SA Stud Book News | Expansion of the genetic merit for growth

Expansion of the genetic merit for growth efficiency for beef cattle.  Go Back

Due to continued research and development by SA Stud Book, stud breeders and buyers of stud beef cattle now have a wider choice of traits to use for selecting animals to use as parents in their herds. The genetic merit for growth and feed efficiency now include three new traits for which breeding values were not previously available in South Africa. The new breeding values are for residual feed intake (RFI), residual gain (RG) and residual feed utilisation (RFU). These new traits will complement the existing traits for which genetic merit (BLUP breeding values) are available. Stud Book’s selection values for cow and growth efficiency, that take profitability of beef production into account, rank potential selection candidates on genetic merit, according to specific production systems and the role a specific breed plays in them. Profitability is defined as the income, based on output and product price, given that input costs are accounted for.

Residual feed intake (RFI), residual gain (RG) and ultimately, residual feed utilisation (RFU) are defined as the growth efficiency performance of an animal as deviation from its “expected” performance, given its daily feed intake. For example, RFI, as a phenotypic measurement, is the deviation from its expected intake needed for maintenance, based on its live weight and growth rate.

By adding residual gain (RG) and residual feed utilisation (RFU), the limitations of residual feed intake (RFI) as sole selection criteria, are addressed.

The availability of these new breeding values is not limited to breeds with large numbers. Breeds, such as the South African Braunvieh, actively taking part in growth tests for young bulls where intake is recorded, are now also included in this exciting development. Breeders and buyers of Braunvieh cattle now share in the advantages offered by these BLUP breeding values, including RFI, RG and RFU. The breeding values will be published on the Logix Web site and will soon also be available on

The scientific foundation, models and genetic parameters associated with these developments will be presented as a scientific paper by Dr Bobbie van der Westhuizen at the forthcoming conference of the South African Society for Animal Science to be held from 18 to 21 September 2017 in Port Elizabeth..

Japie van der Westhuizen
Acting General Manager: SA Stud Book
25 August 2017


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