VTechWorks Repository :: Browsing by Author "Swecker, William S. Jr."

Browsing by Author "Swecker, William S. Jr."

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Assessing the Effect of Nitrogen Sources, Rates and Time of applications on Yield and Quality of Stockpiled Fescue and Tall Fescue Pastures
Yarber, Elizabeth Lee (Virginia Tech, 2008-08-01)
In Virginia, tall fescue [(Schedonorus phoenix (Scop.) Holub,) formally known as Festuca arundinacea L.] can be found on more than 4 million ac of hay and pastureland. Two separate experiments were conducted at three different geographical locations over two growing seasons. The objective of Experiment 1 was to evaluate the influence of N sources and rates on yield and nutritive value of stockpiled tall fescue. Experiment 2 examined the effect of split spring and fall N applications at various rates on yield and nutritive value of tall fescue pastures. The first experiment was conducted at three locations (Blacksburg, Blackstone, and Steeles Tavern, VA) while the second experiment was conducted only at the Blacksburg and Steeles Tavern locations. In Experiment 1, the N sources included ammonium nitrate, ammonium sulfate, urea, urea + AgrotainÂ®, Environmentally Smart NÂ® (ESN), Nutrisphere (NSN), NitaminÂ® (Blackstone only), pelleted biosolids (Blackstone only), and broiler litter (Steeles Tavern only) applied at 0, 28, 56, 84, and 112 kg plant available N (PAN) ha-1. Plots were harvested in mid-December (Blacksburg and Steeles Tavern) and late January (Blackstone). The yield of the stockpiled tall fescue in 2006 ranged from 1,300 to 2,900, 1,700 to 3,000, and 2,600 to 3,300 kg DM ha-1 for the Blacksburg, Steeles Tavern and Blackstone locations, respectively. In 2007, however, the yield response to N rate and sources was significantly less than that of 2006 due to low rainfall. At the Blacksburg location, ammonium sulfate and ESN resulted in higher CP concentrations, ranging from 11-14% and 12-20% for 2006 and 2007 growing seasons, respectively. Similar variation (12-20%) was observed for the Steeles Tavern location in 2006. In general, the ADF and NDF content decreased as N rate increased from 0-112 kg ha1. Although the source and rate that resulted in high yield and nutritive value varied across location and years, N rates and sources improved the quality and yield of stockpiled fescue. Experiment 2 utilized urea which was applied in the fall at the rates of 0, 45, 90 or 135 kg N ha-1. followed by spring application of 0, 45, 90 or 135 kg N ha-1. A total of 16 treatment combinations per replication were used. Yields ranged from 1,900 to 3,600 kg DM ha-1 and 700 to 2,500 kg DM ha-1 in 2007 and 2008, respectively. At the Steeles Tavern location, yields ranged from 3,100 to 5,700 kg DM ha-1 and 2,500 to 5,100 kg DM ha-1, in 2007 and 2008, respectively. In both years CP increased with increasing N fertilization. On a dry matter basis, CP values ranged from 14 to 23% for both years. Treatments did not affect on NDF and ADF values. Split fall/spring N applications did not maximize yield of cool-season grass pastures in these experiments.
Assessment of redox markers in cattle
Burke, Nathaniel Caleb (Virginia Tech, 2007-07-26)
Metabolic redox status may have important implications to cattle health and production. Antioxidants and biomarkers of oxidative stress were evaluated in cattle under three phases of management. Each phase stood alone as a treatment model, and managerial aspects during the phase were evaluated as potential moderators of redox balance. Yearling heifers were used to assess the impact of fescue toxicosis and heat stress on selected markers in study 1. Intravaginal temperatures, ADG, serum prolactin, plasma malondialdehyde, and whole blood Se, along with peripheral blood mononuclear cell glutathione peroxidase, glutathione reductase, and reduced:oxidized glutathione were determined during summer grazing. Results suggested that endophyte consumption does not promote oxidative stress in cattle. Heat stress may alter glutathione redox of white blood cells. In study 2, effects of gradual weaning strategies (anti-suckle nose clip and fenceline wean) and transport were evaluated in calves. Calf weights, Se and malondialdehyde in plasma, along with glutathione peroxidase and glutathione reductase in leukocytes were measured at -7, 0, 1, and 7 days surrounding weaning and transport. Little benefit of gradual weaning was detected, and oxidative stress may have been negligible. In study 3, the influences of grain- and forage-based diets were compared in finishing steers pre- and post-harvest. Total antioxidant capacity and malondialdehyde concentration of plasma, along with serum alpha-tocopherol, beta-carotene, and gamma-tocopherol were measured. Antioxidants and lipid oxidation were assessed in beef. Forages promoting plasma antioxidant capacity may protect cattle against oxidative stress. Antioxidants derived from forages inhibit lipid oxidation in pasture-finished beef.
Bovine Coccidiosis: Dynamics of infection in grazing cattle and the potential role of stress and immunity
Lucas, Aaron Scott (Virginia Tech, 2011-08-02)
Eimerian parasites infect cattle worldwide. Information on the infection dynamics of these parasites is lacking in the central Appalachian region of the United States. Studies aimed at characterizing the seasonal dynamics of eimerian parasites in this region were carried out in order to assess the impact of these organisms in grazing systems. In these studies the prevalence of Eimeria spp. infection was highest in calves less than one year of age and subsequently decreased to stable levels in older animals. Although E. bovis was the most common species identified in calves, heifers and cows, mixed species infections dominated. Additional studies were carried out to investigate the effect of stress on Eimeria spp. infection in beef calves. Lower stress, two-stage, weaning methods had no effect on Eimeria spp. infection dynamics in beef calves. These findings must be interpreted in light of the fact that calves used in this study were not managed in a way typical of many calves in the U.S.A. The fact that they were only transported short distances, never commingled, or exposed to a livestock market may explain why a rise in post weaning FOC was not observed. A model of stress- induced coccidiosis was developed using dexamethasone and E. bovis challenge. In this model, an oral challenge of at least 500,000 sporulated E. bovis oocysts in addition to dexamethasone injection at 7 days post challenge increased subsequent FOC. Further investigation of the immune response to E. bovis challenge during times of stress indicates that stress-induced suppression of cell mediated immunity and E. bovis challenge are required to increase subsequent oocyst shedding. These findings may represent the mechanism associated with stress-induced outbreaks of coccidiosis reported to occur in beef cattle in the United States.
Carbohydrate and Fat Supplementation in Grazing Mares and Foals
Hoffman, Rhonda M. (Virginia Tech, 1997-06-30)
The objective of these studies was to design an optimal nutritional supplement suitable for grazing horses using fat and fiber to replace the grain and molasses in the traditional sweet feed. Thoroughbred mares and foals grazing bluegrass/clover pastures were used in these studies, twenty mares and their foals in 1994 to 1995, and twenty mares and foals in 1995 to 1996. Seasonal variation in pasture was examined, and the need for supplementation of nutrients and fibers was assessed. The nutritional status of grazing mares, foals, weanlings and yearlings, fed either a starch and sugar supplement (SS) or a fat and fiber supplement (FF), was examined using growth measurements, radiographic bone evaluations, milk composition and glucose tolerance tests. These studies suggest that fiber may be an important component of an ideal supplement for improved grass/legume pastures. Seasonal variation in pasture indicated an increase in hydrolyzable and rapidly fermed carbohydrates during periods of rapid growth. The FF supplement may have buffered seasonal changes and the increased hydrolyzable carbohydrate content in rapidly growing pasture, as evidenced by smoother growth curves in the yearlings. Young horses, after weaning until the following May, had lower estimated bone mineral content when fed the FF supplement. The lower bone mineral content in the FF supplemented horses may have been due to decreased absorption of calcium or metabolic and hormonal changes associated with adaptation to the different energy sources in the supplements. Milk composition of FF supplemented mares was influenced in ways likely to improve foal health. The FF supplemented mares had enhanced linoleic acid content, which may reduce the risk of gastric ulcers in foals, and increased immunoglobulin G concentration, which may enhance passive immunity. The carbohydrate status of mares, as assessed by glucose tolerance tests, indicated a slower glucose clearance that could be a metabolic adaptation of the mares to the SS and FF supplements.
Comparison of Luteolysis and Timed Artificial Insemination Pregnancy Rates after Administration of PGF2a in the Muscle or the Ischiorectal Fossa in Cattle
Holland, Sarah C. (Virginia Tech, 2015-09-09)
Prostaglandin F2α (PGF2α) is commonly given to female cattle intramuscularly (IM) for the synchronization of estrus. A novel site for administration of PGF2α that improves beef quality assurance is the ischiorectal fossa (IRF). The objective of this study was to determine whether administration of PGF2α in the IRF results in a similar physiologic response to administration of PGF2α given IM. Yearling angus-cross heifers (n=112) were blocked by weight and randomly assigned within blocks to be injected with 5 mL PGF2α either IM in the neck or in the IRF. Blood samples were taken at 0, 8, 16, 24, 36, and 48 h post-injection. Serum samples were analyzed for progesterone concentration using a radioimmunoassay. Progesterone concentration curves for each heifer were plotted to determine luteolysis. The median times to luteolysis for neck and IRF injections were 18.1 hrs and 20.0 hrs, respectively (p=0.06). Angus cross commercial beef cows (n=1471) at least 30 days post-partum were blocked by age and randomly assigned to be injected with 5 mL PGF2α either IM in the neck muscle or in IRF as part of a 7-Day CO-Synch + CIDR ovulation protocol. Pregnancy diagnosis was performed via ultrasound at 60 days post insemination. Results were analyzed with Proc Glimmix (SAS). Pregnancy rates for neck and IRF injections were 52.6% and 57.2%, respectively (p=0.06). In summary, injection of PGF2α in the IRF for estrus synchronization and lysis of the corpus luteum did not differ from injection in the neck muscle. Utilizing the ischiorectal fossa as an injection site for PGF2α may be considered as an alternative that more closely aligns with beef quality assurance objectives.
Comparison of Neospora seroprevalence in Virginia dairy herds with high and low abortion rates
Murphy, Julia M. (Virginia Tech, 1998-06-30)
Neospora has become a commonly recognized infectious cause of abortion in dairy cattle. The organism is associated with mid to late term abortion outbreaks with rates exceeding 30% in some herds. Cows infected with this organism exhibit no other clinical signs. While this disease has been reported in other parts of the country, no assessment of Neospora seroprevalence has been undertaken in the Southeast. This study sampled commercial dairy herds to assess Neospora seroprevalence in dairy cows and investigate its significance as an abortifacient agent in Virginia. Twenty four herds participated in the study. Twelve herds had DHIA reported annual abortion rates of 6% or greater (high abortion rate herds) and twelve herds had abortion rates of 2% or less (low abortion rate herds). High abortion rate herds were each paired to a low abortion rate herd (control) herd within the same county. A single blood sample was collected from all cows confirmed to be 90 to 240 days pregnant, with a maximum of thirty samples per herd. A random sample of cows was selected in herds with more than 30 pregnant cows between 90 and 240 days gestation. Neospora antibody titers were determined using a serum ELISA test at the California Veterinary Diagnostic Laboratory. Both mean and median seroprevalence of high and low abortion rate herds were compared using the Mann-Whitney Rank Sum test and the Median test, respectively. No significant difference was found in either case (p=0.56, p=0.41). These findings suggest that Neospora does not contribute significantly to the average abortion rate in Virginia's dairy cattle.
Comparison of three estrus detection systems during summer heat stress in a large commercial dairy herd
Peralta, Oscar A. (Virginia Tech, 2003-06-12)
The objective of the study was to compare three systems for detection of estrus and combinations of these systems on a large commercial dairy (1000 lactating cows) during stress of summer heat. At 37 to 45 days in milk (DIM), 266 cows were fitted with a HeatWatch (HW) device (HeatWatch; DDx Inc., Boulder, CO), an activity (A) sensor (ALPRO; DeLaval Inc., Kansas City, MO), and observed visually (V) twice daily. Pregnancy status was determined by uterine palpation 35 to 49 d following artificial insemination (AI). The effects of DIM, parity, physical activity, standing events, months, AI technician, and interval between onset of estrus and AI on conception rate were determined using linear contrasts and logistic regression. Efficiencies for detection of estrus, determined by comparing detected periods of estrus with a theoretical total of 707 periods, were 45.8% (V), 33.2% (A), 40.3% (HW), and 71.6% for all three systems simultaneously. Conception rates (LSM ± SE) by method of detection were 16.7 ± 4.9 for HW, 19.8 ± 5.5 for A, 7.9 ± 3.4 for V, 16.3 ± 6.0 for V + A, 27.6 ± 4.6 for V + HW, 21.1 ± 4.9 for A + HW, and 21.9 ± 4.5 for V + A + HW. Conception rate and number of mounts decreased for cows in first versus second and third parity (P < 0.05). For periods of estrus detected by A, the lowest conception rate (P < 0.05) occurred >18 h after the onset of estrus (16.7 ± 7.9). The highest conception rate occurred with the combination of V + HW, which confirms the premise that combination of multiple systems enhances both the efficiency and accuracy of detection.
Development of core-shell nanostructure encapsulating gentamicin as efficient drug delivery system against intracellular Salmonella
Ranjan, Ashish (Virginia Tech, 2009-09-10)
Intracellular pathogens like Salmonella have developed various mechanisms to evade host defenses, and they can establish infections. Treatment and eradication are difficult due to our inability in achieving the optimum concentrations of cell-impermeable aminoglycosides like gentamicin within these cells. In this dissertation, we hypothesize that developing a novel core-shell methodology for incorporating high amounts of gentamicin into the cores with either hydrophilic or amphiphilic shell will be more effective than the free gentamicin in clearing intracellular Salmonella infection. Hydrophilic core-shell nanostructures (N1) were made with block co-polymers of poly (ethylene oxide-b-sodium acrylate) blended with sodium polyacrylate (PAA^-+Na) and complexed with the polycationic antibiotic gentamicin. N1 showed 20-25 fold higher gentamicin loading than the currently existing materials and reduced numbers of viable Salmonella in the liver and spleen compared to free gentamicin. To further improve the rate and route of uptake, the shell of the nanostructures were made amphiphilic by incorporating pluronics F68 (PPO)₆₈ in the block copolymer. We showed that core-shell nanostructures encapsulating gentamicin having (PPO)₆₈ in the shell (N2) enhances the rate and modulates the route of uptake into macrophages, thus promoting significant reduction in the intracellular Salmonella in-vitro and in-vivo. The main drawback of N2 was its poor stability at physiological pH of 7.4, 0.1 M NaCl. Therefore, core-shell nanostructures encapsulating gentamicin containing pluronic P85 (PPO)₈₅ in the shell (N3) with improved colloidal and ionic stability were designed. N3 achieved significant intracellular reduction of vacuolar Salmonella (0.53 log₁₀) and cytoplasm resident Listeria (3.11 log₁₀) compared to free gentamicin in-vitro. However, greater reduction of Listeria suggested that sub-cellular localization of bacterium influences targeting by N3. Even though oral administration of N3 was not effective compared to free gentamicin, parenteral (I.P.) administration significantly reduced the intracellular Salmonella from liver and spleen compared to free gentamicin and appeared to have no abnormal in-vivo toxicity. In summary, core-shell nanostructures encapsulating gentamicin (N) with improved encapsulation efficiency and different shell chemistry (N1, N2 and N3) were developed with enhanced efficacy against intracellular Salmonella. The novel gentamicin delivery approach developed in this study may be applicable for therapy of many intracellular infections.
Effect of Feeding Different Protein and Energy Supplements on Performance and Health of Beef Calves During the Backgrounding Period
Austin, Robert Jesse (Virginia Tech, 2001-08-15)
Newly received or weaned calves are highly susceptible to the incidence of bovine respiratory disease. In addition to high levels of stress, decreased feed intake and exposure to foreign antigens result in increased morbidity and possibly death losses. Four backgrounding trials were conducted to examine the effects of protein and energy supplements to stressed calves consuming different forages. Body weights, rectal temperatures and blood samples were taken on d 0, 7, 14, 28 and 42. Supplements consisted of corn or mixtures of corn and soybean meal. In trial 1, 48 heifers (average BW = 219 kg) fed fescue hay in drylot, were allotted to four treatments: no supplement, 15% CP supplement (0.5% BW), 15% CP supplement (1.0% BW) and 30% CP supplement (0.5% BW). Supplemented heifers had higher (P<0.05) ADG than unsupplemented heifers by 42 d. Heifers fed the 30% CP supplement had higher (P<0.05) plasma urea-N by d 42. In trial 2 (pasture study 1), 36 steers (average BW = 217 kg) grazed stockpiled tall fescue and were allotted to three treatments: no supplement, a 15% CP supplement (0.5% BW), and a 15% CP supplement (1.0% BW). After wk 1, ADG was lower (P<0.05) for supplemented calves. At the end of the trial, steers supplemented at 0.5% BW had higher (P<0.05) ADG than steers supplemented at 1.0% BW. Glutathione peroxidase levels were lower (P<0.05) for supplemented steers on d 28. For trial 3 (pasture study 2), 48 steers (average BW = 202 kg) grazed stockpiled tall fescue and were allotted to three treatments: no supplement, corn (1% BW), and 15% CP supplement (1% BW). After wk 1, ADG was higher (P<0.05) for steers supplemented with corn. Steers supplemented with 15% CP supplement had the lowest (P<0.05) ADG after 7 d. At d 42, supplemented steers gained faster (P<0.05) than unsupplemented steers. For trial 4 (pasture study 3), 48 steers (average BW = 202 kg) grazed stockpiled tall fescue or fescue-alfalfa and were allotted to two treatments: no supplement and a 15% CP supplement (0.5% BW). During wk 1, steers grazing fescue had higher (P<0.05) ADG than steers grazing fescue-alfalfa. During wk 1, supplemented steers had a higher (P<0.05) morbidity scores. At d 42, ADG was higher (P<0.05) for supplemented steers. No consistent differences were detected in forage and blood serum mineral concentrations in all trials. Glutathione peroxidase activity increased (P<0.05) for all trials on d 14, regardless of supplementation. Supplementation improved ADG by d 42 but did not affect overall health status of calves in all trials.
Effect of Form and Amount of Phosphorus and Phytase Supplementation on Phosphorus Utilization by Ruminants
Shanklin, Rachel Kristina (Virginia Tech, 2001-07-11)
The use of animal manures to replace commercial fertilizer has increased the economic and environmental sustainability of agriculture. However, this practice has resulted in excess P being applied to the soil in some areas. Excess P may run-off into surface water and leach in the ground, causing eutrophication. Decreasing the amount of P fed and improving the utilization of P are two possible nutritional solutions to this problem. Two experiments were conducted to investigate the effects of levels of dietary P, chemical form of P, and phytase supplementation in ruminants. For Exp. 1, 24 steers (average BW = 229 kg) were allotted to two diets containing 0.12 and 0.19% dietary P for a 112-d growth trial. The steers were individually full-fed, weighed every 14 d, and blood samples were collected every 28 d. The steers fed the 0.12% P diet had increased (P<0.02) ADG during the first 28 d, after which there were no differences. They also had higher (P<0.05) feed intake. By d 56 serum P for the 0.12% P group was lower (P<0.01), and this difference continued for the remainder of the trial. For Exp. 2, 18 wether lambs (average BW = 23 kg) were allotted to the following six diets for each of two metabolism trials: 1) a negative control diet deficient in P, 2) control diet supplemented with inorganic P, 3) control diet supplemented with phytic acid, 4) control diet supplemented with phytic acid and phytase, 5) control diet supplemented with cottonseed meal, and 6) control diet supplemented with cottonseed meal and phytase. Each metabolism trial was preceded by a 5 wk depletion phase in which the lambs were fed a low-P diet. The metabolism trials consisted of a 10 d preliminary period followed by a 10-d collection of feces and urine. On the final day ruminal fluid, blood, and saliva were collected. At the end of the second metabolism trial 10th rib bones were collected from each lamb. Absorption of P was lowest (P<0.0001) for the low-P treatment, compared to the other treatments. There was no treatment effect on saliva P. Ruminal fluid P was higher (P<0.05) for lambs receiving P supplementation. Within supplementation treatments, ruminal fluid P was higher (P<0.05) for lambs fed organic P than for those fed inorganic P. Feeding CSM resulted in higher (P<0.001) ruminal fluid P than phytic acid. The addition of phytase to the diets with organic P resulted in more (P<0.04) P in the ruminal fluid. There was a decrease (P<0.003) in serum P associated with the low-P treatment. There was no difference in bone ash or breaking strength.
The effect of supplementation strategy, stress level, and tall fescue type on performance of fall-weaned beef calves
Pickworth, Carrie Lynn (Virginia Tech, 2005-06-20)
The beef cattle marketing structure imposes stress on calves due to weaning, transport, commingling, and adaptation to new diets, resulting in a weakened immune systems at the height of disease risk, frequently causing bovine respiratory disease. Backgrounding programs facilitate opportunities for calves to overcome stressors by building immunity, and adapting the rumen to high concentrate diets for improved feedlot performance. Four experiments were conducted to compare backgrounding strategies and effects of supplementation frequency performance and the effects of the ruminal environment. In Exp. 1, 48 weaned steers were used to investigate the effects of transportation and supplementation frequency, while in Exp. 2, 36 heifers were used to investigate only supplementation frequency. No differences in gains were observed due to transportation stress or supplementation frequency. Weaning stress resulted in elevated (P < 0.05) creatine kinase and neutrophil:lymphocyte ratios during the first week. In Exp. 3, 48 calves were used to compare the effect of tall fescue type on performance and health. Calves on novel endophyte fescue had higher ADG (P = 0.07) than on endophyte-infected fescue. Experiment 4 investigated the changes in ruminal environment due to supplementation frequency. No differences were observed between supplementation frequencies for ruminal pH, ammonia, or VFA concentration, and DM, or CP digestibility. Therefore, the rumen maintained a hospitable environment to promote bacterial protein synthesis and fiber digestion with every 48 h supplementation. Backgrounding calves with high fiber co-product supplements or on novel endophyte fescue can enhance calf performance.
The Effect of Three Fescue Types and Lakota Prairie Grass on Copper Status, Dry Matter Intake, and Alkaloid Appearance of Beef Steers
Stewart, Robert Lawton Jr. (Virginia Tech, 2006-10-27)
Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] is an important forage crop in the United States and covers over 14 million ha. The presence of Neotyphodium coenophialum, an endophytic fungus in tall fescue, is associated with several disorders in grazing livestock, but also increased persistence of tall fescue. These disorders, commonly called fescue toxicosis, are responsible for large economic losses in the beef cattle industry each year. This research examined the effect of three fescue types [endophyte-infected Kentucky 31 tall fescue (E+), endophyte-free Kentucky 31 tall fescue (E-), non-ergot alkaloid-producing endophyte Q4508-AR542 tall fescue (Q)], and Lakota prairie grass (L; Bromus catharticus Vahl.) on animal response, alkaloid appearance, DMI, and copper status. Ergovaline (EV) is the most abundant ergot alkaloid in tall fescue and has previously been considered the causative toxin in fescue toxicosis. More recently it is simpler ergot alkaloids, such as lysergic acid amide (LSA) have been implicated. The objective of the first project was to evaluate animal performance and alkaloid (EV and LSA) appearance in forage and ruminal fluid of steers grazing E-, Q, E+, and L. Average daily gains were greater (P < 0.05) on E-, Q and L compared to E+, and there was a trend (P = 0.11) for gains on E- to be higher than with Q. The seasonal appearance of LSA in ruminal fluid was similar to the seasonal pattern of alkaloids in E+ forage. Ergovaline was not detectable in ruminal fluid of steers grazing E+. Alkaloids were not detectable in forage or ruminal fluid of steers grazing E-, Q, or L. The appearance of LSA in ruminal fluid of steers grazing E+ suggests that this alkaloid may contribute to fescue toxicosis. Low DMI of animals grazing E+ tall fescue is considered a key factor in decreased animal performance compared to other fescue types. The objective of the second project was to evaluate DMI of steers grazing E-, E+, Q, and L pastures using the alkane technique. Dry matter intake of steers grazing E- was greater (P < 0.001) than Q, E+, and L and DMI of steers grazing Q and E+ were similar (P > 0.10) in 2004. In 2005, DMI did not differ (P = 0.23) among fescue types. These results suggest that decreased DMI effects ADG of steers grazing E+ compared to those grazing E-, and lower DMI of Q suggests that the fescue variety Q4508 may not be the optimal variety for the incorporation on non-ergot alkaloid-producing endophytes. Reactive oxygen metabolites such as superoxide (O₂⁻) are produced by both endogenous and exogenous sources and an accumulation of these compounds can result in oxidative stress. Copper/zinc superoxide dismutase (SOD) is a Cu-based antioxidant metalloprotein that acts as a defense against oxidative stress by the scavenging of O₂⁻. Neotyphodium-infected tall fescue is typically lower in Cu which could potentially increase oxidative stress of animals grazing this forage. Therefore the objective of the third project was to investigate the Cu and SOD status of steers grazing E-, E+, Q, and L forages. Copper levels of all forages were below the dietary requirement (10μg Cu/g DM) of growing cattle. In 2004, steers grazing E+ exhibited lower (P <0.05) liver Cu compared to E- and Cu intake was lower (P < 0.001). Cu/Zn SOD enzymatic activity and mRNA relative expression did not differ (P > 0.10) among treatments. Copper intake of steers grazing E+ tall fescue was sufficient to maintain, but not replenish liver Cu, and SOD status did not appear compromised by grazing E+ at these Cu levels.
Effect of two finishing systems on claw characteristics in beef steers
Becvar, Ondrej (Virginia Tech, 2006-06-19)
The objective of this study was to evaluate the claw characteristics contributing to the shape and balance of the foot in growing steers. The evaluated parameters included dorsal wall growth, abrasion, length and sole surface area. After animal harvest, the sole horn thickness was measured. Seventy-two yearling Angus-crossbred steers (mean body weight 378±6.2 kg) were allotted for the finishing period (133 days) to two systems (feedlot, pasture). The feedlot steers were fed a corn-grain/corn silage diet and were housed in pens with concrete floors. Steers assigned to the pasture were rotationally stocked on mixed grass-legume pastures. The claw measurements were obtained from medial and lateral claws of the left rear foot on days 0, 56 and 133. Sole thickness measurements were performed on both front feet. Data were analyzed with repeated measures analysis of variance using a mixed effects model. The horn growth of the dorsal wall was greater (P<0.01) in the feedlot steers (29.5±0.7 mm/finishing period) compared to the steers on pasture (21.28±0.8 mm/ finishing period). Claw horn abrasion was also greater (P<0.001) in feed lot steers (24.50±0.92 mm/ finishing period) than in steers on pasture (9.3±0.9 mm/ finishing period). Lateral and medial claws grew (P<0.001) and wore (P<0.001) at different rates in feedlot steers. In the pasture steers the lateral and medial claws did not differ in growth or abrasion. The change in length of the dorsal wall was different (P<0.05) between feedlot and pasture steers. The difference between lateral and medial claw was significant only in the feedlot steers (P<0.001). The final dorsal wall length, as a result of horn growth and abrasion, was different (P<0.05) between finishing systems. Lateral and medial claw (P<0.001) was different in the feedlot steers only. The change in the sole surface area was different (P<0.05) between feedlot and pasture steers and between lateral and medial claw in both finishing systems. In both finishing systems, medial claws exhibited a smaller surface area than lateral claws. The feedlot steers had significantly thicker soles in all locations than steers on pasture. The steers in confinement on concrete floors, fed a corn-grain/corn silage diet exhibited faster horn growth and abrasion rates, yet smaller sole surface area, shorter dorsal walls and thicker sole horn compared to the steers grazing pasture. The difference between lateral and medial claws for all measured parameters, except sole thickness, was significant in the feedlot steers.
Effects of a sustained-release copper bolus on growth and reproductive traits of beef bulls
Giustra, Clinton V. (Virginia Tech, 1995-08-15)
Two experiments were conducted to determine the effects of sustained -release copper (Cu) boluses on growth and reproductive traits of beef bulls. Two groups of bulls were used in consecutive years (n=26 in experiment 1; n=20in experiment 2). Bulls in each experiment were allotted by weight and breed into two equally numbered treatment groups (control (C); treated (T)). Bulls were housed together and offered a balanced diet containing 9 ppm Cu for an ADG of 1.4 kg. Treated bulls in each experiment were given 1 Cu bolus (Cupra,® Pitman-Moore, Mundelein, IL in experiment 1; Copasture â ¢ Copasture- 25 bolus Schering-Plough, Kenilworth, NJ in experiment 2). All bulls were bled, had blood samples taken and had scrotal circumferences (SC) measured on d 0,28,56,84,112, and 140. Blood was collected via jugular venipuncture to determine serum Cu and plasma ceruloplasmin (Cp) concentrations. Breeding soundness examinations (B S E) were conducted on all bulls on d 140 and 185 in experiment 1 and d 168 in experiment 2. Body weight and SC were not affected by treatment in either experiment (P > .05). Serum Cu and plasma Cp concentrations were not affected by treatment in experiment 2 (P > .05). Serum Cu was higher for the T bulls on d 56, 84, and 112 in experiment 1 (P < .05). All serum Cu concentrations for both experiments were within the normal range for cattle. Plasma Cp concentrations were recorded only for d 1, 112, and 140 in experiment 1 and were significantly higher for the C group on d 112 (P < .05). There were no significant effects of treatment on the results of the BSE (SC, percentage of normal sperm, progressive motility, and primary or secondary abnormalities) in either experiment. These data suggest that the Cu bolus in experiment 2 had no effect on body weight gains, SC, serum Cu and plasma Cp concentrations, sperm normality, progressive motility, and primary and secondary abnormalities. These data also suggest that the Cu bolus in experiment 1 had no effect on body weight gains, SC, and sperm normality, progressive motility, and primary and secondary abnormalities; however, treatment in experiment 1 did increase serum Cu concentrations on some but not all days and did not increase concentrations above the normal range for beef cattle. The conclusion made from these experiments is that the sustained Cu boluses used in these studies do not significantly affect growth and reproductive traits in beef bulls with adequate Cu status.
Effects of Calfhood Respiratory and Digestive Disease on Calfhood Morbidity and First Lactation Production and Survival Rates
Rossini, Katherine Lynn (Virginia Tech, 2004-06-08)
Calf health data and first lactation records for 2556 cows born in a commercial dairy herd between June 1998 and June 2001 were studied to determine the effects of calfhood disease on survival and performance. Operator-treated respiratory disease occurrences within the first year of life and digestive disease occurrences within the first 45 d of life were analyzed to determine their effects on calfhood morbidity, age at first calving, 305-d first lactation production, and mortality in first lactation. Of the 2556 records used, 2083 calves contracted respiratory or digestive disease at least once, 1254 calves had digestive disease only, 771 had respiratory disease only, and 191 calves had both diseases. Occurrence of calfhood digestive disease increased the chance of calfhood respiratory disease 2-fold. Age at first calving increased 0.53 mo with multiple occurrences of respiratory disease versus none. Calves born in the winter calved at 25.4 mo, whereas calves born in spring calved at 24.5 mo. Respiratory disease had the largest effect on calves born in the spring, resulting in 23.9 mo age at first calving for no occurrence and 25.4 mo for multiple occurrences. No significant effect of disease was detected for 305-d milk yield, fat yield, or SCC, but protein yield decreased by 0.05 kg/d with increased calf respiratory disease. Although calfhood disease had no influence on illness as a cow, disease-free calves had a 5% advantage in probability of remaining in the herd through 305-d, and an 8% advantage at 730-d compared with calves with 2 or more disease occurrences. In conclusion, calfhood occurrences of respiratory and digestive disease had a slight impact on age at first calving, depending on season of birth, and minimal impact on production performance through 305-d of first lactation. The occurrence of respiratory or digestive disease caused a decrease in survival rate from calving through 305-d in first lactation and 730 d after calving.
Effects of Low and High Sodium Chloride Diets and Furosemide Administration on Cardiac Function, Plasma Electrolyte Concentrations, and the Renin-Angiotensin-Aldosterone System
Swancott, Cindy Marie (Virginia Tech, 1998-04-14)
Congestive heart failure is commonly treated with a low sodium diet and diuretic. The purpose of this treatment is the reduction of preload, or blood volume presented to the diseased cardiac muscle. The purpose of this study was to assess the roles of dietary sodium and furosemide on cardiac function, plasma electrolyte concentrations, and the renin-angiotensin-aldosterone system, in healthy canines. Twenty mixed-breed canines were allotted to one of four groups, Group I - Dogs fed low sodium diet (0.08% sodium), Group II - Dogs fed high sodium diet (1.0% sodium), Group III - Dogs fed low sodium (0.08%) and treated with furosemide (2 mg/kg orally (PO) every twelve hours (BID)), and Group IV - Dogs fed high sodium (1.0%) and furosemide ( 2 mg/kg PO BID). Cardiac function was assessed via echocardiography on days 0, 21,and 53. Plasma electrolyte concentrations were measured on days 0, 21, and 35. Activation of the renin-angiotensin-aldosterone system was evaluated on days 0, 21, 35, and 53. Low and high sodium diet with and without furosemide treatment did not alter cardiac function, plasma sodium, or plasma potassium concentrations. However, furosemide treatment combined with a low sodium diet resulted in the lowest plasma chloride concentrations, on days 21 and 35 (p<0.05). Furthermore, furosemide treatment resulted in significant alterations in the renin-angiotensin-aldosterone system, on days 21, 35, and 53, (p < 0.0001). Furosemide treatment significantly increased renin activity and aldosterone concentration. The interaction between furosemide and the low sodium diet yielded a greater increase in plasma renin activity and plasma aldosterone concentrations than furosemide administration with the high sodium diet. These results suggest direct activation of the renin-angiotensin-aldosterone system by furosemide. Future research is warranted in congestive heart failure subjects, due to the adverse affects of decreased plasma chloride concentrations and activation of the renin-angiotensin-aldosterone system.
The Effects of Naturally Occurring Plant Products on Experimental Haemonchus contortus Infection in Gerbils and Sheep
Squires, Jill Marie (Virginia Tech, 2009-05-01)
Haemonchus contortus is a blood-sucking abomasal helminth of small ruminants responsible for major economic losses to producers worldwide. Widespread resistance to commercial anthelmintics has created a need for alternative methods of parasite control. One method involves using plant products with natural anthelmintic properties. This thesis assessed the efficacy of several plant products against experimental Haemonchus contortus infection in gerbils and sheep. In gerbil assays, animals were orally infected with 600 third-stage Haemonchus larvae and treated once or daily for 5 days with artemisinin, Artemisia annua aqueous or ethanolic extract, an orange oil emulsion, or Asimina triloba ethanolic extract. Nine days post-infection, gerbils were euthanized, their stomachs removed, and the worms counted. Significant anthelmintic activity was not found for artemisinin, A. annua extracts, or A. triloba extract. The orange oil product caused significant parasite reductions up to 87.8% when administered for 5 days. The orange oil emulsion was tested in sheep to evaluate the product against Haemonchus in its natural host. Sheep were orally inoculated with 10,000 Haemonchus larvae and, one month later, dosed with the emulsion once or daily for 3 days. Fecal egg counts were monitored daily starting on the first day of dosing and continuing to 14 days post-dosing. Results showed that a single dose of the product caused highly significant fecal egg count reduction (97.4%) compared to control sheep and that there is no advantage to treating for 3 days. Thus, the orange oil emulsion shows promise as an alternative to commercial dewormers.
Effects of Prepartum Energy and Protein Density on Productivity and Influence of Dietary Iron on Copper Status of Holstein and Jersey Cattle
French, Patrick Douglas (Virginia Tech, 1999-08-16)
In experiment 1, 24 multiparous Holsteins and 24 multiparous Jerseys were assigned at random to one of four diets containing either 1.25, 1.38, 1.50, or 1.63 Mcal NEL/kg DM to determine the effects of prepartum energy density on productivity. Cows were assigned to diets 28 d before expected calving and received a similar diet 0 to 60 d postpartum. Prepartum DMI increased linearly as dietary energy density increased. Non-esterified fatty acids did not differ for energy density and were greater for Holsteins. Milk and 4% FCM increased linearly as dietary energy density increased, although postpartum DMI was quadratic for energy density. Fat yield increased linearly with energy density and protein yield did not differ. Increasing prepartum diet energy density increased yield of milk and 4% FCM. In experiment 2, 26 multiparous and 18 primiparous Jerseys were assigned to one of two CP and rumen undegradable protein (RUP) concentrations 30 d before expected calving to determine the effects of CP and RUP on productivity. Cows received a similar diet 0 to 60 d postpartum. Prepartum CP concentrations were 12 and 15% and prepartum RUP (% of CP) concentrations were 30 and 45%. Dry matter intake was not affected by CP or RUP. Milk yield and 4% FCM yield did not differ for CP or RUP. In addition, milk protein concentration and yield were similar for CP and RUP. Positive calculated metabolizable protein balance for 12% CP and 30% RUP concentrations may have precluded responses to increasing prepartum CP and RUP. In experiment 3, 12 Holstein and 12 Jersey multiparous cows were assigned at random to diets containing 0 or 500 mg FeCO3/kg DM to investigate the effects of dietary Fe on milk production and Cu status. Hepatic Cu did not differ for breeds or Fe supplementation. For Jerseys, hepatic Fe was greater for cows receiving supplemental Fe. Hepatic Zn was similar for breed and Fe supplementation. Plasma Cu was greater for Jerseys compared to Holsteins and did not differ for Fe supplementation. Plasma Fe and Zn did not differ for breeds or Fe supplementation. Iron supplementation did not affect yield of milk or 4% FCM. Dietary Fe did not affect Cu status of Holstein and Jersey cows in this experiment.
Effects of Stress on Several Immune and Health Responses of Weanling Calves
Shank, Alba Maria Montana (Virginia Tech, 2002-07-02)
The effects of weaning stressors on several immune and health responses were measured in three experiments. Sixty-four beef calves from 2 sources were bled on d - 7 (pre-weaning), 0 (weaning), 7, 14, and 21 (post-weaning). Serum selenium (Se), neutrophil and lymphocyte counts, and glutathione peroxidase (GSH-Px) activity for erythrocytes and leukocytes were measured for each calf at each date. Erythrocyte GSH-Px activity remained constant over time, while leukocyte GSH-Px and serum Se increased on d 7 (P<0.0001). Effects of single mineral vs. multi-mineral supplementation were measured for several immune and health responses in 2 trials. Trial 1: 36 heifers weaned on-site at SVAREC were randomly assigned 1 of 2 dietary supplements: 1) no supplement; 2) 15% CP at 0.5% BW; and 1 of 3 injection treatments: 1) no treatment (control); 2) Mu-Se injection; 3) Multi-Min injection. Whole blood Se and serum Cu increased post-weaning and serum Zn decreased post-weaning. Mu-Se-supplemented heifers gained weight faster between d 14-28 vs. Multi-Min-supplemented (P=0.01) or control heifers (P=0.02). Trial 2: 48 steers purchased at auction and transported to SVAREC were randomly assigned to 1 of 4 pasture management systems: 1) control (no treatment); 2) litter fed; 3) litter applied; 4) inorganic fertilizer; and 1 of 3 injection treatments (same as Trial 1). Whole blood Se and serum Cu increased post-stress and serum Zn decreased post-stress. Oxidative burst activity decreased in Mu-Se and Multi-min supplemented steers between d 0-4 vs. control steers (P<0.01). Multi-min-supplemented steers had higher phagocytic activity vs. steers in either Mu-Se or control groups (P=0.04).
Effects of Vitamin E Supplementation in Late Gestation Cattle and Evaluation of Vitamin E, Cholesterol, and Phospholipid Relationships in Bovine Serum and Serum Lipoproteins
Bass, Roger Thompson II (Virginia Tech, 1999-04-21)
The effects of vitamin E supplementation during late gestation were evaluated in dairy or beef cattle in three experiments. Dairy cows were injected with vitamin E and selenium (Se) in one study; beef cows were offered oral vitamin E supplementation via a free-choice vitamin-mineral mix in two studies. Breed-related effects were also evaluated. Jerseys had higher blood Se and lower serum vitamin E concentrations than Holsteins at dry-off and higher blood Se concentrations than Holsteins 3-4 weeks pre-calving and at calving. Selenium supplementation increased blood Se concentrations at calving. Treatment did not affect serum vitamin E concentrations at calving or post-calving, nor blood Se concentrations post-calving. Beef cattle consuming supplemental vitamin E (treatment) had greater responses to treatment when calving in late winter than when calving in late summer. Treated multiparous cows calving in winter had increased serum and colostral vitamin E concentrations but treatment did not affect colostral or serum immunoglobulin G (IgG) concentrations of their calves. Calves from treated, multiparous cows calving in winter had increased 205-day adjusted weaning weights (AWWs). Treatment did not affect colostral vitamin E or IgG concentrations of nulliparous heifers calving in winter, nor serum vitamin E or IgG concentrations, or AWWs of their calves. Six hundred IU supplemental vitamin E/head/day did not affect serum vitamin E concentrations of dams, colostral vitamin E or IgG concentrations, serum vitamin E or IgG concentrations, or growth of calves in the summer-calving herd. Breed-related differences in vitamin E concentrations and AWW occurred in both herds. Consumption of 600-1000 IU vitamin E/cow/day (treatment) during late gestation via a free-choice vitamin-mineral mix increased vitamin E concentrations in serum and the lipoprotein fraction containing no apolipoprotein B (non-ApoB) from 1-2 weeks pre-calving to calving. Treatment group calves had higher vitamin E concentrations in serum and non-ApoB than control group calves. Treatment did not affect cholesterol or phospholipid concentrations in serum or the lipoprotein fractions of either cows or calves. Treatment increased vitamin E cholesterol (VEC) and vitamin E phospholipid (VEPL) ratios in the serum and non-ApoB of cows and calves. Various breed-related differences also occurred.

Browsing by Author "Swecker, William S. Jr."

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