摘要
[Objective]This experiment was conducted to investigate the effects of heat stress on microbial numbers in rumen fluid of dairy cows during different lactating periods by real-time PCR.[Methods]A 2 ×3 crossover design was used and eighteen healthy Chinese Holstein cows were selected.The cows were allocated into three periods based on their parity,average days in milk,and milk yield：early lactation（postpartum 15 to 100 days）,mid-lactation（postpartum 112 to 175 days）and late lactation（postpartum 200 to 230 days）,and six cows in each period.A self-control trial between heat stress period and non-heat stress period was used based on temperature and humidity index（THI）measurement on site.[Results]The results showed as follows：compared with non-heat stress period,heat stress significantly increased the microbial numbers in early lactation,the Ruminococcus flavefaciens number in different lactation and Bacteroides succinogenes number in early and mid-lactation（P 〈0.01）.The total bacteria and Ruminococcus albus numbers in mid-and late lactation and Bacteroides succinogenes number in late lactation were decreased significantly by heat stress（P 〈0.01）.There were strong correlation between THI and the numbers of total bacteria（P 〈0.01）,anaerobic fungi（P 〈0.05）,Ruminococcus albus（P 〈0.01）and Ruminococcus flavefaciens（P 〈0.05）in rumen fluid of dairy cows in early lactation,but the correlation between THI and these indexes in mid-and late lactation were poor.[Conclusion]It is indicated that the rumen microbial numbers in early lactation are more sensitive to heat stress.
[Objective]This experiment was conducted to investigate the effects of heat stress on microbial numbers in rumen fluid of dairy cows during different lactating periods by real-time PCR.[Methods]A 2 ×3 crossover design was used and eighteen healthy Chinese Holstein cows were selected.The cows were allocated into three periods based on their parity,average days in milk,and milk yield：early lactation（postpartum 15 to 100 days）,mid-lactation（postpartum 112 to 175 days）and late lactation（postpartum 200 to 230 days）,and six cows in each period.A self-control trial between heat stress period and non-heat stress period was used based on temperature and humidity index（THI）measurement on site.[Results]The results showed as follows：compared with non-heat stress period,heat stress significantly increased the microbial numbers in early lactation,the Ruminococcus flavefaciens number in different lactation and Bacteroides succinogenes number in early and mid-lactation（P 〈0.01）.The total bacteria and Ruminococcus albus numbers in mid-and late lactation and Bacteroides succinogenes number in late lactation were decreased significantly by heat stress（P 〈0.01）.There were strong correlation between THI and the numbers of total bacteria（P 〈0.01）,anaerobic fungi（P 〈0.05）,Ruminococcus albus（P 〈0.01）and Ruminococcus flavefaciens（P 〈0.05）in rumen fluid of dairy cows in early lactation,but the correlation between THI and these indexes in mid-and late lactation were poor.[Conclusion]It is indicated that the rumen microbial numbers in early lactation are more sensitive to heat stress.
基金
funded by Nonprofit sector (agriculture) research projects (200903003)
