JAY, ARC RESEARCH REPORT WF77-2 MARCH, 1977
THE PRODUCTION OF LIGHTWEIGHT BEEF ON WINTER ANNUAL
PASTURES WITH AND WITHOUT GRAIN SUPPLEMENTAION1'
J. E. Bertrand and L. S. Dunavi 2
"Grass-fed beef" in the southeastern section of th United Bt f/e f om
lightweight animals 12 to 15 months of age that have be n feOn forage or gras
with or without a grain supplement to weights of 600 to 900 1% n e@ jsgucers nd
consumers would benefit greatly if light yearling beef, carrying enough finish, o
grade U. S. Good or better, could be placed on the mar d~iufuf Aent auanti
and at a reasonable price. o'Oride
A pasture mixture composed of rye, ryegrass, and crimson clover normally
offers a long grazing season and produces good gains when rotationally grazed by
growing beef calves during the late fall, winter, and early spring in north Florida.
This type of winter annual pasture is high in digestible protein, minerals, and
vitamins (especially vitamin A) on a dry matter basis; however, it is high in
moisture and low in energy for optimum growth by lightweight beef calves.
The objective of this study was to determine the effects of various levels
of supplemental feed (high in dry matter and energy) on the performance along
with slaughter and carcass characteristics of growing beef steers rotationally
grazing winter annual pastures (a mixture of rye, ryegrass, and crimson clover).
Sixty-four lightweight (average 402 lb.) feeder steers of British breeding
(Angus, Hereford, and Angus X Hereford crosses), grading U. S. Good or better and
each treated with a 36 mg ear implant of RALGRO (Zeranol a protein anabolic
agent), were weighed and allotted at random from breed groups to eight experimental
groups of eight steers each. The eight experimental groups, utilizing two groups
per treatment, were randomly assigned to four levels of supplemental feed on
pasture as follows:
1. 0 = rotational grazing of a 'Wrens abruzzi' rye, 'Gulf' ryegrass, and
'Dixie' crimson clover mixture---unsupplemented with four 1.25 acre
plots for each group initially containing eight steer calves.
2. 1/2% = same pasture mixture, land area, and number of calves as 1 above
--supplemented with an 11% protein high-energy ration at the level of
1/2% of body weight.
3. 1% = same pasture mixture, land area, and number of calves as 1 above---
same ration as 2 above fed at 1% of body weight.
4. 1-1/2% = same pasture mixture, land area, and number of calves as 1
above--same ration as 2 above fed at 1-1/2% of body weight.
The rye was planted in row widths of 7 inches with a grain drill at the rate of
90 lb. per acre. The ryegrass and crimson clover were top-seeded over the rye with
a cultipacker-seeder at the rates of 12 and 10 lb. per acre, respectively. The first
and second rotational pastures for each treatment were planted on October 21 and 22,
1975; while the third and fourth rotational pastures for each treatment were planted
on November 4 and 5, 1975. A commercial fertilizer (4-12-12) was applied to all
pastures at planting time at the rate of 500 lb. per acre. Three applications of
100 lb. per acre each of ammonium nitrate were made during the grazing season.
1/Presented at the 1977 Beef Cattle and Forage Field Day, Agricultural Research
2/Associate Animal Scientist and Associate Agronomist, respectively.
Grazing began on December 9, 1975, and was terminated when the forage was
essentially grazed out (May 17, 1976). Individual animal weights were taken after
an overnight shrink (fast from feed and water) at the beginning and end of the
trial period. Group weights were obtained on all experimental groups every 28
days during the trial at approximately the same time of day. Additional grazer
animals of the same type and weight were weighed when added and removed as needed
to keep the forage uniformly grazed. The supplemental ration was fed once daily.
The feed allowance for each group for each 28-day period was determined on the
basis of initial and previous 28-day weights. Additional feed eaten by grazer
animals was appropriately added or subtracted from the total for each experimental
group. Each experimental group of steers was rotated between the four pasture
plots assigned to it as required for best utilization of good quality forage.
A mineral mixture (consisting of two parts defluorinated rock phosphate and
one part trace-mineralized salt), plain salt, and clean drinking water were avail-
able to the animals at all times.
The composition and cost of the pasture supplemental ration are presented in
Table 1. The proximate analyses of the pasture forage and the pasture supplemental
ration are listed in Table 2.
At the end of the trial, the steers were slaughted by R. L. Ziegler Company,
Inc., Selma, Alabama. Carcass data were obtained under the supervision of a USDA
Analyses of variance on daily gain along with slaughter and carcass data were
conducted according to the method of Snedecor (1946). The multiple range test of
Duncan (1955) was used to test significance between group means.
RESULTS AND DISCUSSION
Performance data of the steers for the 160-day period are presented in Table 3.
Steers fed the 11% protein high-energy ration on pasture at the level of 1-1/2% of
body weight gained 2.42 lb. per head daily. Steers fed the same ration on pasture
at the level of 1% of body weight gained 2.41 lb. per head daily, followed by the
daily gain (2.17 lb. per head) of steers fed the pasture supplemental ration at the
level of 1/2% of body weight and the daily gain (1.96 lb. per head) of unsupplement-
ed steers. Steers receiving the two highest levels of supplemental feed (1-1/2 and
1% of body weight) gained faster (P40.01) than unsupplemented steers.
The animal gain per acre (833 lb.) was highest for steers receiving the
highest level of supplemental feed (1-1/2% of body weight) and lowest (519 lb.) for
unsupplemented steers (Table 3). Steers receiving the two intermediate levels of
supplemental feed (1 and 1/2% of body weight) on pasture had intermediate gains per
acre (701 and 614 lb., respectively). In every instance, because of higher stocking
rates per acre and more rapid gains, steers receiving supplemental feed on winter
annual pastures progressively produced more beef per acre as the level of
supplemental feed was increased.
Economic data of the steers are presented in Table 4. The lowest cost of gain
($19.88/cwt) was obtained with unsupplemented steers, while the highest cost of
gain ($31.83/cwt) was obtained with the highest level of supplemental feed (1-1/2%
of body weight) on pasture. There was a progressive increase in the cost per
hundredweight of gain as the level of supplemental feed on pasture was increased.
Concurrently, there was a progressive increase in the price received per hundred-
weight on a live weight and carcass weight basis as the level of supplemental feed
on pasture was increased. Also, as stated previously, the carrying capacity per
acre and the daily gain increased as the level of supplemental feed was increased
(Table 3). Therefore, the net return per acre was very similar for the four pasture
treatments (Table 4).
Slaughter and carcass data of the steers are also presented in Table 4. The
marbling scores and, therefore, the average carcass grades increased as the level
of supplemental feeding was increased. The average carcass grade of steers on the
highest level of supplemental feed (1-1/2% of body weight) on pasture was higher
(PO0.01) than that of steers receiving the lowest level (1/2% of body weight) and
no supplemental feed. Carcass yield grades increased as level of supplemental feed
increased, indicating that leaner carcasses were produced on the lower levels of
feeding. There were no differences between the four treatments in color of lean and
color of fat. Average carcass yields were higher (P'0.01) for the three supplemental
feeding treatments and apparently was due to proportionately smaller amounts of fill
along with heavier and more highly finished carcasses.
The average daily gain, stocking rate per acre, beef production per acre,
carcass grade, carcass weight, and carcass yield progressively increased as the
level of supplemental feed on pasture was increased. From the standpoint of beef
production per animal and unit of land along with carcass grade and yield, it was
beneficial to furnish supplemental feed to growing beef steers grazing winter
annual pastures. However, the net return to the beef producer from each feeding
regime investigated in this study would depend upon the economic situation (cost
of feeder calves, cost of pasture, cost of supplemental feed, labor, price of
slaughter steers, etc.) existing at the time.
Composition and Cost of the Pasture Supplemental Ration (1975-76) ARC, Jay.
Ingredients % Lb./ton Cost(a)
Corn (ground) 42.375 848 $ 42.40
Sorghum grain (ground) 54.600 1092 50.23
Salt (trace-mineralized) 0.500 10 0.41
Defluorinated rock phosphate 1.500 30 3.00
Urea 45% N 1.000 20 1.60
Zinc bacitracin supplement(b) 0.025 0.5 0.80
Vitamin A supplement(c) + + 0.08
Subtotal $ 98.52
Markup (d) 11.00
Total 100.000 2000.5 $109.52
(a) Based on the following prices: corn (ground) = $100.00/ton, sorghum grain
(ground) = $92.00/ton, salt (trace-mineralized) = $82.00/ton,
defluorinated rock phosphate = $200.00/ton, urea 45% N = $160.00/ton,
Baciferm 40 (zinc bacitracin supplement containing 40 grams of the
antibiotic per pound) = $1.60/lb., and Rovimix A-650 (vitamin A supple-
ment containing 650,000 IU/gram) = $6.00/lb.
(b) Zinc bacitracin added at the level of 20 g/ton or 10 mg/lb. of pasture
(c) Vitamin A added at the level of 4 million IU/ton or 2000 IU/lb. of
pasture supplemental ration.
(d) Mixing, milling, overage, storage, etc.---$11.00/ton.
Proximate Analyses of the Pasture Forage and the
Pasture Supplemental Ration (1975-76) ARC, Jay.
Item forage(a) ration(b)
Moisture, % 82.91 13.46
Crude protein, % 4.52 10.85
Ash, % 1.64 2.90
Ether extract, % 0.95 2.51
Crude fiber, % 3.39 2.66
Nitrogen-free extract, % 6.59 67.62
(a) Pasture forage (mixture of rye, ryegrass, and crimson clover) (average of
four hand-plucked samples collected at intervals during the trial).
(b) Pasture supplemental ration (average of four samples collected at intervals
during the trial).
Performance Data of Growing Beef Steers Fed Various Levels of
Supplemental Ration on Winter Annual Pasture (1975-76) ARC, Jay.
Item O(a) 1/2%(b) l%(c) 1-1/2%(d)
Initial no. of animals 16(e) 16 16 16
Length of grazing, days 160 160 160 160
Avg initial wt, lb. 400 401 397 409
Avg final wt, lb. 714 748 783 796
Avg gain/animal, lb. 314 347 386 387
Avg daily gain, lb. 1.96b** 2.17ab 2.41a 2.42a
Gain/acre, lb. 519 614 701 833
Animal days/acre 265 283 291 344
Stocking rate/acre(f) 1.66 1.77 1.82 2.15
Gain/acre/day, lb. 3.25 3.84 4.39 5.20
Feed/cwt gain, lb.(g) ----- 138 249 355
Feed/animal/day, lb.(g) ------ 3.0 6.0 8.6
(a) Rotational grazing of a rye, ryegrass, and crimson clover mixture (unsupple-
(b) Same pasture mixture as above supplemented with an 11% crude protein high-
energy ration at the level of 1/2% of body weight.
(c) Same pasture mixture as above supplemented with the pasture ration at the
level of 1% of body weight.
(d) Same pasture mixture as above supplemented with the pasture ration at the
level of 1-1/2% of body weight.
(e) Initially, two groups of eight steer calves each.
(f) Additional grazer animals of the same type and weight were added and removed
as needed to keep the forage uniformly grazed.
(g) Does not include pasture.
** Means within rows followed by the same letter are not significantly
Economic, Slaughter, and Carcass Data
of Supplemental Ration on Winter
of Growing Beef Steers Fed Various Levels
Annual Pastures (1975-76) ARC, Jay.
Item 0 1/2% 1% 1-1/2%
Feed cost/cwt gain
Pasture(b) $ 19.88 $ 16.80 $ 14.72 $ 12.39
Pasture supp. ration(c) ------ $ 7.56 $ 13.64 $ 19.44
Total(d) $ 19.88 $ 24.36 $ 28.36 $ 31.83
Avg cost/head of feeder(e) $110.00 $110.28 $109.18 $112.48
Avg feed cost/head of feeder $ 62.42 $ 84.53 $109.47 $123.18
Total cost/head of feeder(d) $172.42 $194.81 $218.65 $235.66
Final value/head(f) $231.53 $253.17 $275.10 $282.62
Net return/head(d) $ 59.11 $ 58.36 $ 56.45 $ 46.96
Net return/acre(d) $ 98.12 $103.30 $102.74 $100.96
Avg price/cwt on foot $ 32.43 $ 33.85 $ 35.13 $ 35.51
Avg price/cwt carcass $ 58.62 $ 59.29 $ 59.93 $ 60.78
Avg carcass grade(g) 11.8b** 12.3b 13,5ab 14.4a
Avg yield grade(h) 1.6b** 2.lab 2.5a 2.6a
Avg marbling score(i) 4.8c* 5.9bc 7.6ab 8.4a
Avg color of lean(j) 3.5 3.7 3.6 3.1
Avg color of fat(k) 2.6 2.8 <2.6 2.4
Avg slaughter wt, lb. 714 748 783 796
Avg carcass wt, lb.(l) 395 427 459 465
Avg dressing percent (carcass yield) 55.3b** 57.1a 58.6a 58.4a
(a) Treatments same as in Table 3.
(b) Pasture cost = $103.18/acre.
(c) Pasture supplemental ration cost = $109.52/ton.
(d) Does not include labor involved in feeding and caring for the animals.
(e) Calf cost = $27.50/cwt (includes cost of animals, hauling, veterinary costs,
(f) Sold to R. L. Ziegler Co., Inc., Selma, Alabama on a grade and yield basis.
(g) 11 = average standard, 12 = high standard, 13 = low good, 14 = average good,
15 = high good, etc.
(h) Yield grades numbered 1 through 5, with yield grade 1 representing the
highest yield of boneless, closely trimmed retail cuts (cutability) and
yield grade 5 the lowest.
(i) 2 = practically devoid, 5 = traces, 8 = slight, 11 = small, etc.
(j) 2 = very light cherry red, 3 = light cherry red, 4 = cherry red, etc.
(k) 1 = white, 2 = cream, 3 = slightly yellow, and 4 = very yellow.
(1) Hot dressed weight.
* Means within rows followed by the same letter are not significantly
** Means within rows followed by the same letter are not significantly