Dr. Chunyan Zhang, PhD, Geneticist, Genesus Inc.
All pig producers will agree, feed is the largest cost of production, accounting for about 55-65% of the total cost. So improvement of feed efficiency has always been a priority in pig breeding and selection programs.
When talking about the feed efficiency, the first measurement comes to many people`s mind would be the feed conversion ratio (FCR: ratio of feed intake to weight gain) which is a simple measure that has been used to improve feed efficiency for many years. But what actually influences feed efficiency selection is more complex.
As a meat producing animal, the direct selection on FCR may result in some undesired responses in terms of growth, health, pork quality, etc. because of underlying correlations between many of these traits. Considering these issues, Genesus has incorporated this thinking into development of its breeding objectives and genetic evaluation which has led to significant improvement of overall pig performance. Let`s explain some reasons below.
Feed intake is a primary factor for growth.
Feed intake levels and patterns differ between pigs in different growth rate. Pigs selected for faster gain exhibit higher feed intake levels compared to those with slow gain potential. A variety of experiments have demonstrated that certain breeds of pigs, notably the Duroc (known for excellent growth rate), have a higher capacity for ad libitum feed intake than other breeds (Whittington et al., 2003).
In general, daily feed intake level is directly related to the respective daily amounts of lean and fat deposited (about 3 to 4 times more energy is required to deposit fat compared to lean tissue) and the efficiencies for utilization of dietary energy for the accretion of body components. So pigs selected for a high lean yield tend to have a lower feed intake. A larger proportion of fat deposition happens in later stage of grow-finishing period which means more feed (energy) is required to maintain the fast growth and yield quality pork.
It is reported that restricted feeding strongly reduces growth rate and carcass fatness and also intramuscular fat level, resulting in decreased meat tenderness or juiciness (Lebret, 2008). The importance of feed consumption and pork quality was discussed previously (http://www.genesus.com/global-tech-report/complex-genetic-relationships/).
Therefore, instead of FCR, we include main feed efficiency components in the routine evaluation for sire lines with aims to improve growth rate, lean yield, meat quality while maintaining good appetite.
Further, good feed intake (appetite) is very helpful for pigs to maintain a reasonable performance under environmental stress or disease challenge. It is well known that pigs exposed to disease respond with reduced feed intake and consequently reduced growth performance (Patience et al., 2015). During a disease challenge, pigs that are mounting an immune response divert critical dietary nutrients away from maintenance and growth to fighting infection. Pigs with a higher feed intake before a disease challenge, even though they will reduce feed intake during the response to the health challenge they will likely perform better and recover sooner than pigs with lower feed intake initially.
Since 2004, Genesus has incorporated individual feed intake recording as part of its genetic improvement program. As a global pig breeding company, Genesus has a systematic breeding program for purebred sire lines which involves weekly genetic EBV evaluation for important economic traits including average daily feed intake, growth rate (days to 120kg), hot carcass weight, backfat depth, loin muscle depth and marbling. Such genetic selection program has led to significant improvement on meat yield efficiency that contributes to customer profitability.
Lebret B. 2008. Effects of feeding and rearing systems on growth, carcass composition and meat quality in pigs. Animal, 2(10):1548-58.
Patience JF et al. 2015. A review of feed efficiency in swine: biology and application. J Anim Sci Biotechnol, 6(1): 33.
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This post was written by Genesus