Very large cows can be difficult to keep in good body condition because of their higher feed demand, and this will reduce fertility. At the lower feed input larger cows are less productive than smaller cows. Breed composition must be managed to maximise hybrid vigour. There are a number of crossbreeding systems which have been applied to beef breeding. The objective of all crossbreeding systems is to optimise the use of hybrid vigour and breed differences.
Hybrid vigour tends to affect reproduction, longevity and disease resistance.
Breed differences control growth rate, mature size and milk production. In practical farming, the value of the hybrid vigour created by different systems needs to be weighed against the management effort required to maintain the system. Mating system Relative weight of calf weaned per Cow served. The savings outlined above are additive.