泌乳盛期与泌乳后期奶牛乳腺氧代谢特征及乳腺健康状况的比较分析

Comparative Analysis on Oxygen Metabolic Traits and Mammary Health Status of Early-Lactating and Late-Lactating Dairy Cows

本试验的目的是比较研究不同泌乳时期荷斯坦奶牛乳腺氧代谢特征、机体健康和乳腺氧化应激间的关系。选取18头泌乳盛期奶牛[泌乳天数(61.80±3.72) d,产奶量(55.65±3.95) kg/d,胎次(2.74±0.19)胎,体重(701±55) kg]和16头泌乳后期奶牛[泌乳天数(289.10±6.78) d,产奶量(12.27±4.70) kg/d,胎次(2.81±0.15)胎,体重(727±63) kg],在同一时间采集上述34头奶牛乳静脉和尾动脉的血液,进行血气参数、血常规指标、氧化应激指标以及乳中氧化应激指标等的检测,并结合上述结果计算乳腺氧气供给等氧代谢指标。结果表明:在乳腺氧代谢方面,泌乳盛期奶牛的乳腺氧总消耗量(P=0.01)极显著高于泌乳后期奶牛;与泌乳后期奶牛相比,泌乳盛期奶牛的尾动脉氧含量(P<0.01)极显著降低,生产单位牛奶的耗氧量(P=0.02)显著降低,乳静脉氧含量(P=0.06)有降低的趋势。在乳腺氧化应激和抗氧化应激方面,泌乳盛期奶牛乳静脉血浆中活性氧(ROS)(P=0.09)、丙二醛(MDA)含量(P=0.07)以及氧化自由基吸收能力(ORAC)(P=0.07)有高于泌乳后期奶牛的趋势;泌乳盛期奶牛乳中MDA含量(P=0.01)极显著高于泌乳后期奶牛,ORAC(P=0.07)、谷胱甘肽过氧化物酶(GSH-Px)(P=0.06)和超氧化物歧化酶(SOD)活性(P=0.07)有高于泌乳后期奶牛的趋势。在血常规方面,与泌乳后期奶牛相比,泌乳盛期奶牛尾动脉血中血小板分布宽度(P<0.01)极显著降低,嗜酸性粒细胞数量(P=0.04)显著降低,血小板平均体积(P=0.07)有降低的趋势,中性粒细胞数量(P=0.07)有升高的趋势。综上可知,与泌乳后期奶牛相比,泌乳盛期奶牛乳腺氧消耗量较高,且乳腺应激较强,该结果提示泌乳盛期耗氧量调控可能是降低该时期奶牛代谢应激的潜在方案,这为泌乳盛期奶牛代谢应激的调控提供了新思路。

The purpose of this experiment was to compare the relationships of mammary oxygen metabolic traits,body health and mammary oxidative stress of Holstein dairy cows in different lactating periods. Eighteen early-lactating cows[days in milk:(61.80±3.72)d;milk yield:(55.65±3.95)kg/d;(2.74±0.19)parities;body weight:(701±55)kg]and 16 late-lactating cows[days in milk:(289.10±6.78)d;milk yield:(12.27±4.70)kg/d;(2.81±0.15)parities;body weight:(727±63)kg]were selected in the current study.The blood samples of mammary vein and caudal artery of these 34 cows were collected in the same time to measure the blood gas parameters,blood routine indexes and oxidative stress indexes,and the oxygen metabolism related indexes such as mammary oxygen supply were calculated combined with the above results. The results showed as follows:in terms of mammary oxygen metabolism,compared with those of late-lactating dairy cows,the mammary total oxygen consumption(P = 0.01)of early-lactating dairy cows was extremely significantly increased,the oxygen content in coccygeal artery(P<0.01)was extremely significantly decreased,the oxygen consumption of producing a unit of milk(P = 0.02)was significantly decreased,and the oxygen content in mammary vein(P = 0.06)tended to decline. In terms of mammary gland oxidation stress and antioxidant stress,the contents of reactive oxygen species(P = 0.09),malonaldehyde(P = 0.07)and oxygen radical antioxidant capacity(P = 0.07)in mammary vein plasma of early-lactating dairy cows were higher than those of late-lactating dairy cows;the malonaldehyde content(P = 0.01)in milk of early-lactating dairy cows was extremely significantly higher than that of late-lactating dairy cows,and the oxygen radical antioxidant capacity(P = 0.07),glutathione peroxidase(P = 0.06)and superoxide dismutase activities(P = 0.07)in milk were higher than those of late-lactating dairy cows. In terms of blood routine,compared with those of late-lactating dairy cows,the platelet distribution width(PDW)(P<0.01)of caudal artery of early-lactating dairy cows was extremely significantly decreased,the eosinophil count(P = 0.04)was significantly decreased,the mean platelet volume(MPV)(P = 0.07)tended to decrease,as well as the neutrophil count(P = 0.07)tended to increase. To sum up,the mammary oxygen consumption is higher and mammary gland stress is stronger of early-lactating dairy cows compared with late-lactating dairy cows,and those results suggest that oxygen consumption regulation during early-lactation period may be a potential solution to reduce the metabolic stress of dairy cows during this period,which provides a new way of metabolic stress regulation in early-lactating dairy cows.