chapter 9 
Advances in Reproductive Biology and 
Their Effects on Animal Improvement 
Back^tjround 
During the past 30 wai's, ii(*\\ U'('hnoIogie\s 
ha\ t' l(ul to a luiulanuMital shilt in the* way the 
I'nited State's produc es meat and li\estoek. One 
sc't ol these' te'('hne)le)gies— the' suhjeet e)f tliis 
se'e tieen— use's kneew le'dgc' eel the' i’('|)re)dueti\ e 
preee'e'ss in larm animals te> ine'reasc' |)r{)duetion. 
I he' impae'ts e)t e'xisting hre'C'ding teelinologies 
have' he't'11 gi e'at, and muc h pre)gi-('ss is still [)Os- 
sil)le thre)ugh the'ir c'e)ntiiuu'd use. I'he deve'lop- 
nu'iit e)l ne'w tee hnoleegies is ine'v itahle as w ell. 
In a marke't ('e’one)my like that of the I'nited 
States, the tacte)i' that most inriuenees the adop- 
tie)n e)f te'e hnole)i'\ is eee)nomies. .New technolo- 
gies in re'pi e)ducti\ e* physiology w ill he used 
widely onlv il the'v increase the etTiciency of 
breeding programs— i.e., only If they provide 
greater control over breeding than present 
methods do, and only if the economic advan- 
tages of the increased control can be recov- 
ered.* 
But economic factors are not the only ones 
that influence technological change— e.g., poul- 
try and livestock production have influenced 
and ha\ e been influenced by: 
• Ciov ernment regulation such as meat grad- 
ing standards: 
• increased aw areness of health effects, such 
■ Vs tlisciisscd in ;ip|). Ill-B, \er\ pai'ly adopters of a technology' 
often ilo .so foi- other than economic reasons. 
as from the use of antibiotics in livestock 
feed; 
• env ironmental concerns, such as the prob- 
lems of w aste removal, especially near fac- 
tory fai’ms: 
• the growth of knowledge, in— e.g., the re- 
productive processes of farm animals and 
the accuracy of evaluating the genetic 
merit of breeding animals; and 
• complementai'v technologies such as re- 
frigerated storage and transportation. 
i\ew technologies, from breeding to food de- 
livery systems, have reshaped the traditional 
.American farm into a modern production sys- 
tem that is increasingly specialized, capitalized, 
and integrated with off-farm services. Applied 
genetics in animal production has been one of 
the forces behind these changes. The technolo- 
gies that have sprung from it include not only 
the new, esoteric techniques for cellular manip- 
ulation discussed in other parts of this report, 
but also more well-known technologies, like ar- 
tificial insemination.* 
• Technologies selected for discussion in this part of the report 
in\'ohe direct manipulation of sex cells. More speculative technol- 
ogies for manipulations at the subcellular level are assessed here 
as well. ,\o effort was made to cover all technologies with potential 
for improving the genetic qualities of livestock— e.g,, management 
techniques like estrus detection and pregnancy diagnosis were 
omitted, as were various other methods for improving reproduc- 
tion efficienev. 
The scientific era in livestock production 
Producing purebred beef livestock has been 
the dominant breeding objective throughout 
most of the 20th century. The open range of the 
.American \\ est and Southwest— the "romantic” 
era in beef cattle production— lasted until about 
1890. (See figure 30.) Then the range was 
fenced-in and the longhorn was replaced with 
new breeds by the turn of the century— the be- 
ginning of the "purebred” era. 
Pedigree records and visual comparison of 
conformation to breed type were the basic tools 
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