Evaluation of Herbal Oils in Various Preparations for Treating Mastitis in Dairy Cattle

The organic dairy industry is growing rapidly in the United States and with its growth is an increasing need for organic treatments for mastitis. Mastitis, or udder inflammation, is often caused by bacterial infection and is conventionally treated with antibiotics. Antibiotics are also used at the end of lactation, known as dry cow therapy, to eliminate existing intramammary infections and prevent new infections from occurring before the next lactation. Organic dairies in the United States are prohibited from using antibiotics in their cattle and thus use alternatives for mitigating mastitis. Mastitis can be measured through culturing milk of cows or measuring the somatic cell count of the milk, which is an indicator of the level of inflammation present and is often transformed into a linear score (SCS). No research has been performed comparing organic and conventional dairies in the southeast where heat and humidity make quality milk production challenging. The goals of the research contained in this dissertation were to compare milk quality on organic and conventional dairies in the southeastern United States and to evaluate two herbal alternatives to antibiotics for use as dry cow therapy.;In the first experiment, organic and conventional dairies in North Carolina were compared during the warm months. Seven organically and 7 conventionally managed dairy herds in North Carolina were surveyed in 2010 to record differences in milking procedures, mastitis detection and treatment, and to determine the prevalence of mastitis-causing organisms and milk quality for each management type. Overall infection rate, SCS, and cowlevel prevalence of several mastitis-causing pathogens were not different between organic and conventional dairies surveyed. Because of the similar prevalence of mastitis-causing organisms in organic and conventional dairies in North Carolina, further studies were planned to evaluate alternatives to antibiotics for mastitis mitigation.;The second experiment evaluated two commercially available alternatives to antibiotics as dry cow therapy on organic and conventional dairies. Phyto-Mast RTM and Cinnatube(TM) are two intramammary products composed primarily of plant-based oils. In a study comparing Phyto-Mast, Cinnatube, Phyto-Mast and Cinnatube, no treatment, and conventional antibiotic and teat sealant dry cow therapy, the herbal products had no negative effects on milk production or SCS and similar cure and new infection rates to the cows receiving conventional dry cow therapy and the untreated cows. However, the cure rate was difficult to assess and compare because of a low initial infection rate.;The potential of Phyto-Mast to cure infections was investigated in the third experiment by testing the antibacterial activity of each of its plant-derived oil ingredients, alone and in combination, in vitro against 3 mastitis-causing pathogens in milk. Only essential oil of Thymus vulgaris (thyme) had a consistently significant antibacterial effect.;The fourth experiment examined Phyto-Mast again as a dry cow therapy, this time compared with an internal teat sealant, the combination of Phyto-Mast and internal teat sealant, and no dry cow therapy to determine if an internal teat sealant had any effect on the efficacy of Phyto-Mast. Though the SCS and cure rates of cows receiving either Phyto-Mast, teat sealant, a combination of the two, or no treatment were not different among treatments, the combination of Phyto-Mast and teat sealant had significantly fewer new infections than no treatment.;Taken altogether, there is a need for alternatives to antibiotics for organic dairy producers throughout the United States. The herbal treatments tested here did not negatively affect milk production or SCS, and were not inferior to conventional dry cow therapy for preventing new infections from occurring during the dry period. Thyme oil, an ingredient of one of the herbal treatments, has significant antibacterial activity when cultured in milk.