Transcript Systems of Crossbreeding – Experiences in Research & Do’s

Systems of Crossbreeding –
Experiences in Research &
Do’s and Don’ts
R. Mark Enns
Colorado State University
Overview
• Crossbreeding systems
• Research experience and
recommendations
Factors to consider when
selecting a system
• Amount of hybrid vigor
– Two types
• Individual
– For weaning weight – 5%
– For weaning rate – 0%
• Maternal
– For weaning weight – 6%
– For weaning rate – 8%
– Total
• Weaning wt per cow exposed – 18%
Kress and MacNeil, 1999
Factors to consider when
selecting a system
• Amount of hybrid vigor
– Two types
• Individual
• Maternal
•
•
•
•
Breed complementarity
Consistency of product
Replacement generation – males and females
Simplicity of the system
– Dr. Gosey calls “management ease” test
• Accuracy of evaluation
– In the future?
• Assumption: Have appropriately selected the
breeds to go into the system
Bourdon, 2000
The Key
Find a system that is beneficial for
the specific production situation
and whose downside is relatively
minor.
Examples
3 breed spatial rotation
Replacement
Breed A
Breed C
X
X
A higher proportion
Breed B
A higher proportion
Breed C
Replacement
Replacement
A higher proportion
Breed A
X
Breed B
Attributes
• Hybrid vigor
• Breed
Complementarity
• Consistency
Increased
hybrid vigor
potential
inversely related to
complementarity
Attributes
• Replacements
yes
• Genetic evaluation
likely
• Simplicity
low
3-Breed Rotation in Time
Most females a higher
proportion Breeds B and C
X
Breed A
Replacement and remaining older females
Most females a higher
proportion Breeds C and A
X
Breed B
Time
Replacement and remaining older females
Most females a higher
proportion Breeds A and B
X
Breed C
Replacement and remaining older females
Most females a higher
proportion Breeds B and C
X
Breed A
Attributes of Rotations in
Time
• Hybrid Vigor--somewhat reduced
• Breed complementarity, consistency of
performance, replacement
considerations, and accuracy of
genetic prediction
• Simplicity – greatly increased
Rotations in time designed
for small producers
Weakness:
Consistency of
decisions over time
Terminal Sire Systems
• Maternal-breed females are mated to
paternal-breed sires
• Goal: to efficiently produce progeny
that are especially marketable
Static Terminal System
Breed C
terminal
X
Purchased F1 AxB maternal
females
F1 C x (A x B) market offspring
Key
• Consider the factors that are most
important to the producer
– Give the program the greatest probability
of success
Comparison of systems
Crossbreeding System
HV
Comp
Const
Ease
ACC
Spatial Rotation
+
-
Varies
Varies
+
Rotation in Time
+
-
varies
++
+
Terminal system
(purchase replacement ♀)
++
++
+
++
+
Composite system
(already formed)
+
+
+
++
+
• Assumption: All of the above produce their own
replacement females except the terminal system
Bourdon, 2000
Numerous other systems
Only limited by the breeder’s
creativity
Rotation/Terminal Systems
Breed A
Breed B
Replacement
X
X
A higher proportion
Breed B
Male offspring
sold
Replacement
A higher proportion
Breed A
Male offspring
sold
Excess (often older) females
F1 C x (A/B) market offspring
Composite/Terminal System
Male
offspring
sold
Younger maternal
composite females
X
Maternal
composite
Older maternal
composite females
X
Terminal
Breed
F1 market offspring
More systems than can be
outlined in a hour
Research – Do’s and Don’ts
• Heterosis will not overcome poor breed choice
– Advantage of Zebu cross dams in Florida for pregnancy rate
was 5.8% units over that in Nebraska (1.8% units)
• Olson et al., 1991
– Holstein Hereford cross had a 23% advantage over HA for
calf weaned/cow-exposed, and Brahman cross a 13%
advantage (Setshwaelo et al., 1990)
• Cross must be appropriate for its production
environment
– Drs. Kress and Franke will discuss next week.
• Continous use of the same breed will
result in loss of heterosis
– Dr. Gosey
• 3 generations of using Angus bulls on F1 cows
resulted in a loss of 87% of hybrid vigor
Crossbreeding works
• Increases in lifetime production due to maternal
heterosis have been estimated at up to 1.44 calves
when calving first as 2 year olds (Cundiff et al., 1992)
defined as cumulative 200 day weight
• Nunez et al., (1991) crossbred cows had lower
probabilities of being culled than straightbreds
(Angus, Hereford, Shorthorns)
• Davis et al. (1994) reported F1 cows averaged 1.2
year longer lifespan than straightbred cows
– Net profit per cow exposed increased ~$75
Do not be tempted to retain replacement
females from terminal sire mating
systems in restrictive environments
Energy consumed to produce calf weight
varies between breeds
– Jenkins et al. (1991)
• In most environments
– At low to moderate resource availability the
British breeds tend to be most efficient at
converting intake into calf weight
– At higher levels of availability (intake) the
continental breed tend be the most efficient
• Jenkins et al. (1994)
Develop a plan and stick to it,
otherwise …
• Using Dr. Gosey’s example
– 15/16 Angus
• Realized that have lost heterosis, so go
back to Hereford bulls
– Use bulls for 3 years and 15% female
replacement rate, 1 year after last crop born
• 38% of females are now F1
• 62% of females are still Angus
• 38% are now F1 and 62% are still Angus
– So switch to a 3rd breed for 3 years
• A year after the last crop is born
– 24 % are HxA
– 38% are Angus
– 39% are new cross
• Point:
– Without a plan and some determination to
maintain focus
• can get quite the collection of different breeds
• Influences marketability
Choose not only breeds but
appropriate animals within breeds
• Colorado State University experience
– Generalization:
• Black baldy cows are adapted to the eastern
Colorado shortgrass prairies
– Can we identify another genotype that
might be adapted to that environment but
bring more performance in the feedlot and
on the rail?
Approach
• Given: Hereford x Angus cross works
well
– Choose a breed from which we could find
animals with similar milk production levels
– Continental breed
Approach
• Given Hereford Angus cross works well
– Choose a breed from which we could find
animals with similar milk production levels
– Continental breed
• Limousin
– HxA and LxA females
EPD Guidelines
Hereford
Percentiles
On NALF Scale
BW
≤ 2.0
20%
≤ 1.6
YW
Milk
60 to 70
8 to 15
55% to 30% 80% to 45%
77 to 87
7.6 to 14.6
2003 Calves
No.
WW
Adj WW
498
Calf
Age
195
Hereford x
Angus
Lim-Flex
23
27
510
195
531
521
2003 Calves
No.
WW
Hereford x
Angus
Lim-Flex
23
27
2004 Calves
No. WW Calf Age Adj WW
Hereford x
Angus
LimFlex
Adj WW
498
Calf
Age
195
510
195
531
521
67
409
156
520
14
456
188
502
• Yearling performance
–Weight and Frame Score
Hereford x Angus
No.
28
Weight
704
Frame
Score
4.7
Lim-Flex
33
685
5.2
19
-.5
Difference
• Yearling performance
Weight
Hereford x Angus
704
FS
4.7
Pelvic
Area
168
Lim-Flex
685
5.2
169
Difference
19
-.5
-1
• Breeding performance
–60 Day breeding season
Hereford x
Angus
Lim-Flex
Difference
% Bred
1st
21days
71
Total
% Bred
93
% Open
7
61
79
21
10
14
-14
• After 1st calf, all rebred except 1
• Although preliminary, we believe we
may have another adapted F1 cross
appropriate to the eastern Colorado
environment
Breed Averages
LimFlex
CW – 793
REA – 12.44
YG – 3.27(2.6)
YG4 – 0%
CAB – 40%
$/cwt - $146.11
Angus
CW – 762
REA – 12.14
YG – 3.45(3.4)
YG4 – 40%
CAB – 20%
$/cwt - $137.90
Last 83 days
Avg Daily Intake – 30.0
ADG – 3.06
Avg Daily Intake – 31.7
ADG – 3.79
$/hd – $1159.20
$/hd – $1050.57
Do’s and Don’ts
• Choose a system that has a high probability
of success
– simplicity
•
•
•
•
Make appropriate breed choice
Make appropriate choice from within breed
Stick to the plan to avoid “mongrelization”
Commercial producers should crossbreed
R. Mark Enns
Dept. of Animal Sciences
Colorado State University
Fort Collins, CO 80523
Phone: 970-491-2722
Email: [email protected]