(SA Brahman Society – September 2019)
The recording of Feed Efficiency is relatively new to SA Brahman – official testing for Residual Feed Intake started when the BGP commenced in April 2015.
Residual feed intake (RFI) is a measure of Feed Efficiency, and is defined as the difference between an animal’s actual feed intake and its expected feed intake, based on its size and growth.
Historically, during traditional phase C tests, a range of indexes had been calculated. However informative, these indexes were limited to the groups of tested animals, and could not be compared outside its own contemporary groups. Only much later, around the commencement of the BGP in April 2015, did the ARC API started producing RFI values for these records and from this, where the requirements between phase C and RFI overlapped, prediction equations for RFI had been calculated by Mr. Jurgen Hendriks, post-graduate student and Senior Research Technician from the ARC Animal Production institute.
Currently, the ILR2 registration system in the Brahman Office house the recent RFI test results, generated by the BGP, as well as the historic test information including the newly calculated RFI values.
In August 2019, the first trial EBVs for Net Feed were released to the South African and Namibian Brahman Societies for evaluation. A total of 2665 records were used, contributed by both Societies.
How the tests are done
In South Africa, Calan Gate systems are used by most test centers and utilize the test for post weaning (RFIp). 28 Days of adaptation is followed by 84 days of testing, and animals must be between 180 and 280 days of age at the start of adaptation.
In Namibia, the only test facility currently operational, is a Growsafe system privately implemented by messrs. Mecki Schnneider and Ebbie Fischer. According to Namibian marketing requirements, they use the test for finishing (RFIf). Animals must be between 300 and 400 days of age at the start of adaptation.
An electronic tag identifies the animal every time it feeds and records the amount of feed to the nearest 10 grams.
The start and end weights of the animals are used to calculate a predicted weight, which in turn is used to calculate the expected feed intake, against which the actual feed intake is benchmarked, yielding an RFI (residual feed intake) value for each animal. A positive value implies that the progeny of the animal will eat more than the expected amount per day than the progeny of an animal with a negative RFI value, to produce the same amount of meat.
South African Test facilities
Starting in 2015, test facilities at Cedara, Armoedsvlakte, Irene and Sernick were used to test bulls for RFI. In 2016, semen from a number of local and Australian bulls were used to link the test stations and were distributed between breeders of South Africa as well as Namibia.
At this time, only RFI tests were subsidized by the BGP, while traditional phase C tests were done at breeders’ own cost. In 2019 the facilities at Winter Castles in the Eastern Cape and Bufland in Limpopo were added to the list of test centers, where breeders started testing RFI as well as phase C at own cost.
Input cost vs Information gained
These tests are quite expensive, but is believed to be of considerable economic importance. If a breeder were to test three to five bull calves in a contemporary group, represented by at least two sires, it would suffice to provide at least the sires with NFI EBVs. Every time a new sire is introduced, his progeny should be included in such a test group.
With all factors contributing to production cost, there are only a small number which the producer can control. This trait could be one of that number. Through sound selection practices, it will be possible to gain genetic advantage in Net Feed Intake, as it is moderately heritable.