Failure to Conceive Culling Unproductive Cattle from

146 Beef Breeder MANUAL

5.6. Culling Unproductive Cattle from

the Herd Successful beef breeding enterprises rely on an eicient and productive breeding herd. To achieve this, the cows contributing least productivity to the enterprise need to be identiied and removed. This practice is called ‘culling’. Low or lost productivity during a cow’s breeding lifetime can be summarised as: • Failure to conceive • Failure to produce a live calf • Failure to rear that calf to become a healthy weaner. In cases where the causes of these failures are management-related rather than genetic, culling afected animals will have limited impact on future herd productivity. Therefore, sound principles must be applied before the decision to remove a cow from the breeding herd is made.

5.6.1. Failure to Conceive

In eicient and well-managed beef enterprises, most cows that are identiied as non-pregnant after being exposed to the bull for a reasonable period are culled from the herd. This ensures any infertile or genetically sub-fertile individuals are removed from the herd, and the head manager can make the most eicient use of the pasture available. However, for a cow that has successfully raised a calf previously, failure to conceive may well be due to an unfavourable environment rather than undesirable genetics, and culling her from the herd would achieve little in reducing the likelihood of future failures to conceive, if nothing is done to correct the overriding environmental constraint. Assuming fertile and physically sound bulls, cattle can fail to conceive for a number of reasons: Freemartinism: An infertile heifer as a result of sharing the womb with a male twin. She must be culled once identiied, often only as a non-pregnant heifer at pregnancy diagnosis Other Physiological Problems: Any other inherent problem that may impact negatively on conception or pregnancy. Culling non-pregnant heifers will remove these animals from the herd Infection Inhibiting Conception or Causing Abortion: Individuals known to have been afected by reproductive diseases or bacterial infections should be considered for culling from the herd as their reproductive ability may have been compromised by the infection, or they may be a source of future infection of others Nutritional Anoestrus: When cattle body condition score drops to 1.5 or less, the oestrus cycle often ceases, a situation most common in irst calvers or during periods of severe nutritional stress such as drought. Improving nutrition will overcome this issue and culling afected animals will not beneit the herd Fig. 5.17. 147 Cold Winter Climates Figure 5.17. Relationship between body condition score of cattle at calving and the time taken to return to heat. Cows in poorer condition take longer to cycle after calving, and the efect can be partially overcome by improving nutrition post- calving. Source: Graham, J. 1982 Proc. Aust. Soc. Anim. Prod. 14, 309-12.

5.6.2. Failure to Produce a Live Calf