The primary objective was to compare reported antimicrobial usage between conventional and organic dairy farms. A secondary objective was to contrast selected management characteristics of conventional and organic dairy herds. A questionnaire was administered on site to selected dairy farmers located in Michigan, Minnesota, New York, and Wisconsin. Organic herds (n = 32) were smaller and produced less milk than conventional herds (n = 99). Lactating cows in organic dairies were more likely to be housed in tie stalls, whereas most conventional dairies housed cows in free stalls and milked in a parlor. Total mixed rations and purchased feeds were used on more conventional dairy farms compared with organic dairy farms. Conventional dairy producers were more likely to use advice from veterinarians for recommendations of treatment, and organic dairy producers were more likely to rely on advice from other farmers. Based on recall of antibiotic usage in the previous 60 d, 5.1, 84.9, 9.1, and 0.9% of farmers with conventional herds reported treatment of none, 1 to 10%, 11 to 25%, and >25% of milk cows, respectively. Most organic farmers (90.6%) reported no antibiotic treatments of milk cows, whereas 9.4% reported treating 1 to 10% of milk cows. Ceftiofur was the most commonly reported antibiotic for both farm types. Milk replacer containing antibiotics was reportedly used on 49.5% of conventional herds but only on one organic herd (3.1%). Antibiotics were used in heifer calves on 74.7% of conventional herds versus 21.9% of organic herds. Antibiotics to treat mastitis were used on 79.8% of conventional herds but on none of the organic herds. Most organic farms were in compliance with standards in advance of implementation of regulations.

Salmonella spp were isolated from > 90% of dairy farms; however, 25% of farms accounted for > 75% of Salmonella-positive samples. This information is critical for the direction of intervention strategies to decrease the prevalence of Salmonella spp on dairy farms.

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Starch particle size characteristics of 81 diverse corn silage samples, which included 27 combinations of hybrid, planting dates, and harvest dates subjected to 3 different degrees of kernel processing, were determined via vertical shaking through 9 screens with nominal square apertures of 19.0, 13.2, 9.5, 6.7, 4.75, 3.35, 2.36, 1.18, and 0.6 mm and a pan. Starch content of dry matter remaining on each screen and on the pan for each corn silage was determined, and geometric mean particle size (GMPS, mum), starch particles(SP)/g, starch surface area (SSA, cm(2)/g), kernel processing score (KPS), % starch < 4.75 mm, and the percentage of total starch remaining on each screen of the vertical shakers were calculated. Near-infrared reflectance spectra were obtained by scanning 3 types of samples: 1 mm of dried ground corn silage; whole undried, unground corn silage; and undried, unground corn silage that passed through a 19-mm screen. Calibrations to predict GMPS, SP, SSA, and KPS characteristics of corn silage starch were attempted from each spectral origin. Calibrations to predict GMPS, SP, SSA, KPS, and the percentage of total starch retained on screens of the vertical shaker was unattainable (R(2) < 0.45) using spectra obtained from 1 mm of dried ground corn silage or whole undried, unground corn silage. However, reasonable near-infrared reflectance spectra equations (R(2) > 0.81) for GMPS, SSA, and KPS were attained using spectra from undried, unground corn silage that passed through a 19-mm screen. This technique holds promise as a rapid and efficient method to determine particle size characteristics of starch within corn silage.