本试验旨在探索奶牛配种前1周内乳中脂肪蛋白质比(milk fat to protein ratio,FPR)和尿素氮(milk urea nitrogen,MUN)含量对繁殖性能的影响。选择产犊时间接近的第1胎荷斯坦牛1 460头,于配种前1周采集乳样,测定日产奶量、乳成分和MUN含...本试验旨在探索奶牛配种前1周内乳中脂肪蛋白质比(milk fat to protein ratio,FPR)和尿素氮(milk urea nitrogen,MUN)含量对繁殖性能的影响。选择产犊时间接近的第1胎荷斯坦牛1 460头,于配种前1周采集乳样,测定日产奶量、乳成分和MUN含量,并测定试验牛只第1次发情配种泌乳天数、配种情期数、妊娠率、妊娠泌乳天数等繁殖性能指标,用多因素方差分析、Logistic回归分析以及相关和回归分析方法分析FPR和M UN含量与繁殖性能的关系。结果表明:试验牛只配种前1周内FPR和MUN含量分别为(1.35±0.28)和(10.61±2.68)mg/dL。FPR对第1次发情配种泌乳天数的影响达到极显著水平(P<0.01),对其他繁殖性能指标无显著影响(P>0.05);MUN含量对第1次发情配种泌乳天数的影响达到极显著水平(P<0.01),对配种情期数、妊娠率的影响达到显著水平(P<0.05),而对妊娠泌乳天数无显著影响(P>0.05)。FPR与第1次发情配种泌乳天数和妊娠泌乳天数呈极显著负相关(P<0.01),M UN含量与第1次发情配种泌乳天数及妊娠率呈极显著正相关(P<0.01)。MUN含量对第1次配种以及在前2个发情周期内配种是否妊娠的影响达到显著水平(P<0.05)。配种前1周内MUN含量对头胎奶牛配种情期数和第1次发情配种泌乳天数有显著影响,因此,对MUN含量的测定和分析可以作为奶牛繁殖性能的预测和繁殖管理的手段之一。展开更多
The first"modern"type of vehicular bridge was built in Hong Kong China in the 1920s.The need for an efficient transportation system to cope with population growth and enable economic development has demanded...The first"modern"type of vehicular bridge was built in Hong Kong China in the 1920s.The need for an efficient transportation system to cope with population growth and enable economic development has demanded the construction of more and more bridges since the middle of the 20th century.By 2007,Hong Kong had a total of about 1300 vehicular bridges.Four of these bridges,including the Tsing Ma Bridge,Kap Shui Mun Bridge,Ting Kau Bridge,and the cable-stayed bridge on the Hong Kong-Shenzhen Western Corridor,are considered to be major bridges supported by cables.Currently,the Stonecutters Bridge on Route No.8 is under construction and is expected to be completed in late 2009.At the same time,the Hong Kong-Zhuhai-Macao Bridge will be in its detailed design stage soon.While efforts have been made by bridge builders to construct these giant structures,the upkeeping of these valuable assets at a high standard and ensuring their continuous functioning and performance during their intended lifespans will be another important task for bridge engineers.Wind and structural health monitoring system(WASHMS)will play a key role in this respect.展开更多
文摘本试验旨在探索奶牛配种前1周内乳中脂肪蛋白质比(milk fat to protein ratio,FPR)和尿素氮(milk urea nitrogen,MUN)含量对繁殖性能的影响。选择产犊时间接近的第1胎荷斯坦牛1 460头,于配种前1周采集乳样,测定日产奶量、乳成分和MUN含量,并测定试验牛只第1次发情配种泌乳天数、配种情期数、妊娠率、妊娠泌乳天数等繁殖性能指标,用多因素方差分析、Logistic回归分析以及相关和回归分析方法分析FPR和M UN含量与繁殖性能的关系。结果表明:试验牛只配种前1周内FPR和MUN含量分别为(1.35±0.28)和(10.61±2.68)mg/dL。FPR对第1次发情配种泌乳天数的影响达到极显著水平(P<0.01),对其他繁殖性能指标无显著影响(P>0.05);MUN含量对第1次发情配种泌乳天数的影响达到极显著水平(P<0.01),对配种情期数、妊娠率的影响达到显著水平(P<0.05),而对妊娠泌乳天数无显著影响(P>0.05)。FPR与第1次发情配种泌乳天数和妊娠泌乳天数呈极显著负相关(P<0.01),M UN含量与第1次发情配种泌乳天数及妊娠率呈极显著正相关(P<0.01)。MUN含量对第1次配种以及在前2个发情周期内配种是否妊娠的影响达到显著水平(P<0.05)。配种前1周内MUN含量对头胎奶牛配种情期数和第1次发情配种泌乳天数有显著影响,因此,对MUN含量的测定和分析可以作为奶牛繁殖性能的预测和繁殖管理的手段之一。
文摘The first"modern"type of vehicular bridge was built in Hong Kong China in the 1920s.The need for an efficient transportation system to cope with population growth and enable economic development has demanded the construction of more and more bridges since the middle of the 20th century.By 2007,Hong Kong had a total of about 1300 vehicular bridges.Four of these bridges,including the Tsing Ma Bridge,Kap Shui Mun Bridge,Ting Kau Bridge,and the cable-stayed bridge on the Hong Kong-Shenzhen Western Corridor,are considered to be major bridges supported by cables.Currently,the Stonecutters Bridge on Route No.8 is under construction and is expected to be completed in late 2009.At the same time,the Hong Kong-Zhuhai-Macao Bridge will be in its detailed design stage soon.While efforts have been made by bridge builders to construct these giant structures,the upkeeping of these valuable assets at a high standard and ensuring their continuous functioning and performance during their intended lifespans will be another important task for bridge engineers.Wind and structural health monitoring system(WASHMS)will play a key role in this respect.
