Abstract
Simple SummaryTannins can be used to improve productive performance, meat quality and antioxidant status of ruminants. The objective of this study was to evaluate the effects of dietary tannin supplementation on productive performance, carcass characteristics, meat quality and blood serum antioxidant status of sheep through a meta-analysis. Only studies with weaned or older sheep were included. The sheep included in the present study were between 2 and 6 months old, and between 12 and 31 kg of body weight. Tannin supplementation improved productive performance, carcass yield, meat oxidative stability and blood serum antioxidant capacity. This suggests that the inclusion of tannins in sheep diets could be used to improve growth and reduce oxidative stress in animals, and to improve meat quality and shelf life.The objective of this study was to evaluate the effects of dietary supplementation with tannins (TANs) on productive performance, carcass characteristics, meat quality, oxidative stability, and blood serum antioxidant capacity of sheep through a meta-analysis. Using Scopus, Web of Science, ScienceDirect, and PubMed databases, a systematic search was performed for studies published in scientific journals that investigated the effects of TANs supplementation on the variables of interest. Only studies with weaned or older sheep were included. The data analyzed were extracted from 53 peer-reviewed publications. The sheep included in the present study were between 2 and 6 months old, and between 12 and 31 kg of body weight. The effects of TANs were analyzed using random-effects statistical models to examine the standardized mean difference (SMD) between treatments with TANs and control (no TANs). Heterogeneity was explored by meta-regression and a subgroup analysis was performed for covariates that were significant. Supplementation with TANs did not affect dry matter intake, pH, color (L* and b*), Warner–Bratzler shear force, cooking loss and meat chemical composition (p > 0.05). Supplementation with TANs increased daily weight gain (SMD = 0.274, p < 0.05), total antioxidant capacity (SMD = 1.120, p < 0.001), glutathione peroxidase enzyme activity (SMD = 0.801, p < 0.001) and catalase (SMD = 0.848, p < 0.001), and decreased malondialdehyde (MDA) concentration in blood serum (SMD = −0.535, p < 0.05). Supplementation with TANs decreased feed conversion rate (SMD = −0.246, p < 0.05), and the concentration of MDA (SMD = −2.020, p < 0.001) and metmyoglobin (SMD = −0.482, p < 0.05) in meat. However, meat redness (SMD = 0.365), hot carcass yield (SMD = 0.234), cold carcass yield (SMD = 0.510), backfat thickness (SMD = 0.565) and the Longissimus dorsi muscle area (SMD = 0.413) increased in response to TANs supplementation (p < 0.05). In conclusion, the addition of tannins in sheep diets improves productive performance, antioxidant status in blood serum, oxidative stability of meat and some other characteristics related to meat and carcass quality.
Highlights
Antibiotics have been used for several decades as growth promoters in animals [1]
A selection of titles and abstracts was performed excluding simulation studies, review articles, studies not conducted in sheep, invitro studies, and articles that did not include the variables of interest
Except for neutral detergent fiber (NDF), ether extract (EE) and organic matter (OM) content, no significant differences were observed between the control and TANs treatment for the rest of the nutritional components of the diet
Summary
Antibiotics (e.g., monensin) have been used for several decades as growth promoters in animals [1]. The inappropriate use of these products results in an accumulation of toxic residues in meat, which can affect the health of the consumer [2,3]. The emergence of bacterial strains resistant to the antibiotic effects [4] as well as the prohibition of these compounds in some countries [5] have led the industry and researchers to search for alternative products with similar effects as antibiotics, but of natural origin. Tannins (TANs), which are derived from plants, have received special attention and are among the most studied bioactive compounds, in ruminants [1]. TANs are a group of polyphenolic compounds present in a wide variety of plants, which can be grouped into hydrolysable tannins (HTs) and condensed tannins (CTs) based on their chemical structure [6,7]. TANs can produce positive effects in animals, such as those of the antioxidant, antimicrobial, antiparasitic, immunomodulatory, and anti-inflammatory varities [1,6]
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