Fat deposition in yak during different phenological seasons

Abstract

The present study aimed to clarify the effects of phenological seasons on fat deposition in yak. A total of 18 male yaks (4-years-old, n = 6/group) grazed in the same pasture and slaughtered in April, August and September, respectively. The results showed that the fat in longissimus dorsi (LD) and visceral fat increased gradually from April to September (P < 0.01), and the tenderness, lightness (L*), marbling score and cooking holding percentage of LD were improved; whereas subcutaneous fat increased early time (P < 0.01), and maintained stable later time. Gas chromatography (GC) analysis demonstrated that the proportion of unsaturated fatty acids (UFAs), especially polyunsaturated fatty acids (PUFAs), decreased gradually in LD (P < 0.01). The fat synthesis in the liver, fat and fatty acids transport in the blood increased and arrived at a maximum early time, and decreased later time. Transcriptome analysis showed that abundant intake of PUFAs by yak from pasture strengthened the peroxisome proliferator-activated receptors (PPARs) signaling in adipose tissue early, whereas the low level of leptin (LEP) affected the adenosine 5’-monophosphate -activated protein kinase (AMPK) singling at later time points. The rate of fat synthesis in adipose tissue increased and arrived at a maximum level, and then decreased. Thus, this study provides a theoretical basis for the improvement of the meat quality of yak and molecular breeding.