Download Fundamentals of Feed Efficiency

Symposium: Fundamentals of Feed Efficiency: Animal to Genome
17
Feed efficiency in the real world: An industry perspective. K.
Christensen*, OK Foods Inc., Fort Smith, AR.
The measurement of feed efficiency in the broiler industry is one of pri­
mary measurements used to monitor and evaluate broiler performance.
It has a significant impact on the competitiveness in the marketplace as
nearly 70% of the cost of raising a commercial broiler is feed. Although
feed costs may shift up or down, it will always represent the highest input
cost in commercial poultry production. Feed efficiency has improved
dramatically since the establishment of the commercial chicken busi­
ness. Due to significant improvements primarily in genetic selection and
nutrition, growth rates have increased (resulting in higher body weights
in fewer growth days) as has feed efficiency. Market weights of broilers
have nearly doubled while feed conversions have dropped 20 points
or more. Feed costs, however, have steadily increased the past several
years due to supply, export pressure and the production of ethanol from
corn. The loss of certain feed additives traditionally used to support
feed conversion and a small but increasing interest by consumers to
purchase chickens raised without antibiotics have resulted in an industry
wide loss of efficiency and added to production costs. Although feed
efficiency will continue to improve through genetic selection, nutrition
and management, an effort to develop new strategies to manage produc­
tion efficiency that may focus on intestinal physiology (e.g., lowering
intestinal inflammation, manipulating microbial environment or even
at the cellular level) is the new frontier that will bring technologies to
further improve production efficiency in the poultry industry.
Key Words: feed efficiency, poultry industry, gut health
18
Impact of gastrointestinal ecology on feed efficiency. G.
Tellez*, University of Arkansas, Fayetteville.
The fields of immunology, neuroendocrinology, microbiology, nutrition
and metabolism are rapidly converging. The gastrointestinal tract (GIT)
is not only the largest immune and endocrine organ; the enteric nervous
system contains more neurons than the periphery nervous system. The
GIT also represents the greatest exposed surface to environmental fac­
tors (e.g., food, feed ingredients, microbes). However, a wide range of
factors associated with diet and infectious disease agents can negatively
affect the delicate balance among the components of the chicken gut
and, as a result, affect health status and production performance of birds
in commercial poultry operations. The surface of the GIT mucosa is not
a static barrier that simply prevents microbial invasion but a critical
interface for microbiota–immune system interactions. The impact on
gut health often comes from microbial imbalance in the gut, because this
microbiota affects host nutrition, protection, and gut development. Any
gut damage caused by pathogens will also lead to poor gut health, which
will, in turn, affect nutrient utilization efficiency. Subclinical forms of
infection with no obvious signs of lesions such as Coccidiosis or Necrotic
enteritis are often financially more devastating than acute, short-term
infections. Likewise, dietary factors that modulate the immune system
and gut microbiota should be considered when formulating diets and
managing feeding practices. Marked changes in socio-economic status,
cultural traditions, population growth and agriculture are affecting diets
worldwide for humans and animal production. Understanding how
diet ingredients and nutritional status influence the composition and
dynamic operations of gut microbial communities, and the innate and
adaptive arms of the immune system, represents an area of scientific
need, opportunity and challenge. This review focuses on intestinal
6
microbiota–immune interactions leading to intestinal homeostasis,
and show that these interactions at the GIT mucosal surface are critical
for driving not only for feed efficiency but also for both protective and
pathological immune responses systemically.
Key Words: gut health, inflammation, microbiota, feed efficiency
19
Nutrigenomics applications to feed efficiency and nutrient
utilization. S. E. Aggrey*1, F. González-Cerón1, J. Lee1, A. B. Kar­
nuah1, and R. Rekaya2, 1Department of Poultry Science, University of
Georgia, Athens, 2Department of Animal and Dairy Science, Univer­
sity of Georgia, Athens.
Gene expression profiles of feed efficiency phenotypes in chicken
are generally unknown. We have studied the global and targeted gene
expression differences in 2 chicken populations divergently selected
for low (LRFI) or high (HRFI) residual feed intake (RFI) at d 35 and
42. Using duodenal tissue, a global view of gene expression differences
between LRFI and HRFI suggested that RFI can be explained by dif­
ferences in cell division, growth, proliferation and apoptosis, protein
synthesis and lipid metabolism. Chickens selected for improved RFI
achieve efficiency by reducing feed intake with no change in weight
gain upregulating CD36, PPARα, HMGCS2, GCG and downregulat­
ing PCSK2, CALB1, SAT1 and SGK1. Further, the avian target of
rapamycin (avTOR) pathway was upregulated in LRFI at both ages
compared with the HRFI. Other differentially expressed genes at d 35
include AKT, EEF2, EIF4EBP1, PDK1, RPS6KP1, MLST8, GHRL,
PI3K, FOXO1 and MDM2. At d 42, there was no change in expression
of avTOR target RPS6KP1 and MDM2. There was a positive correlation
between RFI and fecal nitrogen (N). The purine salvage pathway was
activated in the LRFI compared with HRFI at d 42. To maintain growth
in the LRFI birds, excess N was deaminated mostly to generate purine
nucleotides. Generating purine nucleotides primarily from the purine
biosynthesis pathway is energetically costly, and to preserve energy, they
preferentially generate nucleotides from the purine salvage pathway. The
LRFI birds need to generate sufficient nucleotides to maintain growth
despite reduced FI then results in reduced fecal N.
Key Words: gene expression, avTOR, nitrogen recycling, divergent
selection
20
Role of mitochondria in feed efficiency; bioenergetics, genes,
and proteins. W. G. Bottje* and B.-W. Kong, University of Arkansas,
Fayetteville.
With severe drought in 2012, diversion of grain to ethanol production,
and greater global demand for grain, feed efficiency (FE) remains an
important genetic trait in animal agriculture. There are many factors
(e.g., genetics, environmental, nutrition, management, behavioral)
that impact feed efficiency. A major biological component of FE are
mitochondria (physiology, biochemistry) that have been linked to FE
in several animal species. Global gene expression studies conducted in
breast muscle in a male broiler line indicate that a high FE broiler phe­
notype exhibited upregulation of anabolic, energy sensing and energy
coordination genes, and downregulation of cytoskeletal architecture
genes compared with a low FE broiler phenotype. A hallmark of low
FE is greater oxidative stress that includes higher mitochondrial reac­
tive oxygen species (ROS) production, extensive protein damage, and
upregulation of stress responsive genes (e.g., heat shock proteins [HSPs]
Poult. Sci. 92(E-Suppl. 1)
and superoxide dismutase). Certain HSPs (e.g., HSP90, crystalline α B,
ubiquitin specific peptidase 5) that were upregulated in breast muscle
in the low FE broiler phenotype are reported to stabilize misfolded or
damaged proteins. Ubiquitin specific peptidase 5 is associated with
protein ubiquitination that functions to repair damaged proteins, or in
recycling of amino acids following hydrolysis in proteosomes. Ubiquiti­
nation and proteolysis are energetically expensive processes that require
considerable ATP expenditure from input for protein synthesis and then
for protein ubiquitination and degradation. Possibly, additional energy
expenditure required for protein repair contributes to development of
low FE. The underlying cause of higher mitochondrial ROS production
that is a likely cause of greater protein oxidation is not known but may
represent an important component in poor feed efficiency. We suggest
that identifying and ‘fixing’ this problem could help in the ongoing
improvements of feed efficiency being made in animal agriculture.
Key Words: feed efficiency, gene expression, mitochondria, protein
21
Understanding the physiological basis of residual feed intake
and feed efficiency. N. K. Gabler*, J. F. Patience, J. C. M. Dekkers,
and S. M. Lonergan, Department of Animal Sciences, Iowa State Uni­
versity, Ames.
Improving feed efficiency (FE) of meat production livestock is an
important goal for sustainability and profitability. This must be achieved
Poult. Sci. 92(E-Suppl. 1)
without compromising growth rate and meat quality. Compared with
growth and development, our understanding of the molecular biology
and physiology regulating feed efficiency (FE) is relatively limited. In
recent years, this understanding has been enhanced through the study of
residual feed intake (RFI) in selection experiments. RFI is a measure of
FE that is calculated by determining the difference between an individual
animal’s observed and its expected feed intake based on performance.
Therefore, animals with low RFI are more FE than animals with a
high RFI. The main biological factors that contribute to differences in
RFI may include physical activity, feed intake patterns and behavior,
stress, nutrient digestibility and efficiency of utilization, composition
of gain and metabolism. Results from our lines of pigs that have been
divergently selected for high versus low RFI show that changes in body
composition explain some of the variation observed in RFI divergence.
Molecular and physiological explanations for the observed differences
in response to divergent selection based on RFI in pigs will be explored.
Data that support the hypothesis that a significant part of RFI differ­
ences may be related to protein turnover and degradation rates will be
presented. These differences could be linked to mitochondrial function
and oxidative stress in muscle and liver tissues. This work was sup­
ported by USDA-AFRI Competitive Grant #2010–65206–20670 and
#2011–68004–30336.
Key Words: swine, residual feed intake, feed efficiency, mitochondria
7