Abstract
To increase intramuscular fat accumulation, Japanese Black beef cattle are commonly fed a high-grain diet from 10 to 30 months of age. Castrated and fistulated cattle (n = 9) were fed a high-concentrate diets during the early, middle, and late stages consecutively (10–14, 15–22, 23–30 months of age, respectively). Ruminal pH was measured continuously, and rumen epithelium and fluid samples were collected on each stage. The 24-h mean ruminal pH during the late stage was significantly lower than that during the early stage. Total volatile fatty acid (VFA) and lactic acid levels during the late stage were significantly lower and higher, respectively, than those during the early and middle stages. In silico analysis of differentially expressed genes showed that “Oxidative Phosphorylation” was the pathway inhibited most between the middle and early stages in tandem with an inhibited upstream regulator (PPARGC1A, also called PGC-1α) but the most activated pathway between the late and middle stages. These results suggest that mitochondrial dysfunction and thereby impaired cell viability due to acidic irritation under the higher VFA concentration restored stable mitochondrial oxidative phosphorylation and cell viability by higher lactic acid levels used as cellular oxidative fuel under a different underlying mechanism in subacute ruminal acidosis.
Highlights
To increase intramuscular fat accumulation, Japanese Black beef cattle are commonly fed a high-grain diet from 10 to 30 months of age
The occurrence of subacute ruminal acidosis (SARA) defined by a rumen pH
The expression of SLC9A6 (NHE6) and SLC26A3 (DRA) were downregulated during the first period, while they were upregulated during the second period. These results suggest that expression of genes encoding rumen epithelial absorption was suppressed by acidotic insult during the first period, whereas it was restored during the second, enhancing VFA absorption or transporter gene expression in the rumen
Summary
To increase intramuscular fat accumulation, Japanese Black beef cattle are commonly fed a high-grain diet from 10 to 30 months of age. In silico analysis of differentially expressed genes showed that “Oxidative Phosphorylation” was the pathway inhibited most between the middle and early stages in tandem with an inhibited upstream regulator (PPARGC1A, called PGC-1α) but the most activated pathway between the late and middle stages These results suggest that mitochondrial dysfunction and thereby impaired cell viability due to acidic irritation under the higher VFA concentration restored stable mitochondrial oxidative phosphorylation and cell viability by higher lactic acid levels used as cellular oxidative fuel under a different underlying mechanism in subacute ruminal acidosis. The rumen papillae in dairy cattle fed a total mixed ration had increased epithelial desquamation and sloughing scores during early lactation, as well as upregulation of genes encoding desmosome assembly (despoglein[1] and corneodesmosin), epidermal growth factor (EGF) signaling (epiregulin), transforming growth factor β (TGFB). Little is known about the effects of the rumen environment on Japanese Black cattle fattening, in terms of the ruminal pH, fermentation, and epithelial transcriptomes
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