Additive genetic parameters for postweaning growth, feed intake, and untrasound traits in Angus-Brahman multibreed cattle

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Additive genetic parameters for postweaning growth, feed intake, and untrasound traits in Angus-Brahman multibreed cattle
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Elzo, M. A.
Johnson, D. D.
Lamb, G. C.
Maddock, T. D.
Myer, R. O.
Riley, D. G.
Hansen, G. R.
Wasdin, J. G.
Driver, J. D.

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Additive Genetic Parameters for Postweaning Growth, Feed Intake, and
Ultrasound Traits in Angus-Brahman Multibreed Cattle


M. A. Elzo1, D. D. Johnson1, G. C. Lamb2, T. D. Maddock2, R. 0. Myer2, D. G. Riley3,
G. R. Hansen4, J. G. Wasdin1, and J. D. Driver1


Moderate to high estimates of heritability for postweaning feed intake, growth, and ultrasound traits
indicated that selection for these traits would be effective in Angus-Brahman multibreed
populations. Estimates of genetic correlations were too inaccurate to draw firm conclusions. Thus,
additional postweaning feed intake, growth, and ultrasound data needs to be collected at the Feed
Efficiency Facility to obtain reliable correlations for use in multiple-trait genetic evaluation and
selection of purebred and crossbred animals under subtropical conditions.


Summary
Automated feed efficiency facilities permit the
measurement of individual feed intake in large
numbers of cattle of similar age and maintained
under the same feeding regimen and
management conditions. These facilities allow
the construction of large contemporary groups
that have the potential to become an integral
component of national genetic evaluation
programs. Feed consumption, growth, and
ultrasound data collected in these facilities will
provide essential information for the estimation
of variance and covariance components needed
for genetic evaluation of animals for all these
traits and for residual feed intake (RFI). Thus,
the objective of this research was the estimation
of heritabilities for and genetic correlations
between RFI, daily feed intake (DFI), feed
conversion ratio (FCR), postweaning growth
(P WG), ultrasound fat thickness (UFT),
ultrasound percent of intramuscular fat (UIF),
and ultrasound ribeye area (UREA) using data
from a multibreed Angus-Brahman cattle
population collected in an automated feeding
facility located in Marianna, Florida.
Heritabilities were low to moderate for all traits
(0.14 0.06 to 0.34 0.09), except for the high
estimate for UIF (0.78 0.09). Genetic
correlations between RFI, DFI, FCR, and PWG,
and UFT, UIF, and UREA tended be low and to
have large standard errors. This indicates that
additional data from the automated feeding
facility would be needed to obtain informative
correlations for multiple-trait selection.


Introduction
Automated feed efficiency facilities permit the
measurement of individual feed intake in large
numbers of cattle of similar age and maintained
under the same feeding regimen and
management conditions. These facilities allow
the construction of large contemporary groups
that have the potential to become an integral
component of national genetic evaluation
programs. Feed consumption, growth, and
ultrasound data collected in these facilities will
provide essential information for the estimation
of variance and covariance components needed
for genetic evaluation of animals for all these
traits and for residual feed intake. Postweaning
feed intake, growth, and ultrasound data were
collected on a large number of Angus, Brahman,
and Angus x Brahman cattle at the GrowSafe
4000 Feed Efficiency Facility (FEF) of the
University of Florida from 2006 to 2009. The
objective of this research was the estimation of
heritabilities for residual feed intake (RFI), daily
feed intake (DFI), feed conversion ratio (FCR),
postweaning growth (PWG), ultrasound fat
thickness (UFT), ultrasound percent of
intramuscular fat (UIF), and ultrasound ribeye
area (UREA) as well as genetic correlations
among these traits in a multibreed population
composed of Angus (A), Brahman (B), and
crossbred cattle of various A and B fractions
under subtropical conditions.
Materials and Methods
Animals, housing, feeding and management.
Animals were from three Florida farms


1Department of Animal Sciences, University of Florida, Gainesville, FL
North Florida Research and Education Center, University of Florida, Marianna, FL
3Department of Animal Science, Texas A&M University, College Station, TX
4North Carolina State University. Tidewater Research Station. Plymouth. NC










(n = 1,129), one located in Gainesville (n = 751)
and two located in Marianna (n = 93 and n =
285). Calves were born in 2006 (n = 278), 2007
(n = 203), 2008 (n = 348), and 2009 (n = 300).
Approved research protocols for animal care
from the University of Florida Institutional
Animal Care and Use Committee were followed
(IACUC number D477). The dataset contained
feed intake, growth, and ultrasound information
from 208 bulls, 530 heifers, and 391 steers from
six breed groups: A, % A '1 B, Brangus (% A %3
B), 2 A /2 B, 4 A 34 B, and B. These calves
were the offspring of 74 bulls and 451 dams
from these same six breed groups. Numbers of
sires, dams, and calves per breed group are
shown in Table 1. Calves from the three herds
were transported to the FEF postweaning and
assigned to 24 pens (1,162 square feet each; 2
GrowSafe nodes per pen) by sire group (A, /4 A
/4 B, Brangus, 2 A V2 B, 4 A /4 B, and B) and
sex (bull, heifer, and steer) combination. Calves
were identified with half-duplex passive
transponder ear tags (Allflex USA Inc., Dallas-
Fort Worth, TX). The mean stocking density
was 12.6 animals per pen and 6.3 animals per
GrowSafe node. Animals were offered a
concentrate diet composed of various
percentages of corn, corn gluten feed, dried
distilled grains plus solubles, soybean hulls,
cottonseed hulls, chopped grass hay, and a
vitamin-mineral-protein supplement (FRM,
Bainbridge, GA) ad libitum. Dry matter (DM),
crude protein, net energy for maintenance, and
net energy for gain of the diet provided to calves
each year is presented in Table 2. Calves were
allowed to adjust to the diet and the FEF for 14
to 21 d prior to the 70-d trial period. GrowSafe
software recorded feed intake information in
real-time. Weights (lb) and exit velocity (feet
per second) were measured every 2 wk.

Postweaning feed intake, growth, and
ultrasound traits.
Traits were RFI (lb DM/d), DFI (lb DM/d), FCR
(DFI/lb weight gain per day), PWG (lb), UFT
(in), UIF (%), and UREA (in2). Intake traits
were defined on a DM basis. Feed intake,
growth, and ultrasound traits were measured at
the University of Florida FEF in Marianna,
Florida. Phenotypic RFI was obtained as the
difference between expected and actual average


DFI during the 70-d postweaning feeding trial
(Koch et al., 1963; Arthur et al., 2001a; Archer
et al., 1997) within a batch of calves. A batch of
calves was defined as a group of calves from a
particular herd placed in the FEF at the same
time. Expected feed intake was estimated using
a linear regression of average DFI on average
daily gain (ADG) and metabolic mid-weight
within a batch of calves, and across breed groups
and sexes of calves. This model explained 59%
of the variation for average DFI. Ultrasound fat
thickness and UIF within a batch of calves
(Schenkel et al., 2004; Lancaster et al., 2009)
were found to be non-significant and excluded
from the final model. Average daily gain was
estimated using a regression of calf weight on
test day. Metabolic mid-weight was computed as
the sum of the regression estimate for initial
weight plus the regression estimate for ADG
times 35 (midpoint day of trial) raised to the
power of 0.75. Feed conversion ratio was
obtained as the ratio of DFI to ADG.
Postweaning gain was the difference between
the weight of a calf at the beginning and at the
end of the 70-d trial. Ultrasound images were
taken and analyzed by certified technicians
(Tallgrass Beef Co., Sedan, KS, Perryman
Livestock Ultrasound Service, Micanopy, FL,
and Walter and Associates, Ames, IA).

Heritabilities, genetic correlations, and
phenotypic correlations.
Restricted maximum likelihood estimates of
genetic and phenotypic variances and
heritabilities for RFI, DFI, FCR, PWG, UFT,
UIF, and UREA as well as genetic and
phenotypic covariances and correlations among
these traits were computed using ASREML
(Gilmour et al., 2006). Variances and
heritabilities were computed using single-trait
analyses. Covariances and correlations were
computed using 2-trait analyses. The same
model was used for all traits. Fixed effects were
contemporary group (herd-year-pen subclass),
sex of calf (bull, heifer, steer), age of calf,
Brahman fraction of calf nested within sex of
calf, heterozygosity of calf nested within sex of
calf, and mean exit velocity (average of 6
records). Random effects were calf and residual.
Calf effects were assumed to have mean zero
and variance equal to the relationship matrix










times the genetic variance for a given trait
(single-trait analyses), or a 2 x 2 genetic
variance-covariance matrix (2-trait analyses).
Residual effects were assumed to have mean
zero, common variance (single-trait analyses) or
2 x 2 variance-covariance matrix (2-trait
analyses) and uncorrelated.

Results
Estimates of heritability in this Angus-Brahman
multibreed population were low to moderate for
postweaning feed intake and growth traits (0.14
+ 0.06 to 0.33 0.09; Table 3) and for
ultrasound traits, except for the high heritability
estimate for UIF (0.26 0.08 to 0.78 0.09;
Table 4). Heritability estimates for RFI, DFI,
and FCR were lower than estimates in Canada
(0.37 to 0.44; Schenkel et al., 2004), Australia
(0.32 0.05 to 0.38 0.06; Arthur et al., 2001a),
and France (0.32 0.02 to 0.44 + 0.02; Arthur et
al., 2001b). No comparable estimates for PWG
were found in the literature. However,
heritability estimates for ADG were similar
(0.35; Schenkel et al., 2004; 0.31 0.05; Arthur
et al., 2001b) to the PWG heritability estimate
here. The UFT heritability was lower than and
the UREA heritability was similar to estimates
from crossbred cattle (UFT: 0.59 0.14; UREA:
0.39 0.13; Nkrumah et al., 2007) and purebred
bulls of several breeds (UFT: 0.36; UREA: 0.30;
Schenkel et al., 2004). The UIF heritability was
similar (0.75 0.16) to that reported by
Nkrumah et al. (2007) and higher than that
estimated (0.14) by Schenkel et al. (2004).


Most genetic and phenotypic correlations had
large standard errors. The most accurate
estimates of genetic and phenotypic correlations
(Table 3) were the positive ones between RFI
and DFI (less efficient animals had larger feed
intakes) and between DFI and PWG (calves that
ate more gained more weight) and the negative
one between FCR and PWG (less efficient
animals ate more and gained less than more
efficient ones). Genetic and phenotypic
correlations (Table 4) were positive between
UFT and UIF, and near zero between UIF and
UREA. Estimates of genetic (Table 5) and
phenotypic (Table 6) correlations between RFI,
DFI, FCR, and PWG, and UFT, UIF, and UREA
had large standard errors and they were mostly
smaller than those reported by Schenkel et al.
(2004) and Nkrumah et al. (2007).


Literature Cited
Archer. et al. 1997. J. Anim. Sci. 75:2024.
Arthur. et al. 2001a. J. Anim. Sci. 79:2805.
Arthur. et al. 2001b. Livest. Prod. Sci. 68:131.
Gilmour. et al. 2006. VSN International Ltd., Hemel Hempstead, HP1 1ES, UK.
Koch. et al. 1963. J. Anim. Sci. 22:486.
Lancaster. et al. 2009. J. Anim. Sci. 87:1528.
Nkrumah. et al. 2007). J. Anim. Sci. 85:2711.
Schenkel. et al. 2004. Can. J. Anim. Sci. 84:177.














Table 1. Numbers of sires, dams, and calves per breed group
Angus 34 A 4 B Brangus V A V B '4 A3 B Brahman
Sires 12 9 28 8 6 11
Dams 97 68 99 97 42 48
Calves 420 142 184 183 79 121





Table 2. Nutritional analysis of the diet at the Feed Efficiency Facility by year
2006 2007 2008 2009


Dry Matter, %

Crude Protein, %

Net Energy for
Maintenance, mcal/lb DM
Net Energy for Gain,
mcal/lb DM


91.2

17.3

0.8


0.6


90.0


84.5


93.0

12.3

0.6


0.4


Table 3. Estimates ofheritabilities (diagonal), genetic correlations (above diagonal)
and phenotypic correlations (below diagonal) for postweaning feed intake and growth
traits in an Angus-Brahman multibreed population
Trait' RFI DFI FCR PWG


FCR


0.14 + 0.06
0.88 + 0.03
0.34 0.10


PWG 0.07 0.11


0.77 + 0.10
0.21 + 0.07
0.11 + 0.10
0.43 + 0.08


0.24 + 0.27
-0.07 + 0.25
0.18 + 0.07
-0.66 + 0.06


0.14 + 0.25
0.55 + 0.16
-0.82+ 0.11
0.33 + 0.09


1RFI = residual feed intake; DFI = daily feed intake; FCR = feed conversion ratio;
PWG = postweaning gain.










Table 4. Estimates of heritabilities (diagonal), genetic correlations (above diagonal)
and phenotypic correlations (below diagonal) for ultrasound traits in an Angus-Brahman
multibreed population
Trait' UFT UIF UREA
UFT 0.26 + 0.08 0.68 + 0.11 0.28 + 0.18
UIF 0.50 + 0.07 0.78 + 0.09 -0.02 + 0.15
UREA 0.32 + 0.09 0.00 + 0.10 0.34 + 0.08
1UFT = ultrasound fat thickness; UIF = ultrasound percent of intramuscular fat;
UREA = ultrasound ribeye area.


Table 5. Estimates of genetic correlations between postweaning feed intake and
growth traits and ultrasound traits in an Angus-Brahman multibreed population
Trait' UFT UIF UREA
RFI -0.09 + 0.27 0.01 + 0.21 0.01 + 0.25
DFI -0.11 + 0.24 0.16 0.17 0.34 0.19
FCR 0.38 + 0.24 0.17 + 0.19 0.21 + 0.22
PWG -0.54 + 0.21 -0.08 + 0.16 -0.09 + 0.18
1UFT = ultrasound fat thickness; UIF = ultrasound percent of intramuscular fat;
UREA = ultrasound ribeye area; RFI = residual feed intake; DFI = daily feed
intake; FCR = feed conversion ratio; PWG = postweaning gain.





Table 6. Estimates of phenotypic correlations between postweaning feed
intake and growth traits and ultrasound traits in an Angus-Brahman multibreed
population
Trait' UFT UIF UREA
RFI -0.03 + 0.10 0.03 + 0.10 0.03 + 0.10
DFI 0.02 + 0.10 0.12 + 0.10 0.29 + 0.09
FCR 0.18 0.10 0.14 0.11 0.09 0.11
PWG -0.23 + 0.10 -0.05 + 0.10 0.06 + 0.10
1UFT = ultrasound fat thickness; UIF = ultrasound percent of intramuscular fat;
UREA = ultrasound ribeye area; RFI= residual feed intake; DFI = daily feed
intake; FCR = feed conversion ratio; PWG = postweaning gain.




Full Text

PAGE 1

Summary Automated feed efficiency facilities permit the measurement of individual feed intake in large numbers of cattle of similar age and maintained under the same feeding regimen and management conditions. These facilities allow the construction of large contem porary groups that have the potential to become an integral component of national genetic evaluation programs. Feed consumption, growth, and ultrasound data collected in these facilities will provide essential information for the estimation of variance and covariance components needed for genetic evaluation of animals for all these traits and for residual feed intake (RFI). Thus, the objective of this research was the estimation of heritabilities for and genetic correlations between RFI, daily feed intake ( DFI), feed conversion ratio (FCR), postweaning growth (PWG), ultrasound fat thickness (UFT), ultrasound percent of intramuscular fat (UIF), and ultrasound ribeye area (UREA) using data from a multibreed Angus Brahman cattle population collected in an autom ated feeding facility located in Marianna, Florida. Heritabilities were low to moderate for all traits (0.14 0.06 to 0.34 0.09), except for the high estimate for UIF (0.78 0.09). Genetic correlations between RFI, DFI, FCR, and PWG, and UFT, UIF, and UREA tended be low and to have large standard errors. This indicates that additional data from the automated feeding facility would be needed to obtain informative correlations for multiple trait selection. Introduction Automated feed efficiency facilities permit the measurement of individual feed intake in large numbers of cattle of similar age and maintained under the same feeding regimen and management conditions. These facilities allow the construc tion of large contemporary groups that have the potential to become an integral component of national genetic evaluation programs. Feed consumption, growth, and ultrasound data collected in these facilities will provide essential information for the estima tion of variance and covariance components needed for genetic evaluation of animals for all these traits and for residual feed intake. Postweaning feed intake, growth, and ultrasound data were collected on a large number of Angus, Brahman, and Angus x Brah man cattle at the GrowSafe 4000 Feed Efficiency Facility (FEF) of the University of Florida from 2006 to 2009. The objective of this research was the estimation of heritabilities for residual feed intake (RFI), daily feed intake (DFI), feed conversion rati o (FCR), postweaning growth (PWG), ultrasound fat thickness (UFT), ultrasound percent of intramuscular fat (UIF), and ultrasound ribeye area (UREA) as well as genetic correlations among these traits in a multibreed population composed of Angus (A), Brahman (B), and crossbred cattle of various A and B fractions under subtropical conditions. Materials and Methods Animals, housing, feeding and management. Animals were from three Florida farms Additive Genetic Parameters for Postweaning Growth, Feed Intake, and Ultrasound Traits in Angus Brahman Multibreed Cattle M. A. Elzo 1 D. D. Johnson 1 G. C. Lamb 2 T. D. Maddock 2 R. O. Myer 2 D. G. Riley 3 G. R. Hansen 4 J. G. Wasdin 1 and J. D. Driver 1 Moderate to high estimates of heritability for postweaning feed intake, growth, and ultrasound traits indicated that selection for these traits would be effective in Angus Brahman multibreed populations. Estimates of genetic correlations were too inaccurate to draw firm conclusions. Thus, additional postweaning feed intake, growth, and ultrasound data needs to be collected at the Feed Efficiency Facility to obtain reliable correlations for use in multiple trait genetic evaluation and sele ction of purebred and crossbred animals under subtropical conditions. 1 Department of Animal Sciences, University of Florida, Gainesville, FL 2 North Florida Research and Education Center, University of Florida, Marianna, FL 3 Department of Animal Science, Texas A&M University, College Station, TX 4 North Carolina State University, Tidewater Research Station, Plymouth, NC

PAGE 2

(n = 1,129), one located in Gainesville (n = 751) and two located in Marianna (n = 93 and n = 285). Calves were born in 2006 (n = 278), 2007 (n = 203), 2008 (n = 348), and 2009 (n = 300). Approved research protocols for animal care from the University of F lorida Institutional Animal Care and Use Committee were followed (IACUC number D477). The dataset contained feed intake, growth, and ultrasound information from 208 bulls, 530 heifers, and 391 steers from B), A B, A B, and B. These calves were the offspring of 74 bulls and 451 dams from these same six breed groups. Numbers of sires, dams, and calves per breed group are shown in Table 1. Calves from the three herds were transported to the FEF postweaning and assigned to 24 pens ( 1,162 square feet each; 2 GrowSafe nodes per pen) by sire group (A, A B, Brangus, A B, A B, and B) and sex (bull, heifer, and steer) combination. Calves were identified with half duplex passive transponder ear tags (Al lflex USA Inc., Dallas Fort Worth, TX). The mean stocking density was 12.6 animals per pen and 6.3 animals per GrowSafe node. Animals were offered a concentrate diet composed of various percentages of corn, corn gluten feed, dried distilled grains plus solu bles, soybean hulls, cottonseed hulls, chopped grass hay, and a vitamin mineral protein supplement (FRM, Bainbridge, GA) ad libitum. Dry matter (DM) crude protein, net energy for maintenance, and net energy for gain of the diet provided to calves each yea r is presented in Table 2. Calves were allowed to adjust to the diet and the FEF for 14 to 21 d prior to the 70 d trial period. GrowSafe software recorded feed intake information in real time. Weights (lb) and exit velocity (feet per second) were measured every 2 wk. Postweaning feed intake, growth, and ultrasound traits. Traits were RFI (lb DM/d), DFI (lb DM/d), FCR (DFI/lb weight gain per day), PWG (lb), UFT (in), UIF (%), and UREA (in 2 ). Intake traits were defined on a DM basis. Feed intake, growth, and ultrasound traits were measured at the University of Florida FEF in Marianna, Florida. Phenotypic RFI was obtained as the difference between expected and actual average DFI durin g the 70 d postweaning feeding trial (Koch et al., 1963; Arthur et al., 2001a; Archer et al., 1997) within a batch of calves. A batch of calves was defined as a group of calves from a particular herd placed in the FEF at the same time. Expected feed intake was estimated using a linear regression of average DFI on average daily gain (ADG) and metabolic mid weight within a batch of calves, and across breed groups and sexes of calves. This model explained 59% of the variation for average DFI. Ultrasound fat th ickness and UIF within a batch of calves (Schenkel et al., 2004; Lancaster et al., 2009) were found to be non significant and excluded from the final model. Average daily gain was estimated using a regression of calf weight on test day. Metabolic mid weigh t was computed as the sum of the regression estimate for initial weight plus the regression estimate for ADG times 35 (midpoint day of trial) raised to the power of 0.75. Feed conversion ratio was obtained as the ratio of DFI to ADG. Postweaning gain was t he difference between the weight of a calf at the beginning and at the end of the 70 d trial. Ultrasound images were taken and analyzed by certified technicians (Tallgrass Beef Co., Sedan, KS, Perryman Livestock Ultrasound Service, Micanopy, FL, and Walter and Associates, Ames, IA). Heritabilities, genetic correlations, and phenotypic correlations. Restricted maximum likelihood estimates of genetic and phenotypic variances and heritabilities for RFI, DFI, FCR, PWG, UFT, UIF, and UREA as well as genetic an d phenotypic covariances and correlations among these traits were computed using ASREML (Gilmour et al., 2006). Variances and heritabilities were computed using single trait analyses. Covariances and correlations were computed using 2 trait analyses. The s ame model was used for all traits. Fixed effects were contemporary group (herd year pen subclass), sex of calf (bull, heifer, steer), age of calf, Brahman fraction of calf nested within sex of calf, heterozygosity of calf nested within sex of calf, and mea n exit velocity (average of 6 records). Random effects were calf and residual. Calf effects were assumed to have mean zero and variance equal to the relationship matrix

PAGE 3

times the genetic variance for a given trait (single trait analyses), or a 2 2 geneti c variance covariance matrix (2 trait analyses). Residual effects were assumed to have mean zero, common variance (single trait analyses) or 2 2 variance covariance matrix (2 trait analyses) and uncorrelated. Results Estimates of heritability in this An gus Brahman multibreed population were low to moderate for postweaning feed intake and growth traits (0.14 0.06 to 0.33 0.09; Table 3) and for ultrasound traits, except for the high heritability estimate for UIF (0.26 0.08 to 0.78 0.09; Table 4). H eritability estimates for RFI, DFI, and FCR were lower than estimates in Canada (0.37 to 0.44; Schenkel et al., 2004), Australia (0.32 0.05 to 0.38 0.06; Arthur et al., 2001a), and France (0.32 0.02 to 0.44 0.02; Arthur et al., 2001b). No comparabl e estimates for PWG were found in the literature. However, heritability estimates for ADG were similar (0.35; Schenkel et al., 2004; 0.31 0.05; Arthur et al., 2001b) to the PWG heritability estimate here. The UFT heritability was lower than and the UREA heritability was similar to estimates from crossbred cattle (UFT: 0.59 0.14; UREA: 0.39 0.13; Nkrumah et al., 2007) and purebred bulls of several breeds (UFT: 0.36; UREA: 0.30; Schenkel et al., 2004). The UIF heritability was similar (0.75 0.16) to that reported by Nkrumah et al. (2007) and higher than that estimated (0.14) by Schenkel et al. (2004). Most genetic and phenotypic correlations had large standard errors. The most accurate estimates of genetic and phenotypic correlations (Table 3) were the positive ones between RFI and DFI (less efficient an imals had larger feed intakes) and between DFI and PWG (calves that ate more gained more weight) and the negative one between FCR and PWG (less efficient animals ate more and gained less than more efficient ones). Genetic and phenotypic correlations (Table 4) were positive between UFT and UIF, and near zero between UIF and UREA. Estimates of genetic (Table 5) and phenotypic (Table 6) correlations between RFI, DFI, FCR, and PWG, and UFT, UIF, and UREA had large standard errors and they were mostly smaller th an those reported by Schenkel et al. (2004) and Nkrumah et al. (2007). Literature Cited Archer et al. 1997. J. Anim. Sci. 75:2024 Arthur e t al. 2001a. J. Anim. Sci. 79:2805. Arthur et al. 2001b. Livest. Prod. Sci. 68:131. Gilmour et al. 2006. VSN International Ltd., Hemel Hempstead, HP1 1ES, UK. Koch et al. 1963. J. Anim. Sci. 22:486. Lancaster et al. 2009. J. Anim. Sci. 87:1528. Nkrumah et al. 2007). J. Anim. Sci. 85:2711. Schenkel et al. 2004. Can. J. Anim. Sci. 84:177.

PAGE 4

Table 1. Numbers of sires, dams, and calves per breed group Angus A B Brangus A B A B Brahman Sires 12 9 28 8 6 11 Dams 97 68 99 97 42 48 Calves 420 142 184 183 79 121 Table 2. Nutritional analysis of the diet at the Feed Efficiency Facility by year 2006 2007 2008 2009 Dry Matter, % 91.2 90.0 84.5 93.0 Crude Protein, % 17.3 14.1 11.1 12.3 Net Energy for Maintenance, mcal/lb DM 0.8 0.8 0.7 0.6 Net Energy for Gain, mcal/lb DM 0.6 0.5 0.5 0.4 Table 3. Estimates of heritabilities (diagonal), genetic correlations (above diagonal) and phenotypic correlations (below diagonal) for postweaning feed intake and growth traits in an Angus Brahman multibreed population Trait 1 RFI DFI FCR PWG RFI 0.14 0.06 0.77 0.10 0.24 0.27 0.14 0.25 DFI 0.88 0.03 0.21 0.07 0.07 0.25 0.55 0.16 FCR 0.34 0.10 0.11 0.10 0.18 0.07 0.82 0.11 PWG 0.07 0.11 0.43 0.08 0.66 0.06 0.33 0.09 1 RFI = residual feed intake; DFI = daily feed intake; FCR = feed conversion ratio; PWG = postweaning gain.

PAGE 5

Table 4. Estimates of heritabilities (diagonal), genetic correlations (above diagonal) and phenotypic correlations (below diagonal) for ultrasound traits in an Angus Brahman multibreed population Trait 1 UFT UIF UREA UFT 0.26 0.08 0.68 0.11 0.28 0.18 UIF 0.50 0.07 0.78 0.09 0.02 0.15 UREA 0.32 0.09 0.00 0.10 0.34 0.08 1 UFT = ultrasound fat thickness; UIF = ultrasound percent of intramuscular fat; UREA = ultrasound ribeye area. Table 5. Estimates of genetic correlations between postweaning feed intake and growth traits and ultrasound traits in an Angus Brahman multibreed population Trait 1 UFT UIF UREA RFI 0.09 0.27 0.01 0.21 0.01 0.25 DFI 0.11 0.24 0.16 0.17 0.34 0.19 FCR 0.38 0.24 0.17 0.19 0.21 0.22 PWG 0.54 0.21 0.08 0.16 0.09 0.18 1 UFT = ultrasound fat thickness; UIF = ultrasound percent of intramuscular fat; UREA = ultrasound ribeye area; RFI = residual feed intake; DFI = daily feed intake; FCR = feed conversion ratio; PWG = postweaning gain. Table 6. Estimates of phenotypic correlations between postweaning feed intake and growth traits and ultrasound traits in an Angus Brahman multibreed population Trait 1 UFT UIF UREA RFI 0.03 0.10 0.03 0.10 0.03 0.10 DFI 0.02 0.10 0.12 0.10 0.29 0.09 FCR 0.18 0.10 0.14 0.11 0.09 0.11 PWG 0.23 0.10 0.05 0.10 0.06 0.10 1 UFT = ultrasound fat thickness; UIF = ultrasound percent of intramuscular fat; UREA = ultrasound ribeye area; RFI = residual feed intake; DFI = daily feed intake; FCR = feed conversion ratio; PWG = postweaning gain.