Abstract
BackgroundFeed accounts for up to 75% of costs in beef production systems, thus any improvement in feed efficiency (FE) will benefit the profitability of this enterprise. Residual feed intake (RFI) is a measure of FE that is independent of level of production. Adipose tissue (AT) is a major endocrine organ and the primary metabolic energy reservoir. It modulates a variety of processes related to FE such as lipid metabolism and glucose homeostasis and thus measures of inter-animal variation in adiposity are frequently included in the calculation of the RFI index. The aim of this study was to determine the effect of phenotypic RFI status and gender on the expression of key candidate genes related to processes involved in energy metabolism within AT. Dry matter intake (DMI) and average daily gain (ADG) were measured over a period of 70 d for 52 purebred Simmental heifers (n = 24) and bulls (n = 28) with an initial BW±SD of 372±39.6 kg and 387±50.6 kg, respectively. Residual feed intake was calculated and animals were ranked within gender by RFI into high (inefficient; n = 9 heifers and n = 8 bulls) and low (efficient; n = 9 heifers and n = 8 bulls) groups.ResultsAverage daily gain ±SD and daily DMI ±SD for heifers and bulls were 1.2±0.4 kg and 9.1±0.5 kg, and 1.8±0.3 kg and 9.5±1 kg respectively. High RFI heifers and bulls consumed 10% and 15% more (P < 0.05) than their low RFI counterparts, respectively. Heifers had a higher expression of all genes measured than bulls (P < 0.05). A gender × RFI interaction was detected for HMGCS2(P < 0.05) in which high RFI bulls tended to have lower expression of HMGCS2 than low RFI bulls (P < 0.1), whereas high RFI heifers had higher expression than low RFI heifers (P < 0.05) and high RFI bulls (P < 0.05). SLC2A4 expression was consistently higher in subcutaneous AT of low RFI animals across gender.ConclusionThe findings of this study indicate that low RFI cattle exhibit upregulation of the molecular mechanisms governing glucose metabolism in adipose tissue, in particular, glucose clearance. The decreased expression of SLC2A4 in the inefficient cattle may result in less efficient glucose metabolism in these animals. We conclude that SLC2A4 may be a potential biomarker for RFI in cattle.
Highlights
Feed accounts for up to 75% of costs in beef production systems, any improvement in feed efficiency (FE) will benefit the profitability of this enterprise
Summary of phenotypic data The effect of Residual feed intake (RFI) status and gender on Dry matter intake (DMI), feed efficiency, and performance is shown in Table 2 and slaughter details can be found in Additional file 1
Lipogenesis is a key process within adipose tissue in response to increased dietary energy intake [8] it seems likely that impaired function of this metabolically important organ could contribute to lower energetic efficiency in cattle
Summary
Feed accounts for up to 75% of costs in beef production systems, any improvement in feed efficiency (FE) will benefit the profitability of this enterprise. Adipose tissue (AT) is a major endocrine organ and the primary metabolic energy reservoir It modulates a variety of processes related to FE such as lipid metabolism and glucose homeostasis and measures of inter-animal variation in adiposity are frequently included in the calculation of the RFI index. In recent years RFI has been favoured as a measure of FE in beef cattle due to its independence from the production traits used to estimate it [7] and the concept is thought to represent inherent differences in basic metabolic processes related to energetic efficiency [1, 2]. Herd and Arthur suggested that approximately one-third of the biological variation in RFI could be attributed to inter-animal differences in digestion, heat increment of feeding, composition of growth and activity, and the remaining two-thirds could be explained by inter-animal variation in energy expenditure [2, 3]
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