The objective of this study was to determine the role of SLC15A4 in the muramyl dipeptide (MDP)-mediated inflammatory response of bovine rumen epithelial cells (BRECs).  First, changes in the mRNA expression of pro-inflammatory factor genes in BRECs following 10 μg mL^–1 MDP treatments were examined.  RT-qPCR results showed that the expression of pro-inflammatory factor (IL-1β, IL-6, and TNF-α) mRNAs were significantly increased under MDP stimulation (P<0.001).  Moreover, SLC15A4-Knockout (SLC15A4-KO) cells were obtained through lentivirus packaging, transfection, screening, and cell monoclonal culture.  In order to gain further insight into the potential function of SLC15A4, we utilized transcriptome data, which revealed a change in the genes between WT-BRECs and SLC15A4-KO.  Five down-regulated pro-inflammatory genes and 13 down-regulated chemokine genes related to the inflammatory response were identified.  Meanwhile, the down-regulated genes were mostly enriched in the nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways.  The results of RT-qPCR also verified these detected changes.  To further determine the mechanism of how WT and SLC15A4-KO BRECs are involved in inflammatory responses, we investigated the inflammatory responses of cells exposed to MDP.  WT-BRECs and SLC15A4-KO were treated with a culture medium containing 10 μg mL^–1 MDP, in comparison to a control without MDP.  Our results show that SLC15A4-KO BRECs had reduced the expression of genes (IL-6, TNF-α, CXCL2, CXCL3, CXCL9, and CCL2) and proteins (p-p65 and p-p44/42) from the MDP-mediated inflammatory response compared to WT-BRECs (P<0.05).  In this experiment, CRISPR-Cas9 was used to KO the di/tripeptide transporter SLC15A4, and its role was confirmed via the MDP-induced inflammatory response in BRECs.  This work will provide a theoretical basis for studying the pro-inflammatory mechanism of MDP and its application in the prevention and treatment of subacute rumen acidosis in dairy cows.

This paper primarily analyzes the evolution path of China’s pork price by employing the threshold autoregression model (TAR). Considering the unit root test with a threshold effect and heteroskedasticity of the TAR model, we show that the pork price series is a unit root process in each regime, and the heteroskedasticity in the TAR model greatly affects the results of linearity test. We find that the changing process of pork price has two regimes: mild regime and expansion regime. In particular, a change belongs to an expansion regime if it is larger than 0.5881; otherwise, it falls in the mild regime.

This study was carried out to determine the effect of replacement of forage fiber sources from alfalfa and Leymus chinensis with nonforage fiber sources (NFFS) from dried distillers grains with solubles and corn germ meal on calves growth, rumen development and blood parameters. 48 female and 12 male calves ((110.55±15.36) kg of body weight and 12 wk of age) were assigned randomly to four dietary treatments (15 calves/treatment) in a completely randomized design. Experimental diets were: 0% NFFS (control), 9% NFFS (group 1), 18% NFFS (group 2), 27% NFFS (group 3), and contained equivalent neutral detergent fiber and total digestible nutrients, respectively. The dry matter intake was similar among diets, averaging 3.33 kg d-1, and no differences were detected for body weight, withers height, body length and heart girth. In addition, the development of rumen, reticulum, omasum and abomasum also were similar among diets. Dry matter, crude protein, and neutral detergent fiber digestibilities increased with the increasing levels of NFFS in the experimental diets, but had no significant effect. Blood urea nitrogen, total protein and glubulin were not affected by the dietary treatment, but group 3 resulted in the highest (P<0.05) concentrations of glucose and the lowest (P<0.05) concentrations of triglycerides and albumin. In conclusion, dried distillers grains with solubles (DDGS) and corn germ meal (CGM) were available and alternative fiber sources for Holstein calf diets.