The aim of this retrospective study was to investigate the causes and the effects of stillbirth on the number of days open and cow herd survival in subsequent lactation of Holstein Friesian cows. A total of 1371 calvi...The aim of this retrospective study was to investigate the causes and the effects of stillbirth on the number of days open and cow herd survival in subsequent lactation of Holstein Friesian cows. A total of 1371 calvings from research dairy farm were used. Stillbirth in calves was defined as the death of a fetus before or during calving at full term (≥270 days of gestation) or within 24 hours after calving. During the period from January 2006 to December 2017 a percent of 95.04% of the calvings were with live calves, and 4.96% of the calvings were stillbirths. The major causes of stillbirth identified were: calving difficulty, parity of the cows, and sex of the calves at calving. A five point scale was used to assess calving difficulties, and numbers 1, 2 and 3 were considered unassisted calvings and number 4 and 5 as assisted. The twin calvings were not taken into account. Days open were measured as days from first calving to conception, and cow herd survival from first calving to culling or death. Trend test and multivariate data analysis were used. The findings revealed that primiparous cows were at higher risk of having stillbirths compared with multiparous cows. Cows that were at calving male calves were at higher risk of having stillbirths compared with cows that had female calves at calving. Also, cows with assisted calving were at higher risk of having stillbirths compared with cows with unassisted calvings. Cows with stillbirths had a increase mean of days open with 32 days. Cow herd survival was better in the cows with live calves at calving compared with the cows that had stillbirth at calvings.展开更多
Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple trait restricted maximum likelihood procedures with an animal model.Data consisted of ...Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple trait restricted maximum likelihood procedures with an animal model.Data consisted of records of 2496 Chinese Holsteins first lactation cows collected from 1989 to 2000.The model included 21 herd effects,four calving season effects,nine age at first calving effects,6697 animal effects.(Co)variance components of milk yield,fat yield and age at first calving were estimated with the software package for variance component estimation(VCE) by an animal model. The heritabilities were 0.14,0.21,0.38 for milk yield,fat yield and age at first calving,respectively.The estimates of genetic correlation between milk yield and fat yield,age at first calving were 0.96,-0.29,respectively.The estimate of genetic correlation between fat yield and age at first calving was -0.28.展开更多
The results of 439 times of calving interval(CI) from 161 yak cows showed that the average CI is 459(se=131)d. The CI with 3 to 6 calving numbers is 25～48 d shorter than that of 1 to 2 and above 7 calving numbers. Al...The results of 439 times of calving interval(CI) from 161 yak cows showed that the average CI is 459(se=131)d. The CI with 3 to 6 calving numbers is 25～48 d shorter than that of 1 to 2 and above 7 calving numbers. Although slaughtering a great number of calves during the late September and early October do bring about relatively higher calving rate that is mos yak cowst can give 3,4,5 and 6calves during 4,5,6 and 7 years old respectively. This makes major calving months shift from April or May to June.展开更多
Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Fr...Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Friesian heifers;Study 1 comprised 134 consecutively born heifers from the same herd (AFC 764 ± 8 days) and Study 2 contained 445 heifers born on 17 farms (AFC 796 ± 6 days). Growth rates and fertility during rearing were monitored and animals were subsequently divided into four AFC groups for analysis: <23 months, 23 - 25 months, 26 - 30 months and >30 months. The actual AFC reflected both growth rate and heifer fertility, with later calving heifers already lighter by 6 months of age. The proportion conceiving to first service was highest (93% and 84% for Studies 1 and 2, respectively) for the youngest AFC group. Fertility in the first lactation was best in cows calving at 23 - 25 months and worst in the oldest AFC group. Milk production parameters in the first and second lactations were broadly similar between AFC groups but significantly more heifers with an AFC < 26 months calved for a third time. These younger calving animals therefore achieved more days in milk over 5 years, with >44% of their days alive spent in milk production compared with only 18% - 40% in cows calving at ≥26 months. Hence cows with an AFC < 26 months produced the most milk in their first 5 years of life. These results indicate that an AFC of 0.75 kg/d up to 15 months and good heifer fertility and resulted in the best subsequent performance.展开更多
This study was conducted to estimate variance components and genetic parameters for 305 days mature equivalent milk yields (MEM) and calving interval (CAI) of registered Xinjiang Brown cattle. The total records were 3...This study was conducted to estimate variance components and genetic parameters for 305 days mature equivalent milk yields (MEM) and calving interval (CAI) of registered Xinjiang Brown cattle. The total records were 3940 including 2579 for 305-day MEM and 1970 for CAI, which were collected from Xinjiang Urumqi Cattle Breeding farm in China with calving records from 1990 to 2008. Genetic parameters were obtained by multiple trait derivative-free restricted maximum likelihood (MTDFREML) using animal model. The model included year, season, parity and calving interval of calving for 305 days MEM, and year, season and parity of birth for CAI as fixed effects. Heritability for 305 days MEM was moderate (0.39) and in the same range of parameters estimated in management systems with medium production levels. Heritability of calving interval was small (0.02) as fertility traits for Xinjiang Brown cattle. Estimates of genetic and environmental correlations between 305 days MEM and CAI were 0.47 and 0.37, respectively. Estimates of genetic variation and heritability indicated that selection would result in genetic improvement of production traits. Estimates of both heritability and genetic variation for CAI were small, which indicates that genetic improvement would be difficult.展开更多
Good management of the pregnant heifer is crucial to ensure that she is well grown and healthy and calves down easily before joining the milking herd. This study collected primary data on all aspects of heifer managem...Good management of the pregnant heifer is crucial to ensure that she is well grown and healthy and calves down easily before joining the milking herd. This study collected primary data on all aspects of heifer management on 101 UK farms during heifer pregnancy from conception to calving including farm factors and associated costs of system inputs. A cost analysis workbook was developed to calculate the cost of rearing per heifer for each of the study farms. Associations between cost of rearing and farms factors were determined using linear regression and analysis of variance. Heifers had a mean age of conception of 509 d (range 365 - 700 d) and an age at first calving of 784 d (range 639 - 973 d). The mean total cost of rearing during pregnancy was ￡450.36 (range ￡153.11 to ￡784.00) with a mean daily cost of ￡1.64 (range ￡0.56 to ￡2.86). The inputs contributing the most to cost were feed (32.7%), labour (23.8%) and slurry disposal (11.2%). Total purchased and homegrown feed and grazing contributed between 25.5% and 65.4% of total costs with a mean contribution of 43.6%. The cost of rearing was lowest in spring calving herds and highest in all year round calving herds with intermediate values in autumn and multi block calving herds. The main variables influencing the cost were the number of days spent at grass, age at first calving, calving pattern, breed, herd size and region. Each extra day in age at first calving increased the mean cost of rearing during pregnancy by ￡0.33/d whereas every extra day at grass reduced the cost by ￡1.75/d.展开更多
The two ice caps of Svartisen, at the latitude of the Arctic Circle in Norway, supply 60 glaciers, ranging in size from 〉50 to 〈1 km^2. Until the last two decades of the 19th century, the glaciers remained close to ...The two ice caps of Svartisen, at the latitude of the Arctic Circle in Norway, supply 60 glaciers, ranging in size from 〉50 to 〈1 km^2. Until the last two decades of the 19th century, the glaciers remained close to their maximum recent （Little Ice Age） size. In response to the prevailing 20th century climate, they have become smaller, but the changes have varied between glaciers. Climatic factors have not been the sole control of the variations. The response times of small, steep glaciers are shorter than those of the longer, more gently sloping outlet glaciers. Topographic factors may moderate the response of individual glaciers to climate. The 20th century mass balance of several of the larger glaciers was dominated by calving into marginal lakes. The mass balance of Engabreen, the largest outlet of the western ice cap, has been measured every year since 1970 and the cumulative balance to 2008 was a gain of 22.7 m water equivalent. Although the pattern of annual variations probably applies to the other glaciers of Svartisen, it does not indicate their actual changes （gain or loss）. Thus, the Engabreen record is of little utility in water resource planning for the whole area.展开更多
A total of 5852 records concerning daily milk yield, content of protein and fat, and somatic cell count was recorded in two farms (organic and conventional). Somatic cell count was log10- transformed before analysis b...A total of 5852 records concerning daily milk yield, content of protein and fat, and somatic cell count was recorded in two farms (organic and conventional). Somatic cell count was log10- transformed before analysis because was not normally distributed. The mixed model methodology was used according to a repeated-measures scheme, as the restricted maximum likelihood method to estimate lactation curves at different season of calving and at different calving order. Calving order affected milk yield only in the first three calving order with the lowest production levels in the first six months of the year for both farm;no effect could be observed on fat and protein contents. The organic farm shows the minor milk production (7.77 vs8.10 kg/day/head organic and traditional respectively), but good qualitative characteristics of milk, and minor content of Somatic Cell Count. The milk production is major, in traditional farm, in summer respect the winter (10.4 vs6.34 kgof milk/day/ head). In biological farm no difference between seasons were observed. Peak milk yield occurs, for both farms, at around the 6th - 7th wk of lactation.展开更多
The bovine embryos used for nonsurgical transfer should be morulae or blastocysts which are generally obtained from donor cow through superovulation and insemination. Due to the high cost of the embryos, the spread of...The bovine embryos used for nonsurgical transfer should be morulae or blastocysts which are generally obtained from donor cow through superovulation and insemination. Due to the high cost of the embryos, the spread of embryo transfer is influenced to certain extent. In recent years, in vitro fertilization (IVF)technique has been adopted abroad to expand the source of embryos. The methods employed normally were culturing the embryos in rabbit’s or sheep’s oviducts (in vivo culture) to overcome '8—16-cell block', the morula or blastocyst developed in vivo was recovered and then transferred to recipients. However, the research concerning in vitro culture of IVF ova to the morula-blastocvst stage was展开更多
Petermann Glacier is a marine-terminating outlet glacier that had a 70 km-long floating ice tongue prior to a ～ 270 km2 calving event that was observed from satellite sensors in August 2010,shortening the ice tongue ...Petermann Glacier is a marine-terminating outlet glacier that had a 70 km-long floating ice tongue prior to a ～ 270 km2 calving event that was observed from satellite sensors in August 2010,shortening the ice tongue by ～ 27 km.Further,in July 2012,another 10 km was lost through calving.In order to understand these events in perspective,here the authors perform a long-term data analysis of Petermann Glacier calving-front variability and ice velocity for each year in the 1990s-2000s,supplemented by available observations from the previous three decades.Five major （on the order of 100 krm2） calving events are identified,with ～ 153 km2 calved from 1959 to 1961,～ 168 km2 in 1991,～ 71 km2 in 2001,～ 270 km2 in 2010,and ～ 130 km2 in 2012-as well as ～ 31 k m2 calved in 2008.The increased frequency of major calving events in recent years has left the front terminus position retreated nearly 25 km beyond the range of observed in previous decades.In contrast,stable ice-dynamics are suggested from ice-velocity measurements made each year between 1993-2012,which are on average 1063 m yr-1,with limited interannual variability and no significant trend; moreover,there is no apparent relationship between ice-velocity variability and calving events.The degree to which the massive calving events in 2010 and 2012 represent natural episodic variability or a response to atmospheric and/or oceanic changes remains speculative; however,melt-induced weakening of the floating ice tongue in recent years is strongly suggested.展开更多
位于西南极的派恩岛冰川(Pine Island Glacier,PIG)是近年来崩解频繁且前缘变化明显的区域。基于Landsat系列卫星和海洋一号C卫星光学影像、ERS-1和RADARSAT卫星SAR影像及航空影像,利用前缘位置识别和开口盒方法,分析1947—2020年PIG的...位于西南极的派恩岛冰川(Pine Island Glacier,PIG)是近年来崩解频繁且前缘变化明显的区域。基于Landsat系列卫星和海洋一号C卫星光学影像、ERS-1和RADARSAT卫星SAR影像及航空影像,利用前缘位置识别和开口盒方法,分析1947—2020年PIG的前缘变化特征。PIG在近73年至少发生过17次规律性的大规模崩解事件,其崩解周期在1995—2013年间约为6年,2013年至今约为1~2年;由开口盒法计算得到的冰川前缘附近的流速在近73年间呈现上升趋势。结合PIG在1947—2020年间崩解事件的相关研究,总结出厄尔尼诺现象、冰架底部的绕极深层水暖化、底部融化率增加、底部裂隙的发育、冰水混合物的消退以及冰架与海脊间歇接触产生的背应力等是导致PIG发生崩解的可能驱动因子。展开更多
The dairy herd improvement data from Henan Province were analyzed statistically to establish screening criteria for relevant data, thereby laying a foundation for genetic evaluation of dairy cows. With the 2 152 451 t...The dairy herd improvement data from Henan Province were analyzed statistically to establish screening criteria for relevant data, thereby laying a foundation for genetic evaluation of dairy cows. With the 2 152 451 test-day records about 155 893 Chinese Holstein dairy cows collected by the Henan Dairy Herd Improvement Center from January 2008 to April 2016, the dynamics of test times during a complete lactation, test interval during a complete lactation, days in milk （DIM） of first test-day record, daughter descendant number and herd number of bull, age at first calving and pedigree integrity rate among different years and different herd sizes were analyzed by MEANS order of SAS 9.4. In addition, the data that were applicable to genetic evaluation were screened by SQL program. The results showed that during 2008-2015, the number of cow individuals participating in DHI in Henan Province increased from 7 379 to 93 706; the test-day milk yield increased from 19.91 to 24.05 kg; the somatic cell count reduced from 411.09×10^3 to 277.08×10^3 cells/ml; the percentage of cows with DIM ranging from 5-305 d reached 70.92%; the average test times increased from 3.20 to 6.31 times; the test interval decreased from 70.22 to 33.83 d; the dairy cows with age at first calving of 25 months were dominant, accounting for 12.57%; the bulls whose daughter descendant number was 20 or more and the daughters were distributed in 10 or more farms accounted for 6.05%; the one-generation pedigree integrity rate was 82.54%; the percentage of data that could be used for genetic evaluation was screened as 20.67%, which was lower than the results of other similar studies.展开更多
文摘The aim of this retrospective study was to investigate the causes and the effects of stillbirth on the number of days open and cow herd survival in subsequent lactation of Holstein Friesian cows. A total of 1371 calvings from research dairy farm were used. Stillbirth in calves was defined as the death of a fetus before or during calving at full term (≥270 days of gestation) or within 24 hours after calving. During the period from January 2006 to December 2017 a percent of 95.04% of the calvings were with live calves, and 4.96% of the calvings were stillbirths. The major causes of stillbirth identified were: calving difficulty, parity of the cows, and sex of the calves at calving. A five point scale was used to assess calving difficulties, and numbers 1, 2 and 3 were considered unassisted calvings and number 4 and 5 as assisted. The twin calvings were not taken into account. Days open were measured as days from first calving to conception, and cow herd survival from first calving to culling or death. Trend test and multivariate data analysis were used. The findings revealed that primiparous cows were at higher risk of having stillbirths compared with multiparous cows. Cows that were at calving male calves were at higher risk of having stillbirths compared with cows that had female calves at calving. Also, cows with assisted calving were at higher risk of having stillbirths compared with cows with unassisted calvings. Cows with stillbirths had a increase mean of days open with 32 days. Cow herd survival was better in the cows with live calves at calving compared with the cows that had stillbirth at calvings.
文摘Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple trait restricted maximum likelihood procedures with an animal model.Data consisted of records of 2496 Chinese Holsteins first lactation cows collected from 1989 to 2000.The model included 21 herd effects,four calving season effects,nine age at first calving effects,6697 animal effects.(Co)variance components of milk yield,fat yield and age at first calving were estimated with the software package for variance component estimation(VCE) by an animal model. The heritabilities were 0.14,0.21,0.38 for milk yield,fat yield and age at first calving,respectively.The estimates of genetic correlation between milk yield and fat yield,age at first calving were 0.96,-0.29,respectively.The estimate of genetic correlation between fat yield and age at first calving was -0.28.
文摘The results of 439 times of calving interval(CI) from 161 yak cows showed that the average CI is 459(se=131)d. The CI with 3 to 6 calving numbers is 25～48 d shorter than that of 1 to 2 and above 7 calving numbers. Although slaughtering a great number of calves during the late September and early October do bring about relatively higher calving rate that is mos yak cowst can give 3,4,5 and 6calves during 4,5,6 and 7 years old respectively. This makes major calving months shift from April or May to June.
文摘Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Friesian heifers;Study 1 comprised 134 consecutively born heifers from the same herd (AFC 764 ± 8 days) and Study 2 contained 445 heifers born on 17 farms (AFC 796 ± 6 days). Growth rates and fertility during rearing were monitored and animals were subsequently divided into four AFC groups for analysis: <23 months, 23 - 25 months, 26 - 30 months and >30 months. The actual AFC reflected both growth rate and heifer fertility, with later calving heifers already lighter by 6 months of age. The proportion conceiving to first service was highest (93% and 84% for Studies 1 and 2, respectively) for the youngest AFC group. Fertility in the first lactation was best in cows calving at 23 - 25 months and worst in the oldest AFC group. Milk production parameters in the first and second lactations were broadly similar between AFC groups but significantly more heifers with an AFC < 26 months calved for a third time. These younger calving animals therefore achieved more days in milk over 5 years, with >44% of their days alive spent in milk production compared with only 18% - 40% in cows calving at ≥26 months. Hence cows with an AFC < 26 months produced the most milk in their first 5 years of life. These results indicate that an AFC of 0.75 kg/d up to 15 months and good heifer fertility and resulted in the best subsequent performance.
文摘This study was conducted to estimate variance components and genetic parameters for 305 days mature equivalent milk yields (MEM) and calving interval (CAI) of registered Xinjiang Brown cattle. The total records were 3940 including 2579 for 305-day MEM and 1970 for CAI, which were collected from Xinjiang Urumqi Cattle Breeding farm in China with calving records from 1990 to 2008. Genetic parameters were obtained by multiple trait derivative-free restricted maximum likelihood (MTDFREML) using animal model. The model included year, season, parity and calving interval of calving for 305 days MEM, and year, season and parity of birth for CAI as fixed effects. Heritability for 305 days MEM was moderate (0.39) and in the same range of parameters estimated in management systems with medium production levels. Heritability of calving interval was small (0.02) as fertility traits for Xinjiang Brown cattle. Estimates of genetic and environmental correlations between 305 days MEM and CAI were 0.47 and 0.37, respectively. Estimates of genetic variation and heritability indicated that selection would result in genetic improvement of production traits. Estimates of both heritability and genetic variation for CAI were small, which indicates that genetic improvement would be difficult.
文摘Good management of the pregnant heifer is crucial to ensure that she is well grown and healthy and calves down easily before joining the milking herd. This study collected primary data on all aspects of heifer management on 101 UK farms during heifer pregnancy from conception to calving including farm factors and associated costs of system inputs. A cost analysis workbook was developed to calculate the cost of rearing per heifer for each of the study farms. Associations between cost of rearing and farms factors were determined using linear regression and analysis of variance. Heifers had a mean age of conception of 509 d (range 365 - 700 d) and an age at first calving of 784 d (range 639 - 973 d). The mean total cost of rearing during pregnancy was ￡450.36 (range ￡153.11 to ￡784.00) with a mean daily cost of ￡1.64 (range ￡0.56 to ￡2.86). The inputs contributing the most to cost were feed (32.7%), labour (23.8%) and slurry disposal (11.2%). Total purchased and homegrown feed and grazing contributed between 25.5% and 65.4% of total costs with a mean contribution of 43.6%. The cost of rearing was lowest in spring calving herds and highest in all year round calving herds with intermediate values in autumn and multi block calving herds. The main variables influencing the cost were the number of days spent at grass, age at first calving, calving pattern, breed, herd size and region. Each extra day in age at first calving increased the mean cost of rearing during pregnancy by ￡0.33/d whereas every extra day at grass reduced the cost by ￡1.75/d.
文摘The two ice caps of Svartisen, at the latitude of the Arctic Circle in Norway, supply 60 glaciers, ranging in size from 〉50 to 〈1 km^2. Until the last two decades of the 19th century, the glaciers remained close to their maximum recent （Little Ice Age） size. In response to the prevailing 20th century climate, they have become smaller, but the changes have varied between glaciers. Climatic factors have not been the sole control of the variations. The response times of small, steep glaciers are shorter than those of the longer, more gently sloping outlet glaciers. Topographic factors may moderate the response of individual glaciers to climate. The 20th century mass balance of several of the larger glaciers was dominated by calving into marginal lakes. The mass balance of Engabreen, the largest outlet of the western ice cap, has been measured every year since 1970 and the cumulative balance to 2008 was a gain of 22.7 m water equivalent. Although the pattern of annual variations probably applies to the other glaciers of Svartisen, it does not indicate their actual changes （gain or loss）. Thus, the Engabreen record is of little utility in water resource planning for the whole area.
文摘A total of 5852 records concerning daily milk yield, content of protein and fat, and somatic cell count was recorded in two farms (organic and conventional). Somatic cell count was log10- transformed before analysis because was not normally distributed. The mixed model methodology was used according to a repeated-measures scheme, as the restricted maximum likelihood method to estimate lactation curves at different season of calving and at different calving order. Calving order affected milk yield only in the first three calving order with the lowest production levels in the first six months of the year for both farm;no effect could be observed on fat and protein contents. The organic farm shows the minor milk production (7.77 vs8.10 kg/day/head organic and traditional respectively), but good qualitative characteristics of milk, and minor content of Somatic Cell Count. The milk production is major, in traditional farm, in summer respect the winter (10.4 vs6.34 kgof milk/day/ head). In biological farm no difference between seasons were observed. Peak milk yield occurs, for both farms, at around the 6th - 7th wk of lactation.
文摘The bovine embryos used for nonsurgical transfer should be morulae or blastocysts which are generally obtained from donor cow through superovulation and insemination. Due to the high cost of the embryos, the spread of embryo transfer is influenced to certain extent. In recent years, in vitro fertilization (IVF)technique has been adopted abroad to expand the source of embryos. The methods employed normally were culturing the embryos in rabbit’s or sheep’s oviducts (in vivo culture) to overcome '8—16-cell block', the morula or blastocyst developed in vivo was recovered and then transferred to recipients. However, the research concerning in vitro culture of IVF ova to the morula-blastocvst stage was
基金supported by the Trond Mohn Donation to the Mohn-Sverdrup Center at the Nansen Center,the Research Council of Norway’s UK/Netherlands/Norway RAPID programthe project AWAKE under the Polish-Norwegian Research Fund(2009–2011)
文摘Petermann Glacier is a marine-terminating outlet glacier that had a 70 km-long floating ice tongue prior to a ～ 270 km2 calving event that was observed from satellite sensors in August 2010,shortening the ice tongue by ～ 27 km.Further,in July 2012,another 10 km was lost through calving.In order to understand these events in perspective,here the authors perform a long-term data analysis of Petermann Glacier calving-front variability and ice velocity for each year in the 1990s-2000s,supplemented by available observations from the previous three decades.Five major （on the order of 100 krm2） calving events are identified,with ～ 153 km2 calved from 1959 to 1961,～ 168 km2 in 1991,～ 71 km2 in 2001,～ 270 km2 in 2010,and ～ 130 km2 in 2012-as well as ～ 31 k m2 calved in 2008.The increased frequency of major calving events in recent years has left the front terminus position retreated nearly 25 km beyond the range of observed in previous decades.In contrast,stable ice-dynamics are suggested from ice-velocity measurements made each year between 1993-2012,which are on average 1063 m yr-1,with limited interannual variability and no significant trend; moreover,there is no apparent relationship between ice-velocity variability and calving events.The degree to which the massive calving events in 2010 and 2012 represent natural episodic variability or a response to atmospheric and/or oceanic changes remains speculative; however,melt-induced weakening of the floating ice tongue in recent years is strongly suggested.
文摘位于西南极的派恩岛冰川(Pine Island Glacier,PIG)是近年来崩解频繁且前缘变化明显的区域。基于Landsat系列卫星和海洋一号C卫星光学影像、ERS-1和RADARSAT卫星SAR影像及航空影像,利用前缘位置识别和开口盒方法,分析1947—2020年PIG的前缘变化特征。PIG在近73年至少发生过17次规律性的大规模崩解事件,其崩解周期在1995—2013年间约为6年,2013年至今约为1~2年;由开口盒法计算得到的冰川前缘附近的流速在近73年间呈现上升趋势。结合PIG在1947—2020年间崩解事件的相关研究,总结出厄尔尼诺现象、冰架底部的绕极深层水暖化、底部融化率增加、底部裂隙的发育、冰水混合物的消退以及冰架与海脊间歇接触产生的背应力等是导致PIG发生崩解的可能驱动因子。
基金Supported by Science and Technology Open Cooperation Project of Henan Province(162106000017)Science and Technology People-benefiting Plan Project of Henan Province(152207110004)Puyang Science and Technology Plan Project(150109)~~
文摘The dairy herd improvement data from Henan Province were analyzed statistically to establish screening criteria for relevant data, thereby laying a foundation for genetic evaluation of dairy cows. With the 2 152 451 test-day records about 155 893 Chinese Holstein dairy cows collected by the Henan Dairy Herd Improvement Center from January 2008 to April 2016, the dynamics of test times during a complete lactation, test interval during a complete lactation, days in milk （DIM） of first test-day record, daughter descendant number and herd number of bull, age at first calving and pedigree integrity rate among different years and different herd sizes were analyzed by MEANS order of SAS 9.4. In addition, the data that were applicable to genetic evaluation were screened by SQL program. The results showed that during 2008-2015, the number of cow individuals participating in DHI in Henan Province increased from 7 379 to 93 706; the test-day milk yield increased from 19.91 to 24.05 kg; the somatic cell count reduced from 411.09×10^3 to 277.08×10^3 cells/ml; the percentage of cows with DIM ranging from 5-305 d reached 70.92%; the average test times increased from 3.20 to 6.31 times; the test interval decreased from 70.22 to 33.83 d; the dairy cows with age at first calving of 25 months were dominant, accounting for 12.57%; the bulls whose daughter descendant number was 20 or more and the daughters were distributed in 10 or more farms accounted for 6.05%; the one-generation pedigree integrity rate was 82.54%; the percentage of data that could be used for genetic evaluation was screened as 20.67%, which was lower than the results of other similar studies.
