Soybean molasses increases subcutaneous fat deposition while reducing lipid oxidation in the meat of castrated lambs

This study aimed to evaluate the effect of including soybean molasses (SM) on performance, blood parameters, carcass traits, meat quality, fatty acid and muscle (longissimus thoracis) transcriptomic profiles of castrated lambs. Twenty Dorper × Santa Inês lambs (20.06 ± 0.76 kg BW) were assigned to a randomized block design, stratified by BW, with the following treatments: CON - 0 g/kg of SM and SM20 - 200 g/kg of SM on DM basis, allocated in individual pens. The diet consisted of 840 g/kg concentrate and 160 g/kg corn silage for 76 days, with the first 12 days as an adaptation period and the remaining 64 days on the finishing diet. The SM20 diet increased blood urea concentration (P = 0.03) while reduced glucose concentration (P = 0.04). Lambs fed SM showed higher subcutaneous fat deposition (P = 0.04) and higher subcutaneous adipocyte diameter (P < 0.01), in addition to reduced meat lipid oxidation (P < 0.01). Soybean molasses reduced the quantity of branched-chain fatty acids in longissimus thoracis (P = 0.05) and increased the quantity of saturated fatty acids (P = 0.01). In the transcriptomic analysis, 294 genes were identified as differentially expressed, which belong to pathways such as oxidative phosphorylation, citric acid cycle, and monosaccharide metabolic process. In conclusion, diet with SM increased carcass fat deposition, reduced lipid oxidation, and changed the energy metabolism, supporting its use in ruminant nutrition. Overall design: Crossbreed (Dorper X Santa Inês) castrated lambs (n=20) were randomly divided into two experimental groups and subjected to two experimental diets: control (CON, n=10) or 20% inclusion of soybean molasses (SM20, n=10). Briefly, the samples of longissimus thoracis was collected to physcial and chemical meat analysis, as shear force, intramsucular fat, lipid oxidation and others. Upon slaughter the samples of fresh longissimus thoracis was collected and storage in liquid N2 and further -80°C. For the RNA-Seq analysis, four lambs from each CON and SM20 diet were randomly selected.