Fatty acid profiles and adipogenic gene expression of various fat depots in Japanese Black and Holstein steers

- JB and HS steers differed in amount, lipid composition, and gene expression of IMF.
- Higher MUFA, lower PUFA and SFA concentrations were detected in IMF of JB.
- Lipid droplet associated gene expression was up-regulated in IMF of JB.
- Minor breed differences were detected in fatty acid profile of blood and fat depots.

Objective of the study was to assess the breed effect on fatty acid (FA) composition of different adipose tissues and on mRNA expression of genes involved in adipogenesis and fat metabolism. Japanese Black (JB) and Holstein (HS) steers were kept under equivalent conditions with high energy intake resulting in large differences in intramuscular fat (IMF) accumulation in longissimus muscle (LM). The relative FA composition of muscle, intermuscular fat, visceral fat, and perirenal fat was comparable between JB and HS steers. Circulating fatty acids were also similar in both breeds. Most relevant breed effects were identified in IMF, underlining the uniqueness of this adipose tissue site. JB steers had more monounsaturated FA and less saturated FA. Perilipin 1 and adipose differentiation-related protein (ADFP) mRNA levels were higher in IMF of JB. The results suggest advanced maturity of IMF cells in JB and altered local conditions in muscle influencing IMF accumulation and composition.