Adams, Nelson J.

English

Texas A&amp;M Repository

L-215810"'"ServiceTexas Agricultural Extension~---- .....,..-p~~Hdp~P~fJ~----------'SELECTING REPLACEMENT FEMALES:Economically Important CharacteristicsNelson J. Adams*Selection is a process of choosing individuals overothers in anticipation of bringing about a favorablechange in certain characteristics in a cattle herd. Theselection process involves identifying the differencesamong individuals and keeping those animals that aresuperior in the traits identified. Selection for geneticimprovement in cattle is a lengthy process; therefore,traits of economic value must be identified accuratelyand selected for diligently. Economically importanttraits are also referred to as performance traits. Themajor traits influencing total productive efficiency arefertility, mothering ability, rate of gain, efficiency ofgain, longevity and carcass merit. Selection ofcommercial replacement heifers focuses primarily onfertility, mothering ability, rate of gain and longevity.FertilityFertility, or reproductive performance, is basic toan efficient beef cattle operation. The important factorin commercial cow/calf oeprations which affectsproduction costs is the percent calf crop. A highpercentage calf crop decreases the demand forreplacements and increases the selection differentialpossible for other traits. Fertility is low in heritabilityand difficult to measure in heifers. The only way toimprove reproductive performance is by cullingheifers that reach puberty late or fail to conceive atfirst breeding.young heifers, culling should be based on demon-strated performance of the first calf raised.Growth RateGrowth rate is highly associated with economy ofgain and its relation to fixed costs. Differences ingrowth rate can be determined objectively by weigh-ing growing cattle at given intervals. Growth rate is themost commonly measured performance trait. It isimportant to the beef industry, particularly as it relatesto weaning weights in cow/calf operations, gains ofstocker cattle and performance in the feedlot.Intense selection pressure on replacement heifersfor growth rate without proper consideration of repro-ductive traits may be counterproductive. Geneticrelationships of growth, or size, at different ages (birthweight, weaning weight, 12 - or I8-month weight andmature weight) are quite high.Selection on the basis of 12- or I8-month weightleads to significant increases in birth weight andmature size. As larger females are selected, theircalves' birth weights also increase. Heavy birthweights contribute to calving difficulty, reduced sur-vival of calves and reduced rebreeding performance ofcows. Increases in mature weight of cows increasesnutrient requirements for maintenance of the cowherd. These factors may offset the advantages offaster gaining and more efficient progeny.Mothering Ability LongevityMothering ability is critical in a productive cowherd. A cow's ability to wean a healthy, vigorous calf isvital for efficient beef production. Reproduction,calving ease, calf survival, maternal behavior and milkproduction are important components of motheringability. Because this trait is difficult to distinguish in*Extension livestock specialist, The Texas A&M UniversitySystem.Longevity, an animal's productive time in a herd,can be determined partially by subjective evaluation ofthe replacement heifers. The longer animals remainproductive in a herd, the fewer replacements will beneeded. This reduces total herd costs of growing outreplacements to a productive age. Adverse factorswhich affect how long a cow is productive in thebreeding herd include infertility, unsound feet andTexas Agricultural Extension Service. Zerle L. Carpenter, Director. The Texas A&M University System. College Station, Texaslegs, serious eye diseases, udder trouble and anunsound mouth. Selection for longevity is primarilyconfined to such indicators as structural soundnessand breed or family line history within breeds. For-tunately, there is a certain amount of automaticselection for fertility and longevity. Animals whichremain in the herd longer produce more offspring anda larger number of these may be saved forreplacements.SummaryThe merits of selection based on performancerecords (weaning weight, post-weaning growth rateand weight per day of age) are well documented andshould be practiced by all purebred breeders and, tothe extent feasible, by commercial producers. Mostcommercial cow/calf producers cannot keep exten-sive individual performance records and thereforemust rely on less accurate methods. Selection offemales for increased weight increases genetic growthpotential of their calves, but is a poor indicator ofreproductive and maternal performance.Selection is the primary tool available to makegenetic change in straightbred herds. The commer-cial producer has the opportunity to improveefficiency of production and desirability by systematiccrossbreeding. In straightbred and crossbredoperations, intelligent selection and good judgmentmust be practiced for consistent improvement.Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level,race, color, sex, religion, handicap or national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, andJune 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, Texas Agricultural ExtensionService, The Texas A&M University System.lOM-1-86, New AS1

Selecting Replacement Females:  Economically Important Characteristics.

Texas A&M University

L-2158
10"'"
ServiceTexas Agricultural Extension
~---- .....,..-p~~Hdp~P~fJ~----------'
SELECTING REPLACEMENT FEMALES:
Economically Important Characteristics
Nelson J. Adams*
Selection is a process of choosing individuals over
others in anticipation of bringing about a favorable
change in certain characteristics in a cattle herd. The
selection process involves identifying the differences
among individuals and keeping those animals that are
superior in the traits identified. Selection for genetic
improvement in cattle is a lengthy process; therefore,
traits of economic value must be identified accurately
and selected for diligently. Economically important
traits are also referred to as performance traits. The
major traits influencing total productive efficiency are
fertility, mothering ability, rate of gain, efficiency of
gain, longevity and carcass merit. Selection of
commercial replacement heifers focuses primarily on
fertility, mothering ability, rate of gain and longevity.
Fertility
Fertility, or reproductive performance, is basic to
an efficient beef cattle operation. The important factor
in commercial cow/calf oeprations which affects
production costs is the percent calf crop. A high
percentage calf crop decreases the demand for
replacements and increases the selection differential
possible for other traits. Fertility is low in heritability
and difficult to measure in heifers. The only way to
improve reproductive performance is by culling
heifers that reach puberty late or fail to conceive at
first breeding.
young heifers, culling should be based on demon-
strated performance of the first calf raised.
Growth Rate
Growth rate is highly associated with economy of
gain and its relation to fixed costs. Differences in
growth rate can be determined objectively by weigh-
ing growing cattle at given intervals. Growth rate is the
most commonly measured performance trait. It is
important to the beef industry, particularly as it relates
to weaning weights in cow/calf operations, gains of
stocker cattle and performance in the feedlot.
Intense selection pressure on replacement heifers
for growth rate without proper consideration of repro-
ductive traits may be counterproductive. Genetic
relationships of growth, or size, at different ages (birth
weight, weaning weight, 12 - or I8-month weight and
mature weight) are quite high.
Selection on the basis of 12- or I8-month weight
leads to significant increases in birth weight and
mature size. As larger females are selected, their
calves' birth weights also increase. Heavy birth
weights contribute to calving difficulty, reduced sur-
vival of calves and reduced rebreeding performance of
cows. Increases in mature weight of cows increases
nutrient requirements for maintenance of the cow
herd. These factors may offset the advantages of
faster gaining and more efficient progeny.
Mothering Ability Longevity
Mothering ability is critical in a productive cow
herd. A cow's ability to wean a healthy, vigorous calf is
vital for efficient beef production. Reproduction,
calving ease, calf survival, maternal behavior and milk
production are important components of mothering
ability. Because this trait is difficult to distinguish in
*Extension livestock specialist, The Texas A&M University
System.
Longevity, an animal's productive time in a herd,
can be determined partially by subjective evaluation of
the replacement heifers. The longer animals remain
productive in a herd, the fewer replacements will be
needed. This reduces total herd costs of growing out
replacements to a productive age. Adverse factors
which affect how long a cow is productive in the
breeding herd include infertility, unsound feet and
Texas Agricultural Extension Service. Zerle L. Carpenter, Director. The Texas A&M University System. College Station, Texas
legs, serious eye diseases, udder trouble and an
unsound mouth. Selection for longevity is primarily
confined to such indicators as structural soundness
and breed or family line history within breeds. For-
tunately, there is a certain amount of automatic
selection for fertility and longevity. Animals which
remain in the herd longer produce more offspring and
a larger number of these may be saved for
replacements.
Summary
The merits of selection based on performance
records (weaning weight, post-weaning growth rate
and weight per day of age) are well documented and
should be practiced by all purebred breeders and, to
the extent feasible, by commercial producers. Most
commercial cow/calf producers cannot keep exten-
sive individual performance records and therefore
must rely on less accurate methods. Selection of
females for increased weight increases genetic growth
potential of their calves, but is a poor indicator of
reproductive and maternal performance.
Selection is the primary tool available to make
genetic change in straightbred herds. The commer-
cial producer has the opportunity to improve
efficiency of production and desirability by systematic
crossbreeding. In straightbred and crossbred
operations, intelligent selection and good judgment
must be practiced for consistent improvement.
Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level,
race, color, sex, religion, handicap or national origin.
Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and
June 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, Texas Agricultural Extension
Service, The Texas A&M University System.
lOM-1-86, New AS1


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Selecting Replacement Females: Economically Important Characteristics.

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Selecting Replacement Females: Economically Important Characteristics.

Abstract

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Full text

Available Versions

Texas A&amp;M Repository

Texas A&M University

Texas A&M Repository