| The growth and health of dairy cows are affected by the environment,especially the changes in the environment in different seasons.At the same time,environmental changes in different seasons also affect the digestion and metabolism of dairy cows.This experiment studied the effects of different seasons on the digestion and metabolism,blood biochemistry and rumen microbial diversity of dairy cows.It provides a theoretical basis for adjusting the diet composition of dairy cows in Henan area and alleviating the cold and heat stress of dairy cows under production conditions.In the experiment,20 Holstein cows with a body weight（635 ± 39 kg）,lactation period and similar milk production were selected.According to THI,they were divided into four groups,namely spring group,summer group,autumn group and winter group.The pre-test period was 14 days and the test period was 5 days.The test results were as follows:（1）The temperature and humidity index changes significantly in different seasons.The range of THI in spring was 44.15-59.48,the range of THI in summer was 46.30-78.15,the range of THI in autumn was 62.59-64.48,and the range of THI in winter was 38.85-44.78.There were significant differences in temperature and humidity index between different seasons（P<0.05）,which was the biggest in summer and the smallest in winter.（2）Summer has a greater impact on the apparent digestibility of nutrients in dairy cows.The apparent digestibility of DM was the lowest in the summer group,and significantly lower than that in the autumn group（P<0.05）;the apparent digestibility of CP was the lowest in the spring group,and significantly lower than the autumn group（P<0.05）,but there was no significant difference from the summer group.The apparent digestibility of EE was the lowest in the spring group,and was significantly lower than that of the other groups（P<0.05）,and there was no significant difference between the other groups;the apparent digestibility of NDF in the spring and summer groups was significantly lower than that in the autumn and winter groups（P<0.05）;the apparent digestibility of ADF was the lowest in the summer group,but there was no significant difference among the groups;the apparent digestibility of Ca,P and DMI in the summer group were significantly lower than those of the other groups（P<0.05）.（3）Summer and winter have a greater impact on the energy digestion and metabolism of dairy cows.The total energy,fecal energy,digestive energy and metabolizable energy all show a trend of low in summer and winter,and high in spring and autumn.The summer group has the lowest GE,DE,and ME,and was significantly lower than the spring and autumn group（P<0.05）;the winter group has the lowest FE and DE metabolism rate,and was significantly lower than the spring and autumn group（P<0.05）,but there was no significant difference from the summer group;UE in the spring group was significantly lower than that in winter group（P<0.05）,and there was no significant difference among other groups;CH4E was the lowest in the summer group,and significantly lower than that in the autumn and winter groups（P<0.05）;GE digestibility and GE metabolic rate were no significant difference among the groups.（4）Summer and winter have a greater impact on nitrogen metabolism.Nitrogen intake,fecal nitrogen,digested nitrogen,deposited nitrogen,nitrogen use efficiency and nitrogen biological value all showed a trend of low in summer and winter,and high in spring and autumn.The summer group has the lowest NI,MN,DN and RN,and was significantly lower than the spring and autumn group（P<0.05）;the winter group has the lowest FN,and was significantly lower than the other season groups（P<0.05）,but there was no significant difference between the summer group;there was no significant difference in the digestibility of UN and N among the groups;the utilization of N and the biological value of N in the summer group were the lowest,and was significantly lower than that the spring group（P<0.05）.（5）Summer has a greater impact on the nitrogen and phosphorus emissions of dairy cows.Manure DM emissions,manure N emissions,urine N emissions,total N emissions,and total P emissions were the lowest in the summer group,and were significantly lower than other groups（P<0.05）;summer group manure P emissions were the lowest and was significantly lower than the spring and winter group（P<0.05）;the autumn group had the highest urine discharge and urine P discharge,and was significantly higher than the other groups（P<0.05）.（6）Different seasons have an important influence on the metabolism of carbohydrates,lipids,and proteins in the blood of dairy cows.There were no significant differences in serum TP and TG concentrations among the groups;the winter group had the lowest BUN concentration,and was significantly lower than the spring group and summer group（P<0.05）,and there was no significant difference between the other groups;the winter group had the highest GLU concentration,and significantly higher than the autumn group（P<0.05）,and no significant difference among other groups;the summer group had the highest NEFA concentration,which was significantly higher than the spring and autumn groups（P<0.05）,and there was no significant difference between the summer group and the winter group.（7）Different seasons have an important influence on the serum endocrine indexes of dairy cows.The T3 concentration was the lowest in the summer group of the serum,and was significantly lower than the other groups（P<0.05）,the T3 concentration in the spring and winter group was significantly lower than the autumn group（P<0.05）,and there was no significant difference between the spring and winter groups;the T4 concentration was the lowest in the summer group and significantly lower than the autumn and winter groups（P<0.05）,the T4 concentration in the spring and winter groups was significantly lower than the autumn group（P<0.05）;the summer group had the lowest Cor content and was significantly lower than the other groups（P<0.05）,the Cor content in the spring group was significantly lower than that in the autumn and winter groups（P<0.05）,and there was no significant difference between the autumn and winter groups.（8）Summer has an important influence on the rumen fermentation parameters of dairy cows.The pH of the summer group was the highest and was significantly higher than that of the winter group（P<0.05）;the summer group had the highest NH3-N concentration and was significantly higher than other groups（P<0.05）;the summer group had the lowest concentrations of acetic,propionic,and butyric,and significantly lower than the other groups（P<0.05）,there was no significant difference between the other groups.（9）At the phylum level,the phylum Bacteroides,Firmicutes,and Proteobacteria were the dominant phyla of dairy cows.Rumen microorganisms accounted for 90.56%,91.75%,92.24%and 92.73%in groups C,X,Q and D.Among them,the Bacteroides and Firmicutes were not significantly different between the different groups;the abundance of Proteobacteria was the lowest in the group D,and was significantly lower than the group Q;the abundance of Patescibacteria was the highest in the group C,and was significantly higher than the other groups（P<0.05）;the abundance of Fibrobacteres phylum was the lowest in the group X,and was significantly lower than that the other group（P<0.05）.Rumen microbes were at the genus level.Prevotella1 dominates in each group.Succiniclasticum was the highest in the group D and was significantly higher than that the group C（P<0.05）;RuminococcaceaeNK4A214group was the highest in the group X and was significantly higher than the group Q（P<0.05）;PrevotellaceaeUCG-001 was the lowest in the group D,and was significantly lower than the group C and Q（P<0.05）;RuminococcaceaeUCG-014 was the lowest in the group D,and was significantly lower than the group C（P<0.05）.In summary:The digestibility of nutrients and nitrogen and phosphorus emissions of dairy cows in summer were reduced.Energy metabolism and nitrogen metabolism were lower in summer and winter than in spring and autumn.Environmental changes in summer and winter affect the metabolism of carbohydrates,lipids,and proteins in dairy cows,which in turn affects the rumen microflora,leading to changes in rumen fermentation characteristics. |
