This document discusses outbreeding and its classification in animal genetics and breeding. It defines outbreeding as mating animals that are less closely related than the average within a population. There are several types of outbreeding discussed including outcrossing, crossbreeding, grading up, and species hybridization. Crossbreeding involves mating animals from two or more established breeds and has advantages like utilizing heterosis to increase productivity. New breeds have been developed using outbreeding and selection over multiple generations.

1. ANIMAL GENETICS & BREEDING
Outbreeding & its classification
Semester 1st
Animal Resources
Department of Bioresources

2. Outbreeding & its classification
 Outbreeding: Mating of animals which are less closely
related to each other than the average relationship within
the population concerned is known as outbreeding –
according to Prof Jay L. Lush.
• Outbreeding is a system of breeding in which mates are
less closely related than the average members of the
population concerned.
• Mating of unrelated animals is also called the outbreeding.
• Two mated individuals are said to be unrelated if they do
not have a common ancestor in the preceding 4 – 6
generations of their pedigree.

3. Classification of outbreeding
1. Outcrossing
2. Crossbreeding
i. Two breed crossing
ii. Three breed crossing
iii. Criss crossing
iv. Rotational crossing
a) Three-way rotational crossing
b) Four-way rotational crossing, etc
v. Line crossing
a) Incrossing
b) In crossbreeding
3. Grading up
4. Species hybridization

4. Genetic consequences of outbreeding:
i) Outbreeding increases heterozygosity at the cost of
homozygosity.
ii) If the mates are homozygous for contrasting allele
for a given locus then maximum amount of
heterozygosity is attained in F1 generation ( half-
breds).
Population I x Population II
Genotype of Parents TTggRRyy ttGGrrYY
Genotype of Progeny (F1) TtGgRrYy

5. iii) In half-bred (F1) population the frequency of
dominant and recessive alleles at a given locus
becomes equal i.e., p = q = 0.5.
iv) Selfing or self fertilization leads to decrease in
heterozygosity in subsequent generations due to
segregation of genes.
v) Due to heterozygosity, the outbred individuals do
not tend to be breed true.
vi) In many cases the outbreds show their superiority
over the mid-parental value in performance. This is
called heterosis or hybrid vigour.

6. Heterosis: The average superiority of outbreds over their
mid-parental value (parental average) is called heterosis or
hybrid vigour.
Heterosis is expressed in terms of percentage (%).
Heterosis (%) =
𝑿𝑶 −𝑿𝑷 𝒙 𝟏𝟎𝟎%
𝑿𝑷
Where, XO and XP are the average performance of offspring
and mid-parental value respectively.
Example: Suppose the average litter size at weaning in pig is
7.0 for breed A and 8.0 for breed B. The average litter size
of their F1 (half-bred) is 8.5. The heterosis (%) would be
[{8.5 – (7.0 + 8.0)/2}/7.5]x100 = [(8.5 – 7.5)/7.5]x100
= (1/7.5)x100 = 13.33%.

7. Types of outbreeding
1. Outcrossing: Mating of unrelated animals belong to an
established breed is known as outcrossing.
Genetic aspect of outcrossing:
i) The traits of high heritability and largely influenced by
additive gene action.
ii) Outcrossing followed by selection is recommended for
production of seed stock.
iii) As in case of inbreeding, fixation of undesirable genes takes
place.
iv) Outcrossing brings about immediate improvement in herd
and also keeps the door open for future improvement.
v) It is also suitable for improvement of lowly heritable traits.

8. Use of outcrossing:
i) This breeding system is recommended for production of
seed stock of highly heritable traits.
ii) It can also be used for production of commercial stock.
iii) It can be used when a drastic change is required either in
seed stock or in commercial stock.
iv) It is highly effective system of breeding for the traits
mainly influenced by additive gene action, eg., milk yield,
growth rate etc.

9. 2. Crossbreeding:
Mating of animals belong to two different established breeds
is known as crossbreeding. In brief, crossing between two breeds is
known as crossbreeding.
There are a number of crossbreeding systems which could be
used for commercial production. Most commonly used crossbreeding
systems are:
i) Two breed crossing : In this system two different distinct
breeds are used for crossing.
F1 individuals are sold in the market or disposed for commercial
use not for breeding purpose. This breeding system takes advantage
of heterosis since F1s are hybrid.
Example: White Cornish (male) x White Plymouth Rock (female)
F1 WC 50 : WPR 50

10. ii) Three breed crossing: In this system three breeds are taken. At
first male of one breed is crossed with female of second breed, and
F1 crossbred female is crossed with male of third breed. The
crossbred so produced are sold to the market directly for commercial
use not for breeding purpose.
This breeding system utilises individual as well as maternal heterosis.
Example: Three breeds A,B and C are taken and they crossed in the
following fashion:
B male x A female
F1 A50 : B50 female x C male
F2 A25 : B25 : C50
• Both male & female are disposed for commercial use.
• F2 used individual heterosis as well as maternal heterosis.

11. iii) Criss-crossing:
• Only two breeds are involved.
• The males of two breeds are used for crossing over
their crossbred females in alternate fashion.
• After completion of one cycle, the crossbreds will
have 62.5% genetic inheritance of breed of
immediate sire.
• To maintain 62.5% genetic inheritance in subsequent
generations the male and female crossbred
progenies are used crossing continuously.
• This system is used to maintain 62.5% genetic
inheritance of a particular breed.

12. How to maintain 62.5%?
Two breeds A and B are taken. Sire of both the breeds
crossed over their crossbred female progeny in alternate
fashion in subsequent generations so that genetic inheritance
of a particular breed in two breed crossbred progeny becomes
62.5%.
 After establishment of 62.5% genetic inheritance of a
desired breed, the male and female crossbred progenies of
same level of genetic inheritance will be crossed inter-se
generation after generation to maintain 62.5% genetic
inheritance.
 Inter-se mating means the mating of half-bred male and
female among themselves. Generally in crossbreeding two
distinct breeds are crossed. However, in inter-se mating half-
bred males are mated to half-bred females of F1 generation to
produce F2.

13. Schematic diagram of criss-crossing:
Parent A male(100) x B female(100)
F1 A50 : B50 female x B male
F2 A25 : B75 female x A male
F3 A62.5 : B37.5 F
Inter-se mating starts
F3 A62.5 : B37.5 F x A62.5 : B37.5 M
F4 A62.5(HF) : B37.5(Indigenous)
M = Male & F = Female

14. iv) Rotational Crossing:
• Three or more breeds are involved in rotational
crossing.
• When males of three or more breeds are used in
crossing over their crossbred female progeny in
alternate fashion then it is called as rotational
crossing.
• If three breeds are used then it is called Three-
way Rotational Crossing. When 4 breeds are used
then it is called four-way rotational crossing and so
on.

15. • After completion of one cycle in three-way rotational
crossing, the three breed crossbred progeny will have
 56%(4/7) genetic inheritance of the breed of immediate sire
used in crossing,
28% (2/7) genetic inheritance of the breed whose male used
as grand sire and
14%(1/7) genetic inheritance of third breed which used as
great-grand sire.
• There after the selected male and female progeny of
three breed crossbreds will cross among themselves in
inter-se generation after generation to maintain same
level of genetic inheritance of the desired breed.

16. Mating design of 3-way rotational crossing:
• Three breeds namely A,B&C are taken.
Parents A male x B female
F1 A50 : B50 F x C M
F2 A25 : B25 : C50 F x A Male
F3 A62.5 : B12.5 : C25 F x B M
F4 A31.3 : B56.2 : C12.5 F x C Male
F5 A15.5 : B28 : C56.5 Ist cycle of Rotational
Crossing is completed
Inter-se mating starts
A15.5 : B28 : C56.5 F x A15.5 : B28 : C58.5 M
F6 A15.5 : B28 : C56.5
F = female & M = male

17. v) Line crossing: Crossing between two highly inbred lines
is known as line crossing.
Depending upon the number of breeds involved it is two
types.
(a) Incrossing : Crossing between two inbred lines
belong to an established breed is known as incrossing.
(b) In-crossbreeding: Crossing between two inbred
lines belong to two different established breeds is known
as in-crossbreeding.
• Depending upon the percentage of homozygosity of two
lines, the heterotic effect or hybrid vigour will be
exhibited in the line cross progeny.
• Maximum heterozygosity is attained in F1 (half-breds),
so heterosis will be maximum in F1 generation.

18. Features of line crossing:
(i) Superiority of line crosses is mainly attributed due
to heterosis.
(ii) Superiority is also due to successful choice of
inbred lines which bring together the desirable gene
combinations in the hybrids.
(iii) Higher yield in hybrid population is largely due to
uniform production from nearly all individuals rather
than extraordinary yield by some individuals.
(iv) Line crossing is successfully used in poultry, pigs
and laboratory animals which have shorter
generation intervals.

19. Advantages of crossbreeding:
i) It utilizes heterosis, both individual and maternal, so
used for production of commercial stock.
ii) It helps in incorporation of desirable characters into
a population through introduction of new genes from
different breeds or populations.
iii) It increases frequency of desirable genes in the
population.
iv) Crossbreeding makes the foundation for evolving of
new breeds.
v) It increases productivity of farm animals and poultry.

20. 3. Grading up: Progressive improvement of non-descript
females by use of descript sires for several generations is
known as Grading up.
• Grading up is the practice of mating purebred sires of a
given breed to non-descript females and their female
progeny in subsequent generations.
• The first generation offspring carry 50 percent
inheritance of the pure breed.
• The next generation offspring results with 75%
hereditary material of the purebred.
• The proportion of the inheritance from non-descript
females is halved with each cross in subsequent
generations.

21. Mating design of Grading Up programme:
• Sahiwal, the best dairy breed of India, is taken for genetic
improvement of non-descript cattle.
Parents ND 100 Dam x Sahiwal 100 sire
F1 ND50 : S50 F x Sahiwal 100 M
F2 ND25 : S75 F x Sahiwal M
F3 ND12.5 : S87.5 F x Sahiwal M
F4 ND6.25 : S93.75 F x Sahiwal M
F5 ND3.125 : S96.875 F x Sahiwal M
F6 ND1.6 : S98.4
F = female , M = male & S = Sahiwal
NB: Graded animal at 6th generation resemble the purebred.

22. • At sixth generation, the graded animals carry 98.3
% hereditary material of the pure breed. From
genetic point of view they are essentially the same as
purebred.
Uses of Grading Up:
1. Grading up is a system of mating resulting into quick
transformation of a non-descript population into a
group resembling the pure breed.
2. The grading up process is not creative rather
replacing and the quality of graded animals depends
almost entirely upon the genetic quality of the sire
used.

23. Limitation of grading up programme:
i) Lack of adaptability of purebred used for grading
up programme particularly of exotic origin.
ii) The purebreds used must have evidences of
performing well under the environment to which
their offspring are to be subjected. A pilot
project may be of useful before introducing a new
breed on massive scale in an area.
iii) Use of same sire in subsequent generation may
lead to inbreeding, so use of same sire should be
avoided.

24. 4. Species Hybridization :
• Crossing between two different species is known as species
hybridization. It is the crossing between two extreme
divergent populations.
• Species hybrids are generally very hardy and sterile.
Example:
1. Jack (male ass) x Mare (female horse)
Mule
2. Stallion (male horse) x Jennet (female ass)
Hinny

25. 3. Zebra x Horse
(Equus zebra) (Equus caballus)
zebroid
4. Zebra x Donkey
(Equus zebra) (Equus asinus)
Zenkey
5. Cattle x Yak
(Bos Taurus) (Bos grumnies)
Pienniu (in Tibet)

26. 6. Cattle x American buffalo
(Bos taurus) (Bos bison)
Cattalo
7. Zebu cattle x Exotic cattle
(Bos indicus) (Bos Taurus)
XB cattle
8. Goat x Sheep
(Capra hircus) (Ovis aris)
Geep

27. Advantages of outbreeding:
i) It utilizes heterosis, both individual and maternal, so
used for production of commercial stock.
ii) It helps in incorporation of desirable characters from
two or more breeds into a population through
introduction of new genes.
iii) Outcrossing increases frequency of desirable genes in
the population.
iv) Outbreeding/Crossbreeding makes the foundation for
evolving of new breeds.
v) Outcrossing can be used for commercial seed stock
production.
vi) It increases productivity of farm animals and poultry.

28. Crossbreeding for evolution of new breeds of animal:
 Crossing between two or more breeds/ lines/strains
etc. followed by rigorous selection is the basic
principle behind evolution of new breeds.
 Examples of new breeds developed:
(A) Cattle:
1. Karan-Fries : Tharparkar x HF
(37.5 – 50%) (50 – 62.5%)
2. Karan-Swiss : Sahiwal x Brown Swiss
(50%) (50%)
3. Jersind : Jersey x Red Sindhi
at NDRI, karnal

29. 4. Frieswal : HF x Sahiwal at NRC cattle, Meerat
5. Sunandini : BS x desi cattle AICRP cattle, Kerala
6.Jamaica Hope : Jersey x Sahiwal developed at Jamaica
7. Girilanda : Gir x local cattle developed at Brazil
8. Brangus : Brahma x Angus
9. Santa Gertrudis: Brahma x Shorthorn developed at Texas
10. Australian Milking Zebu (AMZ) : Jersey x Sahiwal
developed at Australia for tropical area.
AMZ is resistant to ticks.
11. Beef Master : It is a beef breed developed by crossing
3 breeds i.e., Shorthorn x Hereford x Brahma

30. (B) Sheep:
1. Hissardale : Merino (F) x Bikaneri (M)
2. Columbia : Lincoln (F) x Rambouillet (M)
3. Panama : Rambouillet (F) x Lincoln (M)
4. Corriedale : Merino (F) x Lincoln (M)
5. Bharat Merino : Chokla & Nali x Rambouillet & merino
75% exotic inheritance at Avikanagar
6. Avivastra : Chokla & Nali x Rambouillet & merino
50% exotic inheritance at Avikanagar
7. Avikalin : Malpura x Rambouillet (50%) Avikanagar
8. Avimans : Malpura & Sonadi x Dcorset & Suffolk
50% exotic inheritance at Avikanagar

31. 9. Indian Karakul : Marwari, Malpura & Sonadi x
Russian Karakul (75%) developed
at CSWRI, Bikaner
10. Kashmir Merino : Gaddi, Bhakarwal & Poonchi x
Merino & Rambouillet (50 – 75%)
developed at CSWRI, Avikanagar
(C) Pig :
1. T & D : Tamworth x Desi developed at
RVC, Kanke, Ranchi

32. Thank You