Abstract: To explore the effects and mechanism of high concentrate diet on hepatic and spleen tissues in dairy goats, 14 Guanzhong dairy goats at the early stage of lactation were randomly divided into control group (CG, n=6) and experimental group (EG, n=8). The CG was fed with a normal diet (concentrate:roughage=35:65), and the EG was fed with a high concentrate diet (concentrate:roughage=65:35). The trial lasted for 19 weeks. The milk from all goats was collected at 0, 1, 4, 8, 12, 15, 16, 18 and 19 weeks to analyze milk fat. Every Sunday from 6 to 18 weeks, all sheep feces were collected for pH determination. After autopsy at the end of the experiment, hepatic and spleen tissues were collected and tissue sections were made to observe the morphological changes of the hepatic and spleen tissues. The gene expression of inflammatory cytokines and key proteins of the TLR4 pathway in hepatic and spleen tissues were detected with the RT-qPCR method. The expression level of key proteins in the TLR4 pathway was analyzed using the Western blot method. The results showed that milk fat of EG decreased and was significantly different from those of CG at 16, 18 and 19 weeks (P<0.05). Average fecal pH of EG declined from the 9th week, and the difference was significant between EG and CG from 13 to 18 weeks (P<0.05). Hepatocyte was granule or vacuole degeneration and there was inflammatory cell infiltration around central vein of hepatic lobular. The spleen tissues' change was not obvious. The expression of pro-inflammatory factors IL-6 and TNF-β, as well as TLR4 and NF-κB2 genes were significantly increased in hepatic tissues (P<0.05). The expression of TNF-β, IL-10 and TLR4 genes were significantly increased, while the expression of NF-κB2 was significantly decreased in spleen tissues (P<0.05). p38, JNK, ERK and p65 proteins' expressions in hepatic tissues were not significantly changed, while the expressions of p38, ERK and p65 proteins in spleen tissues showed decreased trend. Those indicated that the decline of milk fat and fecal pH were induced by long-term feeding high-concentration diet. Upregulating of NF-κB gene expression led to the increased expression of IL-6 and TNF-β genes in the hepatic tissues of dairy goats, which caused inflammatory damage to the hepatic tissues, but had no obvious effect on the spleen tissues.

Key words: dairy goat, high concentrate diet, hepar and spleen, inflammatory cytokine