Читать книгу Bovine Reproduction - Группа авторов - Страница 112

All systems agree that the measurement of SC is a compulsory requirement of the BBSE. Additionally, the systems that provide manuals or accreditation programs (ACV and the SFT) emphasize the importance of correct technique when performing the procedure and provide detailed information on how to obtain reliable measurements. They also highlight the need for adequate practical training to master the skill necessary to obtain repeatable measurements.

The interpretation of the SC measurement varies between regions. The traditional interpretation is based on SFT guidelines, where SC standards are based on bull age, with minimal consideration for breed, body condition, or weight. This is the case for the SFT, South Africa, BCVA, and Canadians utilizing the SFT system. The ACV and WCABP systems introduce more complexity in the interpretation, considering more breed and age categories. An example of how the WCABP system differs from the SFT system is that later maturing breeds such as Limousin, Salers, and Blonde d'Aquitaine have a lower SC threshold of 32 cm at 24 months of age compared to the 34‐cm threshold in the SFT, South African, and BCVA systems. The ACV system also considers body weight at the time of SC measurement, recognizing the effect body weight and body condition have on SC [23]. On this point, the ACV system was unique in that for young sale bulls it emphasized the need to interpret SC measurements considering the relationships between breed, age, and weight. In the ACV manual, there is a detailed table providing this information for five breed‐groups of bulls ranging in age from 12 to 27 months. Consistent with the ACV system moving away from a Pass/Fail approach and more toward a risk assessment paradigm, the SC is simply noted on the top of the report (Figure 7.2), with the veterinary interpretation included in the comments section of the report. The information can still be used by breeders to apply selection pressure, but a low reading does not necessarily result in a fail in that category and the bull may still be suitable for sale for use in a commercial herd if semen assessment and other evaluations meet the standards.

Perhaps the most influence these variations in SC interpretation have on the outcome of the BBSE can be attributed to whether the information is used for a direct assessment of whether the bull is ready to join the breeding herd on a given date or whether the information is being used to leverage fertility selection pressure. In this context, a direct measurement regardless of age, weight, or breed would provide useful information on whether a bull is mature and suitable to be introduced into the breeding herd on a given date. In contrast, if information is to be used to generate accurate selection data, variably referred to as estimated breeding valuations (EBVs) or expected progeny differences (EPDs), then interpretation based on weight, age, and breed become important.

These variations on how the SC information can be used leads to the need to be clear on the purpose for which the BBSE is being performed. The argument could be made that the primary purpose of the BBSE is to determine if an individual bull is suitable for purpose on a specific date. In this instance, a one‐off SC measurement close to the time of entering the breeding herd may be suitable. Conversely, the question is raised of whether it is the role of the veterinarian to fail a bull that is producing semen of acceptable quality if the SC measurement, often taken without important context such as accurate age, breed, weight, and body condition score information, doesn't meet the threshold.