Influence of age on the performance of beef cows

A sample of 30.102 calvings in the years 2003 and 2004 allowed for analysing the structure of the population and the potential of suckler cows in the German region of Brandenburg. The structure of the population showed a high proportion of elder cows with more than six calvings (23 percent). As a result only a very small reproduction rate was needed in order to keep the population size. Regarding the calves' weight gain per living day as an indicator for the productive performance of the suckler cows, significant differences were found for cows with different numbers of calvings. The highest gains could be detected for cows with 3 to 6 calvings. The still birth rate for the first calf is twice as high as for the consecutive calvings. The physiology-related increase in the performance of the suckler cows was determined on the basis of a LSQ estimation controlling for the farm, race, quarter of the year when birth took place and age of the mother when the first calving took place. As a result it showed that from the first up to the fifth calving the weight gain performance of the calves increased about 15 percent. The age-related increase in the performance of the suckler cows was strongly determined by the age when the first calving occurred. For cows with an early first calving the increase of performance between first and fifth calving was 20 percent. Cows with a higher age of first calving showed a significantly lower enhancement of only 8 percent. The time between calvings decreased with increasing age of the suckler cows. Hence, the assessment of productive and reproductive performances of suckler cows requires consideration of the number of calvings and the age of the first calving. Nevertheless, the relation between the performance and the structure of the population needs to be taken into account when the population's productivity shall be evaluated.