Recipient Organization
UNIVERSITY OF WYOMING
1000 E UNIVERSITY AVE DEPARTMENT 3434
LARAMIE,WY 82071-2000
Performing Department
Animal Science
Non Technical Summary
Animals have evolved to meet their vitamin D requirement through exposure to sunlight, and most vertebrates obtain the majority of their daily vitamin D requirement from casual exposure to sunlight. However, recent swine management practices severely curtail exposure to sunlight, and the majority of the vitamin D requirement in swine is met through dietary supplementation. Diets are formulated to meet vitamin D requirements; however, current requirements were established to prevent bone disease, and vitamin D requirements necessary for optimal immune function are not known. Since swine are raised in confinement with limited exposure to sunlight, practical implications of vitamin D synthesis from exposure to natural sunlight has not been explored. Since rickets and other bone disorders still occur in swine, and risk of disease due to pathogen exposure is a real and present danger, it is an optimal time to explore limited exposure of pigs to sunlight. The extent and efficiency of vitamin D synthesis in growing pigs and how that influences morbidity in swine operations will be determined. Specifically, we propose to determine the vitamin D status of growing pigs exposed to a chronic (2 weeks of exposure for 1 hr at close to solar noon) compared to a conventionally raised control (no UV exposure) pigs. Exposure of 12 pigs each will occur at the spring equinox and summer solstice. Another 12 pigs will initially be exposed at the summer solstice with a second exposure period at the fall equinox. Health status as determined by logged sickness events as well as final tissue vitamin D status will be determined. The results of the proposed experiments are of importance to meat production practices and may have added value to consumers of pork. Exposure to sunlight in production swine operations lends itself to cost-effective supplementation which has potential health benefits to the growing animal as well as increased nutritive value for the consumer. The results collected as part of this proposal will be disseminated in preliminary form at scientific meetings and through both the scientific literature and information sharing with UW Extension Educators. Completion of these studies would produce results which will assist in meeting several of the USDA NIFA priorities including Global Food Security and Hunger (Priority 1), and also address Livestock Objectives as outlined in the WY Agricultural Experiment Station's Production Agriculture Research Priorities.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The overall purpose of this AES pilot grant is to collect preliminary data to characterize vitamin D synthesis in swine at high altitude. This research will determine how chronic exposure to sunlight affects circulating concentrations of vitamin D, incidence of morbidity and premature death in the pig, and the influence of sunlight exposure on the concentration of vitamin D in the cooked products from those animals.
Project Methods
Methods, Pitfalls and Limitations.All experimental protocols are subject to oversight of the institutional animal care and use committee (IACUC) (approval received 1/22/14). Two groups of weanling pigs will be placed in control (n = 12 [24 total]) and sunlight exposed (n = 12 [24 total]) groups at approximately 15 wk of age and ≈50-60 kg bw. All pigs will be fed a total mixed ration containing 500 IU per kg of Vitamin D3 which is reflective of a commercial swine diet. Pigs will be targeted to be 15 wk of age at the initiation of exposure at the spring equinox (March 20; Group 1) and summer solstice (≈June 21; Group 2).Exposed pigs will be moved to pens outside of the swine confinement building each day near solar noon for one hour during a two week period at the initiation of exposure (March 20 and June 21) and at the conclusion of the experiment approximately summer solstice (June 21 - Group 1) and fall equinox (September 20, Group 2). Pigs are expected to gain approximately 0.7 kg/d and reach slaughter weight (114 kg) at the conclusion of the experimental periods.Blood samples from all pigs will be collected prior to exposure and at the conclusion of exposure. Samples will be collected with a 1", 20 ga vaccutainer needle from the tail vein (level of the 5th coccygeal vertebrae; Muirhead, 1981). Blood will be collected into EDTA treated 10 mL vaccutainer tubes. A subsample (n = 5) of pigs will be intensely monitored to determine vitamin D synthesis and clearance following acute exposure. Pigs will be cannulated (14 ga 5 1/2"; Abbocath- T) in the great saphenous vein to facilitate blood collection prior to (hr 0), and hourly for four hours and then every 4 hrs for 24 hrs with final collection at 36 and 48 hrs. The five exposed pigs will be intensely sampled once at the initiation of sunlight exposure and at the end of the 2 wk exposure period at each of the exposure periods (equinox, solstice and solstice, equinox) for both groups 1 and 2, respectively. These intensely monitored pigs will be slaughtered in the University of Wyoming abattoir to facilitate tissue collection (subcutaneous fat and lean [loin and leg]) for vitamin D analysis.Blood samples will be collected into standard serum or EDTA-treated vaccutainers with plasma collected following immediate cold centrifugation. Serum samples will be analyzed for 25(OH)D concentration via Diasorin 25(OH)D RIA as described above (B. Hollis, Charleston, SC). Plasma samples will be analyzed for parathyroid hormone (a sensitive indicator of Ca status) by ELISA (Porcine Intact PTH ELISA, Immutopics, San Clemente, CA)(Alexander, Seabolt, Rhoads, & Stahl, 2012). For analysis of Vitamin D3, serum and tissue will be freeze-dried and subjected to steroid extraction for HPLC analysis (Jakobsen et al., 2009). UV intensity will be measured during the exposure periods.Sample size Justification. Power analysis with alpha 0.05 and standard deviation of 3.0 ng/mL would detect a difference of 4.6 ng/mL with 12 animals per group.Data Analysis. Plasma hormone and vitamin D concentrations will be analyzed by repeated measures ANOVA (SAS). Tissue samples will be analyzed by GLM procedures of SAS.Potential Pitfalls and Limitations. Although the Alexander lab has measured many blood hormones they have not measured parthyroid hormone (PTH) or vitamin D. With a species specific ELISA available for swine PTH this assay is not expected to be problematic. HPLC equipment is available in CORE facilities at the University of Wyoming. If HPLC is problematic, it is expected that vitamin D content can be analyzed by gas chromatography with expertise and equipment within the Department of Animal Science. White pigs are vulnerable to sun exposure and can sunburn if unprotected. It is not expected that 1 hr of sun exposure would cause tissue damage, but pigs will be evaluated for sunburn each day. At first sign of lasting damage (it is expected that 1 hr of sun will cause a slight and transient pinking of the skin) sun exposure will be shortened. The Alexander lab has vast experience with animal research including blood collection and animal behavior and no other problems are anticipated.