混合型牧草对奶牛产奶量和尿氮排泄的影响

Effects of mixed herbage on milk yield and urine nitrogen excretion in dairy cattle

在标准的多年生黑麦草、白三叶草和意大利黑麦草放牧条件下,通过两期放牧试验,比较了不同牧草对奶牛泌乳后期尿氮排泄和产奶量的影响。试验选择48头年龄不同的荷斯坦奶牛,随机分为4组,每组6个重复,每个重复2头,奶牛饲喂4种牧草中的一种。牧场类型分为T1组为放牧前牧草,以多年生黑麦草为主,T2组为放牧前牧草种植多年生黑麦草+意大利黑麦草为主、T3组以混合型杂草为主,T4组混合型杂草+意大利黑麦草。在1期试验中,在黑麦草类型和混合型杂草类型牧场中,每10头奶牛都安装了尿液传感器来测量尿液氮相关参数(排尿频率、排尿量和氮浓度)。在1期试验中,对4个牧场类型的所有奶牛都进行了泌乳量测量。结果:在黑麦草和混合型杂草类型中苜蓿草含量超过30%,而在混合型杂草牧场中白三叶草和车前草含量超过了30%。黑麦草和混合型杂草类型中的意大利黑麦草量分别是15%和5%。牧场类型对奶牛每排尿次数、日尿氮排泄量均无显著影响(P>0.05)。但T1组较T2和T3组尿素氮含量显著提高了20.95%和27.42%(P<0.05),同时尿氮含量显著提高了20.93%和30%(P<0.05)。与T1和T4组相比,T3组乳尿素氮含量分别降低了15.42%和18.89%(P<0.05)。结论:混合型牧草的含量足以改变尿液氮排泄的日变化模式。用交替类型的牧草饲喂奶牛可以降低营养流失风险,同时对泌乳后期奶牛生产性能无负面效应。

Under the standard perennial ryegrass,white clover and Italian ryegrass grazing conditions,the effects of different herbage on urine nitrogen excretion and milk production in late lactation were compared through two grazing experiments.Forty-eight Holstein cows of different ages were selected and randomly divided into four groups with 6 replicates in each group and 2 replicates in each group.The cows were fed one of the four forage species.Pasture types were divided into:group T1 was pregrazing grass dominated by perennial ryegrass;group T2 was pregrazing grass dominated by perennial ryegrass+Italian ryegrass;group T3 was mixed weed dominated by mixed weed+Italian ryegrass;group T4 was mixed weed+Italian ryegrass.In the phase 1 experiment,every 10 cows in ryes and mixed weed type pastures were fitted with urine sensors to measure parameters related to liquid nitrogen in their urine(frequency,volume,and nitrogen concentration).In the phase 1 trial,lactation was measured for all cows in the four pasture types.Results:in ryegrass and mixed weed types,the content of alfalfa exceeded 30%,while in mixed weed pastures,the content of white clover and plantain exceeded 30%.The amount of Italian ryegrass in ryegrass and mixed weed types was 15%and 5%,respectively.The type of pasture had no significant effect on the number of per urination and daily nitrogen excretion of cows(P>0.05).However,compared with T2 and T3 groups,the urea nitrogen content in T1 group was significantly increased by 20.95%and 27.42%(P<0.05),while the urine nitrogen content was significantly increased by 20.93%and 30%(P<0.05).Compared with T1 and T4 groups,the content of milk urea nitrogen in T3 group decreased by 15.42%and 18.89%respectively(P<0.05).Conclusion:the content of mixed herbage is enough to change the diurnal pattern of urine nitrogen excretion.The risk of nutrient loss can be reduced by feeding cows with alternate types of herbage,and there is no negative effect on the performance of cows in late lactation.