Utilisation and conservation of farm animal genetic resources 47
Chapter 2. Strategies for moving from conservation to utilisation
Box 2.8. Amount of genetic material to be stored in a gene bank to reconstruct a breed. his box presents the amount of genetic material to be cryopreserved to reconstruct, in case of
breed extinction, a population of 25 females and 25 males of breeding age. he number of embryos needed for reconstructing 25 females using exclusively embryos can be
computed as,
N° of embryos = 25 pf × c × sr × sb, Eq. 2.1
where: pf is the probability that the embryo is female; c is the conception rate; sr and sb respectively
the probabilities of survival of the recipient until parturition and of the newborn from birth to breeding age. We assumed not-sexed embryos, thus we will obtain also 25 males.
Breed reconstruction by using only semen is accomplished by creating F1 crosses followed by a series of back-cross generations. he number of semen doses needed for reconstructing 25 females
can be computed as Ollivier and Renard, 1995:
N° of semen doses = d × F × np, Eq. 2.2
where: d is the number of doses needed per parturition; F is the number of females to be
inseminated during the reconstruction process to obtain the inal 25 females, computed as 25 × r + r2 + …. + rn, where r is the inverse of the expected lifetime production of fertile daughters
by female assuming on average np parturitions. By culling females at a given time, we can set np
below the species average: in this way reconstruction time decreases, but r, F and the number of
semen doses will increase. Finally, n is the number of generations of grading up we decide to use.
Because we assumed unsexed semen, at the end we will also obtain 25 males. Please note that the use of sexed semen will substantially reduce the amount of semen to be stored. Some within
family selection is advisable during reconstruction and it should be taken into account by setting the parameter
F. With the option of storing combinations of semen and embryos, reconstruction starts with a
number of females from frozen embryos smaller than 25, followed by their multiplication using semen from the bank until full reconstruction is reached 25 females. In this case the use of
Equation 2.2 will overestimate the number of semen doses because longevity of females is not taken into account. he amount of semen can be computed by computer simulation. If we assume
unsexed semen, at the end of the reconstruction process we will also obtain 25 males. During reconstruction using only semen or semen plus embryos, attention should be given to
minimise loss of genetic variation due to genetic drit.
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48 Utilisation and conservation of farm animal genetic resources
Gustavo Gandini and Kor Oldenbroek
the amount of the material to be stored. Extraction of semen from the epididymus of slaughtered animals ofers additional opportunities in constructing semen banks
Gandini et al., 2007b.
Eiciency of freezing and reproduction techniques is progressively improving, but some diferences still exist among species. Table 2.4 shows the state of the art of cryopreservation
techniques, which includes the eiciency at freezing and ater freezing.
Since the sheep Dolly was recreated from udder somatic cells, by cloning methods we can
re-establish animals from their somatic cells. Other species were cloned by this method as e.g. horse, cattle, pigs, dog, cat, and by cross-species nuclear transfer. Storage of somatic
Example goat breed: A Storage of only embryos assume: pf =.5; c =.4; sr =.9; sb =.8: 174 embryos to be stored.
B Storage of only semen assume: n = 5; d= 2; r =.67 np was set at 3 to avoid reconstruction time above 10 years, than F = 45: 270 semen doses to be stored.
C Storage of embryos plus semen; some results from Boettcher et al., 2005 in this case, no
limitations on number of parturitions were used: np = 4; r =.5: 43 embryos and 65 semen doses or 108 embryos and 45 semen doses.
Time for reconstruction will be: only embryos = 2 years; only semen = 9.4 years; embryos plus semen = 5.4 and 3.2 years, respectively for the two cases reported above. Amounts of embryos
and semen computed above should be doubled to create two storage sites.
Table 2.4. State of the art of cryopreservation, by species: + = routine technique available; 0 = positive research results, = some research hypotheses; – = not feasible in the present state
of art; ? = technique unknown from Hiemstra, 2003, modiied.
Species Semen
Oocytes Embryos
Somatic cells Cattle
+ +
+ Sheep
+ +
Goat +
+ Horse
+ Pig
+ Rabbit
+ ?
+ Chicken
+ -
- Fish - some species
+ Dog
+ ?
? Cat
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