The repeatability of cow performance in beef cattle

The repeatability of a characteristic has been defined as the degree of likeness of repeated records. This degree of likeness is the correlation between records of the same animal. In this study, the characteristics observed were the birth and 187 day weights and the type and condition grades at weaning for successive calves from the same cows.

The age at which the low producing cow can be determined and culled from the herd is of utmost importance to the breeder of beef cattle. If it is known that the average cow will repeat her calf performance each year with a definite increase in weight at birth and meaning until she reaches a maximum production age, then the low producer can be safely culled after producing one calf and the old cow sold before her decline in calf yield begins.

A majority of the reported observations concerning repeatability of performance has been with range Hereford cows. Although these estimates agree in general with those found in the few studies with eastern herds, a varying amount of disagreement exists and may be due to differences in climate conditions, herd management, and grazing facilities.

The foundation stocks for this herd were mature grade Herefords of unknown ancestry, excluding the purebreds, and in a low nutritional state during the initial phase of this study. It is not known whether these factors, especially the supposed heterogeneous heritage of the cows, would essentially alter the repeatability estimates.

The number of animals and ears of production considered in this study are not extensive enough to give conclusive repeatability figures, but it is hoped that they, when considered with the estimates from other herds, will contribute toward determining an average repeatability figure for beef cattle.