Routine recording of claw health status at claw trimming of dairy cattle has been established in several countries, providing valuable data for genetic evaluation. In this review, we examine issues related to genetic evaluation of claw health; discuss data sources, trait definitions, and data validation procedures; and present a review of genetic parameters, possible indicator traits, and status of genetic and genomic evaluations for claw disorders. Different sources of data and traits can be used to describe claw health. Severe cases of claw disorders can be identified by veterinary diagnoses. Data from lameness and locomotion scoring, activity information from sensors, and feet and leg conformation traits are used as auxiliary traits. The most reliable and comprehensive information is data from regular hoof trimming. In genetic evaluation, claw disorders are usually defined as binary traits, based on whether or not the claw disorder was present (recorded) at least once during a defined time period. The traits can be specific disorders, composite traits, or overall claw health. Data validation and editing criteria are needed to ensure reliable data at the trimmer, herd, animal, and record levels. Different strategies have been chosen, reflecting differences in herd sizes, data structures, management practices, and recording systems among countries. Heritabilities of the most commonly analyzed claw disorders based on data from routine claw trimming were generally low, with ranges of linear model estimates from 0.01 to 0.14, and threshold model estimates from 0.06 to 0.39. Estimated genetic correlations among claw disorders varied from -0.40 to 0.98. The strongest genetic correlations were found among sole hemorrhage (SH), sole ulcer (SU), and white line disease (WL), and between digital/interdigital dermatitis (DD/ID) and heel horn erosion (HHE). Genetic correlations between DD/ID and HHE on the one hand and SH, SU, or WL on the other hand were, in most cases, low. Although some of the studies were based on relatively few records and the estimated genetic parameters had large standard errors, there was, with some exceptions, consistency among studies. Various studies evaluate the potential of various data soureces for use in breeding. The use of hoof trimming data is recommended for maximization of genetic gain, although auxiliary traits, such as locomotion score and some conformation traits, may be valuable for increasing the reliability of genetic evaluations. Routine genetic evaluation of direct claw health has been implemented in the Netherlands (2010); Denmark, Finland, and Sweden (joint Nordic evaluation; 2011); and Norway (2014), and other countries plan to implement evaluations in the near future.

No abstract

29Thin film sandwich structures containing a dielectric layer of silicon monoxide approximately 300 to 1000 ~ thick between gold electrodes show a low frequenc~ negative differential resistance, Figures l-a and l-a'. Hickmott has observed a low frequency negative resistance in a wide variety of sandwich structures l • Figure l-a was obtained after applying for a few cycles a triangular waveform having a frequency of 0.05 cps first increasing the voltage to a maximum value and then decreasing it to zero, etc. This mode of operation will be referred to as normal cycling. Note that the peak current for increasing voltage (Figure l-a) is less than that for decreasing voltage (Figure l-a'). This hysteresis effect is found invariably. The sandwich structures studied were fabricated by conventional vacuum coating techniques using high purity gold for the electrode material. The silicon monoxide was evaporated using a baffled tantalum boat at a rate of about 10 ~/sec. The voltage measurement was made by a four-terminal method to minimize the voltage drop in the electrodes. Removing the voltage at various points in the cycle and reapplying it at either the following or successive points when the voltage is zero, causes a change in the current-voltage characteristic that is different from normal cycling. The change in the characteristic is dependent on the point of voltage removal. It can be seen in Figure l-a (normal cycling) that the voltage for maximum current is about 2.4 volts. Removal voltages, with voltage increasing, of less than 1.5 volts have little effect on the characteristic. Reapplication at successive zero pOints would result in the same characteristic. However, a removal voltage of about 2.4 volts (voltage increasing) with reapplication at the next zero results in a higher initial conductance than normal cycling, for example, Figure l-b. More interestingly,perhaps, a removal voltage that is greater than the voltage for maximum current (voltage increasing) gives an initial conductance that is much lower than that for normal cycling.Furthermore, this characteristic has a definite break. It will also be observed that *Supported by the U. S. Office of Naval Research. Based in part on work submitted by Mr. Nielsen in fulfillment of requirements for an advanced degree.

No abstract

Measurements of power line frequency fields resulting from an alley-on (vertical conductor orientation) high voltage transmission line located approximately 30 ft from the recently occupied New Orleans Corps of Engineers District office building were conducted. Two sets of measurements were made.The first after completion of constructionimmediately preceding occupation and the second approximately a year later with the building in use. The results of these measurements are reported. Field reduction (shielding) properties of the structure are discussed.