This breeding value is known as residual feed intake (RFI) and is a measure of feed conversion efficiency.
DairyNZ and LIC research has demonstrated that it is possible to select animals that are more efficient at using feed for body maintenance gain or milksolids production.
Breeding Worth (BW) measures an animal’s total feed conversion efficiency over a lifetime by selecting for the combined effect of producing more milksolids per kg of liveweight, living longer and calving earlier.
By contrast, RFI – which is the difference between predicted feed intake and actual feed intake on a daily basis, is about an animal generating the maximum performance out of a unit of feed consumed.
If a cow consumes 1kg DM (dry matter) less per day for the same level of milksolids production, this saves farmers $85 per year in feed costs for a single cow.
New Zealand Animal Evaluation Limited (NZAEL) manager, Dr Jeremy Bryant says investigations have shown there is economic justification for pursuing RFI as a new trait for BW.
“However, there are still some unanswered questions before we can make definitive conclusions and include RFI in BW,” says Jeremy.
Next research steps
DairyNZ, LIC and CRV Ambreed are investigating a future performance test approach which would involve having bulls in pens for about six weeks and measuring their feed intake and liveweight. From that, RFI breeding values can be estimated.
Jeremy says first they are establishing a group of male and female siblings from common sires and will RFI test them to determine if there is a genetic relationship between males and females. If the relationship is strong enough, i.e. efficiency improvements in bulls are shown in females, then RFI performance testing bulls is justified.
The testing will also involve taking thermal images from an existing population of low and high RFI animals to assess the relationship between heat loss and RFI.
Depending on the results, from 2017, young, elite bulls of breeding companies might be routinely RFI tested and RFI might be included in BW or produced as a stand-alone trait.
The resulting RFI breeding value would allow breeding companies and farmers to more accurately select the most genetically elite animals that maximise farm profit.
What will the research reveal?
- If it is feasable to perfomance test bulls beyond the research phase.
- If the relationship between bull RFI and female RFI is strong enough to translate RFI in bulls to cows.
- If there are other predictors of efficiency that could be routinely measured in commercial or progeny test herds. For example, does more heat loss indicate inefficiency?
This project is funded by dairy farmers through DairyNZ and by the Ministry for Primary Industries as part of the Transforming the Dairy Value Chain Primary Growth Partnership programme.
This article was originally published in Inside Dairy October 2015