A multilocation clinical trial in lactating dairy cows affected with clinical mastitis to compare the efficacy of treatment with intramammary infusions of a lincomycin/neomycin combination with an ampicillin/cloxacillin combination

A study was conducted to compare the efficacy in lactating dairy cows of in tramammary infusions in quarters affected with clinical mastitis between a formulation containing 330 mg lincomycin and 100 mg neomycin in a 10-mL aqu eous solution (LINCOCIN(R) FORTE S, Pharmacia & Upjohn) and a formulation c ontaining 75 mg ampicillin and 200 mg cloxacillin in an oil suspension (AMP ICLOX(TM), Pfizer Animal Health). This study was designed as a multicentre clinical trial involving investiga tors in France, Germany and Belgium and carried out according to the Europe an Commission guidelines on Good Clinical Practices. Cows in the herds were monitored for clinical mastitis. When evidence of clinical mastitis was de tected in a single quarter, a pretherapy milk sample was collected from the affected quarter. After milk sampling, the cow was assigned to one of the two treatment groups at random and treated with an intramammary infusion of one syringe of either LINCOCIN(R) FORTE S or AMPICLOX(TM) for three succes sive milkings in the mastitic quarter. At 4-5, 13-15 and 20-22 days after f irst infusion, the veterinarian returned to the farm to conduct a clinical examination and collect milk samples from the affected quarter. Milk sample s were cultured for the presence of mastitis organisms and somatic cell cou nt. (SCC) was measured. Following a 10-month study period, 256 cases were enrolled in the study. A total of 232 and 189 cases were analysed for clinical cure and for clinical -plus-bacteriological cure, respectively. The proportions of cases cured cl inically and cured clinically-plus-bacteriologically were compared between the two treatment groups. Somatic cell count differences between treatment groups were also tested. The clinical cure rate for LINCOCIN(R) FORTE S (62 .5%) was significantly better than for AMPICLOX(TM) (51.8%) (P = 0.035). Th e clinical-plus-bacteriological cure rate was also significantly better for LINCOCIN(R) FORTE S (38.1%) than for AMPICLOX(TM) (21.7%) (P = 0.005). Amo ng bacteriologically cured cases, the SCC declined in both treatment groups but the SCC was significantly higher for the AMPICLOX(TM) group than for t he LINCOCIN(R) FORTE S group (P = 0.036). In conclusion, clinical cure rate, clinical-plus-bacteriological cure rate, and SCC level were significantly better with LINCOCIN(R) FORTE S than for AMPICLOX(TM).