PROCEDURES FOR CALCULATING LACTATION RECORDS
DAIRY HERD IMPROVEMENT
1985
WIGGANS, G.R.
VOLUME: NCDHIP HANDBOOK
Lactation records are the basic unit of information on a cow's
production for management decisions and genetic evaluation. They
are calculated from information collected on periodic sample days.
The amount of information collected depends on the type of testing
plan. The most common plans require weighing the milk at all
milkings and collecting a composite sample during the approximate
24-hour period of the sample day. Variations include 1) AM-PM (AP)
plans, for which only one milking is weighed and sampled each
sample day for herds milked two times a day (2X) and only one or
two milkings are weighed and one milking sampled each sample day
for herds milked three times a day (3X); 2) AP Component Sampling
(APCS) plans, for which all milkings are weighed each sample day,
but only one milking is sampled; and 3) Milk-Only (MO) plans, for
which no sampling is done. (See Fact Sheet H-11 for a complete list
of testing plans and codes and Fact Sheet E-1 for definitions.)
In general, a lactation record is calculated by using three steps:
1. estimate the sample-day yield for milk and components;
2. estimate the yield from the previous sample day through the
current sample day (credit for the test interval); and
3. add the test interval credits for the lactation to determine
the lactation yield.
Factors used by the Northeast Dairy Records Processing Laboratory
for estimating yields and adjusting credits differ from those
presented here. Other dairy records processing centers (DRPC's) may
not have adopted the latest equations or adjustments.
Estimating Sample-Day Yields (Step 1)
Sample-day yields and component percentages are estimated from
yield weighed and sampled on sample day. The method for calculating
sample-day yield depends on whether all milkings on sample day are
weighed and sampled. If the measured milkings have abnormal yield
or percentage values, this information must be estimated or the
test interval merged with the following one.
All Milkings Weighed and Sampled (Most Common Testing Plans)
If all milkings are weighed and sampled on sample day, the recorded
milk weights are added to obtain the sample-day milk yield.
Component percentages from the composite sample are used as the
sample-day component percentages. The sample-day milk yield is
multiplied by the sample-day component percentages to estimate the
sample-day component yields.
For example, Cow 29 gave 23.0 pounds of milk at the 6:30 a.m.
milking and 17.0 pounds of milk at the 4:30 p.m. milking. Her
composite sample was 4.0 percent fat and 3.5 percent protein. Cow
29's sample-day milk yield would be 40.0 pounds (the sum of the two
milk weights). Her sample-day component percentages would be 4.0
percent for fat and 3.5 percent for protein (the test results from
the composite sample). Her estimated sample-day component yields
would be her sample-day milk yield multiplied by the appropriate
sample-day component percentages (in decimal form):
40.0 pounds of milk x.040 = 1.60 pounds of fat
40.0 pounds of milk x.035 = 1.40 pounds of protein
If the herd had been milked 3X, the estimated sample-day yields and
percentages would have been calculated the same way except that all
three milk weights would have been summed to obtain the sample-day
milk yield.
Not All Milkings Weighed and Sampled (AP Plans)
For AP plans, milking times for the measured milking and the
milking preceding the measured milking must be recorded. This
information is necessary because factors specific to milking time
and interval are used with the measured milk weight(s) and
component percentages to estimate sample-day yields and
percentages.
To determine the milking interval, the starting and ending times
are averaged for the preceding milking and for the measured
milking. The milking interval is the interval from the average time
for the preceding milking until the average time for the measured
milking. The results are expressed in hours using decimals.
For example, a herd had a measured milking that started at 6:30
a.m. and ended at 9 a.m. The preceding milking started at 4:30 p.m.
and ended at 6:30 p.m. the previous afternoon. The average times
would be 7:45 a.m. for the measured milking and 5:30 p.m. for the
preceding milking. The milking interval would be 14.25 hours
(expressed as a decimal).
Herds milked 2X. For 2X herds, sample-day yields and percentages
are estimated from one measured milking using the factors in Table
1:
sample-day yield2x =
factor2x milk x milk yield for measured milking +
covariate x (days in milk - 158)
sample-day fat percentage2x =
factor2x x fat x fat percentage for the measured milk-
ing sample-day fat yield =
sample-day fat percentage X sample-day milk yield
sample-day protein or solids-not-fat (SNF) yield =
protein or SNF percentage for the measured milking
x sample-day milk yield
TABLE 1. Factors(1) and covariates for estimating sample-day
milk yield and fat percentage from one
measured milking for herds milked two times a day.
Interval preceding Milk yield Fat
measured milkin a.m. milking(2) p.m. milking(2) percentage
(hours) Factor Covariate Factor Covariate factor(3)
<9.00 2.465 0.01566 2.594 0.00834 0.919
9.00- 9.24 2.465 0.01566 2.534 0.01069 0.927
9.25- 9.49 2.465 0.01566 2.477 0.01071 0.934
9.50- 9.74 2.411 0.01578 2.423 0.01126 0.941
9.75- 9.99 2.359 0.01600 2.370 0.01043 0.948
10.00-10.24 2.310 0.01010 2.321 0.00742 0.955
10.25-10.49 2.262 0.00879 2.273 0.00471 0.961
10.50-10.74 2.217 0.00649 2.227 0.00000 0.968
10.75-10.79 2.173 0.00492 2.183 0.00000 0.974
11.00-11.24 2.131 0.00000 2.140 0.00000 0.980
11.25-11.49 2.091 0.00000 2.099 0.00000 0.986
11.50-11.74 2.052 0.00000 2.060 0.00000 0.992
11.75-11.99 2.014 0.00000 2.022 0.00000 0.997
12.00-12.24 1.978 0.00000 1.986 0.00000 1.003
12.25-12.49 1.943 0.00000 1.951 0.00000 1.008
12.50-12.74 1.910 0.00000 1.917 0.00000 1.013
12.75-12.99 1.877 0.00000 1.884 0.00000 1.018
13.00-13.24 1.846 0.00000 1.852 -0.00418 1.023
13.25-13.49 1.815 0.00000 1.822 -0.00510 1.028
13.50-13.74 1.786 -0.00369 1.792 -0.00678 1.033
13.75-13.99 1.757 -0.00569 1.763 -0.00747 1.037
14.00-14.24 1.730 -0.00766 1.736 -0.01123 1.042
14.25-14.49 1.703 -0.00801 1.709 -0.01039 1.046
14.50-14.74 1.677 -0.00733 1.683 -0.01000 1.050
14.75-14.99 1.652 -0.00696 1.683 -0.01000 1.054
>=15.00 1.628 -0.00518 1.683 -0.01000 1.058
1 Factors for milk and fat yields may be calculated by
factor=1/intercept + slope x milking interval) where the intercepts
and slopes are in thefollowing table:
Intercept
Yield trait a.m. p.m. Slope
Milk .0654 .0634 .0363
Fat .1965 .1939 .0254
Factors for fat percentage are the ratio of the fat yield factor to
the milk yield factor.
2 Time at start of measured milking determines whether a.m. or p.m.
factors are used.
3 Factors for fat percentage appropriate for both a.m. and p.m.
milkings.
The formula for estimating sample-day milk yield is adjusted to
account for differences in the time available to the cow for
producing milk (the milking interval). A second adjustment is made
through the covariate (which is set to 0 at 158 days, the midpoint
for a 305-day record) because for unequal milking intervals, a
cow's stage of lactation affects the influence that the length of
the preceding interval has on milk production.
The formula for sample-day fat percentage also is adjusted to
account for the effect of milking interval on fat percentage.
Protein and SNF percentages are not affected by milking interval.
Therefore, the percentage for the sampled milking is used as the
sample-day percentage.
As an example, assume that Cow 29 now is in the herd with a
measured milking at 6:30 a.m. and a milking interval of 14.25
hours. She has been in milk for 250 days. Her milk yield for the
measured milking was 23.0 pounds, and her sample was 4.0 percent
fat and 3.5 percent protein. From Table 1, the factor for
estimating sample-day milk yield with a 14.25-hour milking interval
preceding a measured a.m. milking is 1.703; the covariate is
-.00801. The factor for estimating sample-day fat percentage is
1.046. Therefore,
sample-day milk yield =
(1.703 x 23.0) + ( -.00801) x (250 - 158)=
38.4 pounds of milk
sample-day fat percentage =
1.046 x 4.0 = 4.2 percent for fat
sample-day fat yield ==
.042 x 38.4 = 1.61 pounds of fat
sample-day protein yield =
.035 x 38.4 = 1.34 pounds of protein
Herds milked 3X. For 3X herds, two consecutive milkings must be
weighed with samples collected at one of these milkings. Sample-day
milk yield and fat percentage are estimated by
sample-day milk yield3x =
factor3x milk x total milk yield from measured milkings
sample-day fat percentage3x =
factor3x fat x fat percentage from the measured milking.
Formulas for calculating component yields for 3X herds are the same
as those for 2X herds.
The 3X factors for estimating sample-day milk yield and fat
percentage are calculated with the intercepts and slopes in Table
2:
factor3x milk=
1/(intercept for measured milking 1 +intercept for
measured milking 2 + slope x total of the intervals pre-
ceding both measured milkings)
factor3x fat percentage =
(milk intercept for sampled milking + milk slope for
sampled milking x interval preceding sampled milk-
ing)/(fat intercept for sampled milking + fat slope for
sampled milking x interval preceding sampled milk-
ing)
The AP factors for 3X herds should not be confused with factors
that adjust 3X records to a 2X basis. (See Fact Sheet G-2.)
Assume that Cow 29's herd now is milked 3X. She gave 16.0 pounds of
milk at a 5 a.m. milking and 12.0 pounds of milk at a noon milking.
Her sample at the 5 a.m. milking was 4.0 percent fat and 3.5
percent protein. The milking preceding the 5 a.m. milking started
at 7 p.m. the evening before. The factors to estimate sample-day
milk yield and fat percentage would be:
factor milk=
1/{.077 +.068 + [.0329 x (10 + 7)]}
= 1/.704= 1.42
factor fat percentage =
[.077+ (.0329x 10)]/[.186+ (.0186x 10)]
=.406/.372=1.09
Then,
sample-day milk yield3x = 1.42 x (16.0 + 12.0)=39.8
pounds of milk
sample-day fat percentage3x = 1.09 x 4.0 = 4.4 percent
for fat
sample-day fat yield3x = .044 x 39.8 = 1.75 pounds of
fat
sample-day protein3x = .035 x 39.8 = 1.39 pounds of
protein
TABLE 2. Intercepts and slopes for calculating factors to estim. sample-day
milk yield from two consecutive milk weights and component percentages
from samples collected at one milking for herds milked three times a day.
Intercept for milking times
Between 2 a.m. Between 10 a.m. Between 6 p.m.
Yield trait and 9:59 a.m. and 5:59 p.m. and 1:59 a.m. Slope(1)
Milk 0.077 0.068 0.066 0.0329
Fat 0.186 0.186 0.182 0.0186
1 Slope appropriate for all milking regardless of milking time.
All Milking Weighed But Only one Sampled (APCS Plans)
For both 2X and 3X herds, the sample-day milk yield is the sum of
the recorded milk weights. The sample-day fat percentage is
calculated with the formula for fat percentage for AP herds, 2X or
3X as appropriate.
Assume Cow 29 now is in a 2X herd on APCS test. She gave 23.0
pounds of milk at the 6:30 a.m. milking and 17.0 pounds of milk at
the 4:30 p.m. milking. Her sample at the 6:30 a.m. milking was 4.0
percent fat and 3.5 percent protein. The milking interval preceding
the sampled milking was 14.25 hours. Then,
sample-day milk yield = 23.0 + 17.0 = 40.0 pounds of milk
sample-day fat percentage = 1.046 x 4.0 = 4.2 percent for fat
sample-day fat yield = .042 x 40.0 = 1.68 pounds of fat
sample-day protein yield =.035 x 40.0 = 1.40 pounds of protein
Abnormal Sample-Day Yield
Abnormal values of yield or percentage for measured milkings
require modifications of procedures for estimating sample-day
yields.
Milk yield. Milk yield reported as abnormal and differing from
yield from the adjacent sample day by more than a computed
percentage (27.4 +.4 x days in test interval) is estimated from the
preceding sample-day yield according to the method adopted by DRPC
or spanned.
For example, Cow 29 had a sample-day yield of 20.0 pounds of milk
at 85 days, which was reported as abnormal. Her previous sample-day
yield had been 55.0 pounds at 50 days. Her sample-day yield
differed from her preceding sample-day yield by 63.6 percent. For
this cow's 35-day interval, a difference of greater than 41.4
percent is considered abnormal. Therefore, the sample-day yield of
20.0 pounds at 85 days is abnormal and either must be estimated or
spanned.
The most accurate method of estimating sample-day milk yield for an
abnormal sample day is to adjust the sample-day milk yield from the
preceding sample day with the factors used for computing the credit
for the last test interval (see Table 5):
sample-day milk yield =
(2 x factorlast - 1)
x sample-day milk yield from preceding sample day
The factor appropriate for the preceding sample day rather than for
the abnormal sample day should be used.
For first-lactation Cow 29, her estimated sample-day milk yield by
this method would be
sample-day milk yield =
(2 x.97- 1) x 55.0 =.94 x 55.0 = 51.7 pounds of milk
A less accurate method used by many DRPC's for estimating
sample-day milk yield for abnormal sample days Is
sample-day milk yield =
(1 -.0033 x days in test interval)
x sample-day milk yield from preceding sample day
The differences in estimated sample-day milk yield between the two
methods are largest for first lactations.
First-lactation Cow 29's sample-day milk yield estimated by this
method would have been
sample-day milk yield = [1 - (.0033 x 35)] x 55.0 = 48.6 pounds of
milk
For spanning, the abnormal sample-day yield is ignored, and the
test interval is considered to be the interval from the sample day
preceding the abnormal sample day to the sample day following the
abnormal sample day.
Component percentage. If component analysis is not available
because of loss or deterioration of the sample or because of
impossible results, the component percentage from the preceding
sample is used.
Estimating Test Interval Yield (Step 2)
For most test intervals, the interval yield (or credit) is
calculated by multiplying the average daily yield between sample
days by the number of days in the test interval. Average daily
yield is estimated as the average of the yields for the preceding
and current sample days. Therefore,
test interval credit =
[(yield on preceding sample day + yield on sample day)/2] x days in
test interval
As an example, assume that Cow 29 had a sample-day yield of 40.0
pounds at 250 days in milk. Her preceding sample-day yield was 41.0
pounds at 220 days in milk. Therefore, her credit for milk yield
for this test interval would be
test interval credit milk =
[(41.0 + 40.0)/2] x 30 = 1,215 pounds of milk
A theoretically more accurate method, although not currently in use
in the National Cooperative Dairy Herd Improvement Program
(NCDHIP), is to estimate the yield only for the days between sample
days and then add the known yield on sample day. Test interval
credits calculated by this method differ from those in NCDHIP by
half the difference between sample-day yields.
Because of the shape of the lactation curve (Figure 1; small version,
large version), some test interval yields must be adjusted so that
production can be estimated accurately. First and last intervals have a
sample day at only one end of the interval; therefore, the change in yield
during the interval must be estimated. A test interval that spans the peak
of lactation (at approximately 40 days in milk) must have the test
interval yield adjusted to account for above-average yield on unrecorded
days. In addition, if computing a 305-day record, the test interval that
spans 305 days in milk must be adjusted to end on day 305.
Lactation curve for example cow
First Test Interval
The credit for the first test interval can be calculated with the
factors in Table 3:
test interval creditfirst =
factor x yield on sample day x days in milk
The number of days in milk includes both the calving day and the
sample day.
For example, if first lactation Cow 29's first sample day was at 20
days in milk and her sample-day milk yield was 45.0 pounds, her
test interval credit for first interval milk yield would be
test interval credit 1 ==
.80 x 45.0 x 20 = 720 pounds of milk
Test Interval Spanning Lactation Peak
The test interval credit for an interval with a preceding sample
day before 40 days in milk can be calculated with the factors in
Table 4 by
test interval creditpeak =
factor x (yield on preceding sample day + yield on sam-
ple day)/2
x days in test interval
To continue with Cow 29's first lactation as an example, her
second sample day was at 50 days in milk. Her sample-day milk yield
was 55.0 pounds. Therefore, Cow 29's test interval credit for
second interval milk yield would be
test interval credit 2 =
1.02 x [(45.0 + 55.0)/2] x 30 = 1,530 pounds of milk
----------------------------------------------------------------------
PLEASE NOTE: THE FOLLOWING TABLE IS WIDER THAN THE SCREEN. USE THE
RIGHT ARROW KEY TO VIEW THE RIGHT SIDE OF THE TABLE. TO
PRINT THE ENTIRE TABLE YOU MUST FIRST EXPORT THE TABLE
AND USE A WORD PROCESSOR OUTSIDE THE RETRIEVAL SYSTEM.
----------------------------------------------------------------------
TABLE 3. Factors for adjusting sample-day yield for first test interval.
Day of first First lactation Second or later lactation
sample Solids- Solids-
(days in milk) Milk Fat Protein not-fat Milk Fat Protein not-fat
6 0.71 0.69 0.70 0.68 0.74 0.76 0.76 0.73
7 0.72 0.71 0.73 0.70 0.75 0.78 0.79 0.75
8 0.73 0.74 0.76 0.72 0.76 0.80 0.81 0.76
9-10 0.74 0.76 0.79 0.74 0.77 0.82 0.84 0.78
11 0.75 0.79 0.81 0.76 0.78 0.84 0.87 0.80
12-13 0.76 0.81 0.83 0.77 0.79 0.86 0.89 0.81
14-15 0.77 0.83 0.86 0.79 0.80 0.87 0.91 0.83
16-17 0.78 0.85 0.88 0.81 0.81 0.89 0.93 0.84
18-19 0.79 0.87 0.89 0.82 0.82 0.90 0.94 0.85
20-21 0.80 0.89 0.90 0.83 0.83 0.92 0.95 0.86
22-23 0.81 0.90 0.91 0.84 0.84 0.93 0.96 0.87
24-25 0.82 0.91 0.92 0.85 0.85 0.94 0.97 0.88
26-27 0.83 0.92 0.92 0.86 0.86 0.95 0.97 0.89
28-30 0.84 0.93 0.93 0.87 0.87 0.96 0.98 0.90
31-33 0.85 0.94 0.93 0.87 0.88 0.97 0.98 0.91
34-35 0.86 0.95 0.93 0.88 0.87 0.98 0.99 0.91
36-38 0.87 0.95 0.94 0.89 0.90 0.99 0.99 0.92
39-41 0.88 0.96 0.94 0.89 0.91 1.00 0.99 0.93
42-44 0.89 0.96 0.94 0.90 0.92 1.01 0.99 0.93
45-47 0.90 0.97 0.94 0.91 0.93 1.02 0.99 0.94
48-50 0.91 0.97 0.94 0.92 0.94 1.03 0.99 0.95
51-54 0.92 0.98 0.94 0.92 0.95 1.03 0.99 0.96
55-57 0.93 0.98 0.94 0.93 0.96 1.04 0.99 0.97
58-61 0.94 0.99 0.94 0.93 0.97 1.05 1.00 0.98
62-64 0.95 0.99 0.95 0.94 0.98 1.06 1.00 0.97
65-68 0.96 1.00 0.95 0.95 0.99 1.07 1.01 0.99
69-72 0.97 1.00 0.96 0.96 1.00 1.08 1.02 1.00
73-75 0.98 1.01 0.97 0.97 1.01 1.09 1.03 1.02
>75 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Factors are derived from the following regression coefficients:
Yield Regression coefficients
trait Lactation 1 2 3 4
Milk First .605 .0435
Second or later .635 .0435
Fat First .235 .239 -.0225 .000069
Second or later .476 .146 -.0115 .000038
Protein First .136 .316 -.0351 .000130
Second or later .177 .324 -.0366 .000141
Solids- First .342 .180 -.0173 .000066
not-fat Second or later .416 .167 -.0163 .000069
1 The regression function is coefficient 1 + coefficient 2 x day of first
sample
+ coefficient 3 x day of first sample
+ coefficient 4 x (day of first sample)2
----------------------------------------------------------------------
PLEASE NOTE: THE FOLLOWING TABLE IS WIDER THAN THE SCREEN. USE THE
RIGHT ARROW KEY TO VIEW THE RIGHT SIDE OF THE TABLE. TO
PRINT THE ENTIRE TABLE YOU MUST FIRST EXPORT THE TABLE
AND USE A WORD PROCESSOR OUTSIDE THE RETRIEVAL SYSTEM.
----------------------------------------------------------------------
TABLE 4. Factors(1) for adjusting yields for test intervals at peak of lactation.
Day of
preceding sample Days in test interval
(days in milk) Yield trait 1-10 11-19 20-28 29-37 38-46 47-55 56-64 65-75
First lactation
6-7 Milk 1.04 1.06 1.08 1.09 1.11 1.13 1.15 1.16
Fat 1.02 1.03 1.03 1.04 1.05 1.06 1.05 1.05
Protein 1.02 1.05 1.02 1.03 1.03 1.04 1.04 1.04
Solids-not-fat 1.04 1.06 1.07 1.08 1.09 1.11 1.11 1.13
8-10 Milk 1.02 1.03 1.04 1.05 1.07 1.08 1.09 1.10
Fat 1.02 1.02 1.03 1.03 1.03 1.04 1.03 1.03
Protein 1.01 1.01 1.00 1.00 1.01 1.01 1.01 1.01
Solids-not-fat 1.02 1.03 1.03 1.04 1.05 1.06 1.07 1.08
11-13 Milk 1.01 1.02 1.03 1.04 1.05 1.05 1.06 1.07
Fat 1.01 1.01 1.01 1.01 1.02 1.02 1.01 1.01
Protein 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.01
Solids-not-fat 1.01 1.01 1.01 1.03 1.03 1.04 1.05 1.05
14-22 Milk 1.01 1.01 1.02 1.02 1.03 1.03 1.04 1.05
Fat 1.01 1.01 1.01 1.01 1.02 1.01 1.01 1.01
Protein 1.00 1.00 1.00 1.01 1.01 1.01 1.01 1.02
Solids-not-fat 1.00 1.00 1.01 1.02 1.02 1.03 1.03 1.04
23-31 Milk 1.00 1.01 1.01 1.01 1.02 1.02 1.02 1.03
Fat 1.01 1.01 1.01 1.01 1.01 1.01 1.01 1.01
Protein 1.01 1.01 1.02 1.02 1.02 1.02 1.03 1.03
Solids-not-fat 1.00 1.01 1.01 1.02 1.02 1.02 1.03 1.03
32-39 Milk 1.00 1.00 1.01 1.01 1.01 1.01 1.02 1.02
Fat 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Protein 1.00 1.00 1.00 1.00 1.00 1.01 1.01 1.01
Solids-not-fat 1.00 1.00 1.00 1.01 1.01 1.01 1.01 1.01
Second or later lactation
6-7 Milk 1.02 1.04 1.05 1.07 1.08 1.10 1.12 1.13
Fat 1.01 1.01 1.01 1.02 1.03 1.03 1.03 1.03
Protein 1.02 1.01 1.00 1.00 1.00 1.00 1.00 1.01
Solids-not-fat 1.02 1.04 1.04 1.06 1.07 1.08 1.08 1.09
8-10 Milk 1.01 1.03 1.04 1.05 1.06 1.07 1.08 1.09
Fat 1.00 1.00 1.01 1.02 1.02 1.02 1.02 1.02
Protein 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Solids-not-fat 1.01 1.02 1.02 1.03 1.04 1.05 1.05 1.06
11-13 Milk 1.01 1.02 1.03 1.04 1.04 1.05 1.06 1.07
Fat 1.00 1.00 1.01 1.02 1.02 1.02 1.01 1.02
Protein 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Solids-not-fat 1.01 1.01 1.01 1.02 1.03 1.03 1.04 1.05
14-22 Milk 1.01 1.01 1.02 1.02 1.03 1.03 1.04 1.05
Fat 1.00 1.00 1.01 1.02 1.02 1.01 1.01 1.01
Protein 1.00 1.00 1.00 1.00 1.00 1.00 1.01 1.01
Solids-not-fat 1.00 1.00 1.01 1.02 1.02 1.02 1.03 1.03
23-31 Milk 1.00 1.01 1.01 1.01 1.02 1.02 1.02 1.03
Fat 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Protein 1.00 1.00 1.01 1.01 1.01 1.01 1.02 1.02
Solids-not-fat 1.00 1.01 1.01 1.01 1.02 1.02 1.02 1.02
32-39 Milk 1.00 1.00 1.00 1.01 1.01 1.01 1.01 1.02
Fat 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Protein 1.00 1.00 1.00 1.00 1.01 1.01 1.01 1.01
Solids-not-fat 1.00 1.00 1.00 1.00 1.01 1.01 1.01 1.01
(1) Milk factors also can be calculated by
.998 + 1.23/(day of preceding sample)(2)
+.0113 x (days in interval + 1)/ day of preceding sample
for first lactations and by
1.001 -.00042 x day of preceding sample
+.0109 x (days in interval + 1)/day of preceding sample
for second and later lactations. Component factors are available only
from the table.
Interval to 305 days with subsequent sample day
If a cow has a sample day after 305 days in milk, the credit for
the test interval up to 305 days is calculated for a 305-day
lactation record by
test interval credit305 =
[yield on preceding sample day
+ (daily change/2) x (days to 305 days + 1)]
x days to 305 days
where
daily change =
(yield on sample day - yield on preceding sample day)/
days in test interval
Assume that Cow 29 had a sample day at 310 days in milk with a
sample-day yield of 35.0 pounds of milk and her preceding
sample-day yield had been 40.0 pounds of milk at 280 days. Average
daily change in milk yield for the test interval would be
daily change = (35.0 - 40.0)/30 = -.17
The test interval credit for milk yield up to 305 days would be
test interval credit305 =
[40.0 + (-.17/2) x 26] x 25=
(40.0 - 2.21) x 25 = 945 pounds of milk
Last Interval
If a cow terminates her lactation before 305 days in milk or if a
complete rather than 305-day record is to be calculated, the credit
for the last interval is calculated with the factors in Table 5 by
test interval creditlast = factor x yield on last sample
day x days to termination
If a cow is milked past 305 days without a subsequent sample day,
the credit for the last interval is calculated for a 305-day record
with the same formula except that the number of days to 305 days is
substituted for the number of days to termination.
If Cow 29 had been dried off at 290 days rather than having a
sample day at 310 days, the credit for her last test interval milk
yield would have been
test interval creditlast = .99 x 40.0 x 10 = 396 pounds of milk
If Cow 29 had been dried off at 310 days but with no sample day
after 305 days, her credit for the last test interval for a 305-day
record would have been test interval creditlast to 305 days =
.96 x 40.0 x 25 = 960 pounds of milk
Summing the Test Interval Credits To Determine Lactation Yield
(Step 3)
The lactation yield is calculated by summing the credits for all
the test intervals. A 305-day lactation record includes only test
intervals through 305 days in milk. Table 6 shows sample-day
information on milk yield for Cow 29's complete first lactation and
calculation of her 305-day lactation yield for milk.
Calculating Days Milked 3X
The days that a cow is milked 3X also are calculated as part of the
lactation record to provide information for management decisions
and genetic evaluation. The days milked 3X reflect the portion of
the lactation record calculated from 3X sample days. The procedures
for calculating days 3X are determined by the days in milk.
Test Interval Not Spanning 306 Days in Milk
If the cow is milked 2X on one sample day and 3X on the other, the
days 3X for the test interval is one-half the number of days in the
test interval.
For example, if Cow 29 had a 3X sample day at 280 days in milk and
her preceding sample day was 2X at 250 days in milk, her days 3X
for the test interval would be 15 days.
Test Interval Spanning 305 Days in Milk
If the sample day preceding 305 days is 3X and the sample day after
305 days is 2X, the days 3X for the last interval of the 305-day
record is calculated by
days 3X =
(305 - days in milk at 3X sample day)
x {1 - (306 - days in milk at 3X sample day)/[2
x (days in milk at 2X sample day-days in milk at
3X sample day)]}
If Cow 29 had a 3X sample day at 280 days in milk and a 2X sample
day at 310 days, her days 3X for the test interval would be
days 3X =
(305 - 280) x {1 - (306 - 280)/[2 x (310 - 280)]}=
25 x (1 -.43) = 14.25 days
If the sample day preceding 305 days is 2X and the sample day after
305 days is 3X, then
days 3X =
(305 - days in milk at 2X sample day)
x (306 - days in milk at 2X sample day)/[2 x (days in
milk at 3X sample day-days in milk at 2X sample
day)]
If Cow 29 had a 2X sample day at 280 days in milk and a 3X sample
day at 310 days, her days 3X for the test interval would be
days 3X=
(305 - 280) x (306 - 280)/[2 x (310 - 280)] =
25 x.43= 10.75 days
----------------------------------------------------------------------
PLEASE NOTE: THE FOLLOWING TABLE IS WIDER THAN THE SCREEN. USE THE
RIGHT ARROW KEY TO VIEW THE RIGHT SIDE OF THE TABLE. TO
PRINT THE ENTIRE TABLE YOU MUST FIRST EXPORT THE TABLE
AND USE A WORD PROCESSOR OUTSIDE THE RETRIEVAL SYSTEM.
----------------------------------------------------------------------
TABLE 5. Factors(1) for adjusting yields for test interval after last sample day.
Day of
last sample Days in test Interval
(days in milk) Yield trait 5-14 15-24 25-34 35-44 45-54 55-64 65-75
First lactation
40-159 Milk 0.99 0.98 0.97 0.97 0.96 0.95 0.94
Fat 0.99 0.99 0.98 0.97 0.97 0.96 0.95
Protein 0.99 0.99 0.98 0.98 0.97 0.96 0.96
Solids-not-fat 0.99 0.99 0.98 0.97 0.96 0.96 0.95
160-249 Milk 0.99 0.98 0.97 0.96 0.95 0.94 0.93
Fat 0.99 0.98 0.98 0.97 0.96 0.95 0.94
Protein 0.99 0.99 0.98 0.97 0.96 0.96 0.95
Solids-not-fat 0.99 0.98 0.97 0.96 0.95 0.95 0.94
250-305 Milk 0.99 0.97 0.96 0.95 0.94 0.92 0.91
Fat 0.99 0.98 0.97 0.96 0.95 0.94 0.93
Protein 0.99 0.98 0.98 0.97 0.96 0.95 0.94
Solids-not-fat 0.99 0.98 0.97 0.96 0.95 0.94 0.93
Second or later lactation
40-129 Milk 0.99 0.97 0.96 0.95 0.94 0.92 0.91
Fat 0.99 0.98 0.97 0.95 0.94 0.93 0.92
Protein 0.99 0.98 0.97 0.95 0.94 0.93 0.92
Solids-not-fat 0.99 0.98 0.96 0.95 0.94 0.93 0.91
130-184 Milk 0.99 0.97 0.96 0.94 0.93 0.91 0.90
Fat 0.99 0.97 0.96 0.95 0.93 0.92 0.91
Protein 0.99 0.97 0.96 0.95 0.93 0.92 0.91
Solids-not-fat 0.99 0.97 0.96 0.94 0.93 0.91 0.90
185-224 Milk 0.98 0.96 0.95 0.93 0.91 0.89 0.88
Fat 0.98 0.97 0.95 0.94 0.92 0.91 0.89
Protein 0.98 0.97 0.95 0.94 0.92 0.91 0.89
Solids-not-fat 0.98 0.97 0.95 0.93 0.91 0.90 0.88
225-254 Milk 0.98 0.96 0.94 0.92 0.90 0.88 0.86
Fat 0.98 0.97 0.95 0.93 0.91 0.90 0.88
Protein 0.98 0.97 0.95 0.93 0.91 0.90 0.88
Solids-not-fat 0.98 0.96 0.94 0.92 0.90 0.88 0.86
255-279 Milk 0.98 0.96 0.93 0.91 0.89 0.87 0.84
Fat 0.98 0.96 0.94 0.92 0.91 0.89 0.87
Protein 0.98 0.96 0.94 0.92 0.90 0.89 0.87
Solids-not-fat 0.98 0.96 0.94 0.91 0.89 0.87 0.85
280-305 Milk 0.97 0.95 0.92 0.90 0.87 0.85 0.82
Fat 0.98 0.96 0.94 0.92 0.90 0.87 0.85
Protein 0.98 0.96 0.94 0.92 0.89 0.87 0.85
Solids-not-fat 0.98 0.95 0.93 0.90 0.88 0.86 0.83
(1) Factor = 1 -.5 x slope x days in interval/(intercept - slope x day of
preceding sample):
First lactation Second or later lactation
lntercept Slope Intercept Slope
Yield trait (pounds) (pounds/day) (pounds) (pounds/day)
Milk 48.3 .071 71.0 .144
Fat 2.03 .0025 2.78 .0052
Protein 1.67 .0019 2.39 .0045
Solids-not-fat 4.35 .0057 6.54 .0130
----------------------------------------------------------------------
PLEASE NOTE: THE FOLLOWING TABLE IS WIDER THAN THE SCREEN. USE THE
RIGHT ARROW KEY TO VIEW THE RIGHT SIDE OF THE TABLE. TO
PRINT THE ENTIRE TABLE YOU MUST FIRST EXPORT THE TABLE
AND USE A WORD PROCESSOR OUTSIDE THE RETRIEVAL SYSTEM.
----------------------------------------------------------------------
TABLE 6. Sample-day information on milk yield for the first lactation of example Cow 29 and computation
of her 305-day lactation record.
Test Day of sample Sample-day yield Days in test Test-interval
interval (days in milk) (pounds) interval credit (pounds)
1 20 45 20 720
2 50 55 30 1,530
3 85 20.0(51.7)1 35 1,867
4 120 49 35 1,754
5 155 46 35 1,653
6 185 44 30 1,342
7 220 41 35 1,479
8 250 40 30 1,215
9 280 40 30 1,215
10 310 35 30 945
Lactation - - 305 12,293
(1) Abnormal sample day. Test-interval credit calculated with estimated
sample-day yield in parentheses.
תתתתתתתתתתתתתתתתתתתתThe National Dairy Database (1992)תתתתתתתתתתתתתתתתתתתת
תתתתתתתתתתתתתתתתתתתתתתת\NDB\DAIRY\TEXT\DA105700.TXTתתתתתתתתתתתתתתתתתתתתתתת
%f TITLE;PROCEDURES FOR CALCULATING LACTATION RECORDS
%f COLLECTION;DAIRY HERD IMPROVEMENT
%f ORIGIN;Maryland
%f DATE_INCLUDED;June 1992