A growing number of farmers are buying-in calves every year and rearing these animals to beef.

Often when buying calves, farmers return home from the mart with a well-matched group of calves of the same age, breed and gender, with virtually identical weights.

Fast forward the clock one year and there is often a significant difference in the weights of the animals in the group, despite all calves getting the same treatment.

It can often be disheartening in a calf-to-beef system to see calves that are not performing as well as they should be, especially when there have been no setbacks, and many farmers ask: ‘Why is this the case?’

Trials at the ABP Demonstration Farm in Co. Carlow, as part of the processor’s Advantage Beef Programme, have shown that the sire used has a significant impact on the progeny’s weight gain, even within breeds.

In the video below, ABP’s agri-sustainability manager, Stephen Connolly, gives an example of two cattle of the same breed and age that have two different sires.

In the video above, the progeny of two different Aberdeen Angus bulls are in the cattle handling facility and the size difference is significant.

Bull A

The first and the larger animal is the progeny of the Aberdeen Angus bull AA5280.

This bull has a calving difficulty of 3.6 on dairy cows and a carcass weight figure of 8.9kg. The average carcass weight figure for Angus bulls is +6kg.

This bull has a Dairy Beef Index (DBI) value of €79, and within its DBI, the sire’s beef sub-index value is €46.

It is essential that farmers look at the sire’s beef sub-index value because that figure reflects the carcass performance, carcass conformation and feed intake.

The Advantage Beef Programme has set a minimum beef sub-index value of €35 for all progeny in the programme from 2023 onwards.

Bull B

The second, smaller animal visible in the handling unit is also an Aberdeen Angus, of the same weight and age as the first animal.

This animal is sired by the bull AA5407. This bull has a calving difficulty of 2.6 and a carcass figure of 1.3kg. The bull’s DBI value is €72 with a beef sub-index value of €25.


Looking at the overall performance on the ABP Demo Farm, the average weight of the progeny from the bull with the higher beef sub-index value is is 434kg.

The average weight of the progeny from the bull with the lower beef sub-index value is 354kg.

Despite both bulls being of the same breed and the calves being of similar ages and getting the same treatment, there is a substantial 80kg/animal difference in the average weight of the progeny from the two sires.

To put this into context, a grouping of 10 calves from the better bull would weigh approximately 800kg more overall than a grouping of 10 calves from the other bull.

Stephen Connolly advised farmers that are buying calves that they intend on rearing for beef production to know the genetics of the bull they are bred off.

The data has shown time and time again that a bull with a higher beef sub-index will lead to better-performing animals.