184 • Impacts of Applied Genetics— Micro-Organisms, Plants, and Animals 
crease to around 10 million in the next decade if 
milk production continues to increase. 
Artifical Insemination. — An example of 
the interaction between technologies and genet- 
ic improv'ement is shown in table 34. The “pre- 
dicted difference” (PD) in milk production rep- 
resents the ability of individual bulls to genet- 
ically transmit yield— the amount of milk above 
or below the genetic base that the daughters of 
a bull will produce on average due to the genes 
they receive. As indicated in table 34, the pre- 
dicted difference for milk yield transferred via 
the bull shows an improvement from 122 to 908 
lb for active AI bulls in the United States over 
the past 13 years. 
This impressive improvement still lags behind 
what is theoretically possible. A hypothetical 
breeding program could result in an expected 
yearly gain of 220 lb of milk per cow, using AI; 
and the biological limits to this rate of gain are 
not known. In practice, the observed genetic 
trend in the U.S. national dairy herd is about 
100 lb— 70 lb from the PDs of hulls plus 30 lb or 
so from the female, most of which is actually 
carryover effect from the previous use of supe- 
rior bulls. 
AI organizations, many of which are coop- 
eratively owned by dairymen, have not rigor- 
ously applied the principles of AI. Their efforts 
have been limited by reluctance to break with 
traditional selection practices, financial con- 
straints for proper testing of young bulls to pro- 
Table 34.— Predicted Difference (PD) 
of Milk Yield of Active AI Bulls 
Year TO milk (lb) 
1967 122 
1968 198 
1969 205 
1970 276 
1971 301 
1972 346 
1973 348 
1974 336 
1975 425 
1976 501 
1977 558 
1978 748 
1979 908 
SOURCE: Animal Improvement Programs Laboratory, Animal Science Institute, 
Beltsville Agricultural Research Center, USDA. 
duce sires of cows, and too much emphasis on 
nonproductive traits of ciuestionahle economic 
value. The progress that has been made has re- 
sulted from the increased use of AI, the a\ail- 
ability of data through NCDlllP, and the ac'tual 
use of reliable genetic exaluations. If an\' of 
these three factors had been missing, far less 
improvement would ha\ e occuri'ed. 
Semen Storage.— It is doubtful that major 
technological changes in processing semen w ill 
occur. However, since the I'ate of conception is 
as important as the genetic merit of a sir(> to th(> 
economy of a dairy enterprise?, more attention 
will be given to selecting sires of high fei'tility. 
Progress should he made in hanking seiiu'ii by 
AI studs as a hedge against costs of inflation. In 
the future, some of the; ine-re'ase'el e'e)sts e>f he)us- 
ing and feeding hulls will preehahly he* e)ffset by 
semen hanking and earlie*r e'limination of manv 
bulls. 
Sexed Semen.— Se;xing of se*me*n te) pre)eluce* 
heifer cakes (fe)i' dairvme’ii) e)r hull e ak e's (for 
AI organizatieins) has l)e;e*n atte*mpteel \\ithe)ut 
success for many ye;ars. 
Perfect determination of the* se*\ of proge*ny 
could practically elouhle* sele*ction inte'usity in 
two ways— with elams to |)re)eluce* hulls for te*st- 
ing in AI and dams te> proeluce re*plae e*ments. It 
sexed semen is use;el with .in AI plan, the* thi’o- 
retical impi'ei\eme*nl in milk yie*lel woulel he* ;t:t 
Ih per year’, with 2'A Ih elue* to se*le*ction of elams 
for replacements. 
The \ alue; e)f this aelelitional amount pe*r year 
may ne)t seem gre*at for any ineli\ ielual cow , hut 
when it is multiplie*el by a national h(*rd ol 7 
millieen cenvs using ,\l anel is accuimil<ile*el lor 10 
years, the; eceeneimie' \alu(*. at ,S() 10 Ih. is .ihout 
$1.1 hilliem— an a\ e*rage* ol $ I It) million per \ ear 
and $231 millie)n eluring the* IDth u*aiv I he cost 
e)f sexing seme*n is not know n. since* no one h.is 
successfully de)ne* it. II a wa\ is lounef the* cost 
weuild ha\e; to he* unele*r $10 per hi'ceding unit 
teir the pi'ejceelure* to he* e*e e)ne)mie-.il 
Embryo 1’raiisfrr.— I he* transle*i eil li*i 
tilized eggs freem a e eiw tei eihtain |)reige*iw h.is 
been ae;ce)mplishe*el w ith gi e*al sue e e*ss Most 
transle*i\s h;i\ e* in\ eik e*el popular eti' e*\eilie hi l•l•el 
