The Effects Of Energy And Dietary Fiber Levels On Mammary Development In Gilts

The mammary development of gilts is closely related to fertility,and the mammary development of gilts is regulated by a variety of factors,and there are two stages of rapid growth and development of the mammary before lactation,namely early youth（3months）and late pregnancy（3 months）.Mammary development in adolescent gilts is a period of rapid mammary growth,which is affected by many factors,among which studies have found that energy intake is closely related to mammary development.Dietary fiber,which has the title of"the seventh nutrient",is widely used in the diet of gilts,which can improve constipation during pregnancy,reduce stress in delivery of gilts,and improve feculence of sows.However,whether dietary fiber affects mammary gland development has not been reported.Therefore,the purpose of this study was to investigate the effects of dietary energy and fiber levels on the growth and development of mammary glands of reserve gilts and to explore their possible mechanisms.In the experiment,32 LY reserve gilts with similar body weight and backfat in the same batch（weight 91.7±3.7 kg,age 161.5±0.5d）were randomly assigned to four treatment groups,with 8 replicates per treatment and 1 gilt per replicate.In this study,2×2 factor test design was adopted,namely,energy intake level（low energy intake level LE:33.37MJ/d DE,high energy intake level HE:41.87m J/d DE）and fiber intake level（low fiber intake level LF:0.3kg/d DF,high fiber intake level HF:0.6kg/d DF）.During the experiment,2.4 kg of basal diet was fed every day.Soybean oil（0.24 kg/d）was added to the basal diet to provide extra energy,and dietary fiber consisting of inulin and cellulose（0.3 kg/d,the ratio of inulin to cellulose was 1:4）was added to improve the fiber level.The test was carried out on the 19th day after the third incubation period of the reserve sows.Blood was collected before slaughter,the carcass was divided after slaughter,the mammary glands were separated,and the mammary glands samples were stored in the frozen storage tube,sample bag and 4%paraformaldehyde for spare.The difference of protein expression in mammary glands of reserve sows was analyzed by label-free unlabeled technique.The test results showed that:1)High energy intake significantly increased the backfat of the gilt（P<0.05）,the age of the first puberty was advanced（P<0.05）,and also increased the slaughter weight（P<0.05）and slaughter backfat（P<0.05）.2)High energy intake increased the weight of mammary tissue（P<0.05）and the content of mammary fat（P<0.05）.At the same time,the oil red staining of mammary slices also showed an increase in mammary fat content.3)High energy intake significantly increased the DNA concentration in mammary tissues（P<0.05）.4)High energy intake increases the concentration of triglycerides,free fatty acids and total cholesterol in the blood of gilts（P<0.05）,and the addition of high fiber tends to reduce free fatty acids and total cholesterol（P<0.1）.5)High energy intake significantly increased the estrogen concentration in the gilts of gilts（P<0.05）.6)High energy intake can significantly increase the receptor mRNA expression of 5-HT₇ in mammary tissue of gilts（P<0.05）,and significantly increase the mRNA expression of Bax and Caspase-3 in mammary tissues of gilts（P<0.05）.7)Differential protein Wayne analysis was performed for low energy and low fiber,high energy and high fiber,high energy and low fiber and low energy and high fiber respectively（the difference multiple FC of the average abundance level of protein expression was greater than 1.2 or less than 0.83 times and P<0.05 was identified as differential protein）.It was found that after high-energy intake treatment,the expression levels of 53 proteins in the mammry of the female were up-regulated,such as deacetylase and apolipoprotein.A total of 58 proteins,such as glutathione and NADH dehydrogenase,were down-regulated.After high fiber intake,25 proteins were up-regulated in the breast of the reserve sow,such as carboxylpeptidase N subunit 2 and apo C-3.Six proteins were down-regulated,such as NADH dehydrogenase[ubiquinone]1-subcomplex subunit 10 and acetyl-coa synthase.After high energy and high fiber intake,the expression of 10 proteins in the mammary gland of the female was up-regulated,such as paraphergin-soluble protein and dermoglobin.A total of 10 proteins were down-regulated,such as ribulose phosphate isomerase 3 and adenosine kinase 2（AK2）.Among them,the differential proteins that affect the breast development of smothers mainly include apolipoprotein,gludotin,cytochrome C oxidase subunit,stress-induced phosphorylated protein 1,adenosine kinase 2.Proteomics results showed that high energy intake promoted the apoptosis of breast cells in gilts to a certain extent,but the process of apoptosis was significantly inhibited after fiber addition,mainly reflected in that high fiber intake significantly inhibited the expression of AK2 protein in breast tissues of sows,thus inhibiting the apoptosis of breast cells.In summary,increased energy intake of gilts improved growth performance,increased backfat thickness and mammary fat deposition,and advanced age of early puberty.Mammary gland proteomics analysis showed that high-energy diet increased mammary cell apoptosis.Increased fiber intake（inulin and cellulose in a ratio of 1:4）reduced mammary fat deposition and breast cell apoptosis in gilts.