**1. Introduction**

Antibiotics have been commonly used as growth promoters in animals. However, the emergence of bacteria resistant to these drugs has led to the search for alternative products with similar effects to antibiotics, but of natural origin [1]. Dietary supplementation with herbal products seems to be a promising strategy to improve the productive performance, carcass characteristics and meat quality of small ruminants [2]. Some polyherbal mixtures (HM) prepared with medicinal plants have shown positive effects on productive performance, meat and carcass quality characteristics of steers and lambs during the final fattening period [3–5]. On the other hand, in calves, it has been reported that the use of HM can improve growth and health status during the pre-ruminant period until weaning by modifying gene expression [6]. However, the effects of bioactive compounds (for example, saponins and flavonoids) of HM in biological systems, may depend on the efficiency of their absorption and extensive metabolic transformation [7].

Previous studies [8,9] have shown that some plants containing saponins, flavonoids and polysaccharides can improve antioxidant status, ruminal fermentation, immune response and productive performance in sheep. Likewise, some HM containing saponins,

**Citation:** Orzuna-Orzuna, J.F.; Dorantes-Iturbide, G.; Lara-Bueno, A.; Mendoza-Martínez, G.D.; Miranda-Romero, L.A.; López-Ordaz, R.; Hernández-García, P.A. Productive Performance, Carcass Traits, and Meat Quality in Finishing Lambs Supplemented with a Polyherbal Mixture. *Agriculture* **2021**, *11*, 942. https://doi.org/10.3390/ agriculture11100942

Academic Editors: Lubomira Gresakova and Emilio Sabia

Received: 11 August 2021 Accepted: 26 September 2021 Published: 29 September 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

flavonoids and tannins have been shown to have a positive impact on nutrient utilization efficiency in goats [10]. Other products containing saponins have shown positive impact on energy metabolism and on the duodenal flux of amino acids [11], ruminal fermentation rate [12,13], rumen microbial populations [14], and production of volatile fatty acids [12–14]. Similarly, flavonoids can modulate the ruminal microbiome, improve rumen fermentation and metabolic status to improve the productive performance and health of ruminants [15]. Some HM containing flavonoids have shown positive impact on antioxidant status [7], and ruminal microbial populations of lambs [16]. In addition, flavonoid supplementation modifies the expression of genes in the rumen epithelium that could be related to inflammation and animal behaviour modulation [17].

Some plant parts containing saponins have also been used to improve the meat quality of adult goats and kids [18,19]. However, there is limited information on the effects of plants or HM containing saponins, flavonoids, and polysaccharides on the productivity, carcass characteristics, and meat quality of lambs. The botanical origin, the dose, and the composition of the diet used can influence the biological response that saponins have on ruminants [20]. Although, the effects of using saponins in ruminant feed have been investigated in animals fed diets containing a high proportion of forage [11,13]; information on the effects of these bioactive metabolites in ruminants fed high concentrate diet is limited and inconsistent [19,21]. Some saponin extracts improve ruminal fermentation and increase the efficiency of energy use in the animals, which could result in better productive performance [11]. However, the effects of saponins on ruminal fermentation may differ depending on the ruminal pH [22], which varies according to the dietary level of concentrate. Due to the beneficial effects of herbal products and their secondary metabolites, it has been hypothesized that supplementation with HM as a source of saponins, flavonoids and polysaccharides can contribute to improving the productivity of the lambs during the final fattening period, without affecting the quality of the meat or the characteristics of the carcass. The objective of this study was to evaluate the effects of increasing doses of an HM containing saponins, flavonoids, and polysaccharides on the productive performance, carcass characteristics, and meat quality of lambs fed high-concentrate diets.

#### **2. Materials and Methods**
