Fries G F
J Dairy Sci. 1983 Jun;66(6):1303-11. doi: 10.3168/jds.S0022-0302(83)81939-0.
Michigan dairy herds with continuous Dairy Herd Improvement Association records 1969 to 1978 were identified. Herds that were exposed to polybrominated biphenyl in 1974 at concentrations generally not causing residues in tissue or milk fat greater than .3 microgram/g were compared with control herds of comparable size, breed, and location. Analysis of covariance with herd size as a covariable was used to compare measures of herd performance between groups. Relationships of exposure to response within the exposed group were evaluated by multiple regression of the measures on the mean logarithmic concentration of polybrominated biphenyl in tissue with herd size as a second independent variable. Herd size, milk production, and fat production were greater and age was less in exposed herds. Lack of interactions of year by group indicated that all differences predated exposure. Regressions of these characteristics on exposure within years were not significant. Data on other measures were available only for 1976 to 1978. Percent culls, number of culls, and number of new cows were greater for exposed than control herds, but regressions of these characteristics on exposure were negative in some years. Calving intervals were shorter for exposed herds than for control herds, but regressions on exposure were not consistent.
确定了1969年至1978年拥有连续奶牛群改良协会记录的密歇根奶牛群。将1974年接触多溴联苯且组织或乳脂中浓度一般不会导致残留量超过0.3微克/克的牛群与规模、品种和地理位置相当的对照牛群进行比较。以牛群规模作为协变量的协方差分析用于比较两组之间的牛群生产性能指标。通过将这些指标对组织中多溴联苯平均对数浓度进行多元回归，并将牛群规模作为第二个自变量，来评估暴露组内暴露与反应之间的关系。暴露牛群的牛群规模、产奶量和脂肪产量更高，年龄更小。年份与组之间缺乏交互作用表明所有差异在暴露之前就已存在。这些特征在各年份内对暴露的回归不显著。关于其他指标的数据仅在1976年至1978年期间可得。暴露牛群的淘汰百分比、淘汰数量和新奶牛数量均高于对照牛群，但这些特征在某些年份对暴露的回归为负。暴露牛群的产犊间隔比对照牛群短，但对暴露的回归并不一致。
