Target 10 Communicator
January 2011 Edition
IMPROVING FEED CONVERSION EFFICIENCY THROUGH GENETIC MARKERS
Melissa Spain, DPI Echuca
Blood testing calves to work out their feed conversion efficiency may become common practice for dairy farmers according to the latest research conducted by Department of Primary Industries (DPI) Biosciences and Future Farming Systems Research Divisions.
Some animals are more efficient at converting feed (kilograms of dry matter intake) into live weight (kilograms), meaning they require less feed for maintenance and production compared to the rest of the population. The research, conducted at Rutherglen investigates the genetic and physiological traits that are common between more feed efficient dairy heifers.
The project focuses on metabolic feed efficiency, which is the net feed an animal consumes adjusted for its requirements for maintenance and production. The metabolic feed conversion efficiency is based on a measure known as the Residual Feed Intake (RFI). The RFI is the difference between the predicted feed intake for an animal based on its body size and production level, and the amount that the animal actually consumes.
The trial commenced at the DPI feeding facility at Rutherglen where over 900 calves in three batches, were weighed on a regular basis and dry matter intake for each calf was recorded daily via an electronic feed recording system. From the feeding trial, animals were selected based on phenotypical data; how the animals grew based on feed intake and live weight gain.
Project results have shown that there are significant differences between the most efficient group of heifers and the least efficient heifers. The animals containing a higher RFI (10 per cent) and lower RFI (10 per cent) of the sample population have been selected for further study. Calves with the lowest RFI values are the most efficient at converting feed into live weight; they consumed 1.6 kilograms DM less than 10 per cent of calves with the highest RFI values for the same amount of live weight gain.
All animals that participated in the phenotypical study (RFI) will now have their DNA mapped to investigate the differences between their DNA sequences. From the trial 120 calves have been purchased, 60 of these are from the 10 per cent of the lowest RFI animals and the other 60 are from the 10 per cent of animals which have a high RFI.
These animals are the ones of the most interest as they are at the two ends of the population spectrum. Investigation into the subtle differences between the DNA markers and sequences will allow researchers to match up a genetic profile to feed conversion efficiency DNA combinations.
The research has shown that RFI genes for feed conversion efficiency are inheritable which suggests that in the future bulls will be able to be selected based on this trait, provided its economic value is large enough to impact on sire rankings.
This feed conversion efficiency trail has various phases still to be completed, phase one looked at which phenological animals out perform their peers (Calf rearing trial, Rutherglen), the next phase will map the genetic profile of DNA markers within these animals to identify the subtle differences and similarities between the sequences. Once this is completed the link between feed conversion efficiency and milk production will be explored through a milking cow trail to see if higher feed conversion efficient cows come from the high feed conversion efficient calf population.
Using the DNA markers it is possible to predict RFI with moderate accuracy. This is more than double the accuracy of pedigree alone. In the future, farmers will be able to blood test calves at birth or a few days old to genetically determine if they have the DNA markers for high feed conversion efficiency. This will allow farmers to make better informed decisions about which replacement heifers they invest money in.
For more information about the research project contact Bill Wales from the Future Farming Research Division on (03) 5624 2227 or email bill.wales@dpi.vic.gov.au or Ben Hayes from Biosciences Research Division on (03) 9032 7013 or email ben.hayes@dpi.vic.gov.au
