Dissertations

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Characterizing microbial dynamics in continuous cultures ans lactation performance of cows fed gamagrass
(2002-12-19) Eun, Jong-Su; Vivek Fellner, Ph.D., Committee Chair; Jerry W. Spears, Ph.D., Committee Co-Chair; Joseph C. Burns, Ph.D., Committee Member; Gerald B. Huntington, Ph.D., Committee Member
Three experiments were performed to investigate the dynamics of fermentation in continuous cultures and lactation performance of cows fed gamagrass. We first studied the effects of dilution rate and forage to concentrate ratio on fermentation by rumen microbes cultured in fermentors. Methane production, when calculated from stoichiometric equations, did not change with dilution rate or forage to concentrate ratio. When measured from gas taken from fermentor headspace, methane production increased with dilution rate and level of forage in the diet. Compared to actual concentrations, stoichiometric equations consistently underestimated methane output at higher dilution rates and with high forage diets. Higher dilution rates resulted in an increase in microbial yield and microbial efficiency. Increasing the level of concentrate in the diet only increased microbial efficiency. Overall results show that dilution rate and forage to concentrate ratio can alter the partitioning of substrate by rumen microbes. Further that gas production, in particular methane, may not be accurately estimated using stoichiometrics of end product appearance. Twenty lactating Holstein cows were fed gamagrass hay or silage without or with supplemental corn to determine their effects on milk production. Milk yield did not differ among cows fed gamagrass hay or gamagrass silage. Feeding supplemental corn increased milk yield but only at the medium and high levels of corn inclusion. Gamagrass silage increased the conversion of feed nitrogen to milk nitrogen compared to gamagrass hay. Contrary to expectation, gamagrass silage lowered milk urea nitrogen compared to hay. Supplemental corn further reduced milk urea nitrogen. In the last experiment, we investigated the characteristics of microbial fermentation of gamagrass. Increasing corn supplementation in gamagrass silage linearly decreased culture pH whereas ammonia nitrogen was similar across treatments. Corn supplementation to gamagrass silage was an effective strategy to increase microbial capture of rumen degradable protein from gamagrass via enhanced availability of ruminal fermentable energy. However, gamagrass silage without corn supplementation resulted in higher efficiency of microbial growth but at the expense of microbial yield.
Cobalt Requirements of Growing and Finishing Cattle Based on Performance, Vitamin B12 Status and Metabolite Concentrations.
(2003-09-18) Tiffany, Mark Elton; Jerry W. Spears, Committee Chair; Vivek Fellner, Committee Member; Roger L. McCraw, Committee Member; Gerald B. Huntington, Committee Member
Experiments were conducted to determine cobalt requirements for growing and finishing beef cattle, compare the relative bioavailability of different cobalt sources, and evaluate the effects of cobalt on ruminal fermentation. During experiments 1 and 2 steers were fed corn-cottonseed hull-soybean meal-based growing diets, followed by high concentrate finishing diets (diets contained approximately 0.05 mg Co/kg). Dietary treatments for experiment 1 consisted of 0, 0.05, 0.10 and 1.0 mg of supplemental Co/kg DM from CoCO3 or 0.05 and 0.10 mg of supplemental Co/kg DM from Co propionate (CoPr). Treatments were similar for experiment 2 with the exception that the Co supplemented at 1.0 mg/kg was as CoPr instead of CoCO3. Performance was not affected by cobalt source or supplementation during the growing phase of either study. However, cobalt supplementation to the finishing diet increased feed intake, average daily gain, plasma and liver vitamin B12, and plasma glucose, and decreased plasma methylmalonic acid. Supplemental cobalt increased ruminal propionate proportions during the finishing phase, and steers supplemented with CoPr had higher ruminal propionate relative to those supplemented with CoCO3 during the growing phase. During the third study the effects of supplementing cobalt to corn or barley-based finishing diets were evaluated in steers. Supplemental cobalt increased intake, gain, and vitamin B12 and folate status of finishing steers. Steers fed barley gained less, had lower ruminal, plasma, and liver vitamin B12, lower plasma and liver folate, and lower plasma glucose relative to those fed corn-based diets. In the final study, in vitro fermentation characteristics of ruminal microbes fed corn-based diets supplemented with cobalt were evaluated. Within three days, cobalt supplementation resulted in a substantial increase in microbial vitamin B12 production. In addition, ruminal succinate concentrations of the unsupplemented control cultures increased sharply suggesting that the vitamin B12-dependent enzymatic conversion of succinate to propionate had been affected. Based on performance, vitamin B12 status, and metabolite concentrations, 0.15 mg/kg of total dietary cobalt is required for finishing steers.
Computational Modeling of Cell Signaling Network Using Hill Function and Markov Chain Monte Carlo Methods.
(2010-07-06) Davis, Xin; Roger McCraw, Committee Chair; Miles See, Committee Chair; Charles Smith, Committee Member; David Dickey, Committee Member; Vytas A. Bankaitis, Committee Member; Maria Correa, Committee Member; Jason Haugh, Committee Member
Dietary and Genetic Effects on Cellular Copper Homeostasis in Bovine and Porcine Tissues.
(2010-12-07) Fry, Robert Scott; Melissa Ashwell, Committee Chair; Jerry Spears, Committee Chair; Jerry Spears, Committee Chair; ENGLE, TERRY E. (E), Committee Member; Melissa Ashwell, Committee Member; Paul Siciliano, Committee Member; Sung Kim, Committee Member; Randy Wells, Committee Member
Distance Education Teaching Methods and Student Responses in the Animal Sciences.
(2011-12-19) Bing, Jada; Shannon Phillips, Co-Chair; Charlotte Farin, Chair; Charles Whisnant, Member; Koralalage Jayaratne, Member; Charles Stark, Graduate School Representative
Effect of Male Broiler Breeder Feeding Programs on Growth, Reproductive Performance, and Broiler Progeny
(2006-12-14) Romero-Sanchez, Hugo; Jerry W. Spears, Committee Member; Pam Arroway, Committee Member; Sam L. Pardue, Committee Member; John T. Brake, Committee Chair
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.
Effects Of Feeder Space and Feeding Programs During Rearing and Laying On Broiler Breeder Reproductive Performance and Livability.
(2010-10-29) Leksrisompong, Nirada; John Brake, Committee Chair; Edgar Oviedo-Rondon, Committee Chair; Jerry Spears, Committee Member; Charles Stark, Committee Member; Craig Sullivan, Committee Member
Effects of FSH Administration During the Neonatal Period on Adult Sperm Concentrations in Boars
(2008-07-21) Stewart, Kara Roski; Glen Almond, Committee Member; Brenda Alston-Mills, Committee Member; Todd See, Committee Member; William Flowers, Committee Chair
This study was designed to test the effects of neonatal FSH administration on sertoli cell mitosis and adult sperm production in boars. The treatment groups received 100μg⁄kg body weight of FSH (I.M.) every other day from either day 4-22 (early) or day 22-40 (late) after birth. Volumes of FSH were corrected weekly for increases in body weight. Four boars from each treatment group were castrated on days 21, 42, 98 and 330. The testes were evaluated for GATA-4 and PCNA activities and germ cell development. Blood samples were collected weekly through 9 weeks of age and then monthly after 59 weeks of age and evaluated for testosterone, estrogen, FSH, LH and IGF-1 concentrations. Four boars from each treatment group remained intact and were used for weekly semen collection. Volume, concentration and total numbers of spermatozoa were recorded weekly and motility, mobility, and morphology analysis were performed monthly. All data was analyzed using SAS and proc GLM or proc Mixed, where appropriate. Boars in the early treatment group had an increase in testosterone concentrations at 77 weeks of age (p≤.0001). There were no differences among treatment groups in the mass of the seminiferous tubules (p=0.4055) or the number of sertoli cells per organ (p=0.7010). Only boars in the FSH treated groups had sertoli cells undergoing proliferation at day 98. The sperm concentration per ejaculate was higher for the early treatment group compared to controls or the late treatment group (p=0.06). The early treatment group also had increased numbers of primary spermatocytes as adults (p=0.0005). There were no effects of treatment on estimates of semen quality. Overall these results indicate that neonatal FSH treatment increased the length of time over which sertoli cell proliferation occurs during sexual maturation which resulted in an increase in the production of spermatozoa in adults.
The effects of growth modifiers and health status on appetite and growth regulatory mechanisms in swine
(2004-03-17) Oliver, William Thomas; Dr. Glen W. Almond, Committee Member; Dr. C. Scott Whisnant, Committee Member; Dr. Jack Odle, Committee Co-Chair; Dr. Robert J. Harrell, Committee Co-Chair
The objective of the first experiment was to determine the effects of an anti-GnRF vaccine and porcine ST (pST) in group housed boars and gilts. A total of 224 pigs were used in a 2x2x2 factorial design, with the factors being a GnRF vaccine (Improvac, 0 or 2 mL at 13 and 17 wk of age), pST (0 or 5 mg/d from 17 wk of age), and gender. Daily gain was increased by pST (P=.03) and Improvac (P<.001). Feed intake was lower in gilts than boars (P=.01), was decreased by pST (P=.01) and increased by Improvac treatment (P<.01). Lean tissue deposition rate was lower in gilts than in boars P<.01), increased by pST (P<.01) and by Improvac (P=.014). Fat deposition rate tended to be lower in gilts than in boars (P=.06), decreased by pST (P<.01) and increased by Improvac (P<.01). In conclusion, Improvac increased growth rate through increased lean and fat deposition, but concomitant use of Improvac and pST increased lean gain above either alone, while negating the increase in fat deposition in pigs treated with Improvac. The objectives of the second experiment were to determine: 1) the effect of a high (25% fat, HF) or low (2% fat, LF) fat liquid diet on pig performance, and 2) if the limited response to exogenous pST in young pigs is dependent on the source of dietary energy. Diets were formulated to provide a constant lysine:ME ratio and were fed on a pen basis for 9 d. On d 5, pigs within a pen were randomly assigned to receive 0 or 120 mg pST μg BW -1•day -1 for 4 d. Pigs gained 335±9 g/d, which resulted in an ending body weight of 7225±95 g (P>.42). Pigs fed the LF diet consumed more feed than pigs fed the HF diet (P<.01), but calculated ME intake did not differ (P>.20). Pigs fed the HF diet had higher PUN concentrations than pigs fed the LF diet (P<.01). Treatment with pST increased circulating IGF-I (P<.01) and decreased PUN (P<.01) concentration, regardless of dietary treatment (P>.65). Circulating leptin was not affected by dietary treatment (P>.26) or pST (P>.54). These results suggest that the ST/IGF axis is responsive in the young pig and the response is independent of the source of dietary energy. The objectives of the third experiment were to determine: 1) the effect of porcine reproductive and respiratory syndrome virus (PRRSv) and M. hyopneumoniae (M. hyo.) and 2) if exogenous ST can stimulate the IGF system in health-challenged pigs. Pigs were randomly assigned to one of three treatments: 1) Non-infected, ad libitum intake (C); 2) Challenged with PRRSv and M. hyo., ad libitum intake (HC); and 3) Non-infected, pair-fed to HC pigs (PF). HC pigs were infected with M. hyo. during jugular catheterization surgery and with PRRSv 8 d later (d 0). On d 14, pigs within a treatment group were randomly assigned to receive 0 or 120 mg pST μg BW -1•day -1 for 4 days. Initial body weight did not differ (P>.64), but C pigs were heavier than HC and PF pigs on d 21 (P<.01). Disease challenge reduced feed intake beginning on d 7 of infection (P<.04). Basal circulating IGF-I levels averaged 322±22 ng/mL (P>.15) and ST administration increased circulating IGF-I (P<.01). Circulating leptin was not different between treatment groups (P>.29). The mRNA abundance of IGF-I and its receptor were not different between groups in liver or muscle (P>.29). These results indicate that the ST/IGF-I system was not responsible for the growth reduction found in PRRSv and M. hyo. infected pigs.
Effects of Phyzyme XP and Avizyme 1502 on the Performance of Broiler Breeders and their Progeny.
(2011-03-31) Arguelles Ramos, Mireille; Samuel Pardue, Co-Chair; John Brake, Chair; Charles Stark, Member; Jerry Spears, Member
Effects of Three Twice-A-Year Breeding Schedules in Four Breeds of Sheep
(2002-02-12) Pala, Akin; Q.W. Robison, Co-Chair; R.L. McCraw, Co-Chair; C.S.Whisnant, Member; R.E. McDowell, Member
Straightbred populations of Dorset, Finnsheep, Composite I (50% Finnsheep, 25% Dorset, and 25% Rambouillet), and Composite II (50% Finnsheep, 25% Suffolk, and 25% Targhee) sheep were evaluated under three different twice-a-year breeding schedules. Ewes were exposed for 32 d starting on August 13 and February 5 for schedule I, on September 15 and March 10 for schedule II, and on October 22 and April 11 for schedule III. Approximately 100 ewes of each breed were exposed to rams during each breeding season. The experiment was conducted for five complete cycles starting with matings in the fall of 1984 and ending with matings in the spring of 1989. Data were obtained on 9419 lambs produced from 2334 ewes and 257 rams. Traits of primary interest were conception rate, litter size at birth, weaning weight, weaning weight adjusted for conception rate, litter weaning weight and litter weaning weight per ewe exposed. Lactation status had a significant effect on conception rate and litter size while number of lambs suckling did not have a significant effect on conception rate. Composite I ewes had the highest conception rates and litter size (P 0.10), both had larger litters (P < 0.01) than the other two breeds. Ewes giving birth in spring had the highest conception rate and heaviest lambs (P < 0.01). Animals bred in schedule I had the heaviest and largest litters, highest conception rate, heaviest lambs and highest litter weaning weight per ewe exposed (P < 0.01). Efficiency of twice-a-year lambing systems is greatly affected by breeds, breeding schedules and seasons. Twice-a-year lambing programs must use the correct breeding schedule. Further, using composite breeds can be of great benefit.Genetic parameters for conception rate, litter size at birth, weaning weight, weaning weight adjusted for conception rate, litter weaning weight and litter weaning weight per ewe exposed were estimated using REML with animal models. Heritability estimates for conception rate were adjusted to a normal scale. Standard errors of heritabilities for conception rate were calculated using three methods, including bootstrapping. Heritabilities were estimated overall and within breed. Estimates of heritability for conception rate ranged from 0.17 ± 0.01 (Dorset) to 0.27 ± 0.01 (Composite I). Heritability estimates for litter size were 0.08 ± 0.01, 0.19 ± 0.01, 0.14 ± 0.01 and 0.13 ± 0.01 for Dorset, Finnsheep, Composite I and Composite II, respectively. Heritabilities for litter weaning weight and litter weaning weight per ewe exposed were similar across breeds and ranged from 0.31 ± 0.01 to 0.36 ± 0.01. Heritability for weaning weight was higher for Dorset (0.65 ± 0.01) than for Composite I (0.57 ± 0.01). Finnsheep and Composite II had similar heritabilities (0.41 ± 0.01). Overall heritabilities for litter weaning weight, litter weaning weight per ewe exposed, weaning weight, weaning weight adjusted for conception rate, conception rate and litter size were 0.33 ± 0.02, 0.35 ± 0.01, 0.64 ± 0.01, 0.64 ± 0.01, 0.24 ± 0.01 and 0.16 ± 0.01, respectively. Overall Spearman rank-order correlations of litter weight traits with conception rate or litter size ranged from 0.81 to 0.88. Correlations within breed were generally high and positive. Genetic correlations between dry and lactating ewes for conception rate and litter size were small (0.009 and 0.108, respectively), indicating that rank of sires was inconsistent under different environments (lactation status). Selection should be practiced among lactating animals for conception rate and litter size in twice-a-year lambing systems.Heritability estimates were moderate to high for weight traits and low to moderate for reproduction traits, indicating that selection in twice-a-year lambing programs is feasible. There was no substantial evidence that heritabilities and rank correlations were different among the four breeds. Litter weaning weight may be increased along with conception rate and litter size in a selection program based on twice-a-year lambing. Small genetic correlation between dry and lactating ewes indicated that grouping sires according to the lactation status of the ewes is necessary in a selection program.
Estimation of Genetic Parameters for Boar Semen Traits
(2003-07-17) Oh, Sang Hyon; Dr. Gene Eisen, Committee Member; Dr. Billy Flowers, Committee Member; Dr. Todd See, Committee Co-Chair; Dr. Ben McDaniel, Committee Co-Chair
During the last half of the 20th century, the world pork industry has achieved astonishing developments in pig breeding. Now swine farms are larger, ownership more concentrated, and farms have become more industrialized. Artificial insemination (AI) plays an important role in animal breeding increasing utilization of genetically superior sires. Currently boars selected for commercial use as AI sires are evaluated on grow-finish performance and carcass characteristics. The objectives of this study were to (A) estimate genetic correlations between production and semen traits in the boar; average daily gain (ADG), back fat thickness (BF) and muscle depth (MD) as production traits, and total sperm cells (TSC), total concentration (TC), volume collected (SV), number of extended doses (ND), and acceptance rate of ejaculates (AR) as semen traits; (B) to model the variances and covariances of total sperm cells (x 10⁹) over the active lifetime of AI boars; and (C) to compare multiple traits and random regression analyses applied to total sperm cells (TSC). Average heritability estimates were 0.39 for ADG, 0.32 for BF, 0.15 for MD, and repeatability estimates were 0.38 for SV, 0.37 for TSC, 0.09 for TC, 0.39 for ND, and 0.16 for AR. Semen traits showed negative genetic correlations with MD. Genetic correlations would indicate that current selection objectives are having a negative effect on semen traits. Therefore, current AI boar selection practices may be having a detrimental effect on semen production. In random regression analysis for total sperm cells, maximum log likelihood value was observed for sixth, fifth, and seventh order polynomials for fixed, additive genetic and permanent environmental effects, respectively. Best fit as determined by Akaike's Information Criterion was based on a model with sixth, fourth, and seventh order polynomials for fixed, additive genetic and permanent environmental effects, respectively. Best fit as determined by Schwarz Criterion was by fitting fourth, second, and seventh order polynomials for fixed, additive genetic and permanent environmental effects, respectively. Heritability estimates for total sperm cells ranged from 0.27 to 0.61 across age of boar classifications. Heritability for total sperm cells tended to increase with age of boar classification. The cyclic nature of heritability for total sperm cells that was observed over the active lifetime of boars may be due in part to number of observations across seasons limiting our ability to correct for seasonal effects on sperm production. In MTDFREML analysis, heritability estimates of 9, 12, 15, 18, 21, 24, and 27 months of age were, respectively, 0.28, 0.29, 0.26, 0.27, 0.30, 0.79, and 0.41. The results from MTDFREML seemed to be overestimated when compared to random regression. Therefore, random regression methods are the most appropriate to analyze semen traits as they are longitudinal data measured over the boars lifetime.
Evaluation of Absorption and Post-Absorptive Metabolism of Inorganic and Organic Zinc Sources
(2001-03-05) Wright, Cody LeForge; Jerry W. Spears, Chair; Vivek Fellner, Member; Gerald B. Huntington, Member; Matthew H. Poore, Member
A series of experiments was conducted to examine the absorption and post-absorptive metabolism of zinc (Zn) from inorganic and organic sources. Results of an in vivo experiment, using Holstein bull calves as models, suggested that, when Zn was supplemented at 20 mg Zn/kg DM for 98 d, Zn source had minimal impact on plasma or tissue Zn concentrations. However, when Zn was supplemented at 500 mg Zn/kg DM for 12 d, plasma and tissue Zn concentrations were greater in bulls that received Zn proteinate (ZnProt) than in those that received ZnSO and Ca only, uptake and transport of Zn from inorganic and organic Zn sources were similar. However, when added at high concentration in the presence of dietary antagonists, Zn uptake from organic sources appeared to be greater than from inorganic sources. Further research is certainly warranted to more clearly define differences in Zn absorption that may exist between inorganic and organic Zn sources at different dietary levels.
Factors Affecting the Presence of Reactive Oxygen Species in the Fresh and Extended Porcine Ejaculate.
(2009-04-16) Lovercamp, Kyle W.; Sarah Ash, Committee Member; Glen Almond, Committee Member; M. Todd See, Committee Member; William L. Flowers, Committee Chair
Experiment 1 examined changes in ejaculate characteristics, semen quality and membrane lipid peroxidation over time in boars maintained under a 3 times or 1 time per week collection frequency and determined the effects of semen extender and storage time on semen quality and sperm membrane lipid peroxidation. In general, extender and storage time affected sperm quality. Sperm stored in a commercially available 3-day extender were lower for sperm quality and higher for lipid peroxidation after 7 days of storage post-collection compared to a commercially available 5-day extender. Experiment 2 used density gradient centrifugation to separate extended boar sperm into sub-populations for analysis of sperm quality, plasma membrane lipid peroxidation and sperm cell fatty acid composition over a 7 day storage period post-collection. Three ejaculates were collected and analyzed following exposure to three consecutive collection periods. The first ejaculate was collected from boars that had previously been maintained on a 1 time per week frequency. The second ejaculate was collected following a period of five collections in four days (fifth collection analyzed). The third ejaculate was a collected after a period of three days of rest following the collection of the second ejaculate. Collection period affected sperm motility over the storage period post-collection. Collection period, density layer and day of storage post-collection affected the separation patterns of sperm cells using density gradient centrifugation. These results suggest that changes in sperm separation seem to be primarily affected by collection period and day of storage post-collection and to a lesser extent, sperm motility, but not plasma membrane lipid peroxidation. Experiment 3 evaluated the effect of dietary selenium on sperm production and sperm quality. The dietary treatments were a non-supplemented negative control basal diet or the basal diet supplemented at 0.3 ppm with either organic selenium or inorganic selenium. A secondary objective was to examine changes in sperm quality over a six day storage period post-collection. Boars were fed the dietary treatments beginning at the time of weaning. Dietary treatment affected the level of selenium in the blood plasma but not the semen. Dietary treatment did not affect volume, concentration or total sperm in the ejaculate, nor did dietary treatment affect sperm motility, progressive motility, morphology, membrane lipid peroxidation and glutathione peroxidase activity over the 6 day storage period postcollection. Following density gradient centrifugation, sperm motility, progressive motility, morphology and the percentage of sperm recovered were higher in the 90% gradient compared to the 45% gradient on day 1 but not day 6 of storage post-collection. These results indicate that dietary treatment affected selenium levels in the blood, but did not affect sperm production or quality. Boar sperm cells decrease in progressive motility and buoyant density over a six day storage period which appears to affect the sperm motility, progressive motility, morphology and the percentage of sperm recovered in the high and low density layers following density gradient centrifugation, however these changes do not appear to be affected by lipid peroxidation.
Genetics of gilt estrous behavior
(2009-12-11) Knauer, Mark; Dr. Joe Cassady, Committee Co-Chair; Dr. Todd See, Committee Co-Chair; Dr. William Flowers, Committee Member; Dr. Doug Newcom, Committee Member; Dr. Genn Almond, Committee Member
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.
Genetics of Milk Flow Traits in Dairy Cattle.
(2011-08-09) Gray, Kent Andrew; Joseph Cassady, Chair; Christian Maltecca, Co-Chair; Odis Robison, Member; David Dickey, Minor; Michael Dykstra, Graduate School Representative
Growth Performance and the Development of Antibiotic Resistant Bacteria in Swine Fed Growth-promoting Antimicrobials
(2008-04-28) Holt, Jonathan Paul; Eric van Heugten, Committee Co-Chair
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.
Impact of Poultry Age, Season, Litter Quality, and Nutritional Intervention Strategies on Salmonella Prevalence and Populations, Serotypes, Genotypes, and Antibiotic Resistance Profiles
(2007-10-31) Santos, Fernanda Botaro de Oliveira; Brian W. Sheldon, Committee Chair; Donna K. Carver, Committee Member; Lee-Ann Jaykus, Committee Member; Peter R. Ferket, Committee Co-Chair
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.
Improving Early Postnatal Piglet Health, Growth and Development: Effects of Supplemental Milk Replacer, IgG, Glutamine and Glutamic Acid.
(2011-08-19) Cabrera, Rafael; Jack Odle, Chair; Lin Xi, Member; Adam Moeser, Member; Chad Stahl, Member; Ronald D. Nimmo, External; Jaime Collazo, Graduate School Representative
Investigations of Postpartum and Postweaning Factors That May Affect Subsequent Sow Reproductive Performance
(2004-04-05) Belstra, Bradley Aaron; Dr. Glen W. Almond, Committee Member; Dr. C. Scott Whisnant, Committee Member; Dr. M. Todd See, Committee Co-Chair; Dr. William L. Flowers, Committee Chair
Experiment one examined effects of season, parity, genotype, lactation length, and weaning-to-estrus interval on the postweaning duration of estrus (DE) and onset of estrus-to- ovulation interval (EOI) of sows in three farms. Farm x weaning-to-estrus interval, farm x season, and parity x season interactions for DE and EOI were detected. Weaning-to-estrus interval had an inverse relationship with DE and EOI on each farm, but the weaning-to-estrus interval range that exhibited a stepwise decrease of DE and EOI was narrower on farm 1 (3 to 5 days) than farms 2 and 3 (3 to 6 days). Both DE and EOI were 8 h longer in the summer than the spring on farms 1 and 3, but did not differ between seasons on farm 2. On each farm, parity ≥ 3 sows had a 4.5 h longer DE and EOI than parity 1 and 2 sows in the summer, but there were no differences in DE or EOI among parity classes in the spring. Lactation length and genotype had small but significant effects on DE and EOI, respectively. Results of this experiment indicate that factors other than weaning-to-estrus interval, such as season and parity, can significantly alter DE and EOI. However, the effects of season and weaning- to-estrus interval on DE and EOI are apparently farm dependent. Experiment two characterized the urinary excretion of two markers of collagen degradation, hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP), by sows during postpartum uterine involution. A postpartum increase of HP excretion occurred that was temporally consistent with the known pattern of uterine weight loss during involution. The mean molar ratio of HP:LP increased postpartum and confirmed that catabolism of a soft, non-bone tissue dominates this period. Experiment three investigated the use of transabdominal ultrasonography to estimate uterine size. The distance between the abdominal wall and intestines, which sandwich the uterus, decreased 8.7 cm from day 1 to 18 postpartum. Validation of these two techniques to monitor postpartum uterine involution by comparison to postmortem uterine measurements could provide a research tool to test the effects of uterine involution status on subsequent embryo survival and sow reproductive performance.

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