Relationship Of In Vitro Fermentation Parameters Of Total Mixed Rations With Production Performance Of Dairy Cows

This study explored the relationship between the in vitro fermentation parameters of Total Mixed Rations and the production performance of dairy cows,and to establish a predictive model for the production performance of dairy cows.In vitro fermentation experiments were conducted to collect the total mixed rations of(150±5)days of lactating cows in the average lactation period.The experiments evaluated the nutritional value of diets by using in vitro fermentation technology and CNCPS component analysis.The relationship between in vitro fermentation parameters and nutritional characteristics and the production performance of dairy cows were explored.It provided a theoretical basis for quickly and accurately estimating the rationality of the dairy cow formula.Experiment 1:In vitro fermentation technology to evaluate the gas production characteristics and fermentation characteristics of different total mixed rations.This experiment measured the gas production characteristics and fermentation characteristics of 12 kinds of total mixed rations in in vitro fermentations.The results showed that the effective gas production rate and potential gas production of Diet 4 was the largest.Diet 12 had the highest content of acetic acid,while diet 2 also had a high content of acetic acid;Diet 8 had the highest content of propionic acid,while diet 6 also had a high content of propionic acid;diet 3 had the highest content of microbial protein.Experiment 2:Relationship between in vitro fermentation parameters and nutritional valueThis experiment determined the CNCPS components of 12 kinds of total mixed rations,and established correlations between the in vitro fermentation parameters and the protein components and carbohydrate components of CNCPS.The results showed that:There was a certain correlation between the in vitro fermentation parameters and CNCPS components.Experiment 3:Relationship between in vitro fermentation parameters and production performance of dairy cowsThe production performance of dairy cows fed with different total mixed rations was measured in this experiment.The relationship between the in vitro fermentation parameters and dairy productivity was explored.A model was selected by screening predictors to predict the production performance of dairy cows.The results showed that Dairy cows with diet 6 had the highest milk yield;Dairy cows with diet 2 had the highest milk fat percentage;Dairy cows with diet 3 had the highest dairy protein.The correlation analysis showed that there was a significant positive correlation between milk production and propionic acid content(r=0.57,P<0.05),and there was a significant positive correlation between milk fat percentage and acetate acid content(r=0.55,P<0.05).There was a significant positive correlation between milk protein and microbial protein(r=0.91,P<0.05).By regression analysis,the propionic acid was selected as the effective factor in the milk yield prediction model(R~2=0.73,P<0.01);The acetic acid content was selected as the effective factor in the milk fat rate prediction model(R~2=0.91,P<0.01);Microbial protein was selected as the effective factor in the milk protein prediction model(R~2=0.78,P<0.01).The relative error between the predicted value and the actual value of the production performance of the cow was within the allowable range,and the accuracy of the predicted value is higher.The predicted value of the production performance of the dairy cows and the actual value were within the allowable range.Thus,the predicted value was feasible.In summary,this experiment found that there were certain correlations between the in vitro fermentation parameters of different total mixed rations and CNCPS components and production performance of dairy cows.Propionic acid had a high correlation with milk production.Acetic acid had a high correlation with milk fat percentage.Microbial protein had a high correlation with milk protein,and thus used them as predictors to establish a predictive model of production performance.The model had been verified to have a high accuracy and it was feasible to use in in vitro simulated rumen fermentation technology to evaluate the rationality of the dairy cow formula.