| In this study, Boer×Suining White crossbred goats were used to investigate the effects of dietary Cysteamine (CS) and Hainan-mycin (HM) supplementation on the content of intramuscular fat, conjugated linoleic acid (CLA) and fatty acids composition in goats. The possible mechanism was also studied.1. Identification and optimization of the conditions for the determination of fatty acids of intramuscular fat (IMF) by the gas chromatograph (GC)The intramuscular fat of 2g muscle sample in goat was extracted with chloroform/methanol (2:1, vol/vol) according to Folch et al. 40mg IMF was re-dissolved in 2ml hexane, then 0.5M sodium methylate was added to produce fatty acids ethyl ester (FAME). The FAME were separated by a SP2560 capillary column (100m×0.25mm×0.20μm, Supelco Inc, Bellefonte, PA) installed in Agilent 6890N GC, determined by a hydrogen flame ionisation detector (FID). In order to improve separation effect of fatty acids, temperature programme was used: initial oven temperature was 150℃, held for 5 min, subsequently increased to 175℃at a rate of2℃min-1, held for 15 min, then to 200℃at 7℃min-1, held for 20 min, in the end to 220℃at 5℃min-1 and held for 25 minutes. Finally, the fatty acid composition of IMF in goats was analysed qualitatively and quantitatively by comparation with Sigma and Matreya FAME standard.2. The effects of Cysteamine (CS) and Hainan-mycin (HM) on the content of intramuscular fat and CLA in goats90 healthy goats (15±1kg, 3 months of age ) were randomly assigned to three groups: groupâ… was fed with basal diet, groupâ…¡andâ…¢was provided with basal diet supplemented with 900 mg·kg-1 Cysteamine and 5mg·kg-1 Hainan-mycin, respectively. 10 goats from each group were randomly slaughtered to collect longissimus dorsi (LD) and semitendinosus (SD) muscle samples after 60d. The Intramuscular fat (IMF) content was determined by Soxhlet method, and the conjugated linoleic acid (CLA) and other important fatty acids content was analysed with gas chromatography (GC). The IMF content in LD was 62.3% higher compared with that in SD (P＜0.05), and CLA content per g of muscle mass was higher in LD than SD by 41.9% (P＜0.05). There was no significant effect by CS and HM supplementation on the intramuscular fat content in both LD and SD, however, CLA content in IMF of SD was increased by 26.5% with CS supplementation (P＜0.05). Dietary HM increased the CLA content by 10.1% in IMF of LD but no significance (P＞0.05).3. The mechanism of Cysteamine (CS) and Hainan-mycin (HM) on intramuscular CLA in goatsNatural conjugated linoleic acid (CLA) mainly exists in ruminant products, which has special physiological functions. CLA deposited in tissues is formed by trans-oleic acid (TVA) from rumen catalyzed by the stearyl-dehydrogenase (SCD). CS can deplete the endogenous SS and promote secretion of the hormone related to growth, eg: growth hormone, IGF-1, insulin, thyroxine,β-endorphin et al. Growth hormone can affect SCD mRNA expression in animal. There is a hypothesis that CS might affect CLA content of ruminant animals by SCD. To verify the above hypothesis, the semitendinosus muscles and livers of the above experimental animals were sampled to investigate the expression of SCD mRNA. The results showed that dietary supplementation of CS improve the expression of SCD mRNA of goat liver and muscle, but not significantly. The results suggest that the reason that CS increased the CLA content in semitendinosus muscles and the IMF content in goats might result from SCDmRNA expression level partly by CS supplementation. The effect of HM on the expression of SCD mRNA in liver and muscle of goat was not significant compared with CS supplementation. |
