IN VIVO EFFECT OF Origanum vulgare ESSENTIAL OIL ON MICROBIOLOGICAL QUALITY OF RAW MILK FROM SUBCLINICAL MASTITIS AFFECTED COWS

The study aims to test under in vivo condition the effect of Origanum vulgare essential oil (OEO) on the bacteriological quality of raw milk from cows affected by subclinical mastitis. The tested oil extracted from Algerian endemic oregano collected in Setif province (eastern Algeria) was characterised as carvacrol-chemotype using gas chromatography-mass spectrometry (GC-MS). The in vitro inhibitory effect of diluted OEO was tested on control reference strains. Staphylococcus aureus, ATCC 700699 methicillin-resistant seemed more susceptible to OEO than ATCC 25923 methicillin-susceptible. The in vivo trial was conducted on lactating and non-pregnant cows selected according to their California mastitis test scores. The microbiological analysis was applied for 100 units of raw milk samples collected before and three days after the twice a day topical application of OEO diluted with vegetable oil (5%). Results showed the only presence of total aerobic mesophilic bacteria (TMAB) and coagulase-positive staphylococci (CPS) in all samples with values close to the critical limit. After treatment, a significant decrease (P 0.001) in the mean count of TMAB and a non-significant decrease in the number of CPS (P 0.05) were noted. Results indicate that aromatherapy is a promising approach for improving udder health and raw milk microbiota.