The single most important problem limiting high reproductive efficiency in the national dairy herd is poor detection of estrus. Failure to detect estrus or erroneous diagnosis of estrus results in an estimated annual loss of over $300 million to the dairy industry in the US. New technologies for the solution of this problem must be more effective than visual observation and aids currently used to detect estrus. Ideally, technologies that provide the solution for detection problems should provide the following: continuous (24 h/d) surveillance of the cow, accurate and automatic identification of cows in estrus, operation for the productive lifetime of the cow, minimized labor requirements, and high accuracy in identifying the appropriate physiologic or behavioral events that correlate highly with ovulation. New approaches are aimed at providing automation of detection of estrus using electronic technology. Pedometry, implantable impedance sensors, and surface-applied and implantable pressure sensors are in various stages of development and use.

: Living and dead spermatozoa were examined for the effects of sperm concentration level on sperm viability. Semen was collected from two different bulls on each of four collection dates. A ninth bull was collected on all four collection dates as a control for effects of collection date. The ejaculates from these nine bulls were diluted to 30 × 106 spermatozoa/0.5 ml and then serially diluted to 20, 10, 5, or 1 × 106 spermatozoa/0.5 ml French straw. One‐half of the straws for each dilution series was stored 24 hours at 5° C, while the other half was cryopreserved. Spermatozoa were stained with SYBR‐14 and propidium iodide (PI) to assess viability. Flow cytometry yielded dot plots showing three distinct sperm populations: dead red‐stained spermatozoa (PI), viable green‐stained spermatozoa (SYBR‐14), and moribund spermatozoa that stained both red and green (doubly‐stained). Populations were expressed and analyzed in terms of mean percentage of viable spermatozoa and by actual numbers of viable spermatozoa per insemination dose. The mean percentage of living spermatozoa decreased linearly with decreasing sperm concentration; whereas the decrease was parabolic when those same samples were expressed as the mean number of living spermatozoa per insemination dose. The percentage of SYBR‐14‐stained spermatozoa differed among concentration levels and among bulls (P < 0.01). There were no differences among straws from the same ejaculate. The total volume of ejaculated semen and the concentration of spermatozoa in that ejaculate were both significantly positively correlated with the percentage of SYBR‐14‐stained spermatozoa in that semen when it was cryopreserved and diluted to <10 × 106 spermatozoa/0.5 ml. In contrast, there were no significant correlations between the initial ejaculate characteristics and the proportion of SYBR‐14‐stained spermatozoa in the 24‐hour‐stored samples at any concentration. In conclusion, the percentage of viable spermatozoa in an ejaculate significantly decreased with increasing dilution. Further, in cryopreserved samples, the percentage of living spermatozoa <10 × 106 spermatozoa/0.5 ml depended on the original volume and the sperm concentration of that particular ejaculate.

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Effects of management and environmental factors on reproductive performance were evaluated as part of a fertility experiment in four large commercial dairy herds. The herds were selected because they utilized routine herd health programs, kept complete reproduction records on all cows, were enrolled in Dairy Herd Improvement, and would follow the protocol of the experiment. Only data from first services following parturition were utilized, and conception was determined by rectal palpation. Information on over 2800 experimental breedings was collected during 13 mo. Percentage conception to first service was not affected by milk production during current or previous lactations. However, cows with higher production during current or previous lactations. However, cows with higher production during current or previous lactation had longer intervals to first service. Previous days dry did not affect conception or interval to first service significantly. Conception was less for cows with less than 50 days to first service (32%) than for cows with over 50 days to first service (49 to 57%). No differences were found among 10-day intervals to first service of over 50 days. Cows in third and later lactation had lower reproductive performance than cows in first or second lactation. Month of breeding did not affect conception significantly but did affect interval to first service. However, no seasonal trends were apparent. Differences among herds were significant for both conception and interval to first service.

The right testis of 9 anaesthetized rams was removed from the parietal tunica vaginalis and replaced by a surrogate testis (water-filled balloon) through which water of known temperature was circulated. Thermistors were inserted in the surrogate testis, between the scrotal skin and parietal tunica vaginalis on the right side, and deep within the intact left testis. Scrotal surface temperatures over the surrogate and intact testes were measured by infrared thermography. Scrotal surface temperature was correlated (P less than 0.01) with both subcutaneous (r = 0.95) and surrogate (r = 0.91) testicular temperature. The temperature differential between scrotal surface (30.1 +/- 0.1 degrees C) and deep testicular temperature over the intact side (34.9 +/- 0.09 degrees C) was 4.8 degrees C at an ambient temperature between 24.0 and 26.6 degrees C. Contact with the scrotal skin is not required to measure scrotal surface temperature by infrared thermography. This, coupled with the close association between scrotal surface temperature and that of underlying structures, will enhance our ability to understand better testicular temperature regulation and scrotal/testicular function.