This presentation was given at the KHSI Expo in Cookeville, TN (August 2016).

1. Crossbreeding with Katahdins
SUSAN SCHOENIAN
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu -
www.sheepandgoat.com
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2. The “Holy Grail” of sheep production
(Dr. Charles Parker)
Pounds of quality lamb marketed per ewe per year
How do we increase it!

3. How do we increase pounds of quality
lamb weaned per ewe exposed?
Management Genetics
• Management at lambing
• Disease control
• Parasite control
• Predator control
• Nutrition
• Selection
• Crossbreeding****

4. What is crossbreeding?
• Mating individuals of different breeds or types.
x Texel x Hampshire/Suffolk x Lacaunex White Dorper

5. What does crossbreeding actually do?
• Creates new combinations
of genes in crossbred
animals.
• Crossbred animals have
increased heterozygosity
(having dissimilar pairs of
genes for a hereditary
characteristic).
• Heterozygosity is the basis
for hybrid vigor (or
heterosis).

6. Why crossbreed?
• Hybrid
vigor
• Breed
complementarity
• Upgrading
• Make composite
breed

7. Hybrid vigor
• Superiority of crossbred offspring compared to
the average performance of its purebred parents.

8. Breed A
Breed B
First cross (F1)
Purebred average
SUPERIOR
HETEROSIS

9. Estimates of lamb and ewe heterosis effects
Trait Lamb Ewe
Birth weight 3.2 5.1
Weaning weight 5.0 6.3
Pre-weaning ADG 5.3 --
Post-weaning ADG 6.6 --
Yearling weight 5.2 5.0
Conception rate 2.6 8.7
Lambing rate 2.8 3.2
Pre-weaning survival 9.8 2.7
Lambs born/ewe exposed 5.3 11.5
Lambs reared/ewe exposed 15.2 14.7
Litter weaning weight/ewe exposed 17.8 18.0
Effects expressed as percentage of purebred average (Nitter, G. 1978)

10. Lamb heterosis for weaning weight
Purebred lambs Crossbred lambs
A B BA AB
Weight 53 63 62 60
Average 58 61
Heterosis
3 lbs. (61-58)
5.2% (3/58)
Ewe heterosis for lambing rate
Purebred ewes Crossbred ewes
A B BA AB
Weight 1.70 1.90 1.84 1.88
Average 1.80 1.86
Heterosis
0.06 lambs (1.80-1.86)
3.3% (0.06/1.80)

11. Heterosis in the crossbred ram
• Less is known about the effects of
heterosis in the crossbred male.
• It is likely that heterosis
influences traits such as libido,
conception rate, hardiness, and
longevity.
• Increased fertility of crossbred
rams used in spring mating has
been reported.
• Another use of crossbred rams is
to optimize breed composition of
crossbred ewes.
• Usefulness and value of crossbred
rams has not been fully
recognized by US sheep industry.

12. Benefits of heterosis
• Effects of heterosis on one
trait may seem minor, but
when total productivity is
considered, heterotic effects
accumulate to provide a
substantial improvement over
straightbred sheep.
• Combined effects of lamb
heterosis ewe heterosis, and
complementarity can increase
production by 40 to 50%
relative to the average of
purebred flocks of different
breeds.

13. A crossbreeding system using terminal
sires in a meat sheep operation
SCENARIO 1
• Maternal ewes
mated to maternal
rams of the same
breed.
SCENARIO 3
• Maternal ewes
mated to maternal
rams of same breed
(to produce
replacements).
• Maternal ewes
mated to terminal
sire breed (to
produce market
lambs.
• Assume no hybrid
vigor from
production of
crossbred lambs.
SCENARIO 3
• Maternal ewes
mated to maternal
rams of same
breed (to produce
replacements).
• Maternal ewes
mated to terminal
sire breed (to
produce market
lambs.
• Hybrid vigor is
included.

14. SCENARIO 1 SCENARIO 2 SCENARIO 3
100 ewes x maternal ram 35 ewes x maternal ram
65 ewes x maternal ram
35 ewes x maternal ram
65 ewes x maternal ram
Ewe lambs mated Ewe lambs mated Ewe lambs mated
90% of ewes lamb 90% of ewes lamb 90% ewes x maternal lamb
92% ewes x terminal lamb (+2.6%)
1.5 lambs raised per ewe 1.5 lambs raised per ewe 1.5 lambs per ewe x maternal
1.7 lambs per ewe x terminal (+13%)
20 ewe lambs kept for
replacement
20 maternal sired lambs kept
for replacement
20 maternal sired lambs kept for
replacement
Rams purchased Rams purchased Rams purchased
115 market lambs sold at 114
lbs. @ $1.50/lb
27 maternal-sired lambs sold
at 114 lbs @ $1.50
88 terminal-sired lambs sold
at 128 lbs. @ $1.50
27 maternal-sired lambs sold
at 114 lbs @ $1.50
102 terminal-sired lambs sold
at 128 lbs. @ $1.50
$19,665 $4617
$16,896
$21,513 (+9.4%)
$4,617
$19,584
$24,201 (+23.1%)
Source: Strategic use of terminal sire meat breeds to improve flock production,
David L. Thomas & Thomas W. Murphy, University of Wisconsin
Assumptions and Results

15. Composite breeds
• A new breed formed by
crossing two or more breeds,
then selecting within new
crossbred population.
• Appeal of composite breeds:
simple and practical breeding
system to use breed and
heterosis effects, an alternative
to more complex
crossbreeding systems.

16. Crossbreeding systems

17. Terminal crossbreeding systems

18. Do all traits respond to crossbreeding?
• Traits that are lowly heritable
respond the most to
crossbreeding, i.e. have the
most hybrid vigor.
▫ Reproduction
▫ Resistance
▫ Fitness
▫ Longevity
• Crossbreeding (heterosis) has
little to no effect on traits that
highly heritable.
Example: Carcass traits
• As heritability increases,
crossbreeding has little to no
effect.

19. Breed complementarity
• No one breed of sheep is best of
all traits, not even Katahdins!
• Crossbreeding takes advantage
of breed complementarity.
▫ Breed complementarity is the
combining of desirable traits from
two or more breeds into one
animal.
▫ Strengths of one breed will offset
the weakness of another breed.
▫ To maximize the benefits of breed
complementarity, breeds must be
chosen wisely; they must
complement each other.

20. Katahdin criticisms
• They don’t grow fast
enough
• They lack muscling.
• They finish too light
• They have too much
internal fat.
• Their lambs are suitable
for all markets.
▫ Hot house (30-50 lbs)
▫ Commodity (over 120)

21. Improvement of carcass merit while maintaining
parasite resistance in crossbred Katahdin lambs
Feedlot finished, artificial parasite challenge
Katahdin Suffolk Texel
Primary infection no differences
Challenge infection 757 epg 226 epg 462 epg
Worm burdens no differences
ADG not statistically significant
0.71 lbs/d 0.88 lbs/d 0.77 lbs/d
REA different no differences
2.13 in2 2.67 in2 3.04 in2
Leg score 11.0 12.0 12.8
ParasitesGrowthCarcass
West Virginia University and Virginia Tech, 2016

22. Performance of crossbred Katahdin
lambs, pasture-raised
Trait
Sire breed
Katahdin Dorper Texel Suffolk
Birth weight no difference
Weight, d-30 Lighter Intermediate Heavier
Weight, d-120, lbs. 88.0 ± .13 92.6 ± .13 90.4 ± .13 99.2 ± .13
ADG, d 0-240, lb/d 0.29 ± .004 0.31 ± .004 0.31 ± .004 0.35 ± .004
FEC, d-90, epg 1469 2380 1085 1990
FEC, d-120, epg 1159 ± 534 5069 ± 877 1159 ± 534 5069 ± 877
# lambs dewormed 55 ± 7% 67 ± 7% 43 ± 7% 70 ± 8%
Frequency of Tx, # 0.7 ± .1 1.2 ± .2 0.6 ± .1 1.2 ± .2
Age at first Tx, d 173 ± 6 155 ± 7 180 ± 7 157 ± 7
University of Maryland Eastern Shore (2007)

23. Improvement of carcass merit while maintaining
parasite resistance in crossbred Katahdin lambs
90-d summer grazing season
Trait
Sire breed
Katahdin Suffolk Texel
Birth weight, lbs. 9.3 10.1 na
Lambing difficulty no differences observed
Pre-weaning death loss 0.08 0.43 0.11
Adj. weaning weight, lbs. 52.5 56.4 58.0
End weight 64.4 67.9 77.4
ADG 0.132 na 0.198
Fecal egg counts no differences observed
% lambs requiring deworming 63 90 na
West Virginia University and Virginia Tech, 2016

24. What crossbreeding is not
•Indiscriminate
mixing (crossing)
of breeds.
X

25. What crossbreeding is
• Crossbreeding is a systematic use
of breed resources to create
animals of specific type for specific
goals.
1. Crossbred lamb
(terminal cross)
2. Crossbred ewe
3. Crossbred ram
• A good crossbreeding program
combines breeds with
complimentary traits.

26. About crossbreeding with Katahdins
• If crossbred (with wooled
breeds) are retained, they
will probably require
shearing.
• The fleeces from hair x
wool sheep should be
discarded. They should
be discarded. They
should not be mixed with
wool and/or taken to
wool pools.

27. SUSAN SCHOENIAN
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu
www.sheepandgoat.com
Thank you for your attention. Questions? Comments?