Interpretive Summary: Relationship between feed efficiency and slaughter traits of French Charolais bulls.
By: Dr. Thomas Powell
Increasing feed costs have driven the concern about feed efficiency for the world’s beef producers. A recent study reported in the Journal of Animal Science sought to fill gaps in the knowledge base by estimating the genetic parameters for growth, feed efficiency and slaughter traits of young French Charolais bulls. The study was conducted by researchers at the French research institutions of Allice, INRA, and IDELE.
Two generations of French Charolais bulls were used during this long-term study starting in 1979. Data from 4,675 performance tested bulls were available for the study. The generation of 1,466 terminal bulls was produced from 60 of the performance tested bulls selected based on a performance index with 30 high-merit and 30 low-merit bulls identified. 1,427 of the progeny were evaluated for slaughter traits. Three feed efficiency measurements were collected or calculated: Residual feed intake (RFI), feed efficiency (FE) and residual gain (RG). Slaughter traits included carcass yield, carcass composition and the weight of visceral organs.
The most significant conclusion of the study was that it is possible to simultaneously improve growth, feed efficiency and carcass composition. The study showed that feed efficiency is a heritable trait in the French Charolais breed. It singled out RFI as a good candidate for selection since it is possible to select for this trait without having any effects on growth traits. All three of the feed efficiency traits have a positive relationship with carcass composition traits in that more efficient animals were leaner with a greater proportion of muscle. Feed efficiency traits also correlated with a reduction in 5th quarter (the portion of the carcass not used for meat) fat.
Interestingly, two of the efficiency traits (RFI and FE) were strongly associated with several organ traits indicating that selection for RFI and FE may reduce the proportion of visceral organs. The researchers suggest that this may be due to the high energy expenditure associated with the high protein turnover that is typical of visceral organs. If selection for RFI and FE reduces the proportion of these organs, that could translate into more energy available for protein production in other areas of the carcass.
Across this study, all animals were fed the same highly digestible pelleted diet. The next step for this effort will be to identify and investigate potential genotype x environment interactions, particularly with regard to the various feed conditions commonly seen in France beef production.
To view the full article, visit the Journal of Animal Science.