Gordon%20Carstens%20and%20Luis%20Tedeschi

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Defining Feed Efficiency in Beef Cattle
Gordon Carstens and Luis Tedeschi Department of
Animal Science Texas AM University
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Projected global meat production (2001 to
2025)Thomas E. Elam (Feedstuffs, 2004)
Projected world demand for meat will increase 55
by 2025
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Importance of feed efficiency to meet global meat
demands

• Crop yields (33) and feed conversions (15-20)
  will need to increase significantly over the next
  20 years to meet global meat demands in an
  economical and environmentally sustainable
  manner
• We will need to continue to develop tools and
  technologies our producers need to increase
  production through increased efficiency of
  resource use

Thomas E. Elam (Feedstuffs, 2004)
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New technologies available to facilitate
selection for improved feed efficiency

• New feed efficiency traits that facilitate
  selection for improved efficiency independent of
  growth traits
• Innovative RFID-based technology to
  cost-effectively measure feed intake, growth,
  feeding behavior traits in cattle
• Discovery and validation of genetic markers that
  are linked to feed efficiency to facilitate gene
  marker-assisted selection

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Attributes of an ideal feed efficiency trait for
use in genetic selection programs

• Ideal feed efficiency trait for post-weaning
  bulls
• heritable and responds to selection
• independent of growth and mature size
• minimal genetic antagonisms with other
  economically relevant traits (e.g., carcass,
  milk, fertility)
• reflect differences in cow efficiency
• linked in biologically relevant traits associated
  with efficiency of feed utilization (e.g.,
  digestibility, heat production)

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Ratio-based feed efficiency traits--defined

• Gross feed efficiency ratio of live-weight gain
  to dry matter feed intake (DMI)
• Feed conversion ratio (FCR) DMI to gain ratio
• FCR is a gross efficiency measurement of
  efficiency in that it does not attempt to
  partition feed inputs into portions needed to
  support maintenance and growth requirements

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Ratio-based feed efficiency traits

• Feedgain ratio is negatively correlated with
• Postweaning ADG (rg -0.67 Koots et al., 1994)
• Yearling BW (rg -0.60 Koots et al., 1994)
• Cow mature size (rg -0.54 Archer et al., 2002)
• Selection for lower feedgain ratio (improved
  efficiency) will indirectly
• Increase genetic merit for growth
• Increase cow mature size
• Increase in feed costs for the cow herd

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Partial efficiency of growth (PEG)--defined

• PEG attempts to partition feed inputs into the
  portion used for growth
• PEG ADG DMI available for growth
• DMI for growth actual DMI - feed for required
  for maintenance
• Feed for maintenance is computed from feeding
  standards (NRC, 1996)
• PEG is moderately heritable (Arthur et al. 2001),
  and is not as strongly correlated to growth as FCR

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Residual feed intake (RFI)--defined

• RFI is a trait that measures the variation in
  feed intake beyond that needed to support
  maintenance and growth requirements (Koch et al.,
  1963)
• RFI has been shown to moderately heritable (h2
  0.30 to 0.40)
• Unlike feedgain ratio, RFI is not genetically
  related to growth rate or mature size

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How is RFI measured?

• RFI is measured as the difference between an
  animals actual feed intake and the amount of
  feed an animal is expected to eat based on its
  size and growth rate
• DMI ß0 ß1(mid-test BW.75) ß2(ADG)
  residual
• Calves that eat less than expected for their
  weight and ADG will have negative RFI
• Calves that eat more than expected for their
  weight and ADG will have positive RFI

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Relationship between feed intake and growth in
steers
Ate more feed at same ADG Less efficient
Ate less feed at same ADG More efficient
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Comparison of steers with divergent RFI
Performance data during an 77-day growing
trial 538 lb Initial body
weight 535 lb 2.11 lb/d
ADG 2.16 lb/d 1502 lb Expected
feed intake 1509 lb 1717 lb
Actual feed intake 1232 lb 215 lb
Residual feed intake -277 lb
The more efficient steer (negative RFI) gained
the same, but ate 485 lbs less feed than the less
efficient steer (positive RFI)
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Summary of studies used in meta analysis
Type of Study Source of calves Breed Gender Diet ME, Mcal/lb
Growing Studies N 514 . Initial BW 604 lb Spade Ranch Braunvieh Crossbred Steer 0.94
Growing Studies N 514 . Initial BW 604 lb King Ranch Santa Gertrudis Steer 0.97
Growing Studies N 514 . Initial BW 604 lb Camp Cooley I Brangus Heifer 0.95
Growing Studies N 514 . Initial BW 604 lb Camp Cooley II Brangus Heifer 0.95
Finishing Studies N 320 . Initial BW 789 lb King Ranch Santa Gertrudis Steer 1.36
Finishing Studies N 320 . Initial BW 789 lb McGregor Research Center Red Angus Steer 1.24
Finishing Studies N 320 . Initial BW 789 lb Cornell Study I Angus/ Simmental Steer 1.30
Finishing Studies N 320 . Initial BW 789 lb Cornell Study II Angus Steer 1.35
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Relationships between feed intake and growth in
growing and finishing calves-- Meta analysis
results
Growing calves (n 514), Dry matter intake,
lb/day
Finishing calves (n 320), Dry matter intake,
lb/day
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Relationships between feed efficiency and growth
traits in growing and finishing calves--Meta
analysis results
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Relationships between feed efficiency traits and
ADG in growing calves
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Relationships between feed efficiency and intake
traits in growing and finishing calves--Meta
analysis results
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Performance data of growing calves with low and
high RFI
Low and high RFI calves were 0.50 SD from
average RFI (0.0 1.80 lb/d))
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Performance data of finishing calves with low and
high RFI
Trait Low RFI (most efficient) High RFI (least efficient) change
Number of calves 93 87 --
ADG, lb/d 3.11 3.13 1
Actual DMI, lb/d 18.6 23.4 26
Feedgain ratio 6.05 7.63 26
Partial eff. growth 0.31 0.21 -32
RFI, lb/d -2.25 2.36 --
Average feed costs/120 days -18.90 19.80 39.00
Low and high RFI calves were 0.50 SD from
average RFI (0.0 1.96 lb/d))
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Relationships between feed efficiency and
carcass traits in growing and finishing
calves--Meta analysis results
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Summary of phenotypic relationships between feed
efficiency and component traits
Favorable Phenotype ADG Initial BW DM intake
? FCR higher lower less
? PEG higher lower less
? RFI not correlated not correlated less
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Additional merits of RFI as an efficiency trait

• RFI is less influenced by initial age BW
• RFI is less influenced by previous plane of
  nutrition
• Post-weaning RFI more likely to be associated
  with efficiency in mature cows
• RFI is more associated with biologically relevant
  traits associated with efficiency of feed
  utilization

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Relationships between feed efficiency measured in
growing heifers and mature cows

• Efficiency traits measured in Angus heifers and
  mature open cows
• Fed the same diet during post-weaning and mature
  cow studies
• 751 females measured

Cow measurements Cow measurements Cow measurements
rg FCR DMI BW
Heifer FCR 0.20 0.20 -0.54
Cow measurements Cow measurements Cow measurements
rg RFI DMI BW
Heifer RFI 0.98 0.64 -0.22
(Archer et al., 2002)
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RFI is linked to biological traits associated
with efficiency of feed utilization
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Commercialization of feed efficiency
technologies Beef Development Center, Millican TX
Pen 1
Pen 2
Each test pen equipped with nine feed bunks to
facilitate 65-70 bulls
GrowSafe feed bunks
Weight reader panels
Feed alley
Wireless communications data transfer
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Summary statistics of the first two bull tests
conducted at the Beef Development Center
Trait Test 1 Test 2
Start of test July 04 November 04
No. of Angus bulls 99 115
No. of Brangus bulls 16 26
No. of other breeds 5 10
Initial BW, lb 812 810
ADG, lb/day 3.17 3.81
DMI, lb/day 18.7 22.2
Feed conversion ratio, DMI/ADG 6.05 5.91
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Results from 1st feed efficiency test at the Beef
Development Center
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Multiple-trait selection index for growing bulls
Feedlot Profit Index (FPI)

• Index objective increase profitability of
  grow/finish market progeny
• Economic weighting factors derived for DMI, ADG
  and slaughter weight data generated from 426
  individually fed Charolais-cross steers (Alberta,
  Canada)
• Selection index development constructed using
  data from 1st Beef Development Center test
• Feedlot profit index b1RFI b2ADG b3adj.
  365-d YW
• ranges from 80 to 120
• the higher the better

Crews et al. (2005)
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RFI of bulls from the 2nd BDC test (Fall 2004)
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Performance data of low and high Feedlot Profit
Index bulls from 2nd BDC test
Trait Low FPI bulls (lt 95 least efficient) High FPI bulls (gt 105 most efficient) change
No. of bulls 37 38 --
ADG, lb/day 3.54 4.09 17
Actual DMI, lb/day 23.4 21.3 -9
Feedgain ratio 6.62 5.15 -22
RFI, lb/day 1.6 -1.7 --
Adj 365-d BW 1045 1035 -1
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Contributors to Research Program Texas
Agriculture Experiment Station
Ron Randel Monte Rouquette Charles Long
David Forrest Luis Tedeschi Tom Welsh Rhonda
Miller
Casey Thies Monte White Trent Fox Erin
Brown Phillip Lancaster Flavio Ribeiro Brandi
Bourg
David Forbes Bill Holloway
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Thanks for your attention!Questions?

• Industry supporters
• Beef Development Center
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• Support for research
• TAES Beef Initiative
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