Nutrition and Management: Using Frame Size to Predict Growth and Development

This is a fact sheet from the Nutrition and Management section of the Alberta Feedlot Management Guide,Second Edition published September 2000. The 1200 page guide is available for purchase on CD-ROM.

Introduction

The North American feeder cattle population has become increasingly variable over the last 25 years. The importation of many breeds and intensive use of crossbreeding has resulted in large changes in breed composition, size, propensity to fatten, muscling, growth potential and carcass characteristics. These changes have increased the variability in the growth and development among feeder cattle during the growing and finishing phases. Much of this variation in growth, feedlot performance and carcass composition can be described by genotype or biological type. However, precise identification of biological type has become difficult for a large portion of the feeder cattle population because of within breed variability, crossbreeding and loss of animal identity. Today there are more than 80 breeds of cattle recognized in North America. In Alberta, results from a survey conducted on 3,400 herds from 1986 to 1991 revealed that more than 90% of commercial cow-calf managers were practicing some form of crossbreeding; approximately 65% were producing at least three-way cross calves.

Frame size is a convenient way of describing skeletal size within age of cattle and under normal feeding and management is related to the live weight at which a feeder animal will reach a constant level of fatness. It is a moderately heritable characteristic in cattle. Primarily, there are two types of frame scoring systems used in the beef industry:

• frame size by measurement, and;
• frame size by visual appraisal.

This system is used by the seedstock industry as another method of evaluating the fat-lean ratio of an individual animal in a performance program. Traditionally, it has not been used in the fed cattle industry as it requires actual hip height and age within gender. An example is the Kansas State University frame scoring system. This system is based on eleven frame scores for male (Table 1) and female (Table 2) cattle between 5 and 48 monthsof age. The University of Missouri also has a system based on seven frame sizes.

Table 1. Kansas State University Frame Score Chart. Bulls - 5 to 21 months. Bull hip heights are listed in inches.

Age in months	Farme Score
	1	2	3	4	5	6	7	8	9	10	11
5	33.3	35.3	37.3	39.3	41.3	43.4	45.5	47.5	49.6	51.7	53.8
6	34.8	36.8	38.8	40.8	42.7	45	47	49	51	53.2	55.2
7	36.2	38.1	40.2	42.2	43.9	46.2	48.2	50.2	52.2	54.3	56.3
8	37.4	39.3	41.3	43.3	45	47.3	49.4	51.4	53.5	55.5	57.5
9	38.5	40.3	42.3	44.3	46.1	48.5	50.5	52.5	54.5	56.6	58.5
10	39.4	41.2	43.3	45.3	47	49.3	51.3	53.3	55.3	57.5	59.5
11	40.2	42.1	44.2	46.2	48	50.2	52.2	54.2	56.2	58.3	60.3
12	41	43	45	47	49	51	53	55	57	59	61
	1	2	3	4	5	6	7	8	9	10	11
13	41.7	43.8	45.8	47.6	49.6	51.6	53.8	55.8	57.8	59.8	61.8
14	42.4	44.4	46.5	48.3	50.1	52.3	54.4	56.4	58.3	60.5	62.5
15	43	45	47	49	50.8	53	55	57	58.8	61	63
16	43.5	45.5	47.5	49.5	51.3	53.5	55.5	57.5	59.3	61.5	63.4
17	44	46	48	50	51.6	53.8	55.8	57.8	59.8	62	63.8
18	44.4	46.5	48.5	50.4	52	54.2	56.3	58.3	60.3	62.4	64.3
19	44.8	46.9	48.9	50.8	52.5	54.7	56.8	58.8	60.7	62.8	64.8
20	45.3	47.3	49.3	51.2	52.8	55	57	59	61	63	65
21	45.7	47.5	49.5	51.5	53.1	55.2	57.3	59.3	61.3	63.3	65.3

Frame Size by Visual Appraisal

In 1979, recognition of the large amount of variability in the feeder cattle population led the USDA to revise their feeder grade standards to include evaluations for skeletal or frame size and muscle thickness. It also led The National Academy of Sciences-National Research Council (6) to incorporate frame size as a factor influencing the nutrient requirements of growing and finishing cattle. However, recently the Nutrient Requirements of Beef Cattle (7) has been adjusted to remove frame size as a factor influencing nutrient requirements.

The USDA frame score is determined by visual appraisal and is used in the fed cattle industry. Along with a subjective evaluation of muscling, the USDA feeder grade standards system has the potential to be used to cluster feeder cattle into uniform finishing groups three to five months before slaughter. Both the USDA and Agriculture and Agri-Food Canada recognize three frame sizes for feeder cattle: large, medium and small. The following description is adapted from the USDA frame size specifications and has been modified to reflect the modern feeder animal.

Table 2. Kansas State University Frame Score Chart. Heifers - 5 to 21 months. Heifer hip heights are listed in inches.

Age in months	Frame Score
	1	2	3	4	5	6	7	8	9	10	11
5	33	35	37	39.1	41.2	43.2	45.3	47.4	49.5	51.5	53.5
6	34.1	36.2	38.2	40.2	42.2	44.4	46.5	48.5	50.5	52.6	54.6
7	35.2	37.2	39.2	41.2	43.2	45.4	47.5	49.5	51.5	53.5	55.5
8	36.1	38.1	40.2	42.2	44.2	46.2	48.2	50.2	52.5	54.5	56.5
9	37	39	41	43	45	47	49	51	53.2	55.2	57.2
10	37.7	39.7	41.7	43.7	45.7	47.7	49.7	51.7	53.7	55.7	57.7
11	38.4	40.4	42.4	44.4	46.5	48.5	50.5	52.5	54.5	56.5	58.5
12	39	41	43	45	47	49	51	53	55	57	59
	1	2	3	4	5	6	7	8	9	10	11
13	39.6	41.5	43.5	45.5	47.5	49.5	51.5	53.5	55.5	57.5	59.4
14	40.1	42	44	46	48	50	52	54	55.8	57.8	59.8
15	40.6	42.5	44.5	46.5	48.5	50.4	52.3	54.3	56.2	58.2	60.2
16	41	42.8	44.9	46.9	48.9	50.7	52.7	54.7	56.6	58.5	60.5
17	41.4	43.2	45.2	47.2	49.2	51	53	55	57	58.8	60.8
18	41.7	43.5	45.5	47.5	49.5	51.4	53.3	55.2	57.2	59.1	61
19	42	43.8	45.8	47.8	49.8	51.7	53.5	55.5	57.5	59.3	61.3
20	42.2	44.1	46	48	50	51.9	53.8	55.7	57.6	59.5	61.4
21	42.5	44.4	46.3	48.3	50.2	52	54	56	57.9	59.8	61.7

Large frame size


“Feeder cattle which have minimum qualifications for this grade are thrifty, have large frames, and are tall and long bodied for their age. Large frame steers with average muscling would not be expected to produce 13 mm of subcutaneous fat at the twelfth rib until their live weight exceeded 544 kg (1,200 lb). Heifers would not be expected to produce 13 mm of subcutaneous fat at the twelfth rib until their live weight exceeded 454 kg (1,000 lb).” Thirteen mm of subcutaneous fat at the twelfth rib is approximately equivalent to Canada A2 and US Choice grades. Modern large framed steers are unlikely to have 13 mm of backfat at 1,200 lb. This level of backfat would be reached when live weight exceeded 612 kg (1,350 lb) for steers and 544 kg (1,200 lb) for heifers.

Medium frame size

“Feeder cattle which have minimum qualifications for this grade are thrifty, have slightly large frames, and are slightly tall and long bodied for their age. Steers with average muscling would be expected to produce 13 mm of subcutaneous fat at the twelfth rib at live weights of 454 kg (1,000 lb) to 544 kg (1,200 lb). Heifers would be expected to produce 13 mm of subcutaneous fat at the twelfth rib at live weights of 386 kg (850 lb) to 454 kg (1,000 lb).” Again, these live weights should be increased by 68 kg (150 lb) to reflect the modern animal.

Small frame size


“Feeder cattle in this grade have small frames, are shorterbodied and not tall as specified for the medium frame grade. Steers would be expected to produce carcasses with 13 mm of subcutaneous fat at the twelfth rib at live weights of less than 454 kg (1,000 lb) for steers and less than 386 kg (850 lb) for heifers.”

These live weights must also increase 68 kg (150 lb) to reflect the modern animal. What USDA calls small framed are virtually extinct.

Frame sizes differ in linear body measures
Dr. Daryl Tatum and his colleagues at Colorado State University (10, 11) conducted studies to quantify visually perceived differences in the USDA feeder grade standards of frame size and muscling thickness (muscle thickness reflects differences in muscle:bone ratio among cattle of similar fatness). Yearling feeder steers were purchased in early spring from cattle producers and livestock markets in Colorado, western Nebraska and southeastern Wyoming. Three hundred and twenty-four steers were specifically selected by eye from the initial group to represent the three USDA frame size and three USDA muscle thickness categories. Means and standard deviations for various linear body measurements are presented in Table 3.

These results show that visual assessment of frame size is somewhat effective in identifying measurable differences in frame size and shape. Differences in frame size were reflected by differences in absolute hip height. For example, at a 95% confidence limit, the hip height of large framed steers ranged from 116.5 to 130.3 cm; it ranged from 108.6 to 122.4 cm for medium framed steers and from 102.1 to 115.9 cm for small framed steers. It is unlikely that frame size would be completely effective in predicting days on feed to a fat constant endpoint since there is considerable overlap among frame size categories in all linear body measures. The 95% confidence limits on these traits was determined by adding and subtracting two standard deviations from the mean (e.g., 123.4 cm - (3.5 cm x 2) = 130.4 cm).

Table 3. Effect of Frame Size on Linear Body Traits in Yearling Feeder Steers.

Traits	Frame Size			Standard Deviation
	Large	Medium	Small
bw, kg	374	328	298	39.2
hg, cm	169	161	156	8.8
hw, cm	43.8	41.6	40.4	2.6
sw, cm	46.1	44.5	43.2	2.7
fc, cm	41.9	40.9	39.9	3
bl, cm	133	126	120	5.9
hh, cm	123	116	109	3.5
ft, mm	2.2	2.4	2.6	1.3

bw=body weight; hg=heart girth; hw=hip width; sw=stifle width; fc=forearm circumference; bl=body length; hh=hip height and
ft=subcutaneous backfat thickness. Source: (12)

Concepts of Growth and Development

A brief review of the process of growth and development is necessary to understand why frame size affects feedlot performance and carcass composition. Growth from conception to maturity is an orderly process. The growth of the fetus, or prenatal growth, is characterized by differential growth rates of various organs and systems. The central nervous system, heart, liver and kidney, which have functional importance during fetal growth, undergo a greater proportion of their total growth early. This is followed by the development of the skeletal system, the muscles and finally the adipose or fat tissue (Figure 1). Thus, at birth there are about two parts of muscle to one part bone in the carcass of a calf. Since muscle grows relatively faster than bone during the postnatal period, there are about five parts of muscle to one part bone in the carcass at slaughter. Fat growth starts out relatively slowly and, at birth, only makes up a small amount of the carcass. Fat deposition increases slowly from birth to weaning and then, given an adequate plane of nutrition, will begin to increase exponentially during the finishing phase. Since fat is the most variable tissue in the body, manipulation of carcass composition by genetic and nutritional means depends largely on controlling the proportion of fat.

Growth from birth to maturity is characterized by a growth curve. This curve can be observed by plotting body weight against age (Figure 2).


Figure 1. Carcass Composition of Cattle from Birth to Slaughter. Adapted from John McKinnon, Manitoba Agriculture Factsheet.


Figure 2. Typical Growth Curves for Beef Heifers of a Small Framed Breed Group. (Goonewardene et al. 1981 Can. J. Anim. Sci. 61:1041-1048).

Frame Size Affects Growth and Carcass Development

It is well documented that different breeds or breed crosses grow and fatten at different rates. Generally, the early fattening breeds are of British beef breed origin (i.e., Hereford, Angus, Red Angus, Shorthorn) while the major continental European breeds (Charolais, Simmental, Limousin, Maine Anjou, Salers) are late fattening. Early fattening biological types tend to be small to medium framed while late fattening biological types tend to be medium to large framed. These differences cause changes in the proportion of major carcass tissues (muscle, bone and fat) at the same chronological age.

In 1993, Dolezal, Tatum and Williams (5) reported the results of a study which showed the effect of age, frame size and muscle thickness on feeder cattle performance and carcass traits. Only the effect of frame size is reported in Table 4. Large framed steers required 51 more days on feed than medium framed steers and 75 more days than small framed steers. Large framed steers were also111 kg heavier at slaughter than medium framed steers and 179 kg heavier than small framed steers. These differences are reflected in hot carcass weight and, to a lesser degree, in dressing percentage. Generally, thin muscled (No. 3), dairy-type steers within each frame size required more days on feed than thick (No. 1) muscled steers. Moderate (No. 2) muscled steers of each frame size were intermediate. Thus large framed, thin muscled steers will require the most time on feed and the heaviest weights to reach a fat constant endpoint. Interestingly, small framed, thin muscled steers were next in days on feed required to reach a fat constant endpoint.

Table 4. Effect of Frame Size on Steers Fed to a Constant Fat Thickness of 13.5 mm (5).

Frame size	Time on feed, d	Slaughter wt, kg	Hot carcass wt, kg	Dressing %
Large	214a	644a	407a	63.2a
Medium	163b	533b	335b	62.8a
Small	139c	465c	286c	61.5b

^a,b,c Means in the same column within trait with a different letter, are significantly different (P < 0.05).


Figure 3. A schematic diagram of the average daily gain (ADG), weight and carcass composition of small, medium and large framed feeder cattle (adapted from Price (9)).

Figure 3 illustrates the general relationship between average daily gain, weight and frame size. Large framed steers, both within and among breeds, grow faster, have greater daily dry matter intake, have more days on feed, have increased slaughter weight at a constant carcass fat level and begin to fatten at heavier weights and older ages than their medium and smaller contemporaries. Researchers at the University of Arizona have shown that there is a difference in the rate at which different frame size cattle deposit fat. Small framed cattle deposit lipids at a faster rate during the time they are consuming a high energy diet than either medium or large framed cattle. One reason for this could be the lower rates of fat mobilization exhibited by the small framed animals.

Figure 3 also illustrates that regardless of frame size, all steers can be fed to reach a level of fatness and weight desired by the marketplace. In the study by Dolezal and coworkers (5), small framed steers fed as long yearlings were comparable in weight to medium framed calves and yearlings at slaughter. Therefore, deferred concentrate feeding (i.e., backgrounding; grazing systems using minimal grain feeding) for small framed cattle could be used to enable them to conform to conventional weights and grade specifications. Feeding large framed steers as long yearlings would result in slaughter weights well beyond those desired by the market. Thus, it is possible to develop feeding and management programs which target specific frame sizes, muscling types and biological types for specific markets.

In many feedlots throughout North America the current practice is to market entire pens of cattle on a single date. In most cases these cattle have not been sorted to pens based on objective traits describing their rate of growth and fattening. As a result, large, medium and small framed feeders are mixed together in the same pen and marketed together on the same date. Figure 3 illustrates that this practice results in what can be referred to as the Goldilocks Syndrome; some cattle are too fat, some cattle are too thin, while only a few are just right. Recent estimates place the cost of carcass yield and quality non-conformities at $43 (CAN) per head slaughtered in Canada and $81 (US) per head slaughtered in the United States (National Cattlemen’s Association 1995). This differences is at least partially attributed to the USDA grading system which has emphasized marbling for much longer than the Canadian grading system. Increased marbling often comes at a cost of reduced feed efficiency and overweight and over-fat carcasses.

Frame size affects fat distribution
In cattle there are four major fat depots: intermuscular or seam fat, subcutaneous or back fat, intramuscular or marbling and internal fat (kidney, pelvic and heart). Intermuscular fat is the largest fat depot, while internal fat is the smallest. The shifting of these fat depots by genetic or nutritional means could have a dramatic effect on carcass quality and net worth. Tatum and coworkers at Colorado State University (11, 12) reported that beef breeds had a high ratio of subcutaneous to intermuscular fat and a low proportion of internal fat. Dairy breeds had a low ratio of subcutaneous to intermuscular fat and a high proportion of internal fat. These authors concluded that cattle selected intensely for traditional characteristics tend to deposit a higher proportion of fat subcutaneously while cattle selected for milk production tend to deposit a high proportion of fat internally. Existing information concerning fat partitioning of the continental breeds indicates that they tend to occupy an intermediate position relative to British and dairy breeds. Berg and others at the University of Alberta have shown that small framed cattle have an increased proportion of subcutaneous relative to intermuscular and internal fat, while large framed cattle produce the opposite effect. Increased frame size was associated with lower proportions of subcutaneous fat and higher proportions of internal fat.

Can Frame Size Be Used to Predict Days on Feed?

Studies conducted by Basarab and Milligan with 1,200 large and medium framed yearling steers at three feedlots in Alberta revealed that the relationship between hip height and days on feed to a slaughter constant endpoint (7.9 mm carcass backfat thickness or 647 kg slaughter weight, which ever came first) was poor. Stated another way, hip height only accounted for 3% to 6% of the variation in days on feed to a slaughter constant endpoint. Other measures of body dimensions such as body length and stifle length were also poorly correlated and only accounted for 4% to 5% of the variation in days on feed to a slaughter constant endpoint. In these studies, live animal backfat thickness and weight measured three to five months before slaughter accounted for 30% to 50% of the variation in days on feed to a slaughter constant endpoint.

Studies conducted by Basarab, Brethour and co-workers in 1997/98 (1), at two large commercial feedlots in Alberta, used a Kansas State University (KSU) sorting system, applied three to four months before slaughter to improve carcass uniformity and net return of finished cattle. The sorting system exploited initial body weight and ultrasound estimates of backfat and marbling to track future carcass merit. This information was combined with economic conditions such as carcass price matrix and production costs to project the number of additional days on feed to maximize profit. Approximately 4,100 yearling steers were randomly assigned to control or KSU sorted groups. In total, there were nine pens of control steers and 15 pens of KSU sorted steers. All pens of cattle within the feedlot were managed and fed the same and were gradually adjusted from a high (70-90%) barley silage diet to a high (75- 80%) barley grain diet over 15-21 days. Steers were on the finishing diet for 63 to 110 days and a whole pen of cattle was marketed when the majority of steers in the pen approached the carcass weight and grade characteristics required for optimal return. This was determined by the feedlot manager using visual appraisal. The KSU sorted steers grew 4 to 6% faster, had a 3 to 5% improvement in feed efficiency and had fewer over-fat carcasses than control steers. These changes resulted in the KSU sorted steers being more profitable by $15 to $26/hd due primarily to improved weight gain and feed efficiency and a more desirable distribution of carcass yield and quality grades.

Summary

In conclusion, measures of frame size alone will have little or no effect on improving carcass uniformity. More detailed feeder specification systems that cluster feeder cattle according to live animal measures of weight, backfat, marbling, muscling and tenderness are required. These systems will be difficult to perfect because of the inconsistency of within breed selection criteria, the diverse goals of crossbreeding programs and the numerous feeding and growth implant programs.

References

1. Basarab, J.A., Brethour, J.R., ZoBell, D.R. and Graham, B. 1999. Sorting feeder cattle with a system that integrates ultrasound backfat and marbling estimates with a model that maximizes feedlot profitability in value-based marketing. Can. J. Anim. Sci. 79: 327-334.
2. Basarab, J.A., Milligan, D., McKinnon, J.J. and Thorlakson, B.E. 1997a. Potential use of video imaging and real-time ultrasound on incoming feeder steers to improve carcass uniformity. Can. J. Anim. Sci. 77:385-392.
3. Berg, R.T. and Butterfield, R.M. 1976. New Concepts of Cattle Growth. Halsted Press, a Division of John Wiley & Sons, Inc., New York.
4. Canadian Beef Quality Audit. 1996. Canadian Cattlemen’s Association, 215, 6715-8th Street N.E., Calgary, Alberta T2E 7H7.
5. Dolezal, H. G., Tatum, J. D. and Williams, Jr., F. L. 1993. Effects of feeder cattle frame size, muscle thickness, and age class on days fed, weight, and carcass composition. J. Anim. Sci. 71: 2975-2985.
6. National Academy of Science-National Research Council. 1984. Nutrient requirements of beef cattle. 6th rev. ed. National Academy press, Washington, DC.
7. National Academy of Science-National Research Council. 1996. National Requirements of beef cattle. 7th rev. ed. National Academy press, Washington, DC.
8. National Beef Quality Audit-1995. Improving the quality, consistency, competitiveness and market-share of beef. National Cattlemen’s Association, Englewood, CO.
9. Price, M.A. 1980. Can Judges judge what hides hide? University of Alberta, Department of Animal Science, Agriculture and Forestry Bulletin, 3:9-12.
10. Tatum, D. J., Dolezal, H. G. and Williams, Jr., F. L. 1986a. Effects of feeder-cattle frame size and muscle thickness on subsequent growth and carcass development. II. Absolute growth and associated changes in carcass composition. J. Anim. Sci. 62: 121-131.
11. Tatum, J. D., Williams, Jr., F. L. And Bowling, R. A. 1986b. Effects of feedercattle frame size and muscle thickness on subsequent growth and carcass development. III. Partitioning of separable carcass fat. J. Anim. Sci. 62: 132-138.
12. Tatum, J. D., Williams, Jr., F. L. and Bowling, R. A. 1986c. Effects of feedercattle frame size and muscle thickness on subsequent growth and carcass development. I. An objective analysis of frame size and muscle thickness. J. Anim. Sci. 62: 109-120.