Evaluating seasonal serum vitamin d levels and growth performance in pigs from organic farmsŠteferl, Tim (Avtor) Hajdinjak, Melita (Avtor) Nadlučnik, Eva (Avtor) Golinar, Irena (Avtor) Štukelj, Marina (Avtor) Podpečan, Ožbalt (Avtor) vitamin Dserum concentrationspigs welfareorganic farmgrowth performanceVitamin D is an essential micronutrient in pig production as it plays an important role in many physiological functions. The aim of this study was to determine serum vitamin D concentration and growth performance in pigs reared on organic farms in different seasons. A total of 109 Krškopolje pigs were selected for this study. Pigs were divided into three groups: low altitude outdoor group A (N = 39), high altitude outdoor group B (N = 36) and indoor group C (N = 34). Blood samples and body weights were collected seasonally in 2022 and 2023. Serum vitamin D levels peaked in summer for outdoor groups A (69.3 ±2.6 ng/ml) and B (65.3 ±4.4 ng/ml) and were the lowest in winter (group A 21.5 ±2.2, group B 35.2 ±2.5). Altitude had no significant effect on vitamin D levels except in winter (p<0.001). Housing type significantly influenced vitamin D levels in every season between groups B and C, and in spring, summer, and autumn between groups A and C. Pigs in the outdoor group A showed higher average final body weights (151.2 ±7.5 kg in 2022 and 146.8 ±3.8 kg in 2023) than those in group C (132.7 ±11.3 kg and 118.5 ±6.9 kg), though this should be interpreted cautiously given variability in initial weights.20252026-08-06 12:50:53Članek v reviji185475UDK: 636.09:616ISSN pri članku: 2385-8761DOI: 10.26873/SVR-2202-2025COBISS_ID: 255874563sl