186 • Impacts of Applied Genetics— Micro-Organisms, Plants, and Animals 
especially when some are incompatible— e.g., it 
is desirable to produce large animals to sell, but 
undesirable to have to feed large mothers to 
produce them. There are also other complica- 
tions. Growth rate has two genetic components^ 
for which one can select— the maternal con- 
tribution (primarily milk production) and the 
calf’s own growth potential. Other traits of in- 
terest are efficiency of growth, carcass quality 
traits (such as tenderness), calving ease, and 
reproductive traits, such as conception rate to 
first service with AI. 
Genetic improvement programs for beef have 
two major advantages over those for dairy cat- 
tle traits such as growth rate and carcass quality 
can he measured in both sexes (whereas one 
cannot measure the milk production of bulls); 
and the traits are moi’e heritable than milk 
production. 
Artificial Insemination. — Between 3 and 
5 percent of the U.S. beef herd is artificially in- 
seminated each year. This low rate is due to sev- 
eral factors, including management techniques 
(range v. confined housing), availability of re- 
lated technologies (especially, until recently, 
estrus synchronization), and the conflicting ob- 
jectives of the indix'idual breeders, ranchers, 
and breed associations. 
Because little is known about the effective- 
ness of AI in spreading specific genes through- 
out the Nation’s beef herds, analysts have con- 
centrated on their reproductive performance. 
Calf losses are heavy throughout the Nation. 
The calf crop— the number of calves alive at 
weaning as a fraction of total number of females 
exposed to breeding each year— is estimated to 
be between 65 and 81 percent. To put these 
data in perspective, USDA^® has estimated that a 
5-percent increase in the national calf crop 
would yield a savings of $558 million per year in 
the supply of U.S. -grown beef. Techniques now 
available can produce such an increase when 
they are integrated into an adequate manage- 
ment program. 
'"II. S. Ueparlnient of /Xgriculture, Agricultural Resea]‘ch Ser\'- 
ice, "Beef I’i'odiiction," ARS National Re.search Program Report No. 
203H0 (VV'a.shington, D.C.: flSD/\, October 1976). 
The standardized measure of weaning weight 
in beef cattle is the weight at 205 days, adjusted 
for sex of calf and age of dam. In a recent study 
in West Virginia— the Allegheny Highlands Proj- 
ect-calf weights ha\ e averaged an increase of 
10 lb per year of participation in the pi'oject, \ ia 
AI and crossbreeding. Estimates of increased 
value of calves statewide, should the same tests 
and AI program be expanded, add up to $3.6 
million per year when calf prices a\ erage $50 
per hundredweight. Rapid adoption of ,\l 
could bring about this kind of increase in as lit- 
tle as 40 to 48 months. 
The costs and returns of ,\l \ arv from farm to 
farm and with the numhei' of cattle in ('strus. In 
general, it becomes more \ aluahle w ith smallei- 
herds, more cows in estrus, higiK'i' conce|)tion 
rates, and better hulls. Eoi- purc'hred herds, 
even larger benefits have been estimated — e.g., 
in a 1969 study, the estimated inci'ease in \alue 
per calf when AI was used was $30.02 on pure- 
bred ranches compared to $3.31 on commercial 
ranches in Wyoming.^® 
A major secondary, or indirect, hi'iicMit of the 
use of AI is feed sa\'ed for other uses. It has 
greatly reduced the numln'r of sires lu'cessaiy 
for stud serxice and, thi’ough radically im- 
proxed milk prodiK'tion, the inimhei- of females 
as xvell. rhese nnluced re(|uirements together 
are e(|uix alent to more' than 1 billion hu of corn 
and other concentrates. Ibis situation xxill he 
further enhanced as beef cattle AI expands 
Synchronization of ilstriis. — Diflerences 
in the rates of application ol AI hetxxeen heel 
and dairy herds can Ix' explained part lx by the 
differing managenuMil .systems loi- the Ixxo 
tyjies of classes of cattle. Dairx herds arc kept 
close to the barai for' milking and are accus 
tomed to being approar hed In humans In con- 
trxrst, beef her'ds may numhei’ a fexx thmrsand 
head on 100, ()()() acr’es ol ar id paslurr* land I he 
detection of estrus under Ihesi* conditions is 
difficult. 
"'R. S. liilklM'. XI R I .IllM-ll P I 1 C\M\ .mil I K 111 kl 1|I X 
Pmgr;im Report on the Xlleghen\ llighl.inil-. I’ii‘|eil '\|, i,;.e 
tou ii, XX . X it.: XX Cst X irgini.i I im eiMt\ l.inii.ii \ is ■ einbi i | i: o 
^"D M Sle\ en.s ;iiul I Xtolir Xrtiliii.il lii-i-iiii i.ili.'o >1 ll.m.:' 
Cattle in XX voming: An I.eonomic Xii.ib sis XX muiiiuk \| i . nlin, , 
lAperiment Station Bulletin \o I'M, I'M.'t 
