174 • Impacts of Applied Genetics — Micro-Organisms, Piants, and Animais 
tional dairy herd.) And economics can also play 
a role; in general, the lower an animal’s value, 
the less practical the investment in the technol- 
ogies, some of which are relatively expensive. 
Several technologies are critical to the introduction 
of others. 
A methodology that could reliably induce 
estrus synchronization increases the economic 
feasibility of AI and embryo transfer. Likewise, 
the refinement of embryo storage and other 
freezing techniques would advance the develop- 
ment of those technologies still being developed, 
like sex selection and embryo transfer. Ad- 
vances in in vitro fertilization will be especially 
useful to a better understanding of basic repro- 
ductive processes and therefore to the devel- 
opment and application of the more speculative 
technologies. 
The technologies interrelate. 
All the technologies combined make possible 
almost total control of the reproductive process 
of the farm animal: a cow embryo donor may be 
superovulated and artificially inseminated with 
stored, frozen sperm; the embryos may be re- 
covered, then stored frozen or transferred di- 
rectly to several recipient cows whose estrous 
cycles have been synchronized with that of the 
donor to insure continued embryonic develop- 
ment. Before the transfer, a few cells may be 
taken for identification of male or female chro- 
mosomes as a basis for sex selection. Finally, 
two embryos may be transferred to each recip- 
ient in an effort to obtain twins. (See figure 33.) 
Techniques not yet commercially applicable 
all require embryo transfer in order to be use- 
ful. They include in vitro fertilization, partheno- 
genesis, production of identical twins, cloning, 
cell fusion, chimeras, and rDNA technology. 
The technologies described in this section are 
designed to increase the reproductive efficiency 
of farm animals, to improve their genetic merit, 
and to enhance general knowledge of the repro- 
ductive process for a variety of reasons, includ- 
ing concern with specific human medical prob- 
lems, such as fertility regulation and better 
treatments for infertility. 
Technologies that are presently useful 
SPERM STORAGE 
The sperm of most cattle can be frozen to 
— 196° C, stored for an indefinite period, and 
then used in in \'i\o fertilization. .Although 
many of the sperm are killed during freezing, 
success rates [or successful conceptions (table 
31)] combined with other adxantages of the 
technologies are enough to ensure w idespread 
use of the technology. Short-term sperm stoi age 
(for one day or so) is also well-(le\eloped and 
widely used. 
The major advantages of storing sperm are 
the increased use of desirable sires in breeding 
(see figure 34), the ease of transport and spread 
of desirable germplasm throughout the country 
and the world, and the sa\ ings fiom slaughter- 
ing the hull after enough sp(>rm has been col- 
lected. The sperm can also he lest(*d for \cne- 
real and other diseases hefoi'(> it is used I hert'- 
fore, the use of sperm banks is e.xpected to in- 
crease. Little change is anticipated in .semen 
processing, other than tin* continued refine- 
ment of freezing protocols, which dilfer for 
each species. 
ARTIFICIAI, I,\SEM1\ VriOV 
The manual placcMuenl of speiin into tin* 
uterus has playcui a ('cnlral role in the ilissemi- 
nation of \aluahl(? g(‘rmplasm thioughoul the 
world’s hertis and fhu'ks. \ irtually all farm spe- 
cies can he artificially inst'minaled. although use 
of the technology \ari(>s widely lor different 
species— e.g., 100 percent of the Nation's domes- 
tic turkeys are produced via AI compan'd with 
less than 5 percent of beef cattU*. lA'en hoiu'v- 
Table 31. — Results of Superovulation in 
Farm Animals 
Average number 
ovulations normally Number of ovulations 
expected with superovulatlon 
Cow 1 6-8 
Sheep 1.5 9-11 
Goat 1.5 13 
Pig 13 30 
Horse 1 1 
SOURCE: George Seidel. Animal Reproduction Laboralor, C' ■ Siai» u 
versily. Fort Collins. Colo 
