Effect of an automated dipping and backflushing system on somatic cell counts.

Postmilking teat disinfection is an effective management practice to prevent transmission of contagious mastitis pathogens from cow to cow. With farms increasing in size and an increase in the number of rotary milking parlors, the need for automation of postmilking teat disinfection is mounting. Automated teat dipping and backflushing (ADB) systems have existed for some years, but their effect on udder health was never examined in a field study on commercial dairy farms. The objectives of this study were, therefore, to evaluate the effect of introducing an ADB system in a herd on (1) bulk milk somatic cell count (SCC), (2) individual cow SCC, and (3) the proportion of newly elevated SCC. Dairy herd improvement data were collected over a 30-mo period on 25 sets of 3 farms. Each set of 3 farms contained a farm that installed an ADB system, one that disinfected teats using dipping after milking, and one that sprayed teats after milking. Data were analyzed using linear mixed models. Bulk milk SCC on farms that sprayed or dipped before installing an ADB system were 16,000 and 30,000 cells/mL lower in the period 6 to 18 mo after installation, respectively, than on farms that continued spraying or dipping the teats after milking. In the same period after installing an ADB system, proportions of cows with elevated SCC were 4.3 and 1.2% lower, respectively, compared with spraying and with dipping. Similarly, proportions of cows that had newly elevated SCC were 1.5% lower and 0.3% higher, respectively, compared with farms that sprayed or dipped. Installing an ADB system had a beneficial effect on bulk milk SCC, individual cow SCC, and the proportion of newly elevated SCC. The effect was most prominent in the period 6 to 18 mo after installation of an ADB system.

Underwater audiogram of a Pacific walrus (Odobenus rosmarus divergens) measured with narrow-band frequency-modulated signals.

The underwater hearing sensitivity of an 18-year-old male Pacific walrus was measured in a pool by using a go/no-go response paradigm and the up-down staircase method. Auditory sensitivity was measured using narrow-band, frequency-modulated signals (1500 ms duration) with center frequencies ranging from 0.125 to 15 kHz. The resulting underwater audiogram (50% detection thresholds) for this individual walrus shows the typical mammalian U-shape. Maximum sensitivity (67 dB re 1 microPa) occurred at 12 kHz. The range of best hearing (10 dB from the maximum sensitivity) was from 1 to 12 kHz. Sensitivity fell gradually below 1 kHz and dropped off sharply above 12 kHz. The animal showed a peculiar insensitivity for 2 kHz signals. His much higher sensitivity for 1.5- and 3-kHz signals indicated that this is a narrow-band phenomenon. Walrus hearing is relatively sensitive to low frequency sound, thus the species is likely to be susceptible to anthropogenic noise. The thresholds found during a small test with four frequencies with signal durations of 300 ms did not differ significantly from those obtained with signal durations of 1500 ms.