Dairy cows are often fed a high-concentrate diet to meet lactating demands, yet long-term concentrate feeding induces subacute ruminal acidosis (SARA) and leads to a decrease in milk fat. Stearoyl-CoA desaturase1 (SCD1) participates in fatty acid biosynthesis in the liver of lactating ruminants. Here, we conducted this study to investigate the impact of lipopolysaccharide derived from the rumen on SCD1 expression and on fatty acid composition in the liver of dairy cows fed a high-concentrate diet. Eight multiparous mid-lactating Holstein cows (455 ± 28 kg) were randomly assigned into two groups in the experiment and were fed a low-concentrate diet (LC) or high-concentrate diet (HC) for 18 weeks. The results showed that the total volatile fatty acids and lactic acid accumulated in the rumen, leading to a decreased rumen pH and elevated lipopolysaccharides (LPSs) in the HC group. The long chain fatty acid profile in the rumen and hepatic vein was remarkably altered in the animals fed the HC diet. The triglyceride (TG), non-esterified fatty acid (NEFA) and total cholesterol (TCH) content in the plasma was significantly decreased, whereas plasma glucose and insulin levels were increased. The expression of SCD1 in the liver was significantly down-regulated in the HC group. In regards to transcriptional regulators, the expression of sterol regulatory element binding transcription factors (SREBF1c, SREBF2) and SREBP cleavage activating protein (SCAP) was down-regulated, while peroxisome proliferator-activated receptor α (PPARα) was up-regulated. These data indicate that lipopolysaccharide derived from the rumen down-regulates stearoyl-CoA desaturase 1 expression and alters fatty acid composition in the liver of dairy cows fed a high-concentrate diet.

Background: Fat is the main substance that provides energy to animals. However, the use of fat in twin Hu lambs has not been investigated. Thirty pairs of male twin lambs were examined to investigate the effects of dietary fat on the metabolism of energy and nitrogen, ruminal fermentation, and microbial communities. The twins are randomly allotted to two groups (high fat: HF, normal fat: NF). Two diets of equal protein and different fat levels. The metabolism test was made at 50-60 days of age. Nine pairs of twin lambs are slaughtered randomly, and the rumen fluid is collected at 60 days of age. Results: The initial body weight (BW) in the HF group did not differ from that of NF group ( P > 0.05), but the final BW was tended to higher than that of NF group (0.05 < P < 0.1). The digestive energy (DE), metabolism energy (ME), DE/ME in the HF group tend to be higher than those in the NF group (0.05 < P < 0.1). Ruminal ammonia nitrogen (NH ₃ -N) and the proportion of total volatile fatty acids (TVFA) are higher than that in the NF group ( P < 0.05). A high throughput sequencing analysis reveals that there were no differences between the two groups in terms of the richness estimates and diversity indices ( P > 0.05). The Proteobacteria and Fibrobacteres phyla were higher than that in NF group ( P <0.05). Conclusions: This study demonstrated that high fat diet before weaning can affect the abundance of several groups of rumen bacteria in rumen, such as significantly increasing phyla Proteobacteria and Fibrobacteres , and genera of Succinivibrio , Alloprevotella , and Saccharofermentans , but significantly decreasing genera of Clostridium IV , Dialister , Roseburia , and Butyrivibrio . And high fat diet improved the performance of lambs at weight gain, energy utilization, and had effect on VFA composition but no effects on serum enzymes and serum hormone.