Carcass Traits, Meat Quality, Hydrolyzed Amino Acid Composition, and GC–IMS Volatile Signal Profiles in Kazakh Lambs Fed Diets Containing Fermented Cottonseed Hulls

Cottonseed hulls, a fibrous by-product of cotton processing, are a potentially valuable unconventional feed resource for ruminants, and microbial fermentation may improve their feeding value. This study preliminarily compared plasma antioxidant status, slaughter performance, meat quality, hydrolyzed amino acids, and tentatively assigned GC–IMS volatile signals among Kazakh lambs fed diets containing wheat straw (WS), cottonseed hulls (CSH), or fermented cottonseed hulls (FCSH). Thirty male lambs were allocated to three groups (10 per group), with one pen per diet; six lambs per group were selected for slaughter. At the animal level, plasma biochemical indices showed no nominal between-group differences, whereas T-SOD activity was nominally higher in CSH and FCSH than in WS. Among slaughter-selected lambs, the FCSH group had nominally higher pre-slaughter live weight and carcass weight than the WS and CSH groups, with no detectable differences in dressing percentage or conventional meat-quality traits. Muscle crude fat was nominally higher in the FCSH group than in the WS group, but not different from the CSH group. TAA, EAA, and EAA/TAA showed no nominal between-group differences. Four individual hydrolyzed amino acids and 11 of 66 GC–IMS signals had unadjusted p < 0.05, but none reached q < 0.05 after Benjamini–Hochberg FDR correction. Because each diet was represented by only one pen, treatment and pen effects cannot be separated, and these animal-level findings should be considered exploratory and require validation with independent pen replication.