Blended rumen undegradable protein sources improve growth performance, and H-FABP expression in fattening lambs

This study evaluated the effects of a mixture of rumen undegradable protein (RUP) sources including soybean meal (SBM), corn gluten meal (CGM) and fish meal (FM) on performance, meat quality, and relative expression of μ-calpain-1 (CAPN1), calpastatin (CAST), and heart- fatty acid binding protein (H-FABP) genes in fattening lambs. Twenty-one male Lori-Bakhtiari lambs (140 ± 15 days of age, 33 ± 2.5 kg) were randomly fed one of the three experimental diets each formulated to contain similar RUP%, containing 13% SBM (RUP1), 5% SBM + 3.5% CGM (RUP2), and 5% SBM + 2% CGM + 2% FM (RUP3) for a period of 60 days. Findings showed that the mixture of three sources of RUP (RUP3) enhanced growth performance (9%), altered meat composition, and modulate the expression of genes related to meat quality. Feeding lambs with RUP3 increased blood total protein and shifted toward more fat deposition in meat (P < 0.05). Meat of lambs in RUP3 showed an increase fat content but a decrease in crude protein percentage (P < 0.05). Fatty acid profile of meat remained unchanged except for an improvement in docosahexaenoic acid (C22:6 n-3) and n-3: n-6 ratio in RUP3 group (P < 0.05). The relative gene expression of H-FABP was upregulated in RUP3 while CAPN1 and CAST remained unchanged. In conclusion, the results suggested that using a blend of RUP sources improved growth performance, altered chemical composition and upregulated H-FABP genes without negative effects on physicochemical properties of meat in fattening lambs.