EVALUATING SEASONAL SERUM VITAMIN D LEVELS AND GROWTH PERFORMANCE IN PIGS FROM ORGANIC FARMS

Vitamin 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. Ocena sezonskih ravni vitamina D v serumu in rastne zmogljivosti pri prašičih z ekoloških kmetij Izvleček: Vitamin D je bistveno mikrohranilo v prašičereji, saj ima pomembno vlogo pri številnih fizioloških funkcijah. Cilj študije je bil določiti koncentracijo vitamina D v serumu in rastno zmogljivost prašičev, vzrejenih na ekoloških kmetijah v različnih letnih časih. Za študijo je bilo izbranih skupaj 109 prašičev krškopoljske pasme. Prašiči so bili razdeljeni v tri skupine: skupino A na nizki nadmorski višini na prostem (N = 39), skupino B na visoki nadmorski višini na prostem (N = 36) in skupino C v hlevu (N = 34). Vzorci krvi in telesne mase so bili odvzeti sezonsko v letih 2022 in 2023. Raven vitamina D v serumu je bila najvišja poleti za skupini A (69,3 ± 2,6 ng/ml) in B (65,3 ± 4,4 ng/ml), ki sta bili na prostem, najnižja pa pozimi (skupina A 21,5 ± 2,2, skupina B 35,2 ± 2,5). Nadmorska višina ni imela pomembnega vpliva na raven vitamina D, razen pozimi (p < 0,001). Vrsta hlevov je pomembno vplivala na ravni vitamina D v vseh letnih časih med skupinama B in C ter spomladi, poleti in jeseni med skupinama A in C. Prašiči v skupini A, ki so bili na prostem, so imeli višjo povprečno končno telesno maso (151,2 ±7,5 kg v letu 2022 in 146,8 ±3,8 kg v letu 2023) kot prašiči v skupini C (132,7 ±11,3 kg in 118,5 ±6,9 kg), čeprav je to treba razlagati previdno, glede na spremenljivost začetnih mas. Ključne besede: vitamin D; koncentracije v serumu; dobrobit prašičev; ekološka kmetija; rast