The usage of antimicrobials either as performance enhancers or for prophylactic and therapeutic purposes in food animals, such as chickens, increases the prevalence of antimicrobial drug resistance among enteric bacteria of these animals. This may be transferred to people working with such animals, e.g. abattoir workers, or the products arising from these animals. In this study antimicrobial drug resistance was investigated for selected enteric bacteria from broilers raised on feed supplemented with antimicrobial growth enhancers, and the people who carry out evisceration, washing and packing of intestines in a high throughput poultry abattoir in Gauteng, South Africa. Poultry farms (n=6) were purposively selected on the basis of allowing for sampling of farms from more than one grow out cycle. Broiler carcases (n=100) were randomly selected per farm five minutes after slaughter and sampled by incising caecae from the rest of the gastro-intestinal tract (GIT). The ends of each caecae were tied off to prevent contamination and to enhance the culturing of anaerobic bacteria. In the laboratory, caecal contents were selectively cultured for Clostridium perfringens, Escherichia coli, Enterococcus faecium, E. faecalis, and vancomycin-resistant enterococci (VRE). Salmonella enterica was isolated using pre-enrichment followed by selective culture. The minimum inhibitory concentration (MIC) micro broth dilution test as prescribed by the Clinical and Laboratory Standards Institute USA (CLSI), previously known as National Committee of Clinical Laboratories (NCCL), was used to determine the susceptibility of the isolates to the following antimicrobials: vancomycin, virginiamycin, doxycycline, trimethoprim, sulphamethoxazole, ampicillin, bacitracin, enrofloxacin, erythromycin, fosfomycin, ceftriaxone and nalidixic acid. The same was done on the faeces of 29 abattoir workers exposed to potentially resistant micro-organisms from broilers and 28 persons used as controls, who had not been equally exposed to potentially resistant micro-organisms from broilers. Both of the human populations had not been treated with antimicrobials within three months prior to sampling. Statistical analysis was done by Fisher’s exact test. No salmonellae and VRE on VRE selective agar (Oxoid UK) were cultured. Two Clostridium perfringens, 168 E. coli, 20 E. faecalis and 96 E. faecium isolates from the broiler caecae were cultured. Fifty four (28 and 26) E. coli, 24 (21 and 3) E. faecalis and 12 (2 and 10) E. faeciumfrom humans were cultured. The figures in brackets represent the abattoir workers and human controls respectively. The majority of E. coli isolates from broilers had MIC’s above the cut off point for the antimicrobials tested. Low resistance was observed among broiler enterococci isolates to vancomycin, virginiamycin, trimethoprim and ampicillin. A comparison of the median MIC’s of isolates from abattoir workers (packers) and the control group revealed significant differences in the median MIC’s for the following antimicrobials; E. faecalis: enrofloxacin (p=0.019). E. faecium, trimethoprim (p=0.01), enrofloxacin (p=0.029) and erythromycin (p=0.03). E. coli: trimethoprim (p=0.012) and ampicillin (p=0.036). Use of antimicrobials as feed additives causes resistance among enteric bacteria from broilers. Significant differences between median MIC’s of abattoir workers (packers) and the control group were observed for therapeutics and not growth enhancers. There was a tendency for isolates from abattoir workers to have a higher median MIC and a higher number of resistant isolates as compared to the control group. In spite of the fact that there was a high level of resistance in the enteric commensal bacteria of broiler caecae, an association could not be shown with that of the human enteric bacteria. It could not be concluded that a significant AMR transfer to poultry abattoir workers existed. This notwithstanding, both the control and experimental group, carried levels of resistance among their enteric bacteria that could be described as being high. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2007. / Paraclinical Sciences / unrestricted

The effects of diet type, amino acid (AA), and apparent metabolizable energy (AME) levels in male broiler diets from d 8 to 21 on blood, small intestine, bone, and growth performance were investigated. Eight experimental diets with 2 protein sources [high inclusion of distiller's dried grains with solubles diet (hDDGS) or high inclusion of meat and bone meal diet (hMBM)], 2 AA densities (moderate or high), and 2 AME densities (2,998kcal/kg or 3,100kcal/kg), were fed to the broiler chicks from 8 to 21 days of age (d). High AME diets may lower feed cost by lowering feed intake. Intestinal morphology changes responded to dietary treatments, which may facilitate nutrients digestion and absorption in high MBM diets as well as in high DDGS diets. In addition, high AA or AME diets from 8 to 20 d improved feed conversion during experimental phase and influenced meat yields at 55 d.

Broiler frames were treated with antimicrobial solutions of 0.5% cetylpyridinium chloride with CitrilowTM (CPC) or 0.1% peroxyacetic acid (PAA) for contact times of 30 to 120 sec and evaluated for their effectiveness at reducing the incidence of Salmonella spp. on broiler frames and decreasing Salmonellae counts on mechanically separated chicken meat (MSC). MSC samples were evaluated for pH, color, cook loss and protein bind. Results from the preliminary study indicated that 0.5% CPC at 60, 90, and 120 sec achieved higher reduction of Salmonellae on whole broiler frames than CPC at 30 sec or any PAA treatments. In contrast, PAA exposure for 60 sec had greater log reduction of Salmonella spp. on MSC than the other PAA or CPC treatments. On average, CPC treatments were lighter (CIE L*) (P<0.05) than PAA treatments, and PAA treatments were more red (CIE a*) and yellow (CIE b*) (P<0.05) than CPC treatments.

The objective of this research was to use Bacillus subtilis-based probiotics alone or combined with various additional antibiotic alternatives (yeast-derived prebiotics and zinc supplementation) to maintain gut health and improve growth performance of antibioticree broilers. Three consecutive studies have been conducted to evaluate dietary effects on intestinal morphology, digestive organ development, microbiota, and growth performance of commercial broilers under different coccidia-challenge circumstances. In the first study, broilers were raised under commercial conditions, without coccidia-challenge (Chapter III). Broilers fed diets supplemented with antibiotics exhibited the highest body weight gain (BWG) from d 15 to 27. Broilers fed diets supplemented with B. subtilis or prebiotics + B. subtilis exhibited higher BWG from d 28 to 41 and higher BWG from d 0 to 41 as compared to birds fed control diets. In the second study, broilers were exposed to a clinical coccidia-challenge (Chapters IV and V). Interaction and main effects of the dietary supplement and coccidial vaccination were studied. Diets supplemented with Prebiotics + B. subtilis facilitated broilers to reach a similar feed conversion ratio (FCR) as to the antibiotic control group from d 0 to 56. Feeding diets supplemented with B. subtilis to coccidial vaccinated broilers reduced microbiota diversity by increasing the proportion of an antibiotic-resistant bacterium, Rikenella microfusus. In the third study, interaction and main effects of the subclinical coccidia-challenge and the dietary supplement were studied (Chapters VI and VII). The dietary anticoccidial supplementation increased feed intake and BWG and decreased FCR of broilers from d 15 to 28. However, dietary B. subtilis supplementation did not improve any growth performance of broilers. The combined use of zinc and B. subtilis lowered the high mortality of broilers fed diet supplemented with B. subtilis or zinc alone. Additionally, the dietary supplementation of zinc lowered the proportion of Clostridium in cecal contents of broilers. In conclusion, different nutrition strategies should be considered when broiler chickens are under different health circumstances. Bacillus subtilis-based probiotics have potential to replace the antibiotics, but not anticoccidial feed additives.

As the international poultry industry searches for antibiotic alternatives, dietary probiotic supplementation has exhibited the ability to decrease FCR, increase live weight gain, and regulate inflammatory responses within the gut of broiler chickens. The in ovo (or in egg) supplementation of probiotics has the potential for promoting early colonization of probiotic bacteria in the gastrointestinal tract and providing enhanced protection against pathogens in the hatchery and grow-out facilities. In the present studies, the in ovo injection of either L. animalis + E. faecium combination or L. animalis + B. licheniformis combination on d 18 of incubation does not negatively affect the chick’s ability to hatch out of the egg. These combinations also influence post-hatch performance, where FCR, gastrointestinal tissue weights, and immune-physiological parameters were impacted under non-challenged and coccidiosis-challenged grow-out conditions. These results indicate the physiological and immunomodulatory role that beneficial bacteria may have on a developing chick.

Research was conducted to evaluate the effect of dietary amino acid (AA) density (Deficient (D), Low (L), High (H), and Excessive (E)) on broiler breast and thigh meat quality. As expected, the feed conversion improved (P<0.05) as AA density increased. No differences (P>0.05) existed among treatments with regard to final pH, cooking loss, shear force, brine absorption proximate analysis, and average consumer acceptability of breast meat. The D AA diet yielded meat with less (P<0.05) moisture, less protein (P<0.05) and more fat (P<0.05) than all other treatments. Increasing AA density in the diet led to increased (P<0.05) concentrations of linoleic and linolenic acid in the thigh meat from the H and E treatments, thus making it more susceptible to oxidation (P<0.05) in comparison to the D and L treatments. Overall, data revealed that all four AA diets yielded high-quality breast and thigh meat with minimal product differences.

Increasingly, nutritionists are challenged to optimize broiler genetic capacity, while considering varying ingredient qualities and pricing, to meet production goals and profitability. Due to scale and cost, university and private research is often used by nutritionists to help make these decisions; thus, requiring these facilities to detect small, incremental improvements. In Chapters 1 and 2, processing data from several nutrition research trials were utilized to evaluate the impact of processing personnel, sample size, and unit of analysis on the detection of dietary differences. By accounting for potential variability between personnel (as a covariant) and selecting an adequate sample size for processing, researchers can reduce variability and improve the accuracy of studies. In Chapter 3, a novel serine protease was investigated to potentially mitigate some of the negative effects of ingredient variability and improve overall performance and processing. Overall, data from this thesis provide practical solutions that can be utilized by academics and the poultry industry to optimize experimental design and broiler performance.

Intensified poultry production to meet global food demands has faced challenges associated with the removal of in-feed antibiotics due to concerns over antibiotics resistance. The reduction of low-dose antibiotics in feed has allowed for reemergence of intestinal diseases that diminish animal welfare and producer economics. Alternative mechanisms to preventing disease are therefore required. The objective of this dissertation was to examine factors that contribute to chicken development and health including intestinal structure and function, environment, and genetic selection. Chapter 2 investigated the host response to infection of the parasite Eimeria maxima that predisposes chickens to a bacterial infection Clostridium perfringens. Intestinal structure, function, inflammatory response, and epithelial composition was examined during a mild subclinical infection. Analysis of E. maxima and C. perfringens as individual infections revealed how each pathogen contributes to a co-infection. E. maxima caused a more severe inflammatory response, increasing pathology scores, shortening intestinal villi, and elongating crypts in the jejunum at peak infection. C. perfringens was shown to manipulate intestinal epithelial composition by influencing stem cells to differentiate into secretory goblet cells. The most deleterious effects were observed when the pathogens were introduced together, increasing pathology scores further, damaging intestinal villi, and increasing crypt depth. The introduction of C. perfringens and E. maxima also increased signaling for the production of reactive oxygen species, stimulation of tumor necrosis factor- that is involved in innate immunity, and decreased transcription of Hes1, which is involved in Notch signaling towards absorptive cell differentiation. Hes1 has previously been shown to be involved in the inflammatory response and could be an area of interest in determining new treatments to prevent or relieve the effects of E. maxima and C. perfringens. Chapter 3 applied an environmental perspective to disease prevention and examined the properties of C. perfringens that allow it to persist in the poultry house environment. Spores resist treatments used to sanitize poultry houses and litter has been shown to be a reservoir for disease, potentially increasing occurrence in certain houses. The metabolic and physiological properties of C. perfringens were utilized to separate the microbe from other poultry litter bacteria to enumerate spores within houses. A selective and differential medium combined with a heat treatment was developed to isolate C. perfringens spores from poultry litter samples. On average, houses that had histories of necrotic enteritis harbored a greater abundance of C. perfringens spores. Colonies that were isolated on the specialized medium were confirmed using PCR as C. perfringens. Lastly, Chapter 4 examined how genetic selection for multiple traits has influenced early intestinal development compared to divergently selected lines based on eight-week body weight. This study showed the morphological and gene expression differences between lines and revealed that most pathways involved in intestinal development are conserved through genetic selection. The major differences between lines were an increase in peptide transporter PepT1 on d5 and d7 in chicks selected for low eight-week body weight (LWS) compared to high weight selected (HWS) chicks and modern broiler Cobb500 chicks. In HWS chicks, the opposite mechanism was observed with an increase in expression of secretory goblet cell marker Muc2. The findings of these studies give multiple perspectives into poultry production and how major factors in management including nutrition, environment, and genetics can be used to increase efficiency while preventing disease. / Doctor of Philosophy / In poultry production, it is important to use management methods that help chickens grow efficiently while preventing illnesses. A few factors that contribute to the success of a producer include the use of nutrition to enhance intestine health and efficiency, a healthy environment in the poultry house, and using genetics to select for multiple traits to increase productivity. These factors have become even more significant after concerns of antibiotic resistance has eliminated the use of in-feed antimicrobials, allowing for reemergence of diseases that were suppressed. Therefore, the objective of this dissertation was to utilize each of these management strategies to determine how a common disease to the poultry industry affects the chicken intestine, how the environment influences the occurrence of this disease, and how genetic selection impacts the early development of chicks that may contribute to how they handle incidences of disease. Chapter 2 investigated how the bacteria Clostridium perfringens and parasite Eimeria maxima that are commonly seen together in the industry impact the intestinal function, structure, and how the chicken's immune systems respond to invasion by these pathogens. The major finds of this chapter included an increased inflammatory response after E. maxima infection that damaged intestinal structures. These pathogens also decreased the expression of a gene involved in absorptive cell formation that contributes to the inflammatory response. In Chapter 3, environment was investigated to determine if poultry houses that harbored more C. perfringens spores, which are resistant to sanitary treatments, predispose chickens to disease. On average, houses with more spores were correlated with increased disease occurrence. The method developed to determine isolate C. perfringens spores can also be used to monitor the abundance in poultry litter and used as a management tool to prevent or diagnose disease outbreaks. In Chapter 4, the influence of genetic selection on early intestinal development was studied using a modern line of broiler chicks compared to chicks selected for low or high body weights. This study gave insight into how intestinal development is mostly conserved after selecting for multiple genetic traits or a single trait (growth). The main differences were greater body weight in the modern line and high weight selected chicks compared to low weight selected chicks and an increase in gene expression of a peptide transporter in low weight chicks and a decrease in secretory cell expression in high weight chicks. These projects investigated multiple management strategies to address intestinal development and response to pathogens, disease occurrence, and genetic selection as tools to shape intestinal structure and composition.

Within commercial broiler production, feed and feed manufacturing costs account for 60 to 70% of production costs. Of these feed costs specifically, ingredients that supply energy and protein represent the highest expenditure, verifying the importance of knowing the nutrient requirements of current broiler strains to ensure accurate least-cost formulation. To reduce these production costs and optimize performance, primary breeder companies and nutritionists continuously strive to improve nutrient utilization of commercial broiler strains. As a result of this, a great magnitude of work is conducted to determine the nutrient requirements for broilers, especially amino acids. Therefore, the overall objective of this dissertation was to utilize processing measurements, multiple statistical models, and economics as a whole to determine the optimal percent digestible Isoleucine:digestible Lysine ratio (dIle:dLys) for Ross 708 x Ross YP male broilers to improve growth performance and economic return. Chapter 2 determined the optimal dIle:dLys ratio for the starter phase (d 0-18), while Chapter 3 determined the optimal ratio for the grower phase (d 14-28), and Chapter 4 determined the optimal ratio for the finisher phase (d 28-42). All experimental diets for each respective growth phase were created from a common deficient corn and soybean meal-based diet. After manufacturing, half was retained to create the summit diet through the addition of crystalline Ile. The remaining five experimental diets for each respective growth phase were obtained by blending proportions of the deficient and summit diets. All dIle:dLys ratios were estimated using quadratic regression (QR; 95% of the asymptote), as well as linear and quadratic broken line models (LBL; QBL). Regression analysis from d 0-18 using multiple regression models estimated the ratios to range from 63-73% for BW and BWG and 68-74% for FCR. Based on the data from the grower phase and using multiple regression models, the estimated ratios ranged from 62-68% for BW and BWG and 67-70% for FCR and are similar to the current breeder nutrient specifications. Data from the finisher phase and once again using multiple regression models estimated the ratios to range from 62-66% for BW and BWG and 63-66% for FCR.

<p>  Broiler chickens are routinely exposed to various conditions, such as heat stress and stocking density, which may negatively influence their welfare status. This study examined the influence of a commercially available proprietary phytogenic feed additive (Probiotech International, Inc.) on welfare measures, environmental measures, productivity, body temperature, and behavior of commercial broiler chickens. Two flocks (Trials 1 & 2) utilized a total of 1,650 Ross 708 broilers housed in two separate rooms with floor pens at Purdue University’s ASREC Poultry Unit. </p> <p>  Trial 1 birds (n = 750) were divided into 20 separate pens (5 pens/treatment): PHD: phytogenic supplementation and raised at standard industry stocking density (37 kg/m²), PLD: phytogenic supplementation and raised at a lowered stocking density (27 kg/m²), CHD: control diet and raised at standard industry stocking density, and CLD: control diet and raised at a lowered stocking density. Due to the aromatic properties of the phytogenic additive, PHD and PLD birds were housed in one room and CHD and CLD birds were housed in another room. The feed supplement was mixed in at an inclusion rate of 0.25 g/kg. Phytogenic supplementation began at 15 d, coinciding with feeding the grower diet, and continued until 42 d when the study concluded. Heat stress was applied to all birds from 30 to 32 d, where the peak temperature did not exceed 34.4ºC. Welfare measures (gait, footpad dermatitis, hock burn, and feather cleanliness) and litter quality were assessed at 27 d and 39 d. Ammonia concentrations were measured at 35 d and 39 d. Productivity (body weight, feed intake, and feed conversion ratio) was measured weekly. Body temperature via thermography of the eye surface was collected at 29, 32, and 34 d. Behavior data were collected at the following periods for 2 continuous days: 23-24 d (Period 1), 31-32 d (Period 2), and 36-37 d (Period 3). </p> <p>  Trial 2 birds (n = 900) were assigned to 25 separate pens (5 pens/treatment) with the same groups as Trial 1, with an additional group (MHD): control diet, housed in the same room as PHD and PLD birds, and raised at standard industry stocking density. Phytogenic supplementation was provided as in Trial 1. Heat stress was again applied to all treatments from 30 to 32 d, where the peak temperature did not exceed 31ºC. Welfare measures and litter quality were collected at 27 d and 38 d. Ammonia concentrations were measured at 27, 31, and 38 d. Productivity was measured from 15 d to 27 d (grower phase), and 27 d to 38 d (finisher phase). Body temperature via cloacal temperature recording occurred at 29, 31, and 33 d. </p> <p>  Welfare data and litter quality were analyzed using PROC LOGISTIC (SAS 9.4); productivity data were analyzed using PROC MIXED (SAS 9.4); behavior data were analyzed using PROC GLIMMIX (SAS 9.4); and eye surface temperature, cloacal temperature, and ammonia concentration were analyzed using a nested mixed model found in the afex package using R (version 4.2.1) and R Studio (R Foundation for Statistical Computing). All statistical differences were considered significant when P < 0.05. Results of Trial 1 indicated that phytogenic supplementation significantly influenced hock burn and feather cleanliness, body weight and feed conversion ratio, ammonia concentration, as well as Period 1 sitting, Period 2 drinking, preening, standing, and wing spreading, and Period 3 drinking, preening, sitting, standing, and walking behaviors. Results of Trial 2 indicated that diet had no effect on any measured parameter. The variation in results suggests that factors such as stocking density or management strategies influenced the measured parameters, rather than diet alone. More research is needed to understand the specific effects of phytogenic feed additives, social and environmental stressors and whether phytogenic feed additives can improve bird performance and welfare under longer heat stress periods.</p>