|
AS-1091, May 1995
John Dhuyvetter, Area Livestock Specialist
North Dakota State University
NDSU Extension Service
Frame scores are an objective, numerical description of cattle skeletal size which
reflect the growth pattern and potential mature size of an animal. Frame score values
typically range from 2 to 9 and are calculated from hip height and age. Frame scores are
frequently reported as supplementary information to weight and other performance data.
They can be used to project mature size, provide an indication of composition, and
characterize performance potential and nutritional requirements of an animal.
Considerable variation exists among cattle for frame size. Optimum frame score and
desired body type will be different among production situations which differ in feed
resources, breeding systems, and market endpoints. Low frame scores are descriptive of
cattle which are short in stature for their age, tend to be early maturing, and finish for
slaughter and mature at lighter body weights. High frame scores are indicative of cattle
that are tall for their age, have a slower rate of maturity, and finish and mature at
relatively heavy body weights. Rate of gain is usually higher for larger framed cattle;
however, large differences in rate and efficiency of gain exist in cattle of similar size.
For cattle developed under a consistent and adequate plane of nutrition for normal
growth, a calculated frame score should be similar regardless of when the animal was
measured. Theoretically an animal should have the same frame score throughout its life.
Inconsistent environmental factors and management can alter skeletal growth rate, which
may result in cattle developing slightly faster or slower than anticipated. As a result
animals may increase or decrease a frame score over time depending on rate of growth.
The Beef Improvement Federation has recommended in its "Guidelines for Uniform
Beef Improvement Programs" that height measurements for the calculation of frame
score be taken at the hip directly over the hook bones as illustrated in Figure 1. Height
measurements can be collected through the use of hip height measuring sticks marketed
specifically for that purpose. Such height sticks are constructed with a sliding arm
containing a bubble level on a pole scaled in height increments. To make a measurement,
the pole is held vertically alongside the animal's hip with the sliding arm positioned
level and directly over the hook bones and a measurement read from the pole where the arm
attaches. For accurate height measurements it is necessary for the animal to have its legs
set squarely and head in a normal position. An alternative to using a height stick and
where the accuracy of individual measurements is not as critical is to place a grid marked
in height increments inside a scale or working chute. As cattle are being worked, a height
can be read off the grid by sighting across the animal's hip. Modifications can also be
made to equip cattle handling chutes with a moveable front to back pull-down measuring
device calibrated to obtain height measurements.
 Figure 1. Proper position for correctly
measuring hip height. Source: BIF Guidelines for Uniform Beef Improvement Programs,
1990
Beef Improvement Federation recommended procedures are available to adjust actual
height measurements to standard performance testing 205-day weaning and 365-day yearling
stages. Hip heights adjusted to 205 days should be collected between 160 and 250 days of
age similar to the range for calculating adjusted weaning weights. Cattle should be at
least 330 days of age for predicting yearling height measurements that are adjusted to 365
days. Age of calf and age of dam adjustment factors and formulas for calculating adjusted
205-day and 365-day hip heights are presented in Table 1. As an example of adjusting an
actual height, the 205-day weaning height of a bull calf born March 1 to a 4-year-old dam
and weaned October 10 measuring 44 inches would be 43.4 inches. {44 + [(205 - 224) *
.033]} * 1.01 = 43.4
Table 1. 205 day and 365 day Height Adjustment Factors
and Formulas
--------------------------------------------------------
205 day Height
Adjusted Height = {actual height + [(205 - actual age)*
age of calf adjustment]} * age of dam adjustment
--------------------------------------------------------
Factors for Adjusting Weaning Height
bulls heifers
Age of Calf .033 .025
Age of Dam
2 and 13 or older 1.02 1.02
3 and 12 1.015 1.015
4 and 11 1.01 1.01
5 through 10 1.00 1.00
--------------------------------------------------------
365 day Height
Adjusted Height = {actual height + [(365 - actual age)*
age of calf adjustment]}
--------------------------------------------------------
Factors for Adjusting Yearling Height
bulls heifers
Age of Calf
under 365 days .033 .025
over 365 days .025 .025
--------------------------------------------------------
--------------------------------------------------------
Source: BIF Guidelines for Uniform Beef Improvement
Programs, 1990
A hip height measurement can be converted to a frame score if the animal's age is
known. Frame scores can be approximated from "height for age" frame score tables
or calculated by mathematical formulas. Separate charts and formulas exist for bulls and
heifers due to differing rates of skeletal growth between sexes. Beef Improvement
Federation frame score charts and calculation formulas are presented in Table 2. As an
example of determining a frame score, a bull measuring 48 inches at 330 days of age would
be estimated to be about a frame score 5 from the chart or calculated to have a frame
score of 4.98 by the formula. [-11.548 + (.4878 * 48) - (.0289 * 330) + (.0000947 * 330 *
330) + (.0000334 * 48 * 330)] = 4.98. Several beef cattle breed associations have
developed their own frame score formulas and charts which are based on average growth and
development within their specific breed and vary slightly from BIF calculations.
Table 2. Frame score formulas and charts for bulls and heifers. Values
within the tables are reported in inches.
---------------------------------------------------------------------------
BULLS
Frame Score = -11.548 + .04878 (Height) - 0.0289 (Days of Age) +
0.00001947 (Days of Age)2 + 0.0000334 (Height) (Days of Age)
---------------------------------------------------------------------------
Age in -------------------------- Frame Score ---------------------------
Months 1 2 3 4 5 6 7 8 9
---------------------------------------------------------------------------
5 33.5 35.5 37.5 39.5 41.6 43.6 45.6 47.7 49.7
6 34.8 36.8 38.8 40.8 42.9 44.9 46.9 48.9 51.0
7 36.0 38.0 40.0 42.1 44.1 46.1 48.1 50.1 52.2
8 37.2 39.2 41.2 43.2 45.2 47.2 49.3 51.3 53.3
9 38.2 40.2 42.3 44.3 46.3 48.3 50.3 52.3 54.3
10 39.2 41.2 43.3 45.3 47.3 49.3 51.3 53.3 55.3
11 40.2 42.2 44.2 46.2 48.2 50.2 52.2 54.2 56.2
12 41.0 43.0 45.0 47.0 49.0 51.0 53.0 55.0 57.0
13 41.8 43.8 45.8 47.8 49.8 51.8 53.8 55.8 57.7
14 42.5 44.5 46.5 48.5 50.4 52.4 54.4 56.4 58.4
15 43.1 45.1 47.1 49.1 51.1 53.0 55.0 57.0 59.0
16 43.6 45.6 47.6 49.6 51.6 53.6 55.6 57.5 59.5
17 44.1 46.1 48.1 50.1 52.0 54.0 56.0 58.0 60.0
18 44.5 46.5 48.5 50.5 52.4 54.4 56.4 58.4 60.3
19 44.9 46.8 48.8 50.8 52.7 54.1 56.7 sa.7 60.6
20 45.1 47.1 49.1 51.0 53.0 55.0 56.9 58.9 60.9
21 45.3 47.3 49.2 51.2 53.2 55.1 57.1 59.1 61.0
---------------------------------------------------------------------------
HEIFERS
Frame Score = -11.7086 + 0.4723 (Height) - 0.0239 (Days of Age) +
0.0000146 (Days of Age)2 + 0.0000759 (Height) (Days of Age)
---------------------------------------------------------------------------
Age in -------------------------- Frame Score ---------------------------
Months 1 2 3 4 5 6 7 8 9
---------------------------------------------------------------------------
5 33.1 35.1 37.2 39.3 41.3 43.4 45.5 47.5 49.6
6 34.1 36.2 38.2 40.3 42.3 44.4 46.5 48.5 50.6
7 35.1 37.1 39.2 41.2 43.3 45.3 41.4 49.4 51.5
8 36.0 38.0 40.1 42.1 44.1 46.2 48.2 50.2 52.3
9 36.8 38.9 40.9 42.9 44.9 47.0 49.0 51.0 53.0
10 37.6 39.6 41.6 43.7 45.7 47.7 49.7 51.7 53.8
11 38.3 40.3 42.3 44.3 46.4 48.4 50.4 52.4 54.4
12 39.0 41.0 43.0 45.0 47.0 49.0 51.0 53.0 55.0
13 39.6 41.6 43.6 45.5 47.5 49.5 51.5 53.5 55.5
14 40.1 42.1 44.1 46.1 48.0 50.0 52.0 54.0 56.0
15 40.6 42.6 44.5 46.5 48.5 50.5 52.4 54.4 56.4
16 41.0 43.0 44.9 46.9 48.9 50.8 52.8 54.8 56.7
17 41.4 43.3 45.3 47.2 49.2 51.1 53.1 55.1 57.0
18 41.7 43.6 45.6 47.5 49.5 51.4 53.4 55.3 57.3
19 41.9 43.9 45.8 47.7 49.7 51.6 53.6 55.5 57.4
20 42.1 44.1 46.0 47.9 49.8 51.8 53.7 55.6 57.6
21 42.3 44.2 46.1 48.0 50.0 51.9 53.8 55.7 57.7
---------------------------------------------------------------------------
Frame score provides an indication of an animal's growth curve, which can be used to
project expected finishing weight for slaughter cattle, or mature weight for breeding
cattle. Table 3 provides an estimate of mature cow weight and expected slaughter weight at
finish for steers and heifers by frame score. These projections are for average cattle;
actual weights will also vary due to differences in muscling, body length, condition and
other factors.
Table 3. Relationship of frame size to projected
mature cow weight and slaughter weight at Choice
Quality Grade.
----------------------------------------------------
BIF
Numerical USDA Mature Steer Heifer
Frame Feeder Calf Cow Slaughter Slaughter
Score Frame Size Weight Weight Weight
----------------------------------------------------
2 Small 955 850 700
3 1030 950 800
----------------------------------------------------
4 Medium 1100 1050 900
5 1175 1150 1000
----------------------------------------------------
6 Large 1250 1250 1100
7 1320 1350 1200
8 1395 1450 1300
9 1470 1550 1400
----------------------------------------------------
Source: Adapted from Boggs, South Dakota State
University, 1991
Greater mature cow weight is associated with increased frame scores, which results in
additional feed required for maintenance because of a larger body mass. Stocking rates and
quantities of feed need to be adjusted to meet the demands of larger cows. Provided
necessary feed is available, larger cows generally meet their higher requirements. Under
favorable management, reproductive rates tend to be similar across frame size; however,
when the availability of feed becomes restricted, larger framed cattle are more
susceptible to reproductive failure. Increasing mature size is a concern and may require
adjusting replacement heifer development programs in order to insure they reach heavier
prebreeding weights necessary to attain puberty.
Large frame size is also associated with greater growth potential, longer finishing
periods, and heavier slaughter weights. The generally preferred range for carcass weights
of 650 to 850 pounds suggests the need to produce feeder cattle with a 5 to 7 range in
frame scores. The current USDA feeder cattle grading system is based on the factors of
frame size and muscle thickness. Three frame score designations are included: large,
medium, and small, which relate to an evaluation by appearance of an animal's skeletal
height in relation to its age and the weight at which an animal will produce a choice
quality carcass with about .5 inches external fat at the 12th rib. Large frame steers and
heifers would not be expected to produce choice carcasses until their live weight exceeds
1200 and 1000 pounds, respectively. Medium frame steers would be expected to produce
choice carcasses at live weights of 1000 to 1200 pounds, and heifers at 850 to 1000
pounds. Small frame steers and heifers would produce choice carcasses at live weights of
less than 1000 and 850 pounds, respectively.
An indication of frame size is very important when estimating growing and finishing
cattle nutrient requirements and projected feed intake. Although larger framed cattle will
generally have increased intakes, energy concentration in the feed that is used for gain
(NEg) is lower than that of medium framed cattle. Furthermore, protein requirements for
large framed steers have been based on medium framed steers that weigh 15% less. This
results in a greater protein requirement for large compared to medium framed cattle.
Frame score is considered to be moderately to highly heritable. As such, frame score
can be significantly changed through selection, primarily achieved through sire selection.
With an heritability estimate of .40, about 40% of a bull's difference in frame score from
herd average will be passed on to progeny.
Frame score measurements are descriptive of animal type and growth patterns in beef
cattle. They are useful in evaluating animal nutritional requirements, characterizing
target market weights, and aid in selection decisions.
AS-1091, May 1995
North Dakota State University
NDSU Extension Service
|
