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EXPLANATIONS AND CALCULATIONS CONTEMPORARY GROUP FORMATION Pedigree: A tabulation of ancestors, usually
those of the three to five most recent generations. Pedigrees that combine genealogy with records of performance
and EPDs of the individual and his ancestors are useful in promoting individuals.
A major role of progressive performance-testing organizations involves
providing such pedigrees to their members. Performance
pedigrees discourage reporting of incomplete or selected performance data and
provide a concise picture of the performance history of an individual.
A
performance pedigree should at least include individual performance and progeny
information (if available) on the animal, sire, dam and maternal grandsire, and
EPDs for pertinent traits of the individual.
BIF recommends that the following individual performance information be
included on each performance pedigree:
Individual
weights should not be reported on performance pedigrees due to large environmental
variations. Number
of progeny and average performance ratios for each individual or group of individuals
used in the calculation of EPDs must be reported.
EPDs
and progeny ratios may be added for additional traits that are considered important
and may be included on the performance pedigree. On
the Cow/Sire Performance Pedigree Report, there will be sporadic numbers/names
listed on the top half of the page. On
the left side of the report appears the ID, the middle section will name the parents
with the sire listed first and the dam below that.
To the right of that might be more names and numbers to indicate the paternal
grandparents and the maternal grandparents, respectively.
Measurement of Yearling Weight (365 days):
Yearling weight should be computed and reported separately for each sex. In on-the-farm or ranch tests, the postweaning
period should start on the date weaning weights are obtained (for example, actual
weaning weight is used as initial weight on test). Because age-of-dam affects weaning weight,
it is appropriate in on-farm tests to add postweaning gains in a 160-day, postweaning
period to 205-day weaning weight, adjusted for age of dam to arrive at adjusted
365-day weight. The following formula
is recommended:
The
period between weaning weight and final weight should be at least 160 days. The recommended age range for yearling weight
is 320 to 410 days, and the average age for each sex-management group should be
at least 365 days. It is recommended that
the number of days between weaning and final weight be the same for all animals
of the same sex in a herd. With this procedure, one need obtain only weaning weight and yearling
weight on each animal. All growth periods
in the animal’s life are included in this procedure. Yield Grade (YG) can be expressed in
whole numbers from one to five or in tenths of a grade. Expressing yield grade in tenths of a grade
is desirable in making comparisons, although in retail marketing, decimals are
dropped. Yield grades are calculated by
the following formula: YG=2.50
+ (2.5 x Adj. Fat thickness, in.) +
(0.2 x Kidney, pelvic, and heart fat, %) +
(0.0038 x Hot carcass wt., lb.) +
(-0.32 x Rib-eye area, sq. in.) Accuracy is the information used to calculate
EPDs for a particular animal that includes pedigree information, its own performance
data and information on descendants. The data are observations of the trait of
interest and correlated traits. Accuracy
is the measure of how much information is incorporated into the calculation of
the EPD. The accuracy is obtained as: Accuracy=1
- Ö (Prediction error variance) Theoretically,
the prediction error variance is obtained from the inverse of the coefficient
matrix of the mixed model equations. However,
in most applications the coefficient matrix is too large to invert, hence approximations
of the necessary inverse elements are often used. Each EPD has an accuracy value that can vary
from 0 to 1, based on the amount, relationship and distribution of the data used
to predict the EPD. Since the EPD values
are regressed, they can be compared fairly without the use of accuracy.
Accuracy provides the user with an indication of the likelihood of possible
change in the EPD when more information becomes available. Contemporary
Group Formation: A contemporary
group should consist of calves of the same sex and percentage breeding that were
raised under the same management and environmental conditions, and within an acceptable
age range. It is recommended that the information used to determine contemporary
groups be maintained in the data bank to facilitate any future changes in contemporary
grouping. Contemporary groups of two are
useful in cattle evaluation. Pedigree of single-calf contemporary groups should remain in the
pedigree file, but the data do not contribute to the cattle evaluation. Some items to consider when forming contemporary
groups are: 1. Birth contemporary
groups are formed using herd, year, season, sex, percent breeding and perhaps
embryo transfer status and a breeder-provided pasture or management group code.
The most common season grouping is January-June and July-December; however,
some associations use 90- or 120-day season groupings or group calves together
that are born in a 90-day period. Birth
and weaning contemporary groups should be independent. This facilitates the inclusion of birth weights
from calves that died before weaning. The variation of birth weights within contemporary groups should
be examined. In some cases there is no
variation and the entire contemporary group should be eliminated. This check should also be considered for
weaning and yearling contemporary groups. 2. Weaning contemporary
groups are formed using herd, year, sex, percent breeding, weaning management
code (usually creep vs non-creep), and date that the entire contemporary group
was weighed or processed. Embryo transfer status, breeder-provided pasture or management
group code and record processing date are also used when available and appropriate.
Large ranches have a problem in weighing all calves the same day.
Calves weighed or processed within a 5-day period may be included in the
same weaning or yearling contemporary group if all other management has been the
same. 3. Yearling contemporary
groups are formed using the weaning contemporary group along with a yearling management
code, yearling weigh date or processing date. Embryo transfer status, breeder-provided
pasture or management code, yearling sex and record processing date are also used
when available. Central test station data
can be used if there are at least two animals that were in the same weaning contemporary
group and if those animals continued as contemporaries in the central test. 4. Connectedness
of sires across contemporary groups should be checked; however, when the animal
model with a complete relationship matrix is used in a breed that has a substantial
number of breeders that use artificial insemination, only a small percentage of
the animals are likely to be disconnected Measurement
of Weaning Weight (205 days). Weaning weights are obtained to evaluate
differences in mothering ability of cows and to measure differences in growth
potential of calves. For best estimates
of genetic worth for weaning weight, it is necessary to adjust individual calf
records to a standard basis. It is recommended
that the weaning weight be standardized to 205 days and a mature-dam equivalent,
and that weights be recorded as close to 205 days as possible.
The recommended range is 160 to 250 days.
Calves weaned outside this range should be accounted for by a special management
code and handled as a separate management group. Records of these calves should not be adjusted for age of dam,
because appropriate correction factors are not available. The 205-day
weight (lb.) is computed on the basis of average daily gain from birth to weaning,
using the formula that follows. If actual
birth weight is not available, substitute the appropriate standard birth weight
as designated by the respective breed association for the sire breed of calf.
This
computed 205-day weight is not adjusted for age of dam or sex of calf. Correction factors can be used to adjust
for age of dam and are listed below. Other
herd specific correction factors are provided in the Beef Improvement Federation
handbook.
Note:
For
example: A heifer calf weighed 74 lbs. at birth and 310 at weaning with the weaning
age being 149 days. The cow age is 2 years. 310 - 82 x 205 + 82 + 54 = 450 For
the birth weight, add the original birth weight to the Birth Weight Adjustment
Factor If the birth weight is not known, use the standard birth weight and add
the adjustments to that weight. Most
Probable Producing Ability (MPPA): In commercial herds it is recommended that
MPPA be included on produce-of-dam summaries and that ranking of dams be based
on MPPA for 205-day weaning ratio. This
is necessary to compare dams with different numbers of calf records in their averages.
For example, suppose six cows have the following records of production:
In the example, cow
A has the lowest lifetime average weaning weight ratio. However, this average weaning weight ratio for cow A is based
on only a single calf for which environmental conditions or the calf’s genetic
potential for growth might have been below average compared with the cow’s normal
production. One or more calves from Cows
B or C could also have had a record of 85 or less. All three cows are probably low producers,
but use of MPPA enables more accurate culling and, in this example, indicates
that cows B and C are lightly lower-producing cows than A.
MPPA
of cow D in the example above is computed as follows:
Finishing
and Slaughter Guidelines. 1. Cattle should
be slaughtered when the test group averages 0.35 in. backfat, or prior to 16 months
of age, or a maximum of 1,300 lb. live weight, whichever occurs first.
This corresponds to at least 90 days on feed for yearling cattle and 180
days on feed for calves. Depending on the weight ranges of the cattle
as they go on feed and the number of cattle involved, two or more slaughter dates
may be required. Contemporary grouping
will include slaughter date, therefore each slaughter group must include both
test- and reference-sire progeny. 2. All progeny
can go on feed directly after weaning, or they may be stockered and placed on
feed after the yearling weight is taken. 3. To facilitate
record keeping, cattle should be grouped for finishing at centralized locations
within a state or geographic region. The location of the feedlot should be in
close proximity to a packing plant that has agreed to participate in carcass data
collection. All health and feeding practices
must be consistent with normal industry standards. Expected
Progeny Differences (EPD): To the extent possible, seedstock producers
should use the capabilities of the various breed associations to obtain EPDs on
individuals for the calf performance traits. Most associations are computing EPDs for
birth weight, weaning weight-direct, weaning weight-milk, and yearling weight.
Many associations are now offering EPDs for many other traits and continue
to add new traits. These measures provide the most complete
assessment available of an individual’s likely genetic merit and should be the
basis of selection for the traits they measure.
A bull’s true breeding value never changes;
however, his EPDs, which are estimates of the breeding value, do.
As more information is collected on an animal, or his relatives, his EPDs’
may change in an attempt to pinpoint the true breeding value.
Each EPD has a computed accuracy value which corresponds to how much possible
change may be expected in the animal’s EPD as more information becomes available.
As accuracy values increase, possible change values decrease. Frame
Score Calculations.
If a number greater than 20 is typed for frame score the program assumes
you are typing hip height. The frame score
is then calculated based on the following formulas:
Total Retail Product (%RP): Dikeman,
et al. (1996) have developed an equation that uses traits in the USDA Yield Grade
System to predict percentage of total retail product trimmed to zero (0.0) in.
of surface fat:
Listed below are yield
grade categories and corresponding percentages of retail product trimmed to 0.0
in. surface fat.
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