Applied Beef Cattle Breeding and Selection

Composite Populations

Larry V. CundiffARS-USDA-U.S. Meat Animal Research Center

2008 Beef Cattle Production Management Series-Module VGreat Plains Veterinary Education Center

University of Nebraska, Clay CenterSeptember 18, 2008

Sire breed Dam breed Calf breed Weaning wt

H A HA 430

A H AH 416

A A AA 405

H H HH 395

HA = 430 = .5gH + .5 gA + hIha + mA

AH = 416 = .5gH + .5 gA + hIha + mH

AA = 405 = gA + + mA

HH = 395 = gH + + mH

(.5)(HA + AH) - .5 (AA + HH) = 423 – 400 = 23 = hIah

Estimating Heterosis for a specific two breed cross

HA = 430 = .5gH + .5 gA + hIha + mA

AH = 416 = .5gH + .5 gA + hIha + mH

AA = 405 = gA + + mA

HH = 395 = gH + + mH

In the above equations, HA denotes a crossbred calf with a Hereford sire and an Angus dam.AH denotes a crossbred calf with an Angus sire and a Hereford dam.HH denotes a straightbred calf with a Hereford sire and Hereford dam.AA denotes a straightbred calf with an Angus sire and Angus dam.

gH denotes the additive breed effect for Herefords and gA the additive breed effect for Angus.

hIha denotes effect of individual hetersosis expressed by Hereford X

Angus or Angus X Hereford reciprocal crosses. Note that hIha = hI

ha.

mA denotes the maternal (MILK) breed effect for Angus and mH the maternal breed effect for Hereford dams.

C X A = .5gC + .5 gA + hIca + mA

C X B = .5gC + .5 gB + hICB + mB

C X AB = .5gC + .25 gA + .25gB + .5hIAC + .5hI

BC + .5mA + .5 mB + hM

AB

C X BA = .5gC + .25 gB + .25gA + .5hIAC + .5hI

BC + .5mA + .5 mB + hM

AB

.5[( C X AB) + (C X BA)] – .5[(C X A) + (C X B)] = hMAB

Estimating Maternal Heterosis

C X A = .5gC + .5 gA + hIca + mA

C X B = .5gC + .5 gB + hICB + mB

C X AB = .5gC + .25 gA + .25gB + .5hIAC + .5hI

BC + .5mA + .5 mB + hM

AB

C X BA = .5gC + .25 gB + .25gA + .5hIAC + .5hI

BC + .5mA + .5 mB + hM

AB

In the above equations,

the gA, gB and gC denote additive breed effects for breeds A, B and C respectively.

hICA, hI

CB and hIAC denote individual heterosis effects for C X A (or A X C) , C X

B (or B X C) , and A X C (or C X A) breed crosses, respectively.

mA and mB denote maternal (MILK) breed effects for breeds A and B, respectively.

hMAB denotes maternal heterosis expressed by A X B (or B XA) crossbred dams.

Composite populations can be used to Composite populations can be used to exploit: exploit:

• HETEROSISHETEROSIS

• COMPLEMENTARITY among breeds optimize COMPLEMENTARITY among breeds optimize performance levels for important traits and to performance levels for important traits and to match genetic potential with:match genetic potential with:

Market preferencesMarket preferencesFeed resourcesFeed resourcesClimatic environmentClimatic environment

MARC I¼ Limousin, ¼

Charolais,¼ Brown Swiss,

c Angus and c Hereford

Limousin

Charolais

Angus Hereford

Brown Swiss (Braunvieh)

MARC II ¼ Simmental, ¼ Gelbvieh,¼ Hereford and ¼ Angus

Angus

Simmental

Gelbvieh

Hereford

MARC III ¼ Pinzgauer, ¼ Red Poll,¼ Hereford and ¼ Angus

Pinzgauer

Red Poll

Angus

Hereford

HETEROSIS EFFECTS AND RETAINED HETEROSISIN COMPOSITE POPULATIONS VERSUS CONTRIBUTING

PUREBREDS (Gregory et al., 1992)

Composites minus purebredsComposites minus purebreds

TraitTrait F F11 F F22 F F3&43&4

Birth wt., lbBirth wt., lb 3.63.6 5.05.0

5.1 5.1

200 d wn. wt., lb200 d wn. wt., lb 42.442.4 33.433.4

33.733.7

365 d wt., females, lb365 d wt., females, lb 57.357.3 51.451.4

52.052.0

365 d wt., males, lb365 d wt., males, lb 63.563.5 58.658.6

59.859.8

Age at puberty, females, dAge at puberty, females, d -21-21 -18-18

-17-17

Scrotal circumference, inScrotal circumference, in .51.51 .35.35

.43.43

200 d weaning wt., (mat.), lb200 d weaning wt., (mat.), lb 3333 3636

Calf crop born, (mat.), %Calf crop born, (mat.), % 5.45.4 1.71.7

Calf crop wnd., (mat.), %Calf crop wnd., (mat.), % 6.36.3 2.12.1

200 d wn. wt./cow exp. (mat.), lb200 d wn. wt./cow exp. (mat.), lb 5555 3737

Composite populations Composite populations maintain heterosismaintain heterosis

proportional to heterozygosityproportional to heterozygosity

(n-1)/n or 1 – (n-1)/n or 1 – P Pii22

MODEL FOR HETEROZYGOSITY IN A TWO BREED COMPOSITE

Breed Breed of sireDam ½ A ½ B

½ A ¼ AA ¼ AB½ B ¼ BA ¼ BB

(n-1)/n or 1 – (n-1)/n or 1 – P Pii2 2 = .50= .50

MODEL FOR HETEROZYGOSITY IN A THREE BREED COMPOSITE

Breed Breed of sireDam .50 A .25 B .25 C

.50 A .25 AA .125 BA .125 CA

.25 B .125 BA .0625 BB .0625 CB

.25 C .125 AC .125 BC .0625 CC

1 – 1 – P Pii2 2 = (1 - = (1 - .375.375) = .625) = .625

Weaning Wt Marketed Per Cow Exposed for Alternative Weaning Wt Marketed Per Cow Exposed for Alternative Crossbreeding Systems Relative to Straightbreeding (%)Crossbreeding Systems Relative to Straightbreeding (%)

Straight breeding 0 0 0

2-breed rotation (A,B) .67 .67 15.53-breed rotation (A,B,C) .86 .86 20.04-breed rotation (A,B,C,D) .93 .93 21.7

2-breed composite (5/8 A, 3/8 B) .47 .47 11.02-breed composite (.5 A, .5 B) .5 .5 11.73-breed composite (.5A, .25 B, .25C) .625 .625 14.64 breed composite (.25A,.25B,.25C,.25D) .75 .75 17.5

F1 bull rotation (3-breed: AB, AC) .67 .67 15.5F1 bull rotation (4-breed: AB, CD) .83 .83 19.3

Wean. wt H i Hm marketed System (+ 8.5%) (+14.8%) per cow exp

Composite populationsComposite populations provide for provide for effective use ofeffective use of

• HeterosisHeterosis• Breed differencesBreed differences• Uniformity and end product Uniformity and end product

consistencyconsistency

Genetic Variation in Alternative Mating SystemsGenetic Variation in Alternative Mating Systems

OptimumOptimum

Assumes that the Two FAssumes that the Two F11’s Used are of Similar Genetic Merit’s Used are of Similar Genetic Merit

Genetic potential for USDA Quality Grade and USDA

Yield Grade is more precisely optimized in cattle

with 50:50 ratios of Continental to British breed

inheritance.

CEFFICIENTS OF VARIATION IN PUREBRED AND COMPOSITE POPULATIONS (Gregory et al., 1992)

TraitTrait Purebreds Composites Purebreds Composites

Gestation length, dGestation length, d .01.01

.01.01

Birth wt. Birth wt. .11.11

.12 .12

200 d wn. wt.200 d wn. wt. .09.09

.09.09

365 d wt., females365 d wt., females .08 .08

.08.08

365 d wt., males365 d wt., males .09.09

.09.09

Age at puberty (females)Age at puberty (females) .08 .08

.07.07

Scrotal circumferenceScrotal circumference .07.07

.07.07

5 yr cow wt, lb5 yr cow wt, lb .07.07

.08.08

5 yr height, in5 yr height, in .02.02

.02.02

Steer carcass wt, lbSteer carcass wt, lb .08.08

.08.08

Rib-eye areaRib-eye area .10.10

.10.10

Retail product, %Retail product, % .04.04

.06.06

Retail product, lbRetail product, lb .19.19

.20.20

COMPLEMENTARITY

is maximized in terminal crossing systems

Cow HerdSmall to moderate sizeAdapted to climateOptimal milk production

for feed resources

Terminal Sire BreedRapid and efficient growthOptimizes carcass composition

and meat quality in slaughter progeny

ProgenyMaximize high quality lean beefproduced per unit feed consumedby progeny and cow herd

Rotational and Terminal Sire Rotational and Terminal Sire Crossbreeding ProgramsCrossbreeding Programs

Cow

Age No.

1 20 2 18 3 15

2 Breed Rotation

A B

4 13 5 12 - - - - 12 1

T x (A-B) T x (A-B)

Lbs. Calf/Cow 21% 18%

45%

55%

1/2A - 1/2B

Two Breed Composite

Weaning Wt Marketed Per Cow Exposed for Alternative Weaning Wt Marketed Per Cow Exposed for Alternative Crossbreeding Systems Relative to Straightbreeding (%)Crossbreeding Systems Relative to Straightbreeding (%)

Straight breeding 0 0 0 0

2-breed rotation (A,B) .67 .67 15.5 20.83-breed rotation (A,B,C) .86 .86 20.0 24.14-breed rotation (A,B,C,D) .93 .93 21.7 25.4

2-breed composite (5/8 A, 3/8 B) .47 .47 11.0 17.32-breed composite or F1 bulls (.5 A, .5 B) .5 .5 11.7 17.83-breed composite (.5A, .25 B, .25C) .625 .625 14.6 20.34 breed composite (.25A,.25B,.25C,.25D) .75 .75 17.5 22.2

F1 bull rotation (3-breed: AB, AC) .67 .67 15.5 20.8F1 bull rotation (4-breed: AB, CD) .83 .83 19.3 23.6

Wean. wt Terminal H i Hm marketed crossa

System + 8.5% +14.8% per cow exp (+5% wt/calf)

a Assumes 66 % of calves marketed (steers and heifers) are by terminal sire breed out of more mature age dams and 33% are by maternal breeds (steers only).

SUMMARYSUMMARY

General Considerations

• Rotational SystemsRotational Systems

Provide for more effective use of Provide for more effective use of • HeterosisHeterosis

• Composite populationsComposite populations

Provide for more effective use of Provide for more effective use of • Breed differencesBreed differences• Uniformity and end product consistencyUniformity and end product consistency

Figure 6. Use of heterosis, additive breed effects andComplementarity with alternative crossbreeding systems.

• Advantages of terminal sire crossing systems are not as great Advantages of terminal sire crossing systems are not as great today as 30 years ago due to similarity of breeds for rate and today as 30 years ago due to similarity of breeds for rate and efficiency of growth. efficiency of growth.

• However, differences between British and Continental breeds in However, differences between British and Continental breeds in carcass traits are still significant and relatively large.carcass traits are still significant and relatively large.

• Inter generation fluctuations in mean performance for carcass Inter generation fluctuations in mean performance for carcass traits are still large and significant. traits are still large and significant.

• For carcass traits, uniformity and end-product consistency can For carcass traits, uniformity and end-product consistency can still be enhanced by use of composite populations or hybrid bulls.still be enhanced by use of composite populations or hybrid bulls.

• Adaptation to intermediate subtropical/temperate environments Adaptation to intermediate subtropical/temperate environments can be optimized with greater precision by use of composite can be optimized with greater precision by use of composite populations or hybrid bulls. populations or hybrid bulls.

Implications for Crossbreeding

Module IV Applied Animal Breeding and SelectionHomework questions assigned September 18

To be returned by October 23, 2008(Email to: larry.cundiff@ars.usda.gov)

The Brangus breed has a genetic composition of 5/8 Angus and 3/8 Brahman breeding. 1) What is the expected heterozygosity or level of Brahman X Angus heterosis expected in the

Brangus breed (show work)?

2) How would you expect the effect of heterosis for Brangus to compare to that in a breed with a composition of 5/8 Angus and 3/8 Shorthorn, why or why not? (In other words, would effects of heterosis be the same, or more, or less for Brahman X Angus crosses than for Angus X Shorthorn crosses, why or why not?)

3) What is the expected level of heterosis in a four breed composite founded with ¼ breed A, ¼ breed B, ¼ breed C, and ¼ breed D inheritance (show work)?

4) State the location and describe a typical production environment for cow herds where you reside or provide service.

5) If you were to develop a composite population adapted to this production environment, what

foundation breeds would you select?

6) What proportions of each breed would you use in the composite population?

7) What would the expected level of heterosis be in your composite population (show work)?

8) Why would you select these breeds (Discuss the merits of each breed selected for additive direct and maternal breed effects).