The Inclusion of Prosopis laevigata Pods in Finishing Lamb Diets Affects Performance and Induces Non-Target Metabolomic Modifications in the Liver and Meat

This study assessed the impact of the dietary inclusion of Prosopis laevigata pods (PLPs) on growth performance, carcass traits, and the metabolomic profiles of liver and meat in finishing lambs. A total of 28 crossbred lambs (38 ± 5 kg body weight) were allocated to one of two treatments: a control diet (0 g PLP/kg dry matter, n = 14; CONT) and a diet supplemented with 300 g PLP/kg dry matter (DM) (n = 14; PS). Growth performance was monitored over 25 days. Animals were assigned to a randomized design, and data were analyzed using the General Linear Model (GLM) procedure. Compared with the control diet, PLP inclusion (300 g/kg DM) reduced total body weight gain (p = 0.04) and worsened feed conversion efficiency. Lambs on the control diet also displayed a significantly greater (p = 0.02) rump perimeter. In contrast, lambs fed the 300 g PLP/kg DM diet showed a marked increase (p < 0.05) in the longissimus thoracis et lumborum (LTL) muscle area. Principal component analysis revealed a distinct separation between treatment groups based on the identified metabolites. Liver metabolomic data accounted for 30.6% of the total variability, while meat samples accounted for 45.7%. A total of 21 and 23 metabolites exhibited positive correlations in liver and meat, respectively. Notably, PLP supplementation influenced several metabolic pathways (p < 0.05), including the biosynthesis of unsaturated fatty acids, fatty acid biosynthesis, and sulfur metabolism in both liver and meat. Additionally, phenylalanine metabolism was specifically affected (p < 0.05) in the liver, while steroid biosynthesis was altered (p < 0.05) in meat. Overall, the inclusion of PLPs in the diet of finishing lambs resulted in notable changes to the liver and meat metabolomes, particularly in pathways associated with fatty acid biosynthesis. Although PLP supplementation reduced overall growth performance, it did not negatively impact carcass quality traits; hence, we recommend the inclusion of 300 g PLP/kg DM in finishing lamb diets.