Browsing by Author "Swecker, William S."
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- Effect of feeding high levels of broiler litter on mineral metabolism and health of beef cowsWright, Martha A. (Virginia Tech, 1996)Some cattle producers have reported metabolic disturbances in beef cows fed high levels of broiler litter. Therefore, an experiment was conducted to evaluate mineral metabolism of beef cows fed different levels of broiler litter. Sixty Angus-Hereford crossbred cows ranging in age from 3 to 12 yr were blocked by age, BW, and stage of gestation, and randomly allotted within blocks to three diets: 1) mixed hay, full-fed; 2) 4.1 kg of a mixture of 80% broiler litter and 20% cornmeal plus mixed hay (low-litter diet); and 3) 8.2 kg of the 80% litter and 20% cornmeal mixture plus mixed hay (high-litter diet). Cows fed the litter diets were fed 57 g of magnesium oxide per head per day in the litter-corn mixture. Cows fed the three diets had access to a high-Mg mineral mixture. Experimental diets were fed from January 4, 1995 to April 19, 1995, and calving began on March 15. There were no physical signs of metabolic disturbances in any of the cattle. Blood serum Ca decreased and P levels increased in the cows fed both levels of broiler litter after the first 28 d on experiment. On d 28, average serum Ca values were 8.5 mg / dL for the cows fed hay, compared to 7.9 and 7.6 mg / dL for those fed the low and high levels of litter, respectively (P < .01). The average serum P values were 5.7, 8.2, and 9.1 mg/dL, respectively (P < .01). Generally, serum Ca remained lower and serum P remained higher for the cows fed broiler litter until the end of the winter feeding period (105 d). By mid-summer, serum Ca and P were similar (P > .05) for cows that had been fed the three diets. Serum Mg, Cu, and Zn were not affected by feeding litter. Urinary Ca and Mg, expressed as units per unit of creatinine, did not differ (P > .05) among treatments. Serum parathyroid hormone (PTH) was higher (P < .05) in cows fed the lower level of litter than those fed the higher level in April (105 d). Serum PTH values for cows fed hay were intermediate. Birth weights, rate of gain, and weaning weights of calves did not differ among the three diets. Feeding high levels of broiler litter to beef cows appears to affect serum Ca and P.
- Fibre digestibility, abundance of faecal bacteria and plasma acetate concentrations in overweight adult maresShepherd, Megan L.; Ponder, Monica A.; Burk, A. O.; Milton, Stewart C.; Swecker, William S. (2014)The purpose of the present study was to compare digestibility of grass hay, faecal and plasma volatile fatty acid (VFA) concentrations, and faecal bacterial abundance in overweight and moderate-condition mares. Five overweight adult mixed-breed mares and five adult mixed-breed mares in moderate condition were housed individually and limit-fed orchard grass (Dactylis glomerata) hay at 20 g/kg body weight (as fed) daily for 14 d. Forage DM and fibre digestibility were determined using AOAC methods; digestible energy was measured using bomb calorimetry; plasma and faecal VFA concentrations were determined by use of GC and MS; faecal Firmicutes, Bacteroidetes, Fibrobacter succinogenes, Ruminococcus flavefaciens and total bacteria abundance was determined by quantitative real-time PCR using previously designed phylum-specific 16S ribosomal RNA gene primers. No differences in hay digestibility, faecal VFA concentrations or faecal bacterial abundance were detected between overweight and moderate-condition mares. Mean plasma acetate concentrations were higher (P = 0·03) in overweight (1·55 (range 1·43-1·65) mmol/l) v. moderate-condition (1·39 (range 1·22-1·47) mmol/l) mares. We conclude that the higher plasma acetate in overweight mares should be further investigated as a potential link between gut microbes and obesity in horses.
- Haemonchus contortus Infections in Alpacas and SheepCasey, Sarah Jane (Virginia Tech, 2014-06-02)The blood feeding nematode Haemonchus contortus infects the abomasum of small ruminants and compartment three (C-3) of camelids. Heavy infections may cause severe anemia and death. Alpacas were first introduced into the U.S. in the 1980s. Although not true ruminants, alpacas may become infected with H. contortus and develop the same clinical signs as sheep and goats. Even though alpacas may become infected with the parasite, prior research by Hill et al. (1993) and Green et al. (1996) indicates alpacas may be more resistant to parasitic infection because they found lower numbers of eggs in the feces of alpacas compared to small ruminants. For our research, we hypothesized that given the same exposure to experimental infection, alpacas would be less susceptible than sheep to H. contortus. Experiment 1 was conducted with adult male alpacas (23) and sheep (12) housed in pens to prevent additional exposure to H. contortus. All animals were dewormed orally with a cocktail of fenbendazole, levamisole, and ivermectin. Haemonchus contortus infective larvae were administered orally to alpacas and rams in the following groups:1) 20,000 larvae as a single dose (bolus, n=6 both alpacas and sheep), 2) 20,000 larvae in daily doses of 4,000 larvae for 5 days (trickle, n=5 for alpacas, n=6 for sheep). Two additional groups of alpacas (n=6 each) received either 50,000 larvae as a bolus infection, or in daily doses of 10,000 larvae for 5 days (trickle). Fecal egg counts (FEC) were determined every 2 days from 14 to 42 days post infection (PI) and then at 5 day intervals until day 62 PI. Packed cell volume (PCV), FAMACHA scores, weight, and body condition scores were evaluated weekly. In general, mean FEC were lower in alpacas than sheep (p<0.01), and mean alpaca PCV was affected less by infection than sheep PCV. Experiment 1 results are consistent with our hypothesis that alpacas are less susceptible to H. contortus infection than sheep; however we were unable to determine whether alpaca FEC reflected fewer adult worms or only reduced H. contortus egg production compared to sheep. Experiment 2 was conducted with 16 alpacas and 12 rams and all animals were orally dewormed as in Experiment 1. Haemonchus contortus infective larvae were administered orally to alpacas in the following groups: 1) 20,000 larvae as a single dose (bolus, n=8), and 2) 20,000 larvae in daily doses of 4,000 larvae for 5 days (trickle, n=8). Ram groups (n=6 each) were the same as the alpaca groups. Fecal egg counts were determined at 5 day intervals from days 14 to 49 PI for bolus infected animals and to day 54 PI for trickle infected animals. FAMACHA scores were evaluated weekly. Packed cell volume was evaluated at the beginning and end of the study. All animals were euthanized 49 days after the last infection day. At euthanasia, abomasa and C-3 were harvested for determination of total worm burden and the pH was determined for each sheep rumen and abomasum and each alpaca C-1 and C-3. Mean FEC and total worm burden were significantly lower in alpacas than sheep (p<0.0001 for both FEC and total worm burden). Rumen pH in sheep was higher than C-1 pH in alpacas, but abomasal pH in sheep was significantly lower than C-3 pH in alpacas. Bolus infected sheep had lower FAMACHA scores than the other groups, and PCV was lower on the last day of sampling than the first day of sampling in all groups. The results of Experiment 2 also support our hypothesis that alpacas are less susceptible to H. contortus infection than sheep. However, it is unclear whether the differences are the result of physiological stomach differences between host species or whether other factors, such as immunity or parasite strain are important.
- Induction of anti-ergotamine antibodies in mice and steers and protection against fescue toxicosis in miceRice, Rebecca (Virginia Tech, 1995)Tall fescue (Festuca arundinacea Schreb.) is often infected by the endophytic fungus, Acremonium coenophialum (Morgan-Jones and Gams) The fungus produces ergo peptide alkaloids, especially ergovaline. Consumption of endophyte-infected (ED fescue forage by cattle decreases serum prolactin and average daily weight gains, which results in economic losses for producers. Anecdotal reports suggest cattle with fescue toxicosis may not respond to vaccination. Hyperprolactinemia decreases cell-mediated and humoral immune responses in mice. Therefore, steers grazing EI or endophyte-free (EF) fescue forages were vaccinated to assess humoral immune responses. Steers grazing EI fescue exhibited classical clinical signs of fescue toxicosis, and mounted humoral immune responses to vaccination, despite hyperprolactinemia. Lymphocyte proliferation responses to mitogens in mice fed EI diets were similar to mice fed EF diets. Production of interferon gamma and interleukin-4 was higher by splenocytes from mice fed EI diets, whereas interleukin-2 tended to be lower. Fescue toxicosis may stimulate T helper cell 2 subset of CD4⁺ T cells. The TH2 subset may augment humoral immune responses to vaccination.
- The Omental Fat Band as an Immunomodulatory Microenvironment for Ovarian CancerCohen, Courtney A. (Virginia Tech, 2013-06-11)Cancer research is evolving. Historically concerned with the mechanisms by which malignant cells circumvent cell death signaling and maintain unchecked proliferation, focus has shifted to the complex interactions between the tumor cell and the surrounding microenvironment. Ovarian cancer has one of the highest incidence-to-death ratios of all cancers, and is typically asymptomatic until the later stages, often resulting in metastasis prior to discovery. Naturally occurring phenotypes like lactation and child-bearing (parity) reduce ovarian cancer incidence, but the mechanisms are not understood. As the primary site for ovarian cancer metastasis, and a secondary lymphoid organ capable of mounting potent innate and adaptive immune responses, we believe the omental fat band (OFB) provides a unique opportunity to study complex interactions within the tumor microenvironment. Additionally, we hypothesize that once understood, leukocyte populations within the OFB could be modulated to disrupt the pro-tumorigenic cascade. Using fluorescence-activated cell sorting (FACS) and quantitative realtime PCR (qRT-PCR), we comparatively evaluated the changes in the compositional immune profile of the OFB as a result of parity and cancer. Parous mice were associated with a reduction in macrophages and neutrophils in the OFB, resulting in an inherent "protective state" that was refractory to metastatic cancer cell growth after intraperitoneal implantation. This indicates that the leukocyte populations within the OFB play an important role in tumor development. Therefore we utilized the potent TH1-type immunomodulatory cytokine IL-12 in a membrane-bound form to circumvent reported side effects, such as hepatic and renal damage, cardiotoxicity and death. Targeted IL-12 delivery to the OFB resulted in delayed disease development, although not protection from subsequent challenge. This was also associated with a reduction tumor-associated macrophages (TAMs) and neutrophils (TANs) within the OFB. Kinetic studies demonstrated that these changes were induced by a significant reduction in neutrophil and macrophage chemoattractants early on in the pro-tumorigenic cascade (7 days post-implantation). This work demonstrates that the OFB is a functionally plastic tissue that can be harnessed and re-mobilized to display an anti-tumorigenic microenvironment.
- Selenium supplementation and selected immune responses of beef cattleSwecker, William S. (Virginia Tech, 1990)The effect of selenium (Se) supplementation, by ad libitum salt-mineral mixture (SMM) and/or Se injection, on bovine immune response was evaluated in three experiments. Sixty weaned beef calves, with marginal blood Se (67 μg Se/1), were allotted to one of six Se treatment groups in a 70-day experiment. Antibody responses to lysozyme were lower in calves fed 20 ppm Se salt-mineral mixture (SMM) ad libitum as compared to calves fed 20 ppm Se SMM and injected with 0.1 mg Se + 1.0IU vitamin E/kg body weight, IM, or with calves ad libitum fed 80, 120, 160, or 200 ppm Se SMM. Blood Se on day 70 was higher in calves fed 80, 120, 160, or 200 ppm Se SMM than calves fed 20 ppm Se and injected with 0.1 mg Se + 1.0 IU vitamin E/kg of body weight, IM. An ad libitum 120 ppm Se SMM was compared to Se injection in 80 mid-gestation beef cows that were Se-deficient (50 μg Se/l blood). Supplementation with 120 ppm Se SMM increased blood Se in cows and calves to > 100 μg/l, increased IgG concentrations in colostrum, and increased IgG concentrations in serum of post-suckle calves. Calves from Se-adequate dams had higher Se concentrations in blood and higher average daily gains at 60 days than Se-deficient calves injected with Se at birth. An ad libitum 120 ppm Se SMM was compared to Se injection in 60 Se-deficient (41 μg Se/l blood) weaned beef calves in a 56-day experiment. Calves fed 120 ppm Se SMM and unsupplemented control calves had higher antibody responses to lysozyme than calves injected with 0.1 mg Se + 1.0 IU vitamin E/kg body weight. Blood Se concentrations increased in calves fed 120 ppm Se SMM, did not change in calves injected with 0.1 mg Se/kg body weight, and decreased in control calves. Se treatment did not affect IgA response in tears of calves.
- Shiga Toxin-Producing Escherichia coli: a Public Health Challenge in the Pre-Harvest Stage of the Farm-to-Table ContinuumBaltasar, Patricia Pereira (Virginia Tech, 2016-06-06)Escherichia coli is part of the normal gastrointestinal microbiota of many animals, especially cattle. While most strains are commensal, Shiga toxin-producing E. coli (STEC) can cause severe human illness. Pathogenicity of STEC is associated with genes such as those encoding Shiga toxins, enterohemolysin, and intimin. By targeting these genes, highly sensitive molecular-based techniques help detect potentially harmful STEC. Persistent carriers and environmental contamination may be responsible for maintenance of STEC in cattle farms. Prevalence may be further influenced by diet, distance to contaminated water-sources, wildlife contact, slurry application to pasture, and population density. Relevance in environmental contamination is expected proportional to the amount of STEC shed in feces, but there is no consensus as to which production stage/age is most important. Distribution and transmission of STEC O157 are widely studied, but risk factors for non-O157 STEC are not as well defined. Understanding what contributes for contamination of animals prior to concentration in high-density feedlots may reveal opportunities for upstream control of shedding and transmission. Our purpose was to: (a) determine prevalence of STEC in fecal samples from animals in a cow-calf pasture-based production system; (b) describe effects of age class (dam, calf), spatial distribution of cattle, and time-point of sampling on distribution of strains positive for virulence genes stx1, stx2, eaeA, and hlyA; (c) isolate and identify serotypes present in stx-positive samples; and (d) assess genetic similarity of isolates. Understanding factors that influence distribution of STEC strains may help support on-farm management strategies with potential to yield safer beef products.
- Variation in Eimeria oocyst count and species composition in weanling beef heifersLucas, A. S.; Swecker, William S.; Scaglia, G.; Lindsay, David S.; Zajac, Anne M. (American Society of Parasitology, 2006-10)Rectal fecal samples were collected daily on 10 consecutive days in November 2004 from I I weaned beef heifers to assess daily variation in fecal oocyst count and species composition. Subsequent samples were collected from the same animals on 15 April 2005 and 9 June 2005. Oocyst numbers were determined by the modified McMaster's test, and species were identified by examination of oocysts recovered with the Wisconsin sugar flotation technique. Soil samples were collected from the heifer pasture on 8 June 2005, and oocysts were quantified and identified to species. Mean fecal oocyst counts varied little at all sampling dates ranging from 134-377 oocysts/g. Ten Eimeria spp. were identified in fecal samples collected in November and April and 11 in June. Eimeria bovis was the most common species identified at all samplings. Mean species composition showed little variation during the 10-day sampling period in November, remained similar in April, and varied slightly in June. Twelve Eimeria spp. were identified in soil samples in proportions similar to those seen in fecal samples. The results indicate that clinically normal weanling beef heifers are likely to be infected with a diverse, but relatively stable, community of Eimeria spp.