases, the average feed conversion ratio is increased (P = 0.0001). This finding is of economic relevance in Botswana, because small-scale producers keep the broilers longer to satisfy consumer preferences. But the cost of keeping these birds would be higher than the returns from sales because of decreasing feed efficiency. The average mortality was 9.15%. Diseases or conditions reportedly associated with these deaths included Newcastle disease, infectious bursal disease, diarrhoea, chronic respiratory disease, paralysis of the limbs and coccidiosis. In most cases, productivity parameters recorded in the current study are higher than those used by the Ministry of Agriculture for budgeting purposes. In the present survey, baseline data have been generated on the performance levels in small poultry farms and the production systems have been characterised. In addition to establishing the production standards, it has raised several issues needing attention. The results showed that the future growth of poultry industry in Botswana is constrained by a number of factors including lack of proper knowledge in poultry husbandry and nutrition, irregular supply and poor quality of feeds and breeding stock, inadequate support services and access to credit, as well as a poor marketing infrastructure. It is also clear that intensive systems of raising poultry may not be financially viable long-term in Botswana, because of the strong dependence on external sources for all major inputs (chicks, pullets, feed etc). The Government, in association with organisations such as Botswana Poultry Association, should formulate policies to address these issues. The results from a 35-day feeding experiment, conducted to evaluate the influence of a natural zeolite (Mordenite) on the performance of broiler chickens fed maize-soyabean meal diets, are presented in Part B of the thesis. Four levels of Mordenite (0, 2.5, 5.0 and 7.5%) were incorporated in diets formulated to provide similar levels of apparent metabolisable energy, lysine and methionine plus cysteine. Each dietary treatment was fed to ten replicate pens (4 birds/pen). Inclusion of 2.5% Mordenite improved weight gains of broilers by 4.1% over that from control diet with no Mordenite, but the difference were not statistically significant (P > 0.05). Weight gains of birds fed diets containing 5.0% Mordenite were similar (P > 0.05) to those fed the control diet. There was. however, a significant (P < 0.05) depression in weight gain of birds fed the 7.5% Mordenite diet compared to those fed the diet with 2.5% Mordenite. The detrimental effect on weight gain at this level is due largely to the reduction in feed intake. Feed intake of birds fed diets containing 7.5% Mordcnitc was lower (P < 0.05) than those on the 2.5% Mordenite diets. Inclusion of Mordenite at 2.5 and 5.0% had no effect (P > 0.05) on feed intake compared to controls. Inclusion of Mordenite to levels up to 5% had no effect (P > 0.05) on the feed efficiency of broilers. The inclusion of 2.5% Mordenite. however, caused a numerical improvement in feed utilisation (1.47 versus 1.5lg feed/g gain). Feed efficiency was significantly (P < 0.05) depressed when 7.5% Mordenite was included in the diets. Excreta nitrogen and phosphorus contents were affected linearly (P = 0.001) by increasing levels of Mordenite. Excreta quality scores were not influenced by the inclusion of Mordenite. Overall, the findings are encouraging and showed that the addition of low levels of Mordenite (2.5%) is beneficial in improving broiler production and litter attributes.
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    Surveillance for diseases of poultry with specific reference to avian influenza : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 2008) Lockhart, Caryl Yolanda
    This thesis addresses issues related to surveillance for disease in commercial and non-commercial poultry populations. The motivation for this work has largely arisen from the unprecedented outbreaks of highly pathogenic avian influenza (HPAI) H5N1 that have occurred in 52 countries in Asia, Africa and Europe since 2003. A series of studies are presented using data derived from two countries, Vietnam and New Zealand. The two Vietnamese studies provide in-depth epidemiological analyses of the outbreak of HPAI H5N1 from December 2003 to March 2004. The three New Zealand studies deal with issues related to the development of effective surveillance strategies for HPAI — informed both directly and indirectly by the findings from the Vietnamese studies. This approach provides an example of how ‘lessons’ learnt from countries that have experienced large scale infectious disease epidemics can be used to assist in the design of surveillance activities in (as yet) unaffected countries. The descriptive analyses of the 2003 – 2004 outbreak of HPAI H5N1 in Vietnam indicate that the epidemic was seeded simultaneously in the north and south of the country in the later part of 2003 with 87% of provinces affected by February 2004. HPAI risk was concentrated around the Mekong and Red River Deltas. The broad scale spatial distribution of disease is likely to have been associated with regional differences in the poultry farming, trade in poultry, and environmental conditions such as the presence of bodies of water which would support reservoir species for the virus. A Bayesian zero-inflated Poisson regression model was used to quantify the influence of environmental and demographic factors on the spatial distribution of HPAI positive communes. In areas where disease was reported, our results show that HPAI risk was positively associated with the presence of irrigation and negatively associated with elevation. After controlling for these fixed effects, a single large area of elevated risk in the Red River Delta area was identified, presumably arising from similarities in the likelihood of reporting disease or the presence of factors increasing disease transmission and spread. Further investigations to elucidate likely transmission mechanisms, targeting this area of the country, would be a profitable area of future research. The second part of this thesis presents three studies that address issues related to the development of effective surveillance strategies for HPAI in New Zealand. The first was a cross-sectional study to enumerate the prevalence of backyard poultry ownership in two areas (one urban and the other rural) close to a large provincial city in the North Island of New Zealand. The prevalence of poultry ownership was 2% (95% CI 1% – 4%) in the urban area and 19% (95% CI 12% – 30%) in the rural area. The relatively low numbers of land parcels where poultry are present indicates that these areas, in the event of an infectious disease incursion, would be unlikely to pose a risk for spread of infectious agent. A cross-sectional survey of all members of the Poultry Industry Association of New Zealand was conducted in the later half of 2007. Respondents were asked to document contacts made with other enterprises related to feed, live birds and hatching eggs, table eggs and poultry product, and waste litter and manure. Patterns of contact were analysed using social network analyses. Each of the four networks had scale-free properties, meaning that for each movement type there were small numbers of enterprises that had contacts with large numbers of enterprises (potential ‘super-spreaders’ of disease). The presence of an undetected infectious disease in enterprises with super-spreader characteristics increases the likelihood that an epidemic will propagate rapidly through the population, assuming there is a directly proportional relationship between the number of contacts an enterprise makes and the probability that disease will be transferred from one location to another. While the finding that feed suppliers had large numbers of poultry farm contacts in the feed network came as no surprise, what was of greater interest was that there were small numbers of poultry farms that reported off-farm movements of feed. This should serve as an important reminder for disease control authorities: movement (and other) restrictions applied during the course of an animal health emergency should be applied across a range of industry sectors, recognising that some industry participants may practice activities that are not entirely typical for their enterprise type (e.g. poultry farms on-selling feed to other farms). In the absence of perfect and up-to-date network data, knowledge of the characteristics of individual enterprises that render them more likely to be atypical (e.g. size, type, and geographic location) would be of value, since this information could be used to inform a risk based approach to disease surveillance and control. A scenario tree model was developed as an approach for evaluating the effectiveness of New Zealand’s passive surveillance system for HPAI. The model was developed in two stages. In the first, factors thought to influence the geographic distribution of NAI risk of introduction and spread (and therefore surveillance strategy) were combined to create a spatial risk surface. In the second stage, a scenario tree model of the passive surveillance system for NAI was developed using the spatial risk surface and the HPAI surveillance strategy prescribed by Biosecurity New Zealand. The model was most sensitive to farmers reporting the presence of suspected cases of disease. This implies that the sensitivity of the system as a whole stands to increase if the importance of reporting suspicious clinical signs is reiterated to poultry producers. The studies presented in this thesis have presented a range of techniques and methodological approaches that are sufficiently generic to be used in any country to inform the design of surveillance strategies for a variety of animal diseases, not just those of poultry. Although epidemiology, as a discipline, is endoured with a vast range of analytical techniques that can be used to enhance the understanding of factors influencing the spread of disease among animal populations, the quality of data used to support these techniques is often lacking. The challenge in the years ahead, for both developed and developing countries, is to set in place the appropriate infrastructures to collect details of animal populations consistent in quality over time and space.