Influences on the occurrence of abomasal displacements in German Holstein cows.

The objectives of this study were to analyse risk factors for the prevalenc e of abomasal displacement in German Holstein cows. In the period from 02/0 1/1999 to 01/31/2000 five veterinary surgeons in Northern Lower Saxony regi stered all cases of abomasal displacement in German Holstein cows being und er the official milk recording scheme. In total, the investigation included 160 farms and 9315 cows. An abomasal displacement was registered in 151 Ge rman Holstein cows, corresponding to a frequency of 1.6%. More than 75% of the abomasal displacements appeared during the first 30 days after calving. The left abomasal displacement (74.8%) was recorded more often than the ri ght abomasal displacement (25.2%). Milk recording and pedigree data were su pplied by the VIT (Vereinigte Informationssysteme Tierhaltung), Verden, and merged with the own recordings. The influences of the calving month, the l actation number, the age at calving, the inbreeding coefficient, calving pe rformance, duration of pregnancy, breed of calf sire, calf sire and the bre eding values for the milk performance did not explain a significant part of the variation of the frequency of the abomasal displacement. Significant e ffects of the sire, birth of twins or even more calves and the herd were ob tained for the leftsided abomasal displacement. For the rightsided abomasal displacement and for all abomasal displacements the herd effect was not si gnificant. Heritability estimates using bivariate linear REML models were h (2) = 0.043 +/- 0.012 for the leftsided abomasal displacement, and h(2) = 0 .007 +/- 0.004 for the rightsided abomasal displacement, respectively. Usin g the threshold model the heritabilities yielded estimates of h(2) = 0.51 f or the left abomasal displacement, and for the right abomasal displacement of h(2) = 0.19, respectively.