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Factors affecting bacteriological cure rates (BCR) and new intramammary infections (IMI) during the dry period as well as clinical mastitis (CM) during early lactation were investigated in 414 German Holstein dairy cows receiving dry cow therapy. Cows were treated with either benethamine benzylpenicillin (300,000 IU), penethamate hydriodide (100,000 IU), and framycetin sulphate (100 mg, n = 136), or cefquinome (150 mg, n = 135), or benzathine cloxacillin (1,280 mg, n = 143). Overall BCR, IMI, and CM at parturition were 86.4%, 20.7%, and 4.3%, respectively. The three antibiotic treatments differed only in BCR, with cloxacillin yielding better results than the others. Udder quarters from cows with > 4 lactations had a higher risk of IMI and CM at calving. Chronic changes in udder tissues were linked to a lower BCR and were associated with a higher risk of CM during early lactation. The risk of CM at calving was higher in udder quarters with unspecific or subclinical mastitis before drying off. In conclusion, with antibiotic dry cow therapy, age and health status of the udder appear to be major determinants of IMI and CM during the dry period and early lactation, while BCR was associated with the antibiotic type and udder tissue status.

The internal teat sealant OrbeSeal (Pfizer Animal Health) should prevent new IMI throughout the dry period. The aim of our field studies was to determine the efficacy of infusion with an internal teat seal at dry off in reducing new intramammary infections during the dry period in relation to an untreated control. In experiment 1 128 cows were enrolled from 24 dairy herds in Lower Saxony. Prior to final milking, all quarters were sampled for bacteriological culture and SCC analysis in three weekly intervals. After final milking, all 4 quarters of test group animals were infused with a commercially available internal teat seal. Following calving quarter milk samples were collected between 1 to 3 DIM and again between 8 to 10 and 15 to 17 DIM for culture and SCC analysis. The rate of new IMI during the dry period was 7.4% of quarters in the OrbeSeal-group and 12.7% in the control group, resp. In experiment 2 the new infection rate of udder quarters treated with OrbeSeal was evaluated in a split udder design with 93 cows healthy on all four udder quarters from six dairy farms in North Germany. In this study the front right and rear left udder quarters were treated, while both other quarters served as control. Applied methods occurred like in experiment 1. Here a new infection rate of 2.8% (OrbeSeal group) and in the control group a new infection rate of 11.5% was reached (P < 0.05).

In survival analysis, type traits can be included as covariates to evaluate their use as predictors for survival. One problem in such an analysis is the availability of suitable data. Whereas data on the length of productive life (LPL) of individual cows can be retrieved from milk recording data, for type traits, all cows in the population must be scored for type at least once. In the present analysis, a dataset from the Osnabruck region in northwestern Germany, which fulfilled this requirement in recent years, was used. Data consisted of 169,733 cows with information on LPL for calving years 1980 to 1996 (dataset I) and of 39,233 cows with information on LPL and type for calving years 1990 to 1996 (dataset II). A further dataset (III) contained 43,116 cows from calving years 1987 to 1996 and included information on the housing system for each herd. The basic model included stage of lactation, relative production within herd, change of herd size, and year-season as time dependent effects; age at calving as a time-independent effect; and herd-year-season and sire as random effects. Other effects (information on type, housing system) were included additionally. For data-set II, the scores for 15 linear type traits were also included as corrected phenotypic values, estimated breeding values, and residuals from a previous BLUP analysis. The package Survival Kit 3.0 was used for all analyses. The results indicate a moderate heritability of 0.17 and 0.18 for true and functional LPL (dataset I). Almost all type traits analyzed (dataset II) exceeded a 0.001 level of significance in their effect on survival. The strongest relationships between survival and type were found for udder depth, fore udder attachment, and front teat placement. The main result from the comparison of housing systems (dataset III) was that bedding has a positive effect on survival.