In order to assess Salmonella dynamics in a poultry production setting, two studies were conducted to evaluate how common environmental factors during production influence Salmonella populations in poultry litter. A field study was initially conducted to determine Salmonella prevalence, populations, serotypes, and antibiotic resistance in fresh excreta and litter from commercial North Carolina broiler farms. Litter pH, temperature, ammonia levels, moisture content, and water activity (A_w) were also measured. The purpose of this field study was to assess the populations and prevalence of Salmonella present during grow-out along with how varying environmental growth parameters and management practices impact its growth, persistence and true risk for consumers. Field data were subsequently used to design a laboratory study that observed the combined effects of pH and A_w at a constant temperature on the growth and decline of Salmonella spp. in inoculated litter for the purpose of predicting microbial behavior using statistical modeling. By understanding the growth and death kinetics of Salmonella based on environmental factors found normally during poultry production, production management strategies can be developed to reduce Salmonella populations on birds entering processing plants, thereby reducing the risk of foodborne illness for consumers.

Poult enteritis and mortality syndrome (PEMS), a condition with multifactorial etiology is characterized by an acute, contagious enteric disease of turkey poults between the ages of 2-4 weeks. The current study was conducted to define the role of PEMS-associated agents on poult performance. In the first study, the ?novel? Cornell virus, defined as the reovirus ARVCU98, a small round virus (SRV or ARVCU98) and a turkey astrovirus, Ohio State University isolate (TastOSU), were gavaged orally into the crop of turkey poults. Reduced body weights and reduced relative weights of the bursa of Fabricius, thymus, and liver were observed in virus-challenged poults. The reduced body weight gain and tissue atrophy was exacerbated by the presence of E. coli. In study number two, the possibility of vertical transmission of reovirus via the egg was tested. In ovo inoculation resulted in pathogenic and metabolic alterations in broilers challenged in ovo at day 9 of embryonation with ARVCU98 and the field isolated S1733 (1:100 and 1:500 dilution). In a third study, hyperimmunization of turkey breeder hens against the ARVCU98 reovirus provided limited protection to progeny as indicated by decreased weight gain and loss of lymphoid organ integrity in post hatch ARVCU98-challenged poults. Overall these studies demonstrated that PEMS-associated astrovirus and reovirus affected poult performance by decreasing body weight and altering lymphoid organ integrity, and the addition of E. coli further exacerbated these signs under a controlled environment. Additionally, ARVCU98 reovirus is a turkey isolate, and the evidence presented herein clearly demonstrated that it can infect broilers and that vertical transmission via the egg is a strong possibility.

<p>Large White turkey breeder hens were tested in a 4 X 3 factorial design to evaluate the effect of three different levels of physical feed restriction on subsequent reproductive performance. The feed treatments comprised: Control Control (CC) - ad libitum fed throughout the study, Control Restricted (CR) - feed restricted from 16-24 WOA, Restricted Control (RC) - feed restricted from 3-16 WOA and Restricted Restricted (RR) - feed restricted from 3-24 WOA. Feed restriction was implemented so that restricted fed hens achieved a 45% reduction in BW as compared to Control hens at 16 WOA. From 16-24 WOA restriction was implemented to maintain a slight increase in BW. At the completion of the respective restriction period, hens were gradually released back to ad libitum feeding. At the time of photostimulation (30 WOA) all treatments were divided into sub-treatments by weight: HEAVY, MEDIUM and LIGHT, resulting in four treatments with three sub-treatments within each. All hens continued on ad libitum feeding throughout a 20 wk lay cycle. Body weight (BW) for all treatments differed significantly (P<.05) at 16 and 30 WOA. At the end of lay (53 WOA) treatment CR no longer significantly differed in BW from treatment CC as did treatment RR no longer significantly differ in BW from treatment RC. Treatment CC reached maximum feed consumption at 12-15 WOA, whereas restricted treatments CR, RC and RR did not reach maximum feed consumption until just prior to photostimulation (30 WOA). At the end of the study, cumulative feed consumption was significantly less for restricted treatments. Previous research reported (Trial 1), concluded that restricting hens early in rearing preceding a lay cycle in the Winter season resulted in numerical increases in egg production. The time period for this study (Trial 2) was inverted from that of Trial 1, in that hens were photostimulated for Summer season egg production. For Trial 2, RC and RR hens laid significantly more eggs than did CC and CR hens for the first 1-5 weeks of lay (wol). However, within Trial 2, once house temperature increased to over 80-85 oF RC and RR egg production suffered dramatically, cumulating in a significant decrease in production. Hens restricted early in rearing (3-16 WOA) also cumulatively laid more soft shelled eggs and reported a decrease in hatch of fertile eggs for Trial 2. Determining why hens restricted fed early in rearing decreased egg quality and production soon after peak lay in the Summer season was a focal point of this study. Due to the fact that hens considered ?out-of-production? had circulating levels of prolactin up to 5 times less than that of hens ?in-production?, incubation behavior and broodiness were not considered to be a factor. Therefore, body composition, carcass conformation and hormonal and enzyme activity were analyzed to determine the effect feed restriction had on each of these variables. Early feed restriction reduced the percent body fat of breeder candidates while increasing the percentage of moisture and ash. Relative weights of organ and tissues samples revealed that early feed restriction resulted in a larger percentage of crop, liver and total visera for restricted fed hens. Early feed restriction also increased the percentage of bone structure regarding femur and keel bone development. However, treatments which were restricted fed early exhibited a significant reduction in absolute and relative weight of breast and thigh muscles in comparison to ad libitum fed hens at 15 WOA. Although these differences were not reported at 30 WOA on a relative basis, absolute weights remained significantly different with respect to breast muscle. This same variation with regards to breast muscle was then noted throughout the 20 wk lay cycle. The sub-treatment ?weight?, LIGHT, MEDIUM and HEAVY hens responded very much in the same manner irrespective of their initial treatment (CC, CR, RC and RR). This analysis results in the conclusion that a LIGHT hen is destined to be a LIGHT hen irrespective of her feed allotment. This phenomena is more than likely attributed to the genetic material compiled by each hen. LIGHT hens within each treatment exhibited a greater tendency for compensatory growth as compared to MEDIUM and HEAVY hens. However, egg production suffered within LIGHT hens as these hens at times laid a significantly smaller and undesirable quality of an egg. MEDIUM hens expressed a larger portion of BW through breast muscle, therefore appearing to make them the more reproductively oriented sub-treatment. In fact, MEDIUM hens did lay at a numerically higher hen housed production percentage. In conclusion, if turkey breeder hens are to lay in the Winter season, restricting feed early in rearing can prove economically beneficial. However, if hens are to lay during the Summer season, feed restriction early in rearing appears to be detrimental to subsequent reproduction in that initial breast and fat loss is never fully recuperated for the lay cycle. Therefore, feed restriction should be limited to later in rearing if any economic benefits are to be reported. <P>

Three experiments were conducted to study the impact of growth-promoting levels of various antimicrobials on performance and the development of antibiotic-resistant commensal bacteria in swine. In experiment one, feeding subtherapeutic levels of antibiotics, or high levels of zinc and copper did not improve growth performance of nursery pigs housed in a biosecure facility that were farrowed from sows not previously exposed to antibiotics. In experiment two, feeding nursery pigs obtained from a commercial source high levels of zinc resulted in increased ADG and ADFI compared to pigs fed a diet containing no antimicrobials or high levels of copper. In experiment three, subtherapeutic levels of chlortetracycline improved ADG, ADFI, and G:F for only the first week after weaning. Performance improvements were not observed for finishing pigs fed subtherapeutic levels of virginiamycin compared to pigs fed no antibiotics. High levels of zinc may be as effective as subtherapeutic antibiotics at improving nursery pig performance. The use of antimicrobial growth-promoters in clean, well-managed facilities with high labor inputs will not improve growth performance of swine. Feeding various antimicrobials were ineffective at reducing the total number of commensal bacteria isolated from pigs in any study. Although pigs in experiment one were farrowed from sows not exposed to antibiotics for over 33 years, commensal bacteria isolated from these pigs exhibited resistance to multiple antibiotics. E. coli resistant to neomycin were isolated only from pigs fed diets containing subtherapeutic antibiotics in experiment one. In experiment two, feeding pigs diets containing growth-promoting levels of antibiotics, zinc, or copper resulted in increased percent of E. coli resistant to tylosin, erythromycin, and copper. Feeding a diet with subtherapeutic levels of tylosin and sulfamethazine also increased the percent of Enterococcus resistant to tylosin, sulfamethazine, and erythromycin compared to pigs fed no antimicrobials or high levels of zinc. While fluctuations in antibiotic resistance were observed between treatments in experiment two, there were no differences between treatments in percent of bacteria resistant to any antibiotics at the conclusion of the trial. In experiment three, percent of E. coli and Enterococcus isolated from pigs that were resistant to chlortetracycline and virginiamycin fluctuated when monitored for a 19 week grow/finish study, however no differences in percent of resistant bacteria were observed between pigs fed diets containing no antibiotics or growth-promoting levels of antibiotics at the conclusion of the trial. In the fourth experiment, manure from pigs receiving growth-promoting antibiotics was spread on soil boxes and subjected to a simulated rainfall event to measure antibiotic resistance in water runoff. A greater amount of antibiotic resistant bacteria were recovered from water runoff at the initial sampling period compared to sampling 30 min after runoff began. Percent of antibiotic resistance isolated from swine can fluctuate over time. Development of antibiotic-resistant bacteria may be increased by the use of antimicrobial growth-promoters, however, resistant bacteria are present in swine facilities regardless of the use of their use. These resistant bacteria can potentially enter the environment through land application of manure. Antibiotic resistance will not be easily reversed by removal of antibiotics from livestock feeds.

Poultry-related salmonellosis is an on-going problem that the poultry industry must continue to address. To address these challenges, Salmonella populations present on litter and fecal samples of brooder and grow-out turkey farms were assessed using a quantitative procedure. Furthermore, serotyping, genotyping by pulsed-field gel electrophoresis and antibiotic resistance-susceptibility analyses were used to investigate the diversity of the Salmonella serotypes present on these farms. Additionally, alternative on-farm pathogen intervention strategies including feeding whole or coarsely ground grains, increasing insoluble fiber content of the diet and use of an alternative non-litter cage-based housing design (Broilermatic System) were evaluated. Salmonella litter populations averaged 2 logs higher in 3-wk turkey samples compared to samples from 19-wk birds. Turkey age also influenced Salmonella serotypes, genotypes and antibiotic resistance profiles. Only serovars Javiana and Mbandaka were common between 3 and 19-wk old turkeys. A higher frequency of multidrug resistance was observed in Salmonella isolates recovered from samples of 3-wk birds, on average isolates were resistant to >4 antibiotics tested. Supplementing coarse ground corn and increased insoluble fiber (wood fiber) content into the turkey diet did not adversely impact body weights. However, the treatments did not influence Salmonella colonization or fecal shedding of turkeys. To examine the impact of housing design and addition of whole or coarsely ground grains on performance, intestinal microbial diversity and Salmonella colonization, broilers were reared on four diets consisting of finely or coarsely ground corn and finely ground or whole triticale to market age and Salmonella populations measured. Whole grain supplementation decreased Salmonella cecal populations while rearing broilers on litter floor as opposed to the Broilermatic System resulted in significant reductions in Salmonella cecal populations. Moreover, feeding whole triticale presumably encouraged the proliferation of bacterial populations which may have competitively excluded Salmonella in the ceca of broilers. In conclusion, highly variable Salmonella populations and serotypes were detected across all commercial turkey farms and the use of alternative feed ingredients such as triticale may help to reduce Salmonella colonization in poultry. Moreover, diet composition and grain coarseness as well as housing design can influence the diversity of the commensal intestinal microflora which may help in the control of Salmonella colonization in broiler intestines.

Studies were conducted to develop and analyze gilt estrous behavior traits. Variance components, genetic correlations, and genetic line differences were estimated for gilt estrus, puberty, growth, composition, structural conformation, and first litter sow reproductive measures. Four groups of Landrace-Large White gilts (n=1,225, GIS of NC) from 59 sires and 330 dams were utilized. Heritability (h2) estimates for estrous traits; estrus length, maximum strength of standing reflex with a boar, total strength of standing reflex with a boar, maximum strength of standing reflex without a boar, total strength of standing reflex without a boar, vulva redness, strength of vulva reddening and swelling (VISUAL VULVA), and vulva width were 0.21, 0.13, 0.26, 0.42, 0.42, 0.26, 0.45, and 0.58, respectively. For puberty traits; age at puberty, puberty weight, puberty backfat, and puberty longissimus muscle, h2 estimates were 0.29, 0.39, 0.41, and 0.38, respectfully. The h2 of whether or not a gilt farrowed a litter (STAY1) was 0.14. Age at puberty had favorable genetic associations with estrus length, maximum strength of standing reflex with a boar, vulva redness, STAY1, and age at first farrowing (AFF) (-0.23, -0.32, 0.20, -0.27, and 0.76, respectively). Genetic correlations between estrus length and the standing reflex traits with STAY1 (0.34 to 0.74) and AFF (-0.04 to -0.41) were positive and negative, respectively. Growth rate had unfavorable genetic correlations with estrus length, the standing reflex traits, vulva redness, STAY1, and AFF (0.30, 0.14 to 0.34, -0.19, 0.52, and -0.25, respectfully). Backfat had unfavorable genetic associations with estrus length, age at puberty, and first litter total number born (TNB1) (0.29, -0.26, and 0.47, respectively). Vulva redness and TNB1 had favorable phenotypic and genetic correlations (-0.14 and -0.53, respectively). For estrous traits, crossbred performance was superior to the pure-line average for estrus length, total strength of standing reflex with a boar, vulva redness, VISUAL VULVA, and vulva width. These findings imply the use of F1 females would increase estrus length and improve vulva traits. The unfavorable genetic associations between production and reproduction traits further strengthen the need for a balanced selection objective. Based on these results it was concluded that selection for a younger age at puberty would have correlated responses of improved gilt estrous behavior and sow reproductive lifetime.

The objective of this study was to determine if dairy cow families could be used to select for superior pregnancy rate. Holstein cow records in 13 southern states were obtained from Animal Improvement Laboratory of USDA. Cows were included from historical records dating back to birth year of 1981 or 1982 as the foundation cows. Historical records included cows calving and completing lactations through August, 2005. Cows from various generations were then put in maternal family groups using dam identification within herd. Standardized milk production and pregnancy rate (based on days open) deviations were obtained within herd-year-season. A family value was calculated by averaging the first and second lactations across parity by degree of relationship to the individual (free of progeny information) for generation one though four. Each family entered into one of three groups based on average deviations milk production, pregnancy rate, and combining pregnancy rate and milk into a selection index. Analysis was performed on fifth generation members to determine if milk production and pregnancy rates in the fifth generation were significantly associated with historical performance of the respective cow families. Average of the standardized values for milk production has improved (8,542 to 10,275 kg) from generation one to five while pregnancy rate decreased from (26.91 to 18.28) in the same period for cow families having daughters represented in the fifth generation. After adjustments for sire predicted transmitting ability (PTA), maternal-grandsire PTA, and family group for milk or pregnancy rate in the model the effect of maternal cow family remained highly significant for pregnancy rate (P < 0.05, R2=0.0759) and milk production (P < 0.05, R2=0.1192) when single trait selection was utilized. Utilizing a selection index with equal weights for milk and pregnancy rate the effect of the maternal cow family remained significant (P < 0.05, R2=0.0208) but pregnancy rate was not significant (P > 0.05, R2=0.0106). The findings provide evidence that pregnancy rate and milk production are inherited through the maternal lineage. Thus, there may be potential economic value in considering maternal family history for pregnancy rate when selecting future bull dams.

Four studies were conducted to evaluate the effects of different feeding programs during rearing and production on broiler breeder male growth, fertility, and progeny performance. In Experiment I, the effects of two levels (High and Low) of cumulative nutrient intake during the rearing period to photostimulation at 21 wk of age through different dietary formulations or feeding programs were evaluated. The High cumulative nutrition program supplied 33.5 Mcal ME and 1,730 g CP, while the Low cumulative nutrition program supplied 29.6 Mcal ME and 1,470 g CP. At 21 wk of age in Experiment I-2, males were classified into Heavy or Light BW groups. A cumulative nutrient intake during the rearing period of 29.6 Mcal ME and 1,470 g CP, regardless of diet or feeding program resulted in a male of adequate BW that was able to maintain good fertility throughout the production period and produce broilers with increased 42-d BW. In Experiment III, two levels of dietary CP (12% and 17%) and two feeding programs (Concave and Sigmoid) were evaluated during the rearing period to 26 wk of age. The Concave or 17% CP treatments were unable to sustain fertility after 40 wk of age without an increased allocation of feed. In Experiments II, two antioxidant levels and different source of selenium were evaluated during the production period. In Experiment IV different feeding programs from 16 to 26 wk of age and during the production period were evaluated. The data showed that feed allocation relative to BW affected fertility more than did antioxidant inclusion. Furthermore, slow and consistently increasing feed increments from 16 to 26 wk of age and during the production period improved fertility and favorably impacted progeny performance. In conclusion, when males failed in accumulate adequate nutrients during the rearing period or gain adequate BW, as an indication of ME allocation, after photostimulation fertility declined and significant negative effects were observed in progeny performance.

Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Poultry Science" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.

The aim of this work was to study the apparent asymmetry in the breast muscles in some individual broiler chickens strain "Cobb 500", with a view to revealing the cause(s) of this asymmetrical growth. Birds showing apparent asymmetry in the breast were selected to study their breast muscles anatomically and histochemically in comparison with unselected birds as controls. The skeleton was studied in these birds too. Selected chickens had heavier body and muscle weight, and higher growth rate than the controls. However, no significant differences were obtained between the two sides of the pectoralis or supracoracoideus muscles in either group of chickens, although the degree of asymmetry of the pectoralis muscle in selected chickens was higher than in the controls. The distribution of pectoralis muscle weight (degree of asymmetry) was normally distributed in both groups of chickens. The histochemical study on the pectoralis muscle revealed that there were significant differences in fibre number and diameter between the anterior (region A) and mid part (region B) of the pectoralis muscle in both groups of chickens, in that there were more FG fibres in region B, whereas region A has more FOG and SO fibre number. The diameter of fibre type in region A was significantly larger than in region B. Differences in fibre diameters were obtained between the right and left side of the pectoralis muscle. FG and SO fibres in the left anterior side of pectoralis muscle were growing significantly faster than in the right side in selected chickens, and control (against body weight or muscle weight). However, no significant differences were obtained for fibre numbers per square millimeter either between the two sides in control or in selected chickens. Many measurements on the skeleton were taken to study the shape of the sternum and the rib-cage in both groups of chickens. The essential differences were the depth of the keel, shape of the rib-cage, and the shape of the ribs. In selected chickens, depth of the keel at the right side was significantly deeper than the left, consequently the width and height of the keel in the left side were significantly greater than in the right side. As a result, the breast angle at the right side was significantly larger than the left one. Statistical analysis revealed significant differences in the shape of the ribs between the two sides. Ribs at the left side had significantly greater: arc and chord length, enclosed area and height; than the right side. In addition the orientation dorsal angle of the left ribs was significantly greater than the right. As a result, selected birds had faster bone growth, shorter, and less bone weight than the controls, in addition to the deformities in the shape of the keel, rib-cage, and ribs. From the results, it would appear that the asymmetry in the shape of the keel and rib-cage could be the consequence of the high growth rate in body weight and increased breast muscle weight, without increase of the growth of skeletal mass. Such disproportionate change in body parts could be the result of direct selection for increased amount of breast muscles. This problem could be reduced by restriction of early growth and include the concept of the skeletal growth in the selection-programme indices.