Newman Kari A, Rajala-Schultz Päivi J, Lakritz Jeffrey, DeGraves Fred J
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, Ohio State University, Columbus, Ohio 43210, USA.
J Dairy Res. 2009 Nov;76(4):426-32. doi: 10.1017/S0022029909990033. Epub 2009 Jul 29.
Concentration of natural protective factors (NPFs) which have the ability to inhibit growth of mastitis-causing pathogens increase rapidly following the cessation of milking of dairy cows. One such NPF is lactoferrin, an iron-binding protein present in high concentrations in dry-cow secretions. Earlier studies have demonstrated that intermittent milking at the end of lactation increases levels of NPFs in milk and may decrease prevalence of intramammary infections at calving; however, most of these studies date back several decades and may not apply to current high-producing cows. The objective of this study was to assess whether an intermittent milking schedule prior to dry-off increases the concentration of lactoferrin in mammary secretions at the end of lactation and what other factors influence lactoferrin concentration at dry-off. One week prior to dry-off (pre-dry), cows were randomly assigned to an intermittent milking schedule or they continued to be milked twice daily. Duplicate quarter milk samples for microbiological culture were taken at pre-dry and at dry-off to determine infection status of quarters. Quarter somatic cell counts (SCC) were measured on the day of dry-off. Lactoferrin concentrations were quantified by ELISA. Intermittent milking, mean SCC for the last three months prior to dry-off, SCC at dry-off, lactoferrin concentration at pre-dry, quarter infection status at pre-dry and dry-off, days in milk at dry-off, breed, parity, cumulative milk yield for the final week of lactation and season were considered as potential explanatory variables. Their effect on lactoferrin concentration at dry-off was assessed using a mixed-effects linear regression model. Lactoferrin concentration increased significantly during the final week of lactation for cows on an intermittent milking schedule and was significantly associated with initial lactoferrin concentration and infection status at dry-off.
具有抑制乳腺炎致病病原体生长能力的天然保护因子（NPFs）浓度在奶牛停止挤奶后迅速增加。其中一种NPF是乳铁蛋白，它是一种铁结合蛋白，在干奶牛分泌物中含量很高。早期研究表明，泌乳末期的间歇性挤奶会增加牛奶中NPFs的水平，并可能降低产犊时乳房内感染的发生率；然而，这些研究大多可追溯到几十年前，可能不适用于当前的高产奶牛。本研究的目的是评估干奶前的间歇性挤奶计划是否会增加泌乳末期乳腺分泌物中乳铁蛋白的浓度，以及其他哪些因素会影响干奶时的乳铁蛋白浓度。在干奶前一周（预干奶期），奶牛被随机分配到间歇性挤奶计划中，或者继续每天挤奶两次。在预干奶期和干奶期采集用于微生物培养的重复四分位奶样，以确定各四分位的感染状况。在干奶当天测量四分位体细胞计数（SCC）。通过酶联免疫吸附测定法对乳铁蛋白浓度进行定量。间歇性挤奶、干奶前最后三个月的平均SCC、干奶时的SCC、预干奶期的乳铁蛋白浓度、预干奶期和干奶期的四分位感染状况、干奶时的泌乳天数、品种、胎次、泌乳最后一周的累计产奶量和季节被视为潜在的解释变量。使用混合效应线性回归模型评估它们对干奶时乳铁蛋白浓度的影响。对于采用间歇性挤奶计划的奶牛，乳铁蛋白浓度在泌乳最后一周显著增加，并且与干奶时的初始乳铁蛋白浓度和感染状况显著相关。
