Effects of different rearing systems on intramuscular fat content, fatty acid composition, and lipid metabolism-related genes expression in breast and thigh muscles of Nonghua ducks

Abstract

Rearing system is a critical nongenetic factor influencing meat quality of ducks. In this study, a total of 360 birds were randomly allocated into floor rearing system (FRS) and net rearing system (NRS) to compare their effects on intramuscular fat (IMF) deposition, fatty acid composition, and related gene expression in muscles of Nonghua ducks. Sawdust bedding and stainless mesh bed were equipped in FRS and NRS, respectively. At the eighth week (8w) and 13th week (13w), the breast and thigh muscles of ducks were collected to determine the profiles of lipids composition and the expressions of lipid metabolism-related genes. The IMF content was higher in 13w-FRS than 8w-FRS and 8w-NRS in breast muscle, whereas it was higher in 13w-NRS than other groups in thigh muscle (P < 0.05). C16:1, C20:5(n-3) of muscles were higher in 8w-NRS than 8w-FRS, whereas C18:1(n-9)c, C18:2(n-6)c, Ʃ monounsaturated fatty acid (MUFA), and ƩMUFA/Ʃsaturated fatty acid (SFA) ratio of muscles were higher in 13w-NRS than 8w-FRS and 8w-NRS (P < 0.05). C22:6(n-3), C20:4(n-6) of breast muscle and C20:3(n-6) of thigh muscle were higher in 13w-NRS than 13w-FRS (P < 0.05). Fatty acids variation was studied by principal component analysis, exhibiting extensive positive loadings on principal components. SREBP1, ACADL, and FABP3 were downregulated in breast muscle, whereas PPARα and ELOVL5 were upregulated in thigh muscle of NRS ducks at 13w. Principal components were extensively correlated with lipids composition parameters, and principal components of breast muscle 1 and principal components of thigh muscle 1 were correlated with SREBP1 and PPARα, respectively (P < 0.05). In conclusion, with increasing age, FRS enhanced IMF deposition in breast muscle, and the same promotion in thigh muscle was because of NRS. The variation of fatty acids in muscles was uniform, and the change of single fatty acid was unable to distinguish NRS and FRS. However, as NRS downregulated SREBP1, ACADL and FABP3 in breast muscle and upregulated PPARα and ELOVL5 in thigh muscle, NRS could improve nutrient value and meat quality by increasing ƩMUFA, ƩMUFA/ƩSFA ratio, and important PUFA levels. Therefore, NRS was more recommended than FRS for Nonghua ducks during week 8 to 13 posthatching.

Keywords: Nonghua duck; fatty acid composition; intramuscular fat content; lipid metabolism–related gene; rearing system.

Figure 1

The content of IMF (A-B) and TG (C-D) in breast and thigh muscles of ducks under FRS and NRS. ^a-c indicated a significance (P ＜ 0.05) among 8w-FRS, 8w-NRS, 13w-FRS, and 13w-NRS. Abbreviations: IMF, intramuscular fat; FRS, floor rearing system; NRS, net rearing system; TG, triglyceride; 8w, eight week; 13w, 13th week.

Figure 2

The lipid metabolism-related genes expression of breast and thigh muscles of ducks under FRS and NRS. (A), (C), and (E) depicted related genes expressions in breast muscle; (B), (D), and (F) depicted related genes expressions in thigh muscle. Genes of transcription factors were shown in (A) and (B), genes related to fatty acids synthesis were shown in (C) and (D), and genes related to fatty acids uptake and utilization were shown in (E) and (F). Abbreviations: FRS, floor rearing system; NRS, net rearing system; 8w, eight week; 13w, 13th week. ^a-c indicated a significance (P＜0.05) among 8w-FRS, 8w-NRS, 13w-FRS and 13w-NRS. Genes: acetyl-CoA carboxylase, ACACA; acyl-CoA dehydrogenase long chain, ACADL; carnitine palmitoyltransferase 1A, CPT1A; fatty acid binding protein 3, FABP3, fatty acid transport protein-1, FATP1; elongation of very long chain fatty acids/fatty acid elongase-5, ELOVL5; stearoyl-CoA desaturase, SCD1; sterol regulatory element binding protein 1, SREBP1 and peroxisome proliferator-activated receptor-α, PPARα.