Ch. 9— Advances in Reproductive Biology and Their Effects on Animal Improvement • 181 
4 000 11) ot milk. |)t>r lai'tation. In llie testinfi \ t‘ai' 
(1077-7iS), the suptM'iority sur[)assecl 5,000 II) pt>r 
I'DW This 5,000-11) siipei'iority represents 52 
peri'ent more milk per laetation. 1 ht> inereases 
in protliietion ()t‘r eow I'tvsiilt trom improx ement 
in both management teehni(|iies and genetic 
producing ahilitx . 
SextM'al factors intluence the I'ates of pai tic- 
i[)ation in the XCDllll’ from State to Statt\ from 
region to I'egion, and from breed to breed. In 
some States, expansion of NCDHll’ memhei'ship 
is not a high prioritx of tin* Statt* C'oopiM'atix e 
Kxtension St*r\ ice. In some ai’eas. the I'elatix e 
im[)ortance of dairx ing as an ent(M‘prise is low ; 
therefore, a strong local 1)111 \ organization 
does not exist l,ikex\is(‘, in aia'as where daii'x- 
ing is a part-time operation, daii ymen have less 
time and initiatixe for partici[)ating in the pro- 
gram (although many [)artici|)ate iti .\t4)HIF’s 
unofficial plans). W here dairymen rely on their 
oxx II hulls and use little W in breeding, progeny 
testing is extremely limited. ,\o single factor 
causes dairymen in .some States to take greater 
adx antage of the su[)erior germplasm ax ailahle 
to them rhe importance of strong national 
leadership cannot he ox eremphasized in ex- 
plaining the great differences among breeds in 
participation rates. (See table 33.) Farsighted 
leadership played a large role in dex eloping the 
genetic gain of Holsteins, xx hich represent 90 
percent of the I .S. dairx herd today. 
The genetic gains resulting from XCDHIP are 
inipressixe, suggesting a model for spreading 
genetic superiority throughout the Nation’s 
other herds. XCDHIP also shoxx s the importance 
Table 33.— National Cow-Year and Averages for 
All Official Herd Records, by Breed 
May 1,1 978- Apr. 30,1979 
Cow-years 
Breed (#) Milk (lb) Fat(%) Fat (lb) 
Ayrshire 17,135 11,839 3.96% 469 
Guernsey 57,577 10,858 4.64 504 
Holstein 2,297,684 15,014 3.64 547 
iJersey 89,449 10,231 4.90 501 
'Brown Swiss 24,247 12,368 4.04 500 
Milking shorthorn 2.130 10,451 3.65 381 
Mixed and others. 83,139 13,077 3.80 497 
iSOURCE: U S. Department of Agriculture. Science and Education Administra- 
tion, Dairy Herd Improvement Letter 55. #2. December 1979. pp. 5-6. 
ot combining reliable ex aluation of germplasm 
xxith the use of reproductixe technologies, 
rhese technologies art? of only academic in- 
terest XX hen thex' are used alone; it is xx hen 
superior germplasm can he spread throughout 
the Nation that the .American consumer 
benefits. 
Othi^r spei'ies 
Progeny testing schemes for other species are 
not as dexeloped as tht?y are foi' dairy cattle. 
There ai'e sexeral reasons for this lack of 
testing: 
• Difjiculty in establishing a selection objective 
around which to design a testing program. 
.Milk x'ield and fat content xvere ohxious 
traits for selection in dairy cattle. Other 
species hax e no such simple traits for selec- 
tion. It has been ohserx ed that, “The lack of 
definition of economic selection ohjectixes 
in a precise, soundly based manner is one 
of the serious xxeaknesses of much animal 
breeding of the past.’’’^ 
• Differences in management systems. Artifi- 
cial insemination is essential to the intro- 
duction of superioi' germplasm; where it is 
difficult to practice Al, elaborate testing 
schemes are not useful— e.g., in the Na- 
tion’s beef herds, progeny testing will have 
to await more widespread use of AI. 
Though sxvine are increasingly raised in 
confined housing systems, poor fertility of 
boar sperm after freezing and thawing and 
heat detection difficulties have limited the 
use of AI. 
• Conflicting commercial interests. Beef bulls, 
for example, continue to be sold to some 
extent on the basis of fancy pedigrees and 
lines, with relatively little objective in- 
formation on their genetic merit. Although 
some genetic improvement programs now 
exist, the beef breed associations may not 
support interbreed comparisons because 
some breeds would show up poorly. 
• Conflicts between short- and long-term gains. 
Cross-breeding for the benefits of hybrid- 
'^L. E. .A. Rouson, "Techniques of Livestock Improvement," Out- 
look on Agriculture 6:108, 1970. 
