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.