| Our country is rich in dairy goat breed resources,among which Guanzhong dairy goat has the advantages of excellent milk production performance and strong adaptability.Goat milk is highly similar to human milk,with softer curd formation,easy absorption,high protein and mineral content,and low cholesterol content.However,there are still some problems in the current development of the dairy goat industry,such as shortage of high-quality feed and non-standard feeding and management,which have resulted in a decline in the milk production of dairy goats and reduced the economic benefits of breeding enterprises.Hybrid Broussonetia papyrifera has the advantages of wide adaptability,strong stress resistance,and high resistance to pests and diseases.Its crude protein content exceeds 20%,which can provide more protein for livestock.As a new type of livestock diet,silage hybrid Broussonetia papyrifera has been widely used,but the research on its effect on the lactation performance of Guanzhong dairy goats is not deep enough.Therefore,in this study,12 Guanzhong dairy goat ewes in the lactation period(about 100 days postpartum)with the same average initial body weight(51.5±1.08 kg),the parity is 2 litters,and similar lactation days and milk production were selected and randomly divided into 2 groups.The goats in the control group(CG group)were fed the basal TMR,while the Broussonetia papyrifera group(BP group)was supplemented with10% silage hybrid Broussonetia papyrifera in the diet based on the principle of equal protein.This study firstly analyzed the effect of silage hybrid Broussonetia papyrifera on the lactation performance of dairy goats,and then further explored the molecular mechanism of Broussonetia papyrifera flavone affecting the milk quality of dairy goats.The main results of this study are as follows:1.In order to explore the effect of silage hybrid Broussonetia papyrifera on milk production and lactation-related hormones of dairy goats,this experiment detected the nutritional components of the diets,the average daily feed intake,body weight changes,milk production,content of PRL and E in dairy goats’ serum.The results showed that the contents of NDF,ADF and flavone in the BP group were significantly higher than those in the CG group(P < 0.05).The average daily feed intake of the goats in the BP group was significantly higher than that in the CG group in the third,fourth,fifth and sixth weeks of the experiment(P < 0.01).And the body weight of the milk goats in the BP group and the CG group was only 1.4±1.32 kg before and after the feeding period.The milk yield of the goats in the BP group was significantly higher than that in the CG group from the first week to the sixth week(P < 0.05),and the average daily milk yield increased by 22.34%,with a peak milk yield of 2.49 kg/d.In addition,the PRL content of goats in the BP group was significantly higher than that of the CG group in the first,fourth and sixth weeks(P <0.05),while the E content in the third,fifth and sixth weeks was significantly higher than that in the CG group(P < 0.05).Therefore,feeding silage hybrid Broussonetia papyrifera can improve the average daily feed intake and milk production of dairy goats,and increase the content of lactation-related hormones in serum,thereby promoting lactation.2.In order to further explore the effect of silage hybrid Broussonetia papyrifera on milk quality of dairy goats,the milk components,amino acid and fatty acid composition and content of milk in the CG group and BP group were detected.The results showed that the absolute value of milk fat content(average daily milk yield×milk fat rate)and the absolute value of lactose content(average daily milk yield×lactose rate)in goat milk of BP group were significantly higher than those of CG group(P < 0.05),while the content of each amino acid and the total amount of amino acids were lower than those in the CG group,but the difference was not significant(P > 0.05).In addition,the content of C17:0 in the BP group was significantly lower than that in the CG group(P < 0.05),while the contents of C18:3n-3,EPA and DHA were significantly higher than those in the CG group(P < 0.05).Therefore,feeding silage hybrid Broussonetia papyrifera can increase the content of milk fat,lactose and unsaturated fatty acids(UFA),and reduce the content of saturated fatty acids(SFA)in milk,thereby improving milk quality.3.Based on the nutrient composition of silage hybrid Broussonetia papyrifera,this study speculates that the flavone in hybrid Broussonetia papyrifera may affect the fat synthesis in milk.Therefore,in this study,the flavone extracted from the leaves of Broussonetia papyrifera were added to the medium of goat mammary epithelial cells(GMECs)to detect the content of intracellular triglycerides(TAG),the number of lipid droplets,the m RNA of genes related to fatty acid synthesis,and the expression of prolactin receptor(PRLR)and estrogen receptor(ER)proteins.The results showed that adding 1-4μmol/L Broussonetia papyrifera flavone to the culture medium of GMECs for 48 h could improve the cell viability,and the cell viability reached the peak in the 4 μmol/L treatment,which was significantly higher than that in the CG group(P < 0.05).Subsequently,the GMECs incubated with 4 μmol/L of flavone for 48 h recorded as the BP group.The results showed that compared with the CG group,the accumulation of TAG and the number of lipid droplets in GMECs in the BP group were significantly increased(P < 0.05).The m RNA levels of de novo fatty acid synthesis-related genes ACACA,FASN,and SCD1,long-chain fatty acid activation and transport-related genes ACSL1,transcriptional regulation-related genes SREBP1,PPARA,and PPARG,and triglyceride synthesis-related genes DGAT1,DGAT2 and GPAM were significantly increased(P < 0.05).The expression of ER protein was significantly increased(P < 0.05),but the expression of PRLR protein had no significant change(P > 0.05).Therefore,the flavone can enhance the activity of GMECs,increase the content of TAG and the number of lipid droplets in cells,up-regulate the expression of ER protein,and then promote the synthesis of milk fat.In conclusion,adding 10% silage hybrid Broussonetia papyrifera to the dairy goat diet increased the average daily feed intake and milk production of dairy goats,and the average daily milk production increased by 22.34%.The content of milk fat,lactose and UFA in goat milk increased,while the content of SFA decreased.In addition,the flavone extracted from the leaves of Broussonetia papyrifera can enhance the viability of GMECs,increase the intracellular TAG content and the number of lipid droplets,and upregulate the expression of ER proteins,thereby promoting milk fat synthesis.Therefore,silage hybrid Broussonetia papyrifera can increase the milk yield of Guanzhong dairy goats and improve the quality of goat milk. |
