Analysis Of Factors Affecting Protein Fraction And Utilization Of Alfalfa Hay

China is a vast country with a variable climate,which leads to different mowing stubble,fertility period and varieties affecting the crude protein content of alfalfa hay,so whether these factors have any effect on the quality of alfalfa hay crude protein and consequently on its conversion and utilization efficiency.In this paper,firstly,Bara310SC was selected as the test material and harvested at the first flowering stage of three mowing crops（June 8,July22 and August 23）in 2021 using a single-factor experimental design;secondly,Bara310SC was selected as the test material and harvested at the nutrient growth stage（40 cm height）,bud stage,first flowering stage and full flowering stage of the third crop,respectively.Finally,three alfalfa varieties,including Bara310SC,WL319HQ and Queen,were selected to be harvested at the first flowering stage of the third crop.Based on the determination of conventional nutrient contents of each treatment sample,the CNCPS protein fraction and amino acid composition of each treatment sample were analyzed,and the effects of treatment factors on the crude protein quality of alfalfa hay were compared and analyzed;the crude protein,CNCPS protein fraction and amino acid and their digestibility of alfalfa hay were compared and analyzed by artificial simulated in vitro digestion test.The experimental results showed that:（1）The effect of mowing stubble on crude protein content of alfalfa was significant,with the first stubble having the highest crude protein content,which was significantly different from the other two stubbles（P<0.05）.Mowing stubble had a significant effect on the protein fraction and amino acid composition of CNCPS.The second crop had the highest peritubular protein（PB₂+PB₃）content and the lowest bound protein（PC）content,indicating that the CNCPS protein fraction of the second crop was relatively better;the crude protein digestibility of the second crop was the highest,but it was not significantly different from the other two crops（P>0.05）.The digestibility of amino acids in the first crop was also the highest,but only the digestibility of essential amino acids was significantly different from the other two crops（P<0.05）.（2）The growth period had a significant effect on the crude protein content of alfalfa,which tended to decrease as the growth period was delayed.Similarly,the fertility period had a significant effect on the CNCPS protein fraction of alfalfa hay,with the highest content of peritubular protein（PB₂+PB₃）in the nutritional growth period.The content and digestibility of total,essential and non-essential amino acids tended to decrease with the delay of fertility,but the highest amino acid ratio coefficients were found in the present bud stage,which had the best balance of amino acid composition.（3）Not only the crude protein content but also the quality differed among different alfalfa varieties.For this thesis test,WL319HQ had the highest crude protein content,which was significantly different from the other two varieties（P<0.05）;there were also differences in CNCPS protein fractions,among which WL319HQ had the highest peritubular protein（PB₂+PB₃）content and a lower proportion of binding protein（PC）,indicating that its CNCPS protein fraction was relatively better.There were differences in amino acid composition among different breeds,among which Queen had the highest content of total,essential and non-essential amino acids;however,Bara310SC had the highest amino acid digestibility.WL319HQ had the highest amino acid ratio coefficient score and its amino acid composition was the best balanced.（4）When evaluating the quality of alfalfa hay,in addition to the accurate determination of its crude protein content,further in-depth evaluation of crude protein quality using the CNCPS protein fraction analysis method or the amino acid nutritional value evaluation method can more accurately assess the nutritional value of alfalfa hay.The CNCPS protein fraction evaluation method can further complement the evaluation of the effect of fertility on the crude protein quality of alfalfa hay,and the use of amino acids to evaluate the effect of mowing stubble and fertility on the crude protein quality of alfalfa hay is also highly feasible.