牛奶尿素氮含量的测定及与奶牛繁殖性状的关系
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摘要
牛奶尿素氮(Milk Urea Nitrogen, MUN)是奶牛生产性能测定(Dairy Herd Improvement, DHI)的一个重要指标,并可能监控奶牛的繁殖性能。中国荷斯坦奶牛与国外荷斯坦牛在培育过程、日粮组成和饲养管理等方面有很大的差异,采样时间和测定方法影响MUN测定值的准确性,关于MUN含量与中国荷斯坦奶牛繁殖方面的相关研究还鲜有报道。
本研究以中国荷斯坦奶牛为研究对象,研究了不同测定方法对MUN值的影响(试验一)；采样时间对常规乳成分和MUN含量的影响(试验二)；MUN含量与中国荷斯坦奶牛繁殖性状的关系(试验三)。
本试验分别采用红外法(Foss 4000)、二乙酰一肟法及不同去蛋白处理的尿素氮试剂盒法(水溶法和醚溶法)测定50个奶样中MUN的含量,比较不同方法测得的MUN值之间的差异。结果表明：红外法、二乙酰一肟法、尿素氮试剂盒水溶法的测定结果之间差异不显著(P>0.05)。试剂盒法中,三氯乙酸水溶液测定的MUN值显著高于乙醚溶解法的测定结果值(P<0.01)。因此,实验室可采用二乙酰一肟法和尿素氮试剂盒水溶法测定MUN含量,而三氯乙酸乙醚溶液会增加MUN含量的测定误差。
选择年龄胎次、泌乳天数、产奶量相近的50头泌乳荷斯坦奶牛,于一天内早、中、晚三次挤奶时分别取样,并按照4：3：3的比例均匀混合,采用红外法测定MUN和常规乳成分含量。试验结果为：早、中、晚三班次乳样的MUN与全天混合样差异极显著(P<0.01),乳蛋白和乳糖与混合样之间差异不显著(P>0.05)；早、中、晚三个班次的乳成分含量与全天样的相关系数范围分别为0.562-0.911、0.376-0.938、0.424-0.949；对于MUN和常规乳成分含量,全天样与早上样和中午样、中午样和晚上样、早上样和晚上样都具有极显著的线性相关关系(P<0.01),复相关系数分别为R=0.693-0.947、R=0.502-0.961、R=0.848-0.996。其中,全天样与早上样和中午样的相关程度最高。因此,可以测定早上样和晚上样乳成分含量,结合相应的回归方程可以计算全天样的相应乳成分含量。
测定了255头高产奶牛(平均日奶产量大于25Kg)产后首次配种当天的MUN浓度,跟踪记录奶牛在第一个发情期配种后的妊娠情况,分析人工授精当天MUN值和一次受胎率及产后首次发情配种天数之间的关系。结果表明：人工授精当天MUN值为21.22±5.45mg/dL,255头奶牛中第一次配种妊娠的奶牛有127头,未妊娠奶牛有128头,妊娠奶牛和非妊娠奶牛的MUN值分别为20.20±5.45mg/dL和22.22±5.39 mg/dL,差异极显著(P<0.01)。人工授精当天MUN值与第一情期受胎率呈二次曲线关系(y=-0.001x2+0.039x+0.18,R2=0.936,P<0.01)。MUN含量为18 mg/dL时,第一情期受胎率最高。人工受精当天MUN值与产后首次发情配种天数呈线性相关关系(y=3.169x+17.34,P<0.01),产后首次发情配种天数随配种当天MUN浓度的升高而延长。
综上所述：红外法和二乙酰一肟法测得的MUN值差异不显著,三氯乙酸乙醚溶液会增加MUN值的测定误差；全天样乳成分含量可以通过测定早上样和晚上样相应乳成分,根据相关回归方程计算；MUN含量可作为反映中国荷斯坦泌乳奶牛第一情期受胎率高低和产后首次配种天数的指标,对于平均日产奶量大于25Kg的高产奶牛,配种当天MUN值高于18 mg/dL时,第一情期受胎率降低。人工受精当天MUN值与产后首次发情配种天数呈正相关关系,产后首次发情配种天数随配种当天MUN浓度的升高而延长。
Milk urea nitrogen(MUN) content is one important index of the Dairy Herd Improvement (DHI), could be used as an indicator of the reproductive performance of dairy cows. There are many differences between Chinese and foreign Holstein cows in breeding, management and diets.The simpling time and determination methods also effect the accuracy and precision of MUN content. Little information is available about the relationship between MUN centent and reproductive performance of Chinese dairy cows.This study was conducted to compare the determination methods of MUN content (Experiment 1), the impact of sampling time on MUN content and conventional ingredients in Milk (Experiment 2), the relationship between MUN content and fertility traits of dairy cows (Experiment 3).
This study used infrared method, diacetyl monoxime method and urea nitrogen kit respectively fifty milk samples to compare the difference of MUNconcentration.. The results showed that there was no significant difference in MUN concentration by the Fossomatic 4000 Milk Analyzer, diacetyl monoxime method and urea nitrogen kit (P>0.05). Compared with the distilled water solution with urea nitrogen kit, diethyl ether solution with urea nitrogen kit gave lower MUN concentration (P< 0.01). The results indicated that the MUN concentration were similar between Fossomatic 4000 Milk Analyzer, diacetyl monoxime method and urea nitrogen kit. The determined error appeared when milk simple was dissolved by diethyl ether solution.
In the second study, milk samples were routinely collected from milk meters at the time of the regular morning milking, middle milking and night milking, from 50 lactating Holstein cows, different time milk samples were mixed by 4:3:3 for composite samples representing the entire milking to compare difference of sampling methods on MUN and conventional ingredients in milk. The results showed that there was no significant difference in the content of total protein and lactose percent(P> 0.05), but extremely significant difference in butterfat percentage and the content of MUN, somatic cell count(SCC) (P<0.01), dry matter among milk simpled at different time. There were extremely significant linear correlation between between the composite milk and two of the comprehensive milk from morning simple,middle simple and night simple(R=0.693-0.947、R=0.502-0.961、R=0.848-0.996).A highest correlation coefficient was obtained between the composite milk and the comprehensive milk from morning simple and night simple.The results dicated that although single time of milk simple could not replace the composite milk, but the content of MUN and conventional ingredients in composite milk for DHI can be predicted according the morning simple and night simple.
The trials in this part determined MUN concentration on the day of the first Artifical Insemination (AI) after postpartum and the conception rate after first insemination of two hundred and fifty five lactating Holstein cows fed normal diets formulated for high milk production.The results showed that the mean MUN concentrations on the day of AI averaged 21.22±5.45 mg/dL (n=155). For cows later determined to be pregnant (n=128) and nonpregnant (n=127), MUN concentrations were different (20.20±5.45and22.22±5.39 mg/dL, P<0.01), respectively. There was curve correlation between MUN and the conception rate after first insemination (y=-0.001x2+0.039x+0.18, R2=0.936,P<0.01), the conception rate peaked at 18 mg/dL MUN. The pregnancy rate of cows with MUN concentrations greater than 18 mg/dL was lower than in cows with less MUN.There was a extremely significant linear correlation between MUN concentration on the day of the first Artifical Insemination (AI) after postpartum and days to first service (y=3.169x+17.34, P<0.01). With MUN concentration on the day of the first Artifical Insemination (AI) after postpartum increased,days to first service also increased.
In conclusion, the MUN concentration were similar between Fossomatic 4000 Milk Analyzer, diacetyl monoxime method and urea nitrogen kit, the comprehensive milk from morning simple and night simple can replace the composite milk. There was strong relation between MUN content and the conception rate after first insemination and days to first service. When the MUN content was more than 18 mg/dL, the conception rate after first insemination will be decrease. With MUN concentration on the day of the first Artifical Insemination (AI) after postpartum increased,days to first service also increased.
本研究以中国荷斯坦奶牛为研究对象,研究了不同测定方法对MUN值的影响(试验一)；采样时间对常规乳成分和MUN含量的影响(试验二)；MUN含量与中国荷斯坦奶牛繁殖性状的关系(试验三)。
本试验分别采用红外法(Foss 4000)、二乙酰一肟法及不同去蛋白处理的尿素氮试剂盒法(水溶法和醚溶法)测定50个奶样中MUN的含量,比较不同方法测得的MUN值之间的差异。结果表明：红外法、二乙酰一肟法、尿素氮试剂盒水溶法的测定结果之间差异不显著(P>0.05)。试剂盒法中,三氯乙酸水溶液测定的MUN值显著高于乙醚溶解法的测定结果值(P<0.01)。因此,实验室可采用二乙酰一肟法和尿素氮试剂盒水溶法测定MUN含量,而三氯乙酸乙醚溶液会增加MUN含量的测定误差。
选择年龄胎次、泌乳天数、产奶量相近的50头泌乳荷斯坦奶牛,于一天内早、中、晚三次挤奶时分别取样,并按照4：3：3的比例均匀混合,采用红外法测定MUN和常规乳成分含量。试验结果为：早、中、晚三班次乳样的MUN与全天混合样差异极显著(P<0.01),乳蛋白和乳糖与混合样之间差异不显著(P>0.05)；早、中、晚三个班次的乳成分含量与全天样的相关系数范围分别为0.562-0.911、0.376-0.938、0.424-0.949；对于MUN和常规乳成分含量,全天样与早上样和中午样、中午样和晚上样、早上样和晚上样都具有极显著的线性相关关系(P<0.01),复相关系数分别为R=0.693-0.947、R=0.502-0.961、R=0.848-0.996。其中,全天样与早上样和中午样的相关程度最高。因此,可以测定早上样和晚上样乳成分含量,结合相应的回归方程可以计算全天样的相应乳成分含量。
测定了255头高产奶牛(平均日奶产量大于25Kg)产后首次配种当天的MUN浓度,跟踪记录奶牛在第一个发情期配种后的妊娠情况,分析人工授精当天MUN值和一次受胎率及产后首次发情配种天数之间的关系。结果表明：人工授精当天MUN值为21.22±5.45mg/dL,255头奶牛中第一次配种妊娠的奶牛有127头,未妊娠奶牛有128头,妊娠奶牛和非妊娠奶牛的MUN值分别为20.20±5.45mg/dL和22.22±5.39 mg/dL,差异极显著(P<0.01)。人工授精当天MUN值与第一情期受胎率呈二次曲线关系(y=-0.001x2+0.039x+0.18,R2=0.936,P<0.01)。MUN含量为18 mg/dL时,第一情期受胎率最高。人工受精当天MUN值与产后首次发情配种天数呈线性相关关系(y=3.169x+17.34,P<0.01),产后首次发情配种天数随配种当天MUN浓度的升高而延长。
综上所述：红外法和二乙酰一肟法测得的MUN值差异不显著,三氯乙酸乙醚溶液会增加MUN值的测定误差；全天样乳成分含量可以通过测定早上样和晚上样相应乳成分,根据相关回归方程计算；MUN含量可作为反映中国荷斯坦泌乳奶牛第一情期受胎率高低和产后首次配种天数的指标,对于平均日产奶量大于25Kg的高产奶牛,配种当天MUN值高于18 mg/dL时,第一情期受胎率降低。人工受精当天MUN值与产后首次发情配种天数呈正相关关系,产后首次发情配种天数随配种当天MUN浓度的升高而延长。
Milk urea nitrogen(MUN) content is one important index of the Dairy Herd Improvement (DHI), could be used as an indicator of the reproductive performance of dairy cows. There are many differences between Chinese and foreign Holstein cows in breeding, management and diets.The simpling time and determination methods also effect the accuracy and precision of MUN content. Little information is available about the relationship between MUN centent and reproductive performance of Chinese dairy cows.This study was conducted to compare the determination methods of MUN content (Experiment 1), the impact of sampling time on MUN content and conventional ingredients in Milk (Experiment 2), the relationship between MUN content and fertility traits of dairy cows (Experiment 3).
This study used infrared method, diacetyl monoxime method and urea nitrogen kit respectively fifty milk samples to compare the difference of MUNconcentration.. The results showed that there was no significant difference in MUN concentration by the Fossomatic 4000 Milk Analyzer, diacetyl monoxime method and urea nitrogen kit (P>0.05). Compared with the distilled water solution with urea nitrogen kit, diethyl ether solution with urea nitrogen kit gave lower MUN concentration (P< 0.01). The results indicated that the MUN concentration were similar between Fossomatic 4000 Milk Analyzer, diacetyl monoxime method and urea nitrogen kit. The determined error appeared when milk simple was dissolved by diethyl ether solution.
In the second study, milk samples were routinely collected from milk meters at the time of the regular morning milking, middle milking and night milking, from 50 lactating Holstein cows, different time milk samples were mixed by 4:3:3 for composite samples representing the entire milking to compare difference of sampling methods on MUN and conventional ingredients in milk. The results showed that there was no significant difference in the content of total protein and lactose percent(P> 0.05), but extremely significant difference in butterfat percentage and the content of MUN, somatic cell count(SCC) (P<0.01), dry matter among milk simpled at different time. There were extremely significant linear correlation between between the composite milk and two of the comprehensive milk from morning simple,middle simple and night simple(R=0.693-0.947、R=0.502-0.961、R=0.848-0.996).A highest correlation coefficient was obtained between the composite milk and the comprehensive milk from morning simple and night simple.The results dicated that although single time of milk simple could not replace the composite milk, but the content of MUN and conventional ingredients in composite milk for DHI can be predicted according the morning simple and night simple.
The trials in this part determined MUN concentration on the day of the first Artifical Insemination (AI) after postpartum and the conception rate after first insemination of two hundred and fifty five lactating Holstein cows fed normal diets formulated for high milk production.The results showed that the mean MUN concentrations on the day of AI averaged 21.22±5.45 mg/dL (n=155). For cows later determined to be pregnant (n=128) and nonpregnant (n=127), MUN concentrations were different (20.20±5.45and22.22±5.39 mg/dL, P<0.01), respectively. There was curve correlation between MUN and the conception rate after first insemination (y=-0.001x2+0.039x+0.18, R2=0.936,P<0.01), the conception rate peaked at 18 mg/dL MUN. The pregnancy rate of cows with MUN concentrations greater than 18 mg/dL was lower than in cows with less MUN.There was a extremely significant linear correlation between MUN concentration on the day of the first Artifical Insemination (AI) after postpartum and days to first service (y=3.169x+17.34, P<0.01). With MUN concentration on the day of the first Artifical Insemination (AI) after postpartum increased,days to first service also increased.
In conclusion, the MUN concentration were similar between Fossomatic 4000 Milk Analyzer, diacetyl monoxime method and urea nitrogen kit, the comprehensive milk from morning simple and night simple can replace the composite milk. There was strong relation between MUN content and the conception rate after first insemination and days to first service. When the MUN content was more than 18 mg/dL, the conception rate after first insemination will be decrease. With MUN concentration on the day of the first Artifical Insemination (AI) after postpartum increased,days to first service also increased.
引文
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