Nutrient Composition Of Donkey And Horse Milk And Effects On Gut Microbes

Donkeys'milk and mares'milk are popular among consumers as the special milk products with ethnic characteristics.However,less research have been performed on their nutritional value and potential functions Accordingly,the nutritional components of donkeys'milk and mares'milk,their protein digestion characteristics,and the effects of two dairy products on gut microbiota were studied in order to provide a solid theoretical basis for the production and processing of mares'milk and donkeys'milk.1.Nutritional content of donkeys'milk and mares'milkThe main components of donkeys'milk and mares'milk were analyzed by a milk composition analyzer,showing that donkeys' milk protein content was 1.25%,fat content was 2.09%,and lactose content is 7.59%,while mares' milk protein content was 2.01%,fat content was 1.86%,and lactose content was 5.59%.Moreover,the ratio of casein to whey protein in donkeys'milk and mares'milk was 1:2,1:1,respectively.The protein compositions were further analyzed by SDS-PAGE gel electrophoresis.The results showed that donkeys'milk a and ?-casein took up 90.63%and ?-casein took up 7.29%,while in mares' milk consisted of 90.88%? and?-casein and 8.36%?-casein.The donkeys' milk whey protein is mainly composed of 32.35%?-lactoglobulin and 28.36%?-lactalbumin,whilke mares' milk whey protein is mainly composed of 33.56%?-lactoglobulin and 27.02%?-lactalbumin.Analyses of their amino acids revealed that the content of essential amino acids(6.422%)in donkeys' milk was higher than that of in mares' milk(6.281%).In addition,leucine was higher in donkeys' milk(1.401%),but glutamic acid(3.582%)and natural aspartic acid(1.422%)were higher in mares' milk.It was found that the contents of saturated fatty acids(SFA,2.8%)and monounsaturated fatty acids(MUFA,6.44%)were higher than in donkeys' milk comparing with that in mares' milk(SFA,5.82%;MUFA,2.63%).2.Digestive properties of donkeys'milk and mares'milk proteinsThe digestibility of proteins in donkeys' milk and mares' milk was studied by SDS-PAGE gel electrophoresis.The results showed that the digestibility of the donkeys' milk and mares' milk casein is 97.9%and 96.7%respectively after digestion in the gastric juice for 120 minutes.The digestibility of the donkeys'milk and mares'milk casein in the intestinal juice after 30 minutes was 98.6%and 97.7%respectively.The proteins were almost completely digested.Mares' milk protein was easier to be digested than donkeys'milk protein.Based on the digestibility of donkeys'milk and mares' milk casein in gastric juice and intestinal fluid,it was found that donkeys' milk and mares' milk proteins were mainly digested in intestinal.3.Effects of donkeys' milk and mares' milk on the gut microbiota of miceThe effects of donkeys'milk and mares'milk on the gut microbiota of mice were studied based on high-throughput amplicons sequencing of 16S rRNA gene V3-V4 variable region.Through the analyses of taxonomy of gut microbiota,i.e.phylum,class,order,family,genus.Donkeys' milk was able to improve the abundance of Firmicutes,Bacilli,Lactobacillales,Prevotellaceae,Lactobacillus and Bifidobacterium while mares' milk could promote the abundance of Firmicutes,Clostridia,Lactobacillales,Lactobacillaceae,Lactobacillus and Akkermansia.Compared with the control group,Lactobacillus,Roseburia and Prevotellaceae_NK3B31 in the intestinal microbiota of the donkeys' milk group and mares' milk group were significantly higher than the control group(p<0.05),while abundance of Bilophila,Butyricimonas and Erysipelatoclostridium is significantly reduced.A comparative analysis of the donkeys' milk group and mares' milk group found that the abundance of Akkermansia in the intestinal microbiota of the mares' milk group was significantly increased,while the abundance of Enterococcus and Staphylococcus significantly decreased;the abundance of Alloprevotella,Allobaculum and Bifidobacterium in the intestinal microbiota of the donkeys' milk group increased significantly,while the abundance of Marvinbryantia decreased significantlyThe metabolisms of amino and nucleotide sugars,arginine and proline metabolism and glycolysis/gluconeogenesis of the gut microbiota in mares' milk group mice and donkeys' milk group mice were higher than that in control group mice.The abundance of metabolic pathways in the mares' milk group was higher than in the donkeys' milk group,while acetaldehyde dehydrogenase/alcohol dehydrogenase was mainly enriched in donkeys' milk group mice.Analyses of COG functional categories revealed that mares' milk and donkeys' milk promoted the transport and metabolism of amino acids and carbohydrates.Donkeys' milk mainly increases the abundance of a variety of beneficial bacteria,and mares' milk mainly inhibits the abundance of conditionally pathogenic bacteria or pathogenic bacteria to regulate the intestinal microbiota bringing the positive impacts on the host health.In this research,we found that mares' milk is easy to digest and the two kinds of milks promoted the growth of probiotics Lactobacillus,Bifidobacterium and Akkermansia,showing that they are ideal dairy products.This study lays a foundation for further development of mares' milk and donkeys' milk.