Defining Feed Efficiency in Beef Cattle

Gordon Carstens and Luis Tedeschi Department of Animal Science Texas A&M University

Projected global meat production

(2001 to 2025)

Thomas E. Elam (Feedstuffs, 2004) 160 140 120 100 80 60 40 20 0 Projected world demand for meat will increase 55% by 2025 61% 73% 31% Beef Pork Poultry Lamb 1961 1971 1981 1991 2001 2025

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)

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

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)

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

Ratio-based feed efficiency traits



Feed:gain ratio is negatively correlated with:



Postweaning ADG (r g = -0.67; Koots et al., 1994)



Yearling BW (r g = -0.60; Koots et al., 1994)



Cow mature size (r g = -0.54; Archer et al., 2002)



Selection for lower feed:gain ratio (improved efficiency) will indirectly:



Increase genetic merit for growth



Increase cow mature size



Increase in feed costs for the cow herd

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

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 (h 2 ≈ 0.30 to 0.40)



Unlike feed:gain ratio, RFI is not genetically related to growth rate or mature size

How is RFI measured?



RFI is measured as the difference between an animal’s actual feed intake and the amount of feed an animal is expected to eat based on its size and growth rate DMI =

ß 0

+

ß 1

(mid-test BW .75

) +

ß 2

(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

Relationship between feed intake and growth in steers

32 Ate more feed at same ADG Less efficient 28 24 20 16 12 1.00

1.50

2.00

Ate less feed at same ADG More efficient 2.50

3.00

Average daily gain, lb/day 3.50

Comparison of steers with divergent RFI

Performance data during an 77-day growing trial: 538 lb 2.11 lb/d 1502 lb 1717 lb +215 lb Initial body weight ADG Expected feed intake Actual feed intake Residual feed intake 535 lb 2.16 lb/d 1509 lb 1232 lb -277 lb

The more efficient steer ( negative RFI ) gained the same, but ate 485 lbs less feed than the less efficient steer ( positive RFI )

Summary of studies used in meta analysis

Type of Study Source of calves Growing Studies N = 514 .

Initial BW = 604 lb Spade Ranch King Ranch Camp Cooley I Camp Cooley II Breed Braunvieh Crossbred Santa Gertrudis Brangus Brangus Santa Gertrudis Gender Steer Steer Heifer Heifer Steer Diet ME, Mcal/lb 0.94

0.97

0.95

0.95

1.36

Finishing Studies N = 320 .

Initial BW = 789 lb King Ranch McGregor Research Center Cornell Study I Cornell Study II Red Angus Angus/ Simmental Angus Steer Steer Steer 1.24

1.30

1.35

Relationships between feed intake and growth in growing and finishing calves- Meta analysis results

32 28 24 20 16 12 8 0.5

Growing calves (n = 514), Dry matter intake, lb/day r = 0.61

1.5

2.5

ADG, lb/day 3.5

32 28 24 20 16 12 4.5

8 0.5

Finishing calves (n = 320), Dry matter intake, lb/day r = 0.62

1.5

2.5

ADG, lb/day 3.5

4.5

Relationships between feed efficiency and growth traits in growing and finishing calves- Meta analysis results

0.6

Phenotypic correlations with ADG

0.4

0.2

0 -0.2

0.00

0.03

RFI -0.4

-0.6

0.20

0.11

PEG Growing calves Finishing calves FCR -0.60

-0.58

0.6

0.4

Phenotypic correlations with initial BW

Growing calves Finishing calves 0.28

0.4

0.2

0 -0.2

-0.4

0.00

0.06

RFI PEG -0.25

-0.38

FCR -0.6

Relationships between feed efficiency traits and ADG in growing calves

0.5

0.4

0.3

0.2

4 3 2 1 0 -1 -2 -3 -4 0.5

RFI 1.5

2.5

ADG, lb/day r = 0.0

3.5

PEG 0.1

0 18 0.5

FCR 16 14 12 10 8 6 4 0.5

1.5

2.5

1.5

2.5

ADG, lb/day r = 0.20

3.5

r = -0.60

3.5

Relationships between feed efficiency and intake traits in growing and finishing calves- Meta analysis results

0.6

0.3

Phenotypic correlations

0.65

0.67

with intake

Growing calves Finishing calves 0.25

0.12

0 RFI PEG FCR -0.3

-0.6

-0.57

-0.64

-0.9

Performance data of growing calves with low and high RFI †

3.0

2.5

2.0

1.5

1.0

ADG, lb/day Low Medium RFI Group† High 26 Dry m atter intake, lb/day Brangus heifers I Brangus heifers II 24 22 Braunvieh steers 20 18 Santa Gertrudis steers 16 Low Medium RFI Group† High

†Low and high RFI calves were ± 0.50 SD from average RFI (0.0 ± 1.80 lb/d))

Performance data of finishing calves with low and high RFI †

Trait Number of calves ADG, lb/d Actual DMI, lb/d Feed:gain ratio Low RFI (most efficient)† 93 3.11

18.6

6.05

High RFI (least efficient)† % change 87 - 3.13

23.4

7.63

1% 26% 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))

Relationships between feed efficiency and carcass traits in growing and finishing calves- Meta analysis results

0.4

Phenotypic correlations with final rib fat thickness

0.33

0.2

0.11

0.11

0.21

0.4

0.2

Phenotypic correlations with final ribeye area

0.11

0.02

0.00

0 0 -0.2

RFI PEG -0.15

FCR -0.2

RFI -0.14

PEG -0.10

FCR -0.11

-0.4

Growing calves Finishing calves -0.38

-0.4

Growing calves Finishing calves -0.6

-0.6

Summary of phenotypic relationships between feed efficiency and component traits

Favorable Phenotype



FCR



PEG



RFI ADG higher *** higher * not correlated Initial BW lower ** lower ** not correlated DM intake less * less *** less ***

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

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 r g Heifer FCR r g Heifer RFI Cow measurements FCR 0.20

DMI 0.20

BW -0.54

Cow measurements RFI DMI BW 0.98

0.64

-0.22

(Archer et al., 2002)

RFI is linked to biological traits associated with efficiency of feed utilization

Trait Heat production (calorimetry) Heat production (slaughter balance) Methane DM digestibility RFI 0.68

0.56

0.44

-0.33

FCR 0.37

NR NS -0.11

Reference

Nkrumah et al. 05 Basarab et al. 03 Nkrumah et al. 05 Brown et al. 05

Feeding duration Meal frequency 0.43

0.19

0.01

0.08

Lancaster et al. 05

Correlations in bold are significantly different from zero; P < .05

Commercialization of feed efficiency technologies Beef Development Center, Millican TX

Pen 1 GrowSafe feed bunks Pen 2 Each test pen equipped with nine feed bunks to facilitate 65-70 bulls Weight & reader panels Feed alley Wireless communications data transfer Data Analysis: Networked TAMU computer for data acquisition & analysis Data Capture: Computer at BDC

Summary statistics of the first two bull tests conducted at the Beef Development Center

Trait Start of test No. of Angus bulls No. of Brangus bulls No. of other breeds Initial BW, lb ADG, lb/day DMI, lb/day Feed conversion ratio, DMI/ADG Test 1 July ‘04 99 16 5 812 3.17

18.7

6.05

Test 2 November ‘04 115 26 10 810 3.81

22.2

5.91

Results from 1 st feed efficiency test at the Beef Development Center

4 3 2 Bull: #818: Act. DMI: 20.5 Exp. DMI: 18.4

RFI: +2.1 1 0 -1 -2 -3 -4 1.0

1.5

2.0

2.5

3.0

3.5

ADG, lb/day 4.0

Bull: #616: Act. DMI: 16.3 Exp. DMI: 18.4

RFI: -2.1

4.5

5.0

5.5

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: from 1 st constructed using data Beef Development Center test Feedlot profit index = b

1

• RFI + b

2

• ADG + b

3

• adj. 365-d YW = ranges from ≈ 80 to 120 = the higher the better

Crews et al. (2005)

RFI of bulls from the 2 nd BDC test (Fall 2004)

3 2 1 6 5 4 FPI = 83 0 -1 -2 -3 -4 -5 2.0

FPI = 106 2.5

Low Feedlot Profit Index (< 95) High Feedlot Profit Index (> 105) 3.0

3.5

4.0

ADG, lb/day 4.5

FPI = 93 FPI = 128 5.0

5.5

Performance data of low and high Feedlot Profit Index bulls from 2 nd BDC test

Trait No. of bulls ADG, lb/day Actual DMI, lb/day Feed:gain ratio RFI, lb/day Adj 365-d BW Low FPI bulls (< 95; least efficient) 37 3.54

High FPI bulls (> 105; most efficient) 38 % change - 4.09

+17% 23.4

6.62

+1.6

1045 21.3

5.15

-1.7

1035 -9% -22% - -1%

Contributors to Research Program Texas Agriculture Experiment Station

David Forrest Luis Tedeschi Tom Welsh Rhonda Miller Ron Randel Monte Rouquette Charles Long Casey Thies Monte White Trent Fox Erin Brown Phillip Lancaster Flavio Ribeiro Brandi Bourg David Forbes Bill Holloway

Thanks for your attention!

Questions?

Support for research:



TAES; Beef Initiative



TCFA



NCBA



SARE Industry supporters:



Beef Development Center



Spade Ranch



Chapman Ranch



King Ranch



Camp Cooley Ranch



Vassberg Ranch