Bacterial counts on the surface of the teats of cows milked under different methods of udder preparation, including cows milked by hand and stimulated by suckling a calf

摘要

The teat skin is one of the main sources of microbial contamination of raw milk as well as a source of mastitis infection. This study assessed the microbial load of the teat skin following the application of the different practices for preparing the udder, including the use of calf suckling to stimulate the letdown of milk. Thirty-six cows milked by machine were included in one experiment. Two teats of each cow were sampled for bacteriology before and after using one of three methods of udder preparation, as follows: rinsing with water and drying with single paper towels (A); method A plus pre-dipping with an iodine teat dip (4,000ppm) and drying with single paper towels (B); wiping teats using a commercial wet non-woven wipe pre-soaked with a solution containing chlorexidine (C). The second experiment included 16 cows milked by hand. The calf of each cow was allowed to suck the four teats for a few seconds, and then two teats per cow were sampled for bacteriology. Samples were collected before, after calf sucking and following teat pre-milking treatment (as for group C, above). Statistical analysis was conducted on transformed (log10) data with tTBC=log10(TBC+0.5) using a Kruskal-Wallis test. Each treatment was analysed considering the difference in tTBC after the use of either method of preparation of the udder or calf sucking. For groups A, B and C (first experiment), tTBC values were reduced 1.8, 2.2 and 2.4, respectively. In the second experiment, tTBC increased significantly (P0,05) after calf sucking (from 3.2 to 4.3). After disinfection the tTBC was significantly reduced to 2.0. These results show that: (a) teat rinsing with water and wiping dry reduces the number of microorganisms on the teat skin, but the reduction is significantly higher when teats are disinfected; (b) calf sucking before milking increases significantly the number of microorganisms on teat skin; (c) the number of microorganisms on teat skin can be reduced more than 10 times after calf sucking if teats are disinfected. Very low numbers or no growth of coliforms were observed in all cases.