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Understanding Days to Calving EBVs

Reproductive performance is a key determinant of profitability in a beef cattle enterprise. Consequently, selection for improved reproductive performance should be an important consideration for all beef cattle producers.

One major component influencing a beef enterprise’s reproductive performance is the fertility of the female herd. The job of a female in a beef producing herd is to conceive, preferably as early in the joining period as possible, carry a foetus during gestation, deliver a live calf and raise it until weaning within every 12-month period of her breeding life. A female that does not do this is failing to do her job and eroding herd profitability.

While many producers manage the reproductive performance of their female herd using different management strategies, in particular the culling of females that fail to get in calf, research has shown that female fertility is influenced by the genetics of the breeding herd. Consequently, Days to Calving EBVs provide a useful tool that breeders can use to improve the genetics of their females for fertility, in association with their routine management and culling strategies.

Interpreting Days to Calving EBVs

Days to Calving EBVs are estimates of genetic differences between animals in the time from the start of the joining period (i.e. when the female is introduced to a bull) until subsequent calving. Days to Calving EBVs are expressed in days and are calculated from the joining records submitted for both heifers and mature cows.

The Days to Calving EBV promotes cows that calve earlier in the season compared to those that calve later, while penalising cows that do not calve. Variation in days to calving is mainly due to differences in the time taken for females to conceive after the commencement of the joining period.

Lower, or more negative, Days to Calving EBVs are generally more favourable. For example, a bull with a Days to Calving EBV of -5 days would be expected to produce daughters that conceive earlier in the joining period than the daughters of a bull with a Days to Calving EBV of +5 days. Females with shorter Days to Calving EBVs also tend to be those that show early puberty as heifers and return to oestrous earlier after calving.

For more information regarding Days to Calving EBVs, please contact staff at your BREEDPLAN processing centre.