Fattening lambs with divergent residual feed intakes and weight gains: Unravelling mechanisms driving feed efficiency

Important achievements have been made to improve feed efficiency of farm livestock, but molecular mechanisms determining utilization remain unclear. The objective this work was identify the reasons behind divergent efficiencies in fattening lambs. Twenty newborn male Assaf lambs were fed milk replacer (MR) ad libitum using an automatic feeder, and weaned progressively during last 7 days artificial suckling period (50 total). Then, all offered a complete pelleted diet phase. During period, weighed twice weekly daily dry matter intake measured. These data used estimate residual (RFI), weight gain (RWG), body (RIG). Animals ranked according RIG, then assigned two experimental groups (n = 10 per treatment): group EFFI including most efficient (with negative values for RIG) NEFFI with least (positive RIG). relevant results revealed that traits these not associated differences digestibility or ruminal fermentation parameters (P > 0.05). However, presented lower concentration glucose (95.4 vs. 88.2 mg/dL; P < 0.05) cholesterol (62.8 55.1 serum. effects might be related gene expression enzymes involved key metabolic pathways liver (e.g., PDHA1OA, CYP3A4). Moreover, bone formation growth also compromised by genes protein synthesis, such as those encoding ribosomal proteins RPL22L1), being aligned albumin observed serum animals (35.56 33.89 g/L; A pro-inflammatory profile at both locations, ileum, having one down regulation anti-inflammatory cytokines innate immune response IL-4 TGF-?) can explain, partially, increased expenditure energy redirected from accretion towards alleviation systemic inflammation.