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

## TL;DR

Adding Prosopis laevigata pods to lamb diets changes liver and meat chemistry but does not harm carcass quality.

## Contribution

The study reveals new insights into the metabolomic effects of Prosopis laevigata pods in lamb diets.

## Key findings

- Lambs fed Prosopis laevigata pods had lower weight gain and worse feed efficiency.
- Pod inclusion increased loin muscle area and altered liver and meat metabolomes.
- Key metabolic pathways like fatty acid biosynthesis were affected by the pods.

## Abstract

Prosopis laevigata pods are a locally available feed resource that could help reduce feeding costs in lamb production, but their effects on animal performance and meat characteristics need to be clarified. This study evaluated the inclusion of Prosopis laevigata pods in diets for finishing lambs and their effects on growth, carcass traits, and chemical changes in the liver and meat. Twenty-eight lambs were fed either a control diet or a diet containing Prosopis laevigata pods for 25 days. Lambs receiving the supplemented diet showed lower body weight gain and poorer feed conversion efficiency compared with lambs fed the control diet. However, carcass quality was not negatively affected, and lambs fed Prosopis laevigata pods showed an increase in loin muscle area, which is an important trait for meat yield. In addition, the supplemented diet caused clear changes in the chemical composition of liver and meat, mainly related to fat synthesis and fat-related processes. The results suggest that Prosopis laevigata pods can be included in finishing lamb diets as an alternative feed ingredient without compromising carcass traits, supporting the use of local resources in animal production.

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.