Agri Kultuur January / January 2018 | Page 29

100 days after calving), 200-day-not-in-calf rate (the percentage of cows not pregnant within 200 days after calving). The drivers of these rates are: the 80-day submission rate (the percentage of cows that have been inseminated by 80 days after calving and the conception rate (the inverse of the number of services per conception). A similar first South African survey was conducted using about 69 000 service records in 24 640 lactations from 9 046 cows in 14 Holstein herds. Using calving dates and service records of cows, the following fertility traits were derived, i.e. the intervals calving to first service (CFS) and days open (DO), services per conception (SPC) and whether cows were inseminated before 80 days post partum (FS80d), whether cows were confirmed pregnant before 100 (Preg100d), and 200 days post partum (Preg200d). In Table 1 the level of reproduction management of these herds is compared to the Australian InCalf survey guidelines. Table 1. The mean and standard deviation (SD) of fertility traits of Holstein cows in 14 herds in comparison to InCalf guidelines (DIM: days in milk) InCalf guidelines Traits Calving to first service (days) First service befor e 80 DIM (%) Services per conception Days open (days) Cows pregnant before 100 DIM (%) Cows pregnant before 200 DIM (%) Mean 77 64 2.55 134 36 71 Cows became pregnant in 85% of lactations. Although average values for traits may be acceptable from a management point of view, large variations were observed, i.e. coefficients of variation for CFS and SPC were 39 and 70%, respectively. The mean interval for CFS was 77 days, but only 64% of first services occurred within 80 days after calving. The Australian survey indicated that 73% of cows are serviced for the first time within 80 days after calving by good managers. The DO interval was high and variable, being 134±74 days. Only in 36 and 71% of all lactations were cows confirmed pregnant within 100 and 200 days postpartum, respectively. With the exception of the percentage of first services within 80 days after calving, the means for the different fertility traits were lower than the values indicated in the “seek advice” column for Australian dairy farmers. Based on these values, the average standard of reproduction management is SD 30 48 1.79 74 48 45 Good Seek managers - 73 1.96 - 58 87 advice - <61 >2.32 - <43 <81 poor; however, variations between herds were observed indicating the effect of managers on the reproductive performance of dairy herds. The effect of farm personnel responsible for heat detection and/or artificial insemination is also included here. The effect of herd and calving year on the interval traits CFS and DO is presented in Figure 1. Large differences were found between herds, i.e. minimum and maximum intervals were 75 and 142 days for CFS and 115 and 185 days for DO, respectively. From 1991 to 1994, CFS interval increased by 3.5 days per year. From 1995 onwards, the interval CFS did not show an annual change probably indicating that herd managers were not able to improve this trait or that this level of reproductive performance was accepted. Similarly, the interval DO increased from 127 days in 1991 to 153 days in 2006. Results suggest that farmers seem to have adopted