Replacement of oat grass with highland barley straw: effects on lipid profiles, FA composition and lipogenetic genes expression in Tibetan sheep

Studies associated with regional roughage utilisation in Tibetan sheep have been limited. This study focussed on the mechanism of lipid metabolism and deposition in Tibetan sheep fed local roughage sources. Twenty-four Tibetan sheep weighing 16.1 +/- 1.76kg were randomly assigned to two mixed diets containing the same concentrate mixed with oat grass (OG) or highland barley straw (HBS). The ME and CP of OG diet were 7.16MJ/kg DM and 5.94%, respectively, while in HBS diet were 7.13MJ/kg DM and 7.39%. Lipid profiles in the plasma and liver, fatty acid (FA) composition and lipogenetic genes expression in the muscle and adipose tissue were determined. No difference was observed in DMI, total cholesterol, triglyceride, low-density lipoprotein and high-density lipoprotein levels in the plasma and liver of sheep between two groups (p>.05). Plasma leptin and liver non-esterified fatty acid (NEFA) content in HBS group tended to be greater than that in OG group (p<.01). Sheep in HBS group had greater C18:2, C20:4, PUFA and PUFA/SFA ratio in the longissimus dorsi muscle (p<.05) and lower C17:0 (p=.05) and C20:1 (p<.01) in the perirenal adipose fat. Perirenal C18:0, C20:3 and C20:4 contents in HBS group tended to increase (p<.01). HBS stimulated the mRNA expression of SCD, C/EBP gamma and SREBF1 in the muscle and FASN in the perirenal adipose fat (p<.01), but inhibited HSL, LPL, C/EBP gamma and PPAR gamma expression in the perirenal adipose fat. These results indicated that replacement of OG by HBS promotes PUFA deposition in the muscle and long-chain FAs in the adipose fat of Tibetan sheep. Lipid deposition-related genes (SCD, FASN, HSL and LPL) and lipid metabolism regulators (C/EBP gamma, SREBF1 and PPAR gamma) are involved in the transcriptional regulation.