Abstract
This review examines several molecular mechanisms underpinning oxidative stress in ruminants and their effects on blood and milk oxidative traits. We also investigate strategies to alleviate or repair oxidative damages by improving animal immune functions using novel feed additives. Microbial pathogenic cells, feeding management, and body condition score were some of the studied factors, inducing oxidative stress in ruminants. The predominance of Streptococcus spp. (24.22%), Acinetobacter spp. (21.37%), Romboutsia spp. (4.99%), Turicibacter spp., (2.64%), Stenotrophomonas spp. (2.33%), and Enterococcus spp. (1.86%) was found in the microbiome of mastitis cows with a decrease of d-mannose and increase of xanthine:guanine ratio when Streptococcus increased. Diversity of energy sources favoring the growth of Fusobacterium make it a keystone taxon contributing to metritis. Ruminal volatile fatty acids rose with high-concentrate diets that decreased the ruminal pH, causing a lysis of rumen microbes and release of endotoxins. Moreover, lipopolysaccharide (LPS) concentration, malondialdehyde (MDA), and superoxide dismutase (SOD) activities increased in high concentrate cows accompanied by a reduction of total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), and catalase (CAT) activity. In addition, albumin and paraoxonase concentrations were inversely related to oxidative stress and contributed to the protection of low-density and high-density lipoproteins against lipid peroxidation, protein carbonyl, and lactoperoxidase. High concentrate diets increased the expression of MAPK pro-inflammatory genes and decreased the expression of antioxidant genes and proteins in mammary epithelial tissues. The expression levels of NrF2, NQO1, MT1E, UGT1A1, MGST3, and MT1A were downregulated, whereas NF-kB was upregulated with a high-grain or high concentrate diet. Amino-acids, vitamins, trace elements, and plant extracts have shown promising results through enhancing immune functions and repairing damaged cells exposed to oxidative stress. Further studies comparing the long-term effect of synthetic feed additives and natural plant additives on animal health and physiology remain to be investigated.
Highlights
Uterine wall inflammation known as metritis or pelvic inflammatory disease mostly occurs in negative energy balance (NEB) conditions
Out of 95 carbon energy sources investigated that may promote the growth of Fusobacterium, up to 47 were metabolized by F. necrophorum, enabling it to proliferate in postpartum cows using an array of energy sources, even in animal NEB [36]
Coenzyme A (CoA) and its thioester derivatives are synthesized by prokaryotes and eukaryotes cells and are involved in major metabolic pathways, including the regulation of gene expression and redox activity known as protein CoAlation, strongly induced in response to oxidizing agents and metabolic stresses in exponentially growing bacteria to prevent overoxidation [41]
Summary
Some oxidative stress factors considered and described within this study are the microbial pathogenic cells inducing mastitis and metritis degenerative diseases in dairy cows along with feeding management using different concentrates: forage ratios, with effects on some expressed genes associated with oxidative stress pathways. To address these drawbacks, several studies have been carried out on the dietary supplementation with additives like methionine and lysine amino-acids to evaluate the effects on the cattle oxidative status [12,13,14].
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