Efficacy of two dry cow therapies in Italian dairy herds

Introduction This study was performed to compare efficacy of two intramammary treatments at drying off (either 150 mg of cefquinome, Virbactan®, Virbac or a combination of penethamate hydriodide (100 mg) + benethamine penicillin (280 mg) + framycetin sulphate (100 mg), Mamyzin® A, Boehringer Ingelheim). Materials and Methods A total of 393 cows from two farms in Italy (Emilia region) were randomly allocated to one of the two treatment groups between May and December 2011. The two herds owned 550 and 480 dairy cows, yearly mean bulk milk somatic cell counts being lower than 300,000 cells/ml and mean dry period being equal to 60 and 58 days, respectively. Cows were eligible for inclusion at the time of drying off if they had four functional quarters without significant udder or teat lesions and if they did not receive any antimicrobial or anti-inflammatory treatment in the 30 days before the first quarter milk sampling. Treatment consisted in intramammary infusion of one tube per quarter of the corresponding product after the last milking. Quarter milk samples were taken on all cows twice within seven days before drying off and twice within 14 days after calving for bacteriological analysis and somatic cell counts according to standard laboratory techniques. Cows were monitored during the first 100 days post-calving for the presence of clinical mastitis. Bacteriological cure rate and new infection rate during the dry period were compared between groups at quarter level whereas incidence of clinical mastitis was compared at cow level. Comparisons were made by using either the chi-square or Fisher’s exact test. Results Among the included cows, 63 cases had to be excluded mainly for loss of monitoring (transfer between herds of the same organization) or for disease condition mostly unrelated to udder health. Distribution of cows parity spread between two (54% of cows), three (30%) and four or above (16%). Around 46% of quarters were infected at drying off, major pathogens, coagulase negative Staphylococci (CNS) and Corynebacterium bovis representing respectively 9%, 53% and 11% of positive samples. Gram positive and Gram negative bacteria represented two thirds and one third of major pathogens, respectively. The prevalence of pathogens between drying off and post calving was similar between groups, a decrease being observed for major and minor pathogens, except for mixed infections which increased after calving (Table 1). Bacteriological cure rates were significantly higher in the cefquinome treated group regarding all pathogens and Staphylococcus aureus for quarters with subclinical mastitis at drying off (Table 2). New infection rates (corresponding mainly to CNS and mixed infections without involvement of major pathogens) were not significantly different between groups for quarters uninfected at drying off (25.8% and 32.6% in combination and cefquinome groups, respectively). A decrease of quarter somatic cell counts between drying off and post-calving was recorded in both groups from a mean value around 100,000 cells/ml to circa 10,000 cells/ml. The incidence of clinical mastitis during the first 100 days in milk was low and not significantly different between groups (3.5% in cefquinome treated group vs 5.0% in combination treated group). Discussion Interest of dry cow therapy in this study was confirmed by the decrease of infected quarters through the dry period (both for major and minor pathogens). The higher cure rate observed in the cefquinome treated cows may be due to higher antimicrobial activity or better diffusion towards the infection site. The rather high rate of new infections may partly be due to sampling dates till 14 days post calving, thus reflecting new infections not only during the dry period but also during the very early lactation (either due to poor housing or milking hygiene).