Animal Science Staff Paper 410

File No. 19.263

November, 2001

H.D. Ritchie¹, S.R. Rust¹, K.W.

Bruns², and R.H. Prichard²

Marketing feedlot cattle short of their optimal harvest endpoint runs the risk of decreasing the percent grading Choice, increasing the percent of Selects, and reducing sale weight.Conversely, feeding cattle beyond their optimal endpoint can significantly increase the percent of Yield Grade 4s, negatively impact feed efficiency, and increase cost of gain.It is beyond the scope of this paper to present a full review of literature on the subject of time on feed. Rather, the objective is to briefly review past and current research on this topic and to include financial data when it is available.

Iowa State University

(Strohbehn personal communication)

___________________

¹Department of Animal Science, Michigan State University, East Lansing, MI 48824

² Department of Animal and Range Science, South Dakota State University, Brookings, SD 57007

(personal communication)

Feedlot consultant, Marcus Hoelscher, Hereford, TX, sorted data on several thousand British yearling steers in large commercial feedyards into five 35-day periods, from 0 to 170 days on feed. After 105 days, there was a dramatic decline in feedlot performance as shown in Table 1. Daily gain declined by 41%; feed/gain and cost of gain increased by 49 and 50%, respectively.

Table 1. Effect of time on feed on performance of British yearling steers.
	Feeding period, days			Difference
Item	0-105	106-170		(%)
Average daily gain, lb Feed/gain, lb/lb Cost of gain, $/cwt	2.94 8.5 38.23	1.74 12.7 57.20		-41% +49% +50%

Purdue University

(Hendrix and Forrest, 1985)

Kern Hendrix and John Forrest, Purdue University, analyzed data on Burtish calf-fed steers that were fed for either 200 or 230 days in an Indiana feedlot.

As shown in Table 2, feeding a Yield Grade 3 steer beyond his logical slaughter endpoint by one yeild grade resulted in $47 more feeding costs, $95 less carcass value, and #142 less feeding margin.

Oklahoma State University

(Van Koevering et al., 1995)

The three previous studies involved British-bred steers (Angus, Hereford, etc.). In a study at Oklahoma State University, researchers allotted 256 yearling Continental-British cross steers (725 lb) to four harvest groups, each of which were 14 days apart: 105, 119, 133, and 147 days. Steers were implanted with Compudose® at the start of the trial. Following is a summary of the results:

• Average daily gain plateaued at 119 and 133 days and then declined.
• Average daily gain plateaued at 119 and 133 days and then declined.
• Ribeye area plateaued at 133 days.
• Fat thickness increased linearly up to 147 days on feed.
• Percent Yield Grade 4s increased expotentially from 133 to 147 days (1.56% to 9.38%).
• Marbling score and percent grading Choice plateaued at 133 days.
• Tenderness (shear force) plateaued at 133 days.

The authors concluded that a finishing period of 119 to 133 days appears to be optimal for Continental-British cross yearling steers.

Kansas State and West Texas A & M Universities

(Lawrence et al., 2001)

Data from a total of 60,625 steers and heifers collected in NCBA’s Carcass Data Service were analyzed for relationships among carcass traits. A sample size of this magnitude would undoubtedly consist of a biological mix representative of the entire U.S. cattle population. Their analysis revealed the following:

• Quality grade improved with increasing fat thickness, but after 0.59 in., the percentage of Yield Grade 4 and 5 carcasses increased dramatically faster (11.9% at 0.65 in.; 29.2% at 0.73 in.; 59.3% at 0.81 in.) than the percentage of Choice carcasses.
• Feeding cattle to a fat thickness of 0.55 to 0.59 in. maximized quality grade while minimizing Yield Grade 4 and 5 discounts.

South Dakota State University
(Bruns, 2000)

In a two-year study, straightbred Angus steer calves of known parentage from a single source, averaging 584 lb, were backgrounded for 70 days, then switched to a finishing diet and allotted to five harvest groups to reach carcass weights of 450, 550, 650, 750, and 850 lb. They did not receive implants. The steers originated from a herd which has been selecting for above average growth along with acceptable carcass and maternal traits. Average frame size of the steers in this study was approximately Medium+. Results are summarized in Table 3.

Table 3. Effect of harvest endpoint on feedlot performance and carcass characteristics of straightbred Angus steers.
	Harvest group
Item	1	2	3	4	5
Initial wt., lb Days on feed Avg. daily gain, lb  Final shrunk wt., lb  Dressing %  Carcass wt., lb  Rib fat, in.  Yield Grade  % YG 1s and 2s % YG 4s and 5s Marbling  % Choice and up % Standard Carcass value, $/cwte	620 57 3.16a,b 804a 57.1a 459a .18a 2.2a 100 0.0 SL12a 0.0 25.0 79.00	628 88 3.31a 925b 58.6b 542b .26a,b 2.6a,b 87.5 0.0 SL53a 6.25 6.25 89.44	636 139 2.92b 1043c 62.3c 650c .36b 3.1b 61.1 5.6 SM41b 66.6 0.0 101.56	614 186 3.21a,b 1204d 64.1d 774d .55c 3.8c 6.0 29.4 MT33c 100.0 0.0 102.10	624 250 2.61b,c 1277e 65.6e 838e .75d 4.7d – 83.3 MD90d 100.0 0.0 95.30
a, b,c,d Means with different superscripts differ significantly (P < .05). e Based on a pricing grid that emphasizes quality grade.

As shown in Table 3, rib fat thickness and yield grade increased at a progressively increasing rate until the final harvest group was rapidly approaching an average Yield Grade of 5. This is in general agreement with a previous Oklahoma State University study involving medium frame Angus x Hereford steers (May et al., 1992). Marbling, on the other hand, increased in a linear fashion. This is in contrast to the commonly-held belief that marbling is a late maturing tissue and the last fat depot to express itself.

Additional analysis of the data revealed that carcasses reached a Yield Grade of 3.0 at 642 lb carcass weight and that a Small degree of marbling occurred at a carcass weight of 586 lb. Furthermore, the greatest advances in marbling relative to total carcass fatness occurred prior to a carcass weight of 662 lb. In a separate analysis of carcass value, using a grid with an emphasis on quality grade, value per cwt of carcass peaked at the third and fourth harvest groups.

This is an interesting study because it does, in fact, suggest that marbling is not a late developing tissue. Furthermore, it suggests that nutrition and management practices during backgrounding and early finishing may have a greater influence on eventual quality grade than previously thought.

A companion trial was conducted on 79 additional contemporary steers in year one of the study described above. These steers were allotted to three harvest groups targeted to reach carcass weights of 650, 750, and 850, respectively. Results are summarized in Table 4.

Table 4. Feedlot performance and carcass characteristics of straightbred Angus steers fed to three different harvest endpoints.
	Harvest group
Item	1	2	3
Initial weight, lb Days on feed Average daily gain, lb  Dry matter intake, lb/d Feed/gain, lb/lb  Final shrunk weight, lb  Carcass weight, lb  Rib fat, in.  Marbling   % Mid-Choice and up % Low Choice % Select Yield Grade  % Yield Grade 1s % Yield Grade 2s % Yield Grade 3s % Yield Grade 4s Carcass valued:    Price, $/cwt    Total value, $/hd Cost of gaine:    $/cwt     Total cost, $/hd Feeding margin, $/hdf	562 143 3.28a 20.0 5.88a 1033a 648a .60a SM40a 22.2 48.2 29.6 3.1a 0.0 44.4 51.9 3.7    101.80 659.66    43.99a 207.19 452.47a	578 200 3.04b 20.2 6.67a,b 1189b 736b .73b MT81b 77.0 23.0 0.0 3.9b 0.0 7.7 53.9 38.5    103.11 758.89    48.01a 293.34 465.55	589 249 2.58c 19.6 7.69b 1232c 778c .82c MD23b 92.3 7.7 0.0 4.1b 0.0 0.0 42.3 57.7    100.81 784.30    55.12b 354.42 429.88
a,b,c with different superscripts differ significantly (P < .05). d Based on a pricing grid that emphasizes quality grade. e Feed cost, $115/ton DM; yardage, 30¢/hd/d.

The author noted that steers in Group 3 stalled out in gain after 200 days on feed. Consequently, it was necessary to harvest them before they reached their targeted carcass weight of 850 lb. In spite of this decline in performance, they continued to accumulate significantly more rib fat than steers in Group 2. However, their marbling score did not differ significantly from Group 2. Numerical yield grade increased dramatically in Groups 2 and 3, resulting in high percentages of Yield Grade 4s. Carcass price per cwt did not differ significantly among groups because quality grade premiums were offset by Yield Grade 4 discounts. Total carcass value increased with time on feed as a result of increasing carcass weight. Because of declining feed efficiency, cost of gain increased with time on feed, especially in Group 3. Feeding margin (carcass value minus cost of gain) peaked in Group 2 and then declined.

This study suggests that feeding non-implanted Medium+ frame straightbred Angus steers beyond a targeted carcass weight of approximately 750 lb is not likely to be profitable.

DISCUSSION

Although this paper is only a partial review of the subject, it seems clear that feeding cattle to their optimal harvest endpoint can have a marked impact on profitability. This is becoming increasingly important as the industry moves toward carcass-based marketing systems. The challenge is to determine the optimal harvest endpoint on a given group of cattle. Improvement in the classification of feeder cattle would enhance the estimation of subsequent performance of individual feeder animals by the assembly of more uniform outcome groups for feeding (Bruns and Pritchard, 2001). Numerous factors affect harvest endpoint, including source/origin, parentage, breed/ biological type, weight, age, sex, frame size, condition, muscle, health, nutrition, and implant protocols. Data management systems are being developed as a means of documenting “histories” that encompass these and other factors. In the future, it will be important for cow/calf producers and backgrounders to build such histories in order to market their cattle more effectively to feedyards and for feedyards to market more effectively to packers/processors. Eventually, without this kind of information, it will become increasingly difficult to market cattle at anything but a discounted price.

REFERENCES

Bruns, K.W., 2001. Alometric growth of adipose tissue in beef cattle. Ph.D. Thesis, South Dakota State University, Brookings.

Bruns, K.W. and R.H. Pritchard, 2001. Sorting cattle - a review. J. Anim. Sci. (submitted).

Hendrix, K.S. and J.C. Forrest, 1985. The high cost of overfeeding cattle. Beef, October, 1985.

Hoelscher, M.A., 2001. Personal communication.

Lawrence, T.E., D.A. King, T.H. Montgomery, and M.E. Dikeman, 2001. Relationships among selected beef carcass characteristics. J. Anim. Sci. 79(Suppl. 2):55 (Abstract).

May, S.G., H.G. Dolezal, D.R. Gill, F.K. Ray, and D.S. Buchanan, 1992. Effects of days fed, carcass grade traits, and subcutaneous fat removal on postmortem muscle characteristics and beef palatability. J. Anim. Sci. 70:444-453.

Strohbehn, D.R., 2001. Personal communication. Van Koevering, M.T., D.R. Gill, F.N. Owens, H.G. Dolezal, and C.A. Strasia, 1995. Effect of time on feed on performance of feedlot steers, carcass characteristics, and tenderness and composition of longissimus muscles. J. Anim. Sci. 73:21-28.

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