Effects Of Feeding Different Levels Of High-Moisture Corn On Rumen Fermentation,Production Performance And Rumen Microbial Diversity In Dairy Cows

Amidst the COVID-19 pandemic,the China-US trade tensions,and the Russia-Ukraine conflict,the supply of feed ingredients such as main energy sources,protein,and forage for livestock has become tight,especially with the continuous rise in the price of feed ingredients like corn and soybean meal.This experiment uses High-moisture corn as raw material to analyze the effects of feeding different ratios of High-moisture corn instead of conventional corn on rumen fermentation,blood indicators,production performance,and rumen microbial diversity of dairy cows under the same nutritional conditions.The aim is to provide theoretical basis and data support for scientific utilization of High-moisture corn,reducing breeding costs and improving the economic benefits of the pasture.(1)Effects of different ratios of conventional maize and High-moisture corn on rumen fermentation parameters in vitro of dairy cowsUsing a single-factor experimental design,three Holstein cows with rumen fistulas were selected as rumen fluid donors.Conventional corn was used as the control group(100:0).Conventional corn and High-moisture corn were combined in different proportions(70:30,60:40,50:50,40:60,30:70,0:100)for in vitro fermentation tests.The 48-hour in vitro gas production,VFA,p H,NH3-N,and nutrient degradation rate of each combination were measured to calculate the comprehensive combination effect value and select the optimal combination range.The experimental results showed that through the comparative analysis of the results of various fermentation parameters and combination effects,the combination effect of 50:50 of conventional corn and High-moisture corn was the best.(2)Effects of feeding different levels of High-moisture corn on rumen fermentation of dairy cowsSelect 36 Holstein cows with similar average parity,days in milk,milk production,and body condition.Use a single-factor randomized experimental design to divide the experimental cows into three groups,with 12 cows in each group.The control group(CON group)is fed the original TMR diet of the farm,while experimental group 1(T1 group)is fed a TMR diet containing 50% High-moisture corn and 50% conventional corn,and experimental group 2(T2group)is fed a TMR diet containing 100% High-moisture corn.The nutritional and energy levels of the diets are consistent among the groups.The pre-experimental feeding period is 7 days,and the formal experimental period is 60 days.At day 0,30,and 60 of the formal experimental period,3 cows from each group were selected to collect rumen fluid and measure fermentation indicators.The experimental results showed that at day 30 of the formal period,the p H value,NH3-N concentration,and acetate/propionate ratio of the CON group were significantly higher than those of the T2 group(P<0.05);the propionate and TVFA concentrations of the T2 group were significantly higher than those of the CON group(P<0.05);the butyrate concentration of the T2 group was extremely significantly higher than those of the CON group and T1 group(P<0.01),but there was no significant difference between the CON group and T1 group(P>0.05).At day 60 of the formal period,the p H value of the CON group and T1 group were extremely significantly higher than that of the T2 group(P<0.01);the NH3-N concentration of the T2 group was significantly lower than that of the CON group(P<0.05);the propionate and butyrate concentrations of the T2 group were extremely significantly higher than those of the CON group and T1 group(P<0.01);the acetate/propionate ratio of the CON group and T1 group were extremely significantly higher than that of the T2 group(P<0.01);the TVFA concentration of the T2 group was significantly higher than those of the CON group and T1 group(P<0.05).(3)Effects of feeding different levels of High-moisture corn on blood indexes of dairyAt day 0,30,and 60 of the formal experimental period,3 cows from each group were selected to collect tail vein blood and measure their blood antioxidant and immune indicators.The results of blood antioxidant indicators showed that at day 30 of the formal period,the CAT content of the CON group and T1 group were significantly higher than that of the T2 group(P<0.05);the T-AOC content of the CON group was significantly higher than that of the T2group(P<0.05).At day 60 of the formal period,the MDA content of the T2 group was significantly higher than that of the CON group(P<0.05);the CAT content of the CON group was significantly higher than that of the T2 group(P<0.05);however,there was no significant difference in each indicator between the CON group and T1 group(P>0.05).The results of blood immune indicators showed that at day 30 of the formal period,the Ig A and Ig M content of the CON group were significantly higher than those of the T2 group(P<0.05);the IL-6 and TNF-α content of the T2 group were significantly higher than those of the CON group(P<0.05).At day 60 of the formal period,compared with the CON group,the Ig A,Ig M,and Ig G content of the T1 group and T2 group were all lower than those of the CON group;the IL-2,IL-6,and IL-1β content of the T1 group and T2 group were higher than those of the CON group,but the differences were not significant(P>0.05);the TNF-α content of the T2 group was significantly higher than that of the CON group(P<0.05).(4)Effects of feeding different levels of High-moisture corn on performance of dairy cowsAt day 0,30,and 60 of the formal experimental period,the average dry matter intake and milk production were recorded once,and 12 cows from each group were selected for milk sample collection and milk indicator measurement.The economic benefits were also calculated.The results showed that compared with the CON group during the formal period of 0-60 days: 1)the dry matter intake of cows in the T1 group and T2 group decreased by 1.5% and 2.5%,respectively.2)the milk production of cows in the T1 group and T2 group increased by 2.4% and3.5%,respectively.3)the milk fat content and milk urea nitrogen of cows in the T1 group and T2 group showed a decreasing trend,while the milk protein content,milk lactose content,and somatic cell count showed an increasing trend.4)The daily feed cost per cow in the T1 group and T2 group decreased by 1.40 and 1.41 yuan,respectively,but there was no significant difference.(5)Effects of feeding different levels of High-moisture corn on the diversity of rumen microflora in dairy cowsAt day 0,30,and 60 of the formal experimental period,3 cows from each group were selected to collect rumen fluid and extract DNA for 16 S r RNA high-throughput amplification and sequencing to analyze the alpha diversity and structural composition of the rumen microbiota.The experimental results showed that out of 27 samples,200,742,2 effective tags sequences were obtained for subsequent analysis.At day 60 of the formal period,the alpha sample dilution curve tended to flatten,and the chao1 index of the TT2 group was extremely significantly higher than those of the TCON group and TT1 group(P<0.01);the shannon index and simpson index of the TT2 group were significantly higher than those of the TCON group(P<0.05).At the phylum level,the dominant species were Bacteroidetes,Firmicutes,and Proteobacteria.At day 60 of the formal period,the relative abundance of Bacteroidetes in the TCON group was extremely significantly higher than that in the TT2 group(P<0.01);the relative abundance of Firmicutes in the TT2 group was extremely significantly higher than those in the TCON group and TT1 group(P<0.01);the relative abundance of Proteobacteria in the TT1 group was significantly higher than those in the TCON group and TT2 group(P<0.05).At the genus level,the dominant species were Prevotella,Succinivibrionaceae_UCG-001,Succinivibrionaceae_UCG-002,and Muribaculaceae.At day 60 of the formal period,the relative abundance of Prevotella in the TCON group was extremely significantly higher than those in the TT1 group and TT2 group,and the differences among the groups were extremely significant(P<0.01);the relative abundance of Succinivibrionaceae_UCG-001 in the TT1 group was extremely significantly higher than those in the TCON group and TT2 group,and the differences among the groups were extremely significant(P<0.01);the relative abundance of Succinivibrionaceae_UCG-002 in the TCON group and TT1 group was extremely significantly higher than that in the TT2 group(P<0.01).The experiment has shown that feeding the group containing 50% High-moisture corn and50% conventional corn is beneficial for promoting the utilization of NH3-N by rumen microorganisms and rumen fermentation in dairy cows,which can improve milk composition,increase milk production,and increase farm economic benefits;At the same time,there was no significant impact on the antioxidant and immune performance of dairy cows,but excessive feeding of wet stored corn can also affect the diversity and structural composition of rumen microbiota in dairy cows.