The Effect of Reduced Dietary Protein on Adipose Tissue in Local Krškopolje Pigs

The main objective of this study was to evaluate the effect of low-protein (LP) diet on adipose tissue deposition in Krškopolje pigs reared either in organic outdoor (n=2x12) or conventional indoor (n=2x12) system. In the outdoor system, RNA-sequencing revealed the upregulation of 28 genes and downregulation of 37 genes. Upregulated genes were mainly involved in lipid metabolism (ACLY, FASN, ACACA, MOGAT2), oxidative stress, and mitochondrial function. In the indoor system, RNA-sequencing revealed 30 upregulated and 28 downregulated genes. Among the upregulated genes, heat shock proteins (HSP70.2, HSPA6) were detected in pigs on LP diet, while genes involved in the innate immune system (MSR1, TREM2, CSF3R) were downregulated. A total of 48 animals of the Krškopolje pig breed were assigned to 4 treatment groups and reared either in the indoor (n = 2 x 12) or in the outdoor conditions (fenced open area with trees and shelter) (n = 2 x 12). Animals from the outdoor system were reared according to the organic standards and received organic feed ad libitum, while the animals reared in the indoor system received the same amount of feed based on the same ingredients, but of conventional origin. In both systems, animals received either standard (HP group, fed 15% crude protein from 20 to 80 kg, 12.5 % crude protein from 80 to 100 kg and 10 % crude protein from 100 to slaughter) or reduced protein diet (LP group, fed 15% crude protein from 20 to 60 kg and 10% crude protein from 60 kg to slaughter). After slaughter, backfat was collected at the level of the last rib and freezed at -80 °C. Afterwards, RNA was extracted and equal amounts of total RNA from two individuals were pooled together generating 6 pools within each treatment group.