Agriculture Reference
In-Depth Information
are mated with bucks of a meat-type sire breed to produce
two-breed cross offspring. Operationally, it is possible to
allocate one-third of does in the parental breed to produce
purebred offspring for herd replacement. Crossbred kids
for market may be produced by mating the remaining two-
thirds of the does to pure- or crossbred bucks that differ in
breed composition.
In practice, does from an established breed in the region
or indigenous population may be maintained on the farm.
Requirements for bucks may be met either by purchasing
bucks with growth potential from a reputable breeder, or
using semen from meat-type breeds. An alternate breeding
strategy involves breeding a proportion of indigenous
goats to produce purebred offspring for herd replacements.
The remaining indigenous goats may be crossed with
bucks of an improved dairy breed (Saanen, Toggenburg,
Nubian, Damascus or Jamunapari) to produce crossbred
does for milk production. Finally, the mating of crossbred
does to bucks of an improved meat breed (Boer) could
benefi t from potential genetic merit in the specifi c three-
breed cross offspring.
Backcross offspring can be produced by mating the
single cross does to bucks of the sire breed. In practice,
purebred offspring for herd replacement can be produced
from one-third of the female parents. Two-breed cross
offspring are produced by mating the remaining two-third
of the female parent with bucks of the alternate breed
purchased from an outstanding breeder. Selected crossbred
offspring become does that are subsequently mated to
bucks of the sire breed to produce the backcross offspring.
In this procedure, benefi t due to heterosis can occur from
maternal performance of the crossbred female parent and
their backcross offspring. Yet, the full complement of het-
erosis and genetic superiority associated with the parental
breeds will not be realized. In many developing countries,
the need to purchase bucks of one breed to sire both the
single cross and backcross offspring has made this method
popular. The choice of breeds for crossbreeding and the
adaptability of their offspring to the environment where
the offspring will be raised are pertinent to avoid any
detrimental infl uence.
Crossbreeding studies in a number of countries corrobo-
rate performance of offspring derived from single- and
backcross mating surpassed those of their contemporary
purebred offspring. In India, matings based on Alpine and
Saanen bucks with Beetal and Malabari does, Saanen
bucks with Saanen × Malabari does, as well as Angora
bucks with Sangamaneri and Angora × Sangamaneri does
were utilized to compare single- and backcross does with
their contemporary purebreds. Both types of crossbreds
Two-breed cross
Two-breed cross
Parents
A
B
C
D
Offspring
AxB
CxD
Back cross
Three-breed cross
Parents
A
AxB
A
CxD
Offspring
A(AxB)
A(CxD)
Four-breed cross
Four-breed cross
Parents
AxB
CxD
CxD
AxB
Offspring (AxB)x(CxD)
(CxD)X(AxB)
Given A, B, C and D are parental breeds.
Figure 4.2
Crossbred offspring derived from
two, three, and four breeds.
there is only one breed that is superior to all others in lacta-
tion performance, and crossbreeding may not improve
effi ciency of lactation production. Examples of various
crossbreeding systems are shown in Figure 4.2.
There are several approaches to crossbreeding with
considerable merit for improving productivity in goats.
Crossbreeding with more than two breeds depends on the
number of parental breeds or populations available for
crossing, and among parents the order of mating pure
breeds and their crosses. Initially single cross offspring to
be used as parents are produced from the mating of two
purebreds. This is followed by crossing selected male or
female crossbred parents with a purebred or crossbred of
the opposite sex. There is clear evidence to suggest the
genetic basis of average superiority of three-breed cross or
multiple-breed cross over their constituent single crosses
is due to the complementary breed effects in the crossbred
animal, maternal effects due to the breed combination of
the female parent, all supplemented with heterosis for indi-
vidual performance as well as maternal ability.
In goats, crossbreeding strategies for meat production
may involve crossing bucks of meat-type sire breeds with
does of the fecund-type breeds to produce kids with
increased growth rate and carcass quality, while benefi ting
from the reproductive rate and the maternal infl uence of
the doe. In general, locally adapted does of a fecund-type
dam breed exhibiting a high frequency of multiple births
