Abstract
BackgroundBoth genetic background and finishing system can alter fat deposition, thus indicating their influence on adipogenic and lipogenic factors. However, the molecular mechanisms underlying fat deposition and fatty acid composition in beef cattle are not fully understood. This study aimed to assess the effect of breed and dietary silage level on the expression patterns of key genes controlling lipid metabolism in subcutaneous adipose tissue (SAT) and longissimus lumborum (LL) muscle of cattle. To that purpose, forty bulls from two genetically diverse Portuguese bovine breeds with distinct maturity rates, Alentejana and Barrosã, were selected and fed either low (30% maize silage/70% concentrate) or high silage (70% maize silage/30% concentrate) diets.ResultsThe results suggested that enhanced deposition of fatty acids in the SAT from Barrosã bulls, when compared to Alentejana, could be due to higher expression levels of lipogenesis (SCD and LPL) and β-oxidation (CRAT) related genes. Our results also indicated that SREBF1 expression in the SAT is increased by feeding the low silage diet. Together, these results point out to a higher lipid turnover in the SAT of Barrosã bulls when compared to Alentejana. In turn, lipid deposition in the LL muscle is related to the expression of adipogenic (PPARG and FABP4) and lipogenic (ACACA and SCD) genes. The positive correlation between ACACA expression levels and total lipids, as well trans fatty acids, points to ACACA as a major player in intramuscular deposition in ruminants. Moreover, results reinforce the role of FABP4 in intramuscular fat development and the SAT as the major site for lipid metabolism in ruminants.ConclusionsOverall, the results showed that SAT and LL muscle fatty acid composition are mostly dependent on the genetic background. In addition, dietary silage level impacted on muscle lipid metabolism to a greater extent than on that of SAT, as evaluated by gene expression levels of adipogenic and lipogenic factors. Moreover, the response to diet composition evaluated through mRNA levels and fatty acid composition showed interesting differences between Alentejana and Barrosã bulls. These findings provide evidence that the genetic background should be taken into account while devising diet-based strategies to manipulate fatty acid composition of beef cattle tissues.
Highlights
Both genetic background and finishing system can alter fat deposition, indicating their influence on adipogenic and lipogenic factors
The correlation analysis between oleic acid proportions and StearoylCoA desaturase (SCD) expression levels in the subcutaneous adipose tissue (SAT) was showed to be positive and significant. This result is in agreement with previous reports [44] that reported that increased SCD activity is, at least partially, responsible for an elevated oleic acid, the main monounsaturated fatty acids (MUFA), content in ruminant
Taniguchi et al [22] reported a positive correlation between levels of SCD mRNA and MUFA proportion, which led to the conclusion that SCD expression might contribute to the differences in the SAT fatty acid composition between breeds
Summary
Both genetic background and finishing system can alter fat deposition, indicating their influence on adipogenic and lipogenic factors. During the last decades consumers have started demanding animal products of low fat and high polyunsaturated fatty acids content, while maintaining high and consistent quality [1,2]. Subcutaneous and intramuscular adipose tissues are the most important fat depots concerning meat quality traits. It is desirable that cattle carcasses have minimal amounts of fat stored in subcutaneous adipose tissue (SAT), without a detrimental decrease in intramuscular fat [3]. This can be achieved only if the regulation of lipid deposition in intramuscular and other fat depots differs substantially. While during the last decade knowledge of rodents and human fat physiology has progressed rapidly [5], the same information regarding ruminant species is very limited
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