Development Of Probiotic Fermented Milk Replacer And Its Effects Of Calf Growth,Metabolism And Intestinal Microbiota

Milk replacer,known as artificial milk powder,is formulated from skimmed milk powder and whey protein powder,combined with high-quality plant protein and fat through homogenization,sterilization,and spray drying.However,studies have found that there are numerous anti-nutritional factors and allergens in plant protein,making it difficult to be digested and absorbed by claves.Our reaserachaims to reduce the anti-nutrition and immune reactivity of plant-derived materials,and metabolize protein into small molecule peptides by using enzymatic hydrolysis and Lacticaseibacillus casei Zhang,Lacticaseibacillus plantarum P-8,Lacticaseibacillus rhamnosus Probio-M9,Bifidobacterium animalis subsp.lactis V9,Bifidobacterium animalis subsp.lactis Probio-M8 compound probiotic fermentation,using sterilization,enzymatic hydrolysis,fermentation,homogenization and spray drying processes,so as to improve the digestion and absorption efficiency of calves,reduce diarrhea,increase daily weight gain,and reduce mortality.In order to achieve this purpose,the quality of the probiotic-fermented calf milk replacer powder were evaluated by measuring the nutritional indicators,physical and chemical indicators,the number of viable bacteria,and the products of the probiotics firstly,and then the growth and development of the calves in the calf feeding experiment were recorded,calves blood and feces samples were collected,the effects of probiotic fermented calf milk replacer on calf growth,metabolism and intestinal flora were analyzed through metabolomics and metagenomics.Main results are obtained as follows:(1)Nutritional and physicochemical index determination.The probiotic fermented milk replacer has the same nutritional content as commercial milk replacer.The p H value is 5.64,the solubility reaches 96.30%,and the stratification time after brewing is 1h longer than commercial milk replacer.After sterilization,enzymolysis,fermentation,homogenization,spray drying and other processes,the number of viable bacteria of the probiotic fermented milk replacer reached 2.55×10~6CFU/g.Compared with the non-targeted metabonomics determination,the content of L-phenylalanine,protoporphyrin,pantothenic acid and other amino acids and vitamins after enzymatic hydrolysis and fermentation were significantly increased(P<0.05),which may help to improve the digestion and absorption efficiency of calves and ensure the healthy growth and development of calves.(2)The probiotic calf milk replacer has the same nutritional content as the commercial milk replacer,so the weight gain of the two groups of calves is equivalent.However,the increase in body height and oblique length of calves fed with probiotics fermented milk replacer was 8.70%and 11.20%higher than that of calves fed with commercial milk replacer.And the diarrhea rate and mortality rate are lower than that of calves fed commercial milk replacers by 4.29%and 9.45%.(3)Probiotic fermented calf milk replacer does much good to calves:boosting the calves to absorb carbohydrates and protein metabolism;reducing the content of lipids in serum;adding the content of serum alkaline phosphate;promoting the development of calf bones;lowering serum cortisol;improving the content of serum lysozyme,NO,Ig G and inflammatory factors IL-1,IL-2,IL-4 and TNF-?;relieving stress;enhancing the immunity of cattle,and reducing mortality rate of cattle.(4)Probiotic calf milk replacer significantly increases the concentrations of acetic acid,propionic acid,butyric acid and valeric acid in the calf intestine and the contents of arachidene metabolites,bile acid metabolites,sterol metabolites,amino acid metabolites and vitamin metabolites in blood of calves.All of them contribute to the enhancement of the immunity,the growth of bones,the balance of the intestinal microbiota.(5)Probiotic fermented calf milk replacer significantly improves the richness,Chao1,ACE,Shannon and Simpson indexes of calf intestinal microbiota.Abundances of Lacticaseibacillus,Bifidobacterium animalis,Akkermansia muciniphila,Desulfovibrio piger,Enterococcus faecalis,Dorea and other strains in the intestinal microbiota of calves are increased,and the reproduction of harmful bacteria such as Blautia and Treponema is inhibited in the probiotic fermented calf milk replacer.Moreover,the metabolic capacity of carbohydrate,fat and amino acid of intestinal microbiota of calves are enhanced,and the number of antibiotic resistance genes in the calf intestinal microbiota is reduced in the probiotic fermented calf milk replacer.In conclusion,through enzymatic hydrolysis and probiotic fermentation process,a new type of calf milk replacer has been developed.Compared with commercial milk replacer,it has improved the acidity,solubility and brewing stability of milk replacer,and increases the content of beneficial live bacteria,amino acids such as leucine and tryptophan,riboflavin and vitamin such as pantoic acid in the milk replacer.The feeding test found that compared with feeding commercial milk replacer,the probiotic fermented milk replacer increased calf body weight,body height,body oblique length,serum alkaline phosphatase,serum Ig G and other growth performance,and reduced calf diarrhea rate and death rate.Through the determination of calf fecal metabolism,plasma metabolism and fecal metagenomics,the effect of probiotic fermented milk replacer on the physiological state of calves was analyzed.Probiotics fermented milk replacer powder could increase the abundance and diversity of calf intestinal microbiota,increase the content of beneficial bacteria such as Lactobacillus reuteri and Lactobacillus plantarum in the intestine,and increase contents of short-chain fatty acids and carbohydrate active enzyme in intestinal.At the same time,it improves the beneficial metabolites of arachidonic acids,bile acids,sterols,amino acids,vitamins in calf plasma,thereby regulating the balance of intestinal flora and improving the immunity of calves.This study provides a new idea for the development of probiotic fermented milk replacer powder,and also provides reference data for the study of the physiological state of lactating calves.