Reducing the frequency of Salmonella in broiler flocks is important from both the standpoints of food safety consumer protection and industry viability. The goal of this dissertation is to provide a more complete identification, characterization and assessment of significance of the risk factors potentially associated with broiler flock Salmonella status as the flock progresses through sequential segments of the production continuum. The sequential segments of the continuum are: broiler breeders and hatchery, transportation from hatchery to grow-out farm, grow-out, transportation from farm to processing plant and processing. In this study broiler flocks were sampled through an entire grow-out production cycle, starting from the flock?s arrival from the hatchery to the grow-out farm, then, at the end of grow-out, upon arrival to the processing plant, and at the pre-chill and post-chill points of processing. Litter samples and drag swabs of the litter were collected in the grow-out house prior to placement and after the harvest of the flock. Epidemiological tools, questionnaires and checklists, were developed and utilized together with the company production records, soil, climatologic and other data to characterize potential risk factors of grow-out broiler flock Salmonella status. Regression modeling was used to investigate associations between the described risk factors and the sampled flock?s Salmonella status. Interrelationship of the flock and grow-out environment Salmonella status at the sequential production segments was studied as a risk factor. Models were built to describe the risk factors of Salmonella contamination of the litter and drag swabs collected in the grow-out house prior to placement of the birds. Following, models were built to identify the risk factors associated with broiler flock Salmonella status upon delivery from the hatchery to the farm and at the end of the grow-out.

<p dir="ltr">The objective of the experiments conducted for this dissertation was to investigate the effects of exogenous enzymes on nutrient digestibility for broiler chickens and growing pigs. These experiments covered the effects of phytase, protease, and carbohydrases on the nutrient availability of various diet types and ingredients, as well as evaluations of regression methods for determining ingredient energy values. One study investigated a factorial of phytase and dietary phytate levels on the ileal digestibility of amino acids (AA) and phosphorus (P) for broilers and pigs. The results of these experiments indicated that phytase improved the ileal digestibility of P (P < 0.05) and all AA (P < 0.05) for broilers regardless of the dietary phytate level, and the ileal digestibility of P (P < 0.05) and many economically important AA (P < 0.05) for pigs. This study did not reveal any significant interactions between phytase and dietary phytate, but there were a number of numerical differences in the relative effect of phytase in the two diet types. In a subsequent experiment the effects of a factorial of phytase and protease on ileal P and AA digestibility were evaluated for growing pigs. Similarly to the first study, phytase was shown to improve the ileal digestibility of P (P < 0.05) and a majority of AA (P < 0.05). There were limited main effects of protease, however, it was found to decrease the digestibility of Lys, Met, and Thr (P < 0.05). There were a number of significant quadratic interactions (P < 0.05) of protease within phytase level, where the necessary concentration of protease to elicit positive effects was dependent on phytase inclusion. The next study evaluated the effects of two carbohydrase blends on the ileal AA digestibility and energy values of soybean meal. Both enzyme blends elicited modest improvements in the ileal and total tract digestibility of energy, but there were limited effects on the energy values of the test diets. Both enzyme blends improved the apparent metabolizable energy of soybean meal, but the blend with lower activity and no protease inclusion produced the greater results with an improvement of 15.2%. These enzyme blends resulted in the improved ileal digestibility of nearly all AA from soybean meal for broilers. The last study was a validation of the three-point model for the regression method against a four-point model over both the same test ingredient inclusion range or smaller range. This evaluation used both canola meal and wheat as test ingredients to evaluate if changes in dietary energy or protein levels affect the results of this method, which are representative of both cereal grains and protein concentrates, respectively. The results indicated that there was no difference in the three and four-point models for either ingredient as long as the overall range of test ingredient concentration was the same in both models. This proved more important for canola meal, as it was more susceptible to problems with the estimates or variability based on changes in inclusion. Based on the results of these experiments, it is clear that phytase can improve the AA digestibility for both pigs and chickens, but care must be taken when combinations are made with protease. These data indicate that the use of carbohydrase blends can improve the nutrient availability of soybean meal, and this could have significant implications in diet formulation. Lastly, the use of the three-point model for the regression method is appropriate, but is dependent on the inclusion level of the test ingredient test ingredient.</p>

Genetic selection for improved performance has necessitated the frequent update of amino acid requirements to support this improvement. The first objective of this dissertation was to investigate the tryptophan requirement of laying hens in peak production and the lysine and sulfur amino acid requirements of broiler chicks under a phase feeding scenario using different models. Digestible tryptophan requirements were estimated to be 137 for egg production, 133 for egg mass, and 133 for feed efficiency using the linear broken-line model. The lysine and sulfur amino acid requirement were estimated by conducting 3 experiments within the starter phase from 2 to 5, 5 to 8, and 8 to 11 days of age. The linear broken line estimate for digestible lysine was 1.22, 1.17 and 1.16% for BWG and 1.31, 1.21, and 1.14% for FCR in experiments 1, 2, and 3, respectively. The linear broken line estimate for sulfur amino acids was 0.82, 0.81 and 0.94% for BWG and 0.82, 0.80, and 0.90 for FCR in experiments 4, 5, and 6, respectively. The lysine requirements decreased from 2 to 5 to 8 to 11 days, however the sulfur amino acid requirements increased during that same period. This could be due to other roles that sulfur amino acids play in the body other than growth. The second objective of this dissertation was to investigate the effects of a direct fed microbial (DFM) on broilers exposed to a cyclic heat stress in 2 consecutive experiments. In this experiment, the heat stress treatment reduced body weight gain and lean tissue accretion from 0 to 35 d in both experiments. In Experiment 2, when the litter was reused BWG was increased by 36 g/bird with supplementation of DFM. Ileal digestibility at 28 d (2 hr post HS) was improved with DFM supplementation in both experiments. Serum FITC-d increased with HS at both 28 and 35 d. Serum FITC-d was generally decreased with DFM at 28 d but the response was inconsistent at 35 d. Overall, the results suggest that HS reduced broiler performance and DFM treatment improved intestinal permeability and nutrient digestibility responses to HS in both experiments but did not improve performance until built up litter was used in Experiment 2. The last objective of this dissertation was to investigate the effects of sulfur amino acids (SAA) on broilers exposed to a cyclic heat stress. As expected, HS reduced BWG and worsened FCR. The supplementation of SAA had no effect on live performance. At 28 d of age, supplementation of SAA to birds exposed to HS resulted in reduced intestinal permeability. The interaction was lost at 31 d, but HS still increased intestinal permeability (P ≤ 0.05). Potential oxidative damage was reduced by increased SAA supplementation as indicated by an increase in the reduced glutathione to oxidized glutathione ratio. These data suggest that intestinal permeability is compromised acutely to at least three days of heat exposure before the bird can adjust, but oxidative damage is more chronic building over the entire 7 d HS period. SAA might have some protective effect on both intestinal permeability and oxidative stress responses to HS. / Doctor of Philosophy / To provide low-cost meat and eggs to consumers, the poultry industry must focus on improving efficiency as well as reduce the impact of stressors within the environment. This is achieved mostly by genetic selection which has resulted in significant improvements in both egg production in laying hens and body weight in broiler chickens. To support this improvement in growth rate birds would require a higher amino acid dense diet to support the increased protein output. One objective of this dissertation was to update the requirement of three key amino acids (tryptophan, lysine, and sulfur amino acids) in both laying hens and broilers for better formulation of diets. These amino acids that were investigated are essential in poultry diets and cannot be produced by the birds. The results from the tryptophan experiment indicated that laying hens need 137 mg of tryptophan per day to maintain maximum egg production. Results from the lysine and sulfur amino acid requirement experiment in broiler chickens indicated that broilers need 1.31% lysine and 0.90% sulfur amino acids to support maximal growth, but these requirements change over time and would need to be adjusted based on the broiler's age. Heat stress in the poultry industry is a major challenge which can affect the growth rate as well as the welfare of broiler chickens. The second objective of this dissertation was to investigate different strategies to ameliorate the effects of heat stress. Supplementing direct fed microbials or probiotics in broiler diets has been proposed as one of those strategies. An experiment was conducted to investigate the effect of the supplementation of a DFM on broiler chickens exposed to heat stress. The results indicated that the DFM was able to ameliorate the negative impacts of the heat stress on nutrient digestibility and intestinal permeability but did not improve the growth of the chickens. Another experiment was conducted to evaluate another strategy to ameliorate the effects of heat stress on broiler chickens which was the supplementation of sulfur amino acids. The sulfur amino acids are not only used for protein synthesis but have other physiological roles in the body that are important specifically during heat stress. Results from this experiment indicated that sulfur amino acids were able to ameliorate the negative effect of heat stress on intestinal permeability and oxidative stress but did not improve the performance of chickens subjected to the heat stress.

Methionine (Met) is an essential amino acid for animals and also the first limiting amino acid in a broiler diet. The dietary supplemental Met sources include the natural isoform L-methionine (L-Met), the synthetic form DL-methionine (DL-Met) and the synthetic Met precursor DL-2-hydroxy-4 (methylthio)-butanoic acid (DL-HMTBA). The objective of this dissertation was to determine the effect of different dietary Met source supplementation and Met deficiency on a series of physiological and biochemical aspects, including growth performance, global DNA methylation and methyltransferase activity, blood antioxidant profile (e.g., acute phase protein, leukocyte count), intestinal nutrient transporter gene expression, Met converting enzyme gene expression and activity, oxidative stress markers, and a potential pathway related to amino acid signaling. To achieve this goal, male Cobb-500 broilers were raised from day of hatch (d0) to d35 post-hatch and fed a diet deficient in methionine and cysteine (Met + Cys) (control) or the same diet supplemented with 0.22% DL-Met, 0.22% L-Met or 0.31% DL-HMTBA (to provide 0.22% DL-Met equivalent) to meet Met + Cys requirements. Tissues (liver, breast muscle, duodenum, jejunum and ileum) and blood samples were collected at various ages from d0 to d35 for analysis. Met supplementation significantly improved body weight gain and feed efficiency compared to the Met deficient group, but no differences were observed among DL-Met, L-Met and DL-HMTBA for growth performance parameters (P > 0.05). Met supplementation had no effect on red blood cell packed cell volume, white blood cell differential count, hepatic total DNA methylation, DNA methyltransferase and Met oxidase activity, and had limited effects on activation of p70S6K, a key amino acid signaling protein (P > 0.05). Although dietary Met sources did not change oxidative status of the treated chickens, both L-Met and DL-Met but not DL-HMTBA supplementation decreased the level of acute phase protein serum amyloid A compared to the control group (P > 0.05). The effect of Met supplementation on gene expression of nutrient transporters and Met converting enzymes were complex and dynamic. Most of the target genes demonstrated tissue- and development-dependent expression patterns, with few significant treatment effects observed. L-Met and DL-Met but not DL-HMTBA supplementation enhanced the neutral amino acid transporters ATB0,+ and B0AT gene expression in various small intestinal segments. All three Met sources increased monocarboxylic acid transporter (MCT1) gene expression in the jejunum. DL-HMTBA and L-Met fed chickens showed greater hepatic L-HMTBA oxidase (HAO1) gene expression. DL-Met increased glutamic-oxaloacetic transaminase 2 (GOT2) gene expression in the duodenum. An in vitro study with tissue explants, however, did not demonstrate a similar gene expression pattern as that in the in vivo study. Lastly, RNA sequencing results illustrated that Met deficiency could lead to many differentially expressed genes but different supplemental Met sources had no influence on hepatic gene expression profiles. In conclusion, as common dietary supplemental Met sources, L-Met, DL-Met and DL-HMTBA exhibited similarity in impacting intestinal amino acid/peptide/monocarboxylic acid transporter gene expression and Met converting enzyme activity. The regulatory roles of Met as an antioxidant and nutrient signaling in cell metabolism were not affected by different dietary supplemental Met sources. / Ph. D.

High feed ingredient prices have increased the use of by-products containing a high proportion of polyunsaturated fatty acids (PUFA) in pig and chicken feeds. This can increase the oxidation of other feed nutrients as well as causing oxidative stress in animals. Two studies were conducted to evaluate the effects of a dietary antioxidant blend (AOX, ethoxyquin and propyl gallate) in pigs and broiler chickens fed a diet high in oxidants. The objective of the first study was to evaluate the antioxidant blend on growth performance, meat quality, liver function, oxidative status, carcass characteristics, meat quality, and fatty acid profile in pigs. Crossbred barrows (n = 100, 10.91 ± 0.65 kg, 36 ± 2 d of age, Landrace × Duroc) were allotted to 5 treatments based on body weight (BW, 5 replicate pens per treatment, 4 pigs per pen). Treatments included: 1) HO: high oxidant diet containing 5% oxidized soy oil and 10% PUFA source (containing docosahexaenoic acid, DHA, 3.7% of diet); 2) VE: the HO diet with 11 IU/kg of added vitamin E; 3) AOX: the HO diet with AOX (135 mg/kg); 4) VE+AOX: the HO diet with both vitamin E and AOX; and 5) SC: a standard corn-soy control diet. The trial lasted for 118 d; on d 83, the HO diet pigs were switched to the SC diet because the animals were displaying very poor health. Compared with SC pigs, HO pigs had decreased average daily gain (ADG) and average daily feed intake (ADFI) from d 26 to 82 (P < 0.05). However, after switching the HO pigs to the SC diet, the VE treatment became the most stressed treatment with the poorest performance from d 83 to 118 (P < 0.05). The AOX restored pig performance to a level similar to pigs fed the SC diet (P > 0.05) with greater gain to feed ratio (G:F) for the entire period (P < 0.05). The AOX added treatments also attenuated the enlarged liver symptoms and reduced markers of liver stress including total bilirubin and aspartate transaminase, thiobarbituric acid reactive substances (TBARS) and carbonyl concentrations. In addition, the AOX addition in the high oxidant diet restored the lighter carcass weight, less back fat, less lean body mass and smaller loin eye area, decreased dressing percentage and intensive lipofuscin deposition induced by the high oxidant diet. However, the traits of loin muscle redness and belly firmness were not fully corrected by AOX. The second study was to investigate the antioxidant blend and vitamin E on growth performance, oxidative status, meat quality, fatty acid profile, liver function and inflammatory response in broiler chickens. Cobb 500 male broilers (n = 1200, 44.7 ± 0.8 g, d 0) were randomly distributed into 60 floor pens across 6 treatments with 10 replicate pens of 20 chicks each. Treatments included: 1) HO: high oxidant diet with vitamin E at 10 IU/kg, 3% oxidized oil, 3% PUFA source; 2) VE: the HO diet with vitamin E at 200 IU/kg; 3) AOX: the HO diet with AOX at 135 mg/kg, 4) VE+AOX: the HO diet with both vitamin E at 200 IU/kg and AOX at 135 mg/kg, 5) SC: standard control, a corn soy diet with vitamin E at 10 IU/kg, 3% non-oxidized soybean oil, no PUFA source, and 6) PC: positive control, the SC diet with AOX at 135 mg/kg. Compared to the SC birds, the PUFA added treatments (HO, VE, AOX, VE+AOX) groups had greater body weight, ADG and ADFI from d 0 through d 21 (P < 0.05). However, the growth of birds fed the VE treatment fell behind that of other treatments (P < 0.05) during the last 21 d of the trial. Compared to the HO birds, the AOX birds had lower TBARS and greater uric acid concentrations in the plasma, greater gene expression of superoxide dismutase and less drip loss, suggesting enhanced systematic antioxidant capability. In addition, dietary addition of AOX or AOX plus VE moderately improved liver function and reduced inflammation in fat tissue to a level similar to control groups. In both studies, the AOX supplement was effective in preserving PUFA, especially DHA deposition in the back fat of pigs and abdominal fat of chickens. These results suggest that feeding the high oxidant diet caused a series of changes in growth performance, liver function, oxidative status, carcass characteristics and meat quality in pigs, and AOX addition attenuated many of these. The supplementation of AOX also showed some effects on reducing oxidative stress in chickens. However, the effects were not as profound as the pig study. / Ph. D.

Understanding the central nervous systems role in appetite regulation is crucial to cure the obesity epidemic, which is more prevalent than any disease in the United States. Central appetite regulators, known as neuropeptides, are pivotal in understanding appetite regulation. Neuropeptide Y (NPY), a 36 amino acid peptide, plays a major role in regulating the hunger signals from the brain. In all vertebrates studied, it is a strong orexigenic neurotransmitter located throughout multiple nuclei of the hypothalamus. Peripheral hormones associated with hunger are able to activate NPY neurons in the arcuate nucleus, which leads to a cascade of events that activate orexigenic neurons throughout the hypothalamus. Although extensive research has gone into understanding the role of NPY in appetite regulation, the effects of macronutrient composition of diets on NPY function have not been elucidated in non-mammalian species. This research investigates how food intake is affected by dietary macronutrient composition in broiler type chickens that are fed three varying macronutrient diets: high carbohydrate (22% CP, 3000kcal/kg) a broiler starter diet, high fat (60% ME from lard), high protein 30%CP). All diets were formulated to be isocaloric. When chicks are fed the high fat diet central NPY administration has a greater effect on feed intake compared to both the basal and high protein diet. Regardless of what diet the chick is fed from hatch, if they are switched to one of the other two diets post central administration of NPY the high fat diet stimulated feed intake for the longest duration. Although, NPY had the strongest orexigenic effect on chicks fed the high fat diet, in a choice diet situation broiler chicks chose the high protein diet, independent of central NPY administration. / Master of Science

Broilers are raised indoors on high density farms with bedding/litter to trap their manure. Ammonia gas, which is produced as the manure decomposes, has adverse effects on human health, bird welfare and the environment. Using litter amendments can reduce the amount and, consequently, the effects of ammonia emitted from broiler houses. The objective of this study was to determine the effectiveness of a biodegradable litter amendment (BLA) in reducing ammonia emitted from a broiler house. A pilot scale test was set up with six adjacent, individually ventilated rooms and a stocking density of 0.07 m² per bird. The birds were fed with a standard commercial, corn and soybean meal based diet and water was provided ad libitum. The first flock was grown on 10 cm of fresh, kiln-dried pine shavings, while subsequent flocks were grown on top-dressed reused litter. The two treatments (control (CTL) and BLA) were randomly assigned to the six rooms after flock 1, to give three replicates per treatment. The exhaust air from the rooms was sampled for ammonia concentration for two days each week starting at four days of age to determine the amount of ammonia emitted. Over three subsequent flocks, the total mass of ammonia emitted from rooms treated with BLA was 31% to 47% lower than the control. Ammonia emitted per bird grown on treated litter and per kg of harvested bird weight was 32% to 44% lower, and the exhaust fans ran 7% to 22% less than CTL over the same period. For both BLA and CTL, the amount of ammonia emitted generally increased with bird age and litter reuse. The study showed that BLA effectively reduced ammonia emitted from a broiler house and that there are potential energy savings from using the amendment. However, ammonia emitted from the BLA rooms during the final flock was 57% higher than CTL, which was attributed to insufficient water (less than 18% moisture by weight) to support the reaction between BLA and ammonia. / Ph. D.

As productive performance is improved by breed selection, amino acid requirements may change to support this higher performance in poultry. The first objective of this dissertation was to update the valine and tryptophan requirement of small-framed laying hens and the lysine requirement of young broilers using empirical dose-response methods. The tryptophan requirement was estimated as 155.8 mg/d for egg mass, 153.2 mg/d for egg production and 140.4 mg/d for feed conversion ratio using a linear broken line model. For valine, the requirement was highest for egg mass, 597.3 mg/d, followed by egg production, 591.9 mg/d and feed conversion ratio (FCR), 500.5 mg/d. The lysine requirement of young chicks was estimated by conducting four short term experiments from 1 to 3, 3 to 5, 5 to 8 and 8 to 11 days of age, respectively. The lysine requirement from 1 to 3, 3 to 5 and 5 to 8 days of age were not able to be estimated as no dose response was observed on growth performance most likely due to an overestimation of the lysine requirement. Digestible lysine requirement from 8 to 11 days of age was 1.057%, 1.050% and 1.016% based on body weight gain, FCR and pectoralis major weight using a linear broken line model, respectively. In addition to determining amino acid requirements, research was conducted to develop a new bacterial protein meal for use in laying hens diets. The data suggested that diets containing 7.5% of the bacterial protein meal was able to at least maintain egg production in laying hens, but 15% bacterial protein meal resulted in reduced performance. The second objective of this dissertation was to investigate the effects of various concentrations of dietary vitamin D3 on pullet and laying hen performance, eggshell quality and bone health in laying hens. Pullets/hens were randomly assigned to five dietary treatments containing vitamin D3 from 1,681 to 68,348 IU/kg diet from day of hatch until 68 weeks of age. These data suggested that dietary vitamin D3 fed at 68,348 IU/kg resulted in reduced egg production, but vitamin D from 8,348 to 35,014 IU/kg diet maintained egg production, increased egg vitamin D content in a dose dependent manner, and generally increased both eggshell quality and pullet and hen bone mineral status. / Ph. D.

The prophylactic use of antibiotics is rapidly being phased out of poultry operations. Diseases such as coccidiosis are extremely costly, and typically prevented with coccidiostats and antibiotics. New regulation banning antibiotics is mandating a search for new alternatives, such as probiotics and phytogenic feed additives (PFAs). Two separate studies were performed to evaluate the performance and microbial profiles of commercial broilers fed either PFAs or Eimeria challenged broilers fed probiotics. During the probiotics study, 1056 day-old male Ross broiler chicks were assigned to one of 6 treatments, 8 replicates per treatment, with 22 birds per floor pen in a 2x3 factorial arrangement, with DFM mix and coccidiosis challenge being the main factors. Treatments included a non-infected control (NC), a non-infected low level DFM-fed group (DL), a non-infected high level DFM-fed group (DH), an infected control (PC), an infected low level DFM-fed group (DL+), and an infected high level DFM-fed group (DH+). Performance measurements were taken on d0, d7, d14, d21, and d28. Mucosal scrapings from the ileum were obtained on d7, d14, d21, and d28 to determine microbial profiles. On d15, birds in the three infected groups were challenged with a mixed inoculum containing Eimeria maxima, E. tenella, and E. acervulina. Lesion scores were assessed on d21. Body composition was analyzed via Dual Energy X-Ray Absorptiometry (DXA) on d28. Results indicated a trend (P < 0.1) toward improved D28 body composition, lower Clostridium in DFM-fed challenged broilers compared to PC, and higher Bacillus in DH compared to DH+. Results were not significant for BW, BWG, FI, or lesion scores. The second study evaluated the effects of PFA provided as a dietary supplement over a 6-week period on performance and immune responses in broilers. In total, 1056 day-old male chicks were randomly assigned to 8 replicate pens (22 birds/pen) with 6 treatments including a standard corn/wheat basal diet, a basal with antibiotics, and 4 various combinations of PFA (PHY 1, 2, 3, and 4). Performance was assessed on day 7 (D7), 14, 28, and 42. Starter diet was fed D0-14, grower D14-28, and finisher D28-42. Microbial profiling was assessed on D7, 14, and 42, and body composition measured on D42 using Dual Energy X-Ray Absorptiometry (DXA). Results varied by week, but cumulatively, body weight gain (BWG) per bird was higher in PHY1 and 4, statistically similar to AGP and CTRL. With feed conversion ratio (FCR), PHY2 was higher than any other treatment between D0-42, while all other treatments were similar. PCR results were not statistically significant; however, DXA results indicated a higher lean to fat ratio in birds from PHY1-4 when compared to AGP, indicating an overall leaner bird in PHY treatments. The results of these studies suggest that diets supplemented with DFMs or PFAs result in improved broiler performance. / Master of Science / The prophylactic use of antibiotics is rapidly being phased out of poultry operations. Diseases such as coccidiosis are extremely costly, and typically prevented with coccidiostats and antibiotics. New regulation banning antibiotics is mandating a search for new alternatives, such as probiotics and phytogenic feed additives (PFAs). Two separate studies were performed to evaluate the performance and microbial profiles of commercial broilers fed either PFAs or Eimeria challenged broilers fed probiotics. During the probiotics study, 1056 day-old male Ross broiler chicks were assigned to one of 6 treatments, 8 replicates per treatment, with 22 birds per floor pen in a 2x3 factorial arrangement, with DFM mix and coccidiosis challenge being the main factors. Treatments included a non-infected control (NC), a non-infected low level DFM-fed group (DL), a non-infected high level DFM-fed group (DH), an infected control (PC), an infected low level DFM-fed group (DL+), and an infected high level DFM-fed group (DH+). Performance measurements were taken on d0, d7, d14, d21, and d28. Mucosal scrapings from the ileum were obtained on d7, d14, d21, and d28 to determine microbial profiles. On d15, birds in the three infected groups were challenged with a mixed inoculum containing Eimeria maxima, E. tenella, and E. acervulina. Lesion scores were assessed on d21. Body composition was analyzed via Dual Energy X-Ray Absorptiometry (DXA) on d28. Results indicated a trend (P < 0.1) toward improved D28 body composition, lower Clostridium in DFM-fed challenged broilers compared to PC, and higher Bacillus in DH compared to DH+. Results were not significant for BW, BWG, FI, or lesion scores. The second study evaluated the effects of PFA provided as a dietary supplement over a 6-week period on performance and immune responses in broilers. In total, 1056 day-old male chicks were randomly assigned to 8 replicate pens (22 birds/pen) with 6 treatments including a standard corn/wheat basal diet, a basal with antibiotics, and 4 various combinations of PFA (PHY 1, 2, 3, and 4). Performance was assessed on day 7 (D7), 14, 28, and 42. Starter diet was fed D0-14, grower D14-28, and finisher D28-42. Microbial profiling was assessed on D7, 14, and 42, and body composition measured on D42 using Dual Energy X-Ray Absorptiometry (DXA). Results varied by week, but cumulatively, body weight gain (BWG) per bird was higher in PHY1 and 4, statistically similar to AGP and CTRL. With feed conversion ratio (FCR), PHY2 was higher than any other treatment between D0-42, while all other treatments were similar. PCR results were not statistically significant; however, DXA results indicated a higher lean to fat ratio in birds from PHY1-4 when compared to AGP, indicating an overall leaner bird in PHY treatments. The results of these studies suggest that diets supplemented with DFMs or PFAs result in improved broiler performance.

The following study was conducted to investigate the antibacterial and feed additive potential of medicinal plants. Ethanol extracts of different medicinal plants including Curcuma longa (Turmeric), Zingiber officinale (Ginger), Piper nigrum (Black Pepper), Cinnamomum cassia (Cinnamon), Thymus vulgaris (Thyme), Laurus nobilis (Bay leaf), and Syzgium aromaticum (Clove) were tested using the disc diffusion method for their antimicrobial activity against the common poultry pathogens E. coli, S. typhimurium, E. faecium, and E. faecalis. Cinnamon extract (CE), at 130 mg/disk, exhibited antibacterial activity against E. coli, S. typhimurium, and E. faecalis. Thyme extract (TE), at 30 mg/disk, exhibited antibacterial activity against E. coli, E. faecium, and E. faecalis while the remaining medicinal plants extracts showed no activity. The minimum inhibitory concentration (MIC) of the cinnamon and thyme ranged from 31.25 to 250 mg/ml by the dilution method. From this in vitro antibacterial study, cinnamon and thyme were selected for a 21-d feeding trial in broilers to study their influence on feed consumption, body weight gain, and feed conversion. There were 6 dietary treatments groups: 1) negative control (NC) containing no plant extracts or antibiotic, 2) positive control (PC) containing BMD (bacitracin) at 50g/ton of feed, 3) Diet 1 plus low level of cinnamon extract (LCE) at 290 gm/100 kg of feed, 4) Diet 1 plus high level of cinnamon extract (HCE) at 580 gm/ 100 kg of feed, 5) Diet 1 plus low level of thyme extract (LTE) at 290 gm/100kg of feed, and 6) Diet 6 plus high level of thyme extract (HTE) at 580 gm/100 kg of feed. No significant changes in body weight gain were observed with the cinnamon extracts compared to the NC or PC at 7, 14, or 21 d. The HTE reduced body weight gain compare to the NC and PC at 7, 14, and 21 d (P < 0.02). No difference in feed efficiency was observed with any of the treatments except LCE which reduced feed efficiency compared to other treatments. No difference in feed consumption was found among any of the treatments. These results suggest that cinnamon and thyme have antibacterial activity in vitro, and thyme has an activity that reduces body weight. Since cinnamon caused no significant change in body weight gain compared to positive or negative controls, it warrants further study as a substitute for antibiotics in the diet. / Master of Science