Value of Preconditioning
F. M. Pate and J. R. Crockett
Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
F. A. Wood, Dean for Research
VALUE OF PRECONDITIONING BEEF CALVES
F. M. Pate and J. R. Crockett
Dr. Pate is an Associate Professor (Associate Animal Nutritionist)
and Dr. Crockett is an Associate Professor (Associate Animal Geneti-
cist) at the Agricultural Research and Education Center, Belle Glade,
/ istitut of FeIrd H AMrcltuFrali SEklce
This public document was promulgated at an annual cost of
$1489 or a cost of 14.91 per copy to present information on the
cost and benefits of preconditioning weaned calves for
subsequent feedlot finishing.
Introduction ............................................ 1
Procedure .............................................. 1
Preconditioning ....................................... 2
Nutrition-Management Treatments ................... 2
Medication Treatments ............................ 4
Feedlot Finishing ..................................... 4
Data Collection ....................................... 4
Results and Discussion .................................... 5
Preconditioning at the Ranch ............................ 5
Animal Performance ................................ 5
Cost and Returns ................................. 5
Feedlot Finishing ...................................... 8
Effect of Nutrition-Management Treatments .......... 8
Effect of Medication Treatments .................... 8
Effect of Preconditioning on Feedlot Finishing Cost ... 9
Economic Summary of Calf Preconditioning .............. 9
Summary and Conclusions ................................. 9
Literature Cited ......................................... 14
Acknowledgements ....................................... 14
VALUE OF PRECONDITIONING BEEF CALVES
Major feedlot management problems are the occurrence of
disease, death loss, and poor performance of weaned calves dur-
ing the first weeks of feeding. It has been estimated that these
production losses cost $10 to $20 per animal (6)1. The problems
have been associated directly with the tremendous stress placed
on feeder calves during transition from the ranch to the feedlot.
During a period of 2 to 3 days (sometimes longer) calves were
weaned, sold through a public auction (often sorted and resold),
trucked as far as 3000 miles and placed in a completely different
environment. Many of these calves traveled from the south-
eastern states to the Midwest and Southern Great Plains.
To reduce disease incidence and improve performance of
feeder calves in the feedlot, beef industry leaders devised a calf
management program termed preconditioningg". Feeders, re-
searchers, extension personnel, and veterinarians formed a na-
tional program of specific recommendations for preconditioning
(5, 8). Briefly, this management procedure was to wean, medi-
cate, and bunk feed calves 3 to 4 weeks prior to shipping.
A criticism of the above preconditioning program has been
the lack of controlled studies on costs of preconditioning and
subsequent returns to the feeder calf producer and feedlot oper-
ator. This study was conducted to evaluate a calf precondition-
ing program with Florida produced calves. The objectives were
1) to determine cost and returns to the ranch, where feeder
calf production was the major enterprise, and 2) to determine
the effect of preconditioning on subsequent animal performance
and disease in the feedlot.
The study involved 3 trials initiated in the fall seasons of
1973, 1974, and 1976, denoted as trials 1, 2, and 3, respectively.
Calves in these studies were typical Florida produced crossbred
calves with varying percentages of Brahman, Angus, Hereford,
and Charolais breeding. All calves were from cows grazing im-
proved permanent pastures at Lykes Bros. Inc., Ranch Division
at Brighton, Florida. The experimental design is outlined in
1Numbers in parentheses refer to literature cited.
Table 1. Outline of experimental procedure.
Number of trials: 3
1) Calves shipped to feedlot at weaning.
a) Trials 1 and 2 100 steers each.
b) Trial 3 60 steers and 40 heifers.
2) Calves fed at ranch 3 to 4 weeks postweaning, then shipped
a) Trial 1 50 steers, fed 21 days.
b) Trial 2 50 steers, fed 24 days.
c) Trial 3 60 steers and 40 heifers, fed 27 days.
1) Calves not medicated.
2) Calves medicated with IBRa, PI-3a, Leptoa, and mixed bacteria
bovine formula lb vaccines; drenched with levamisole HCle;
treated with coumaphosd pour-on (for grubs); injected with
Vitamins ADE (2cc)e.
a) Trial 1 30 days preweaning.
b) Trial 2 28 days preweaning.
c) Trial 3 at weaning.
Feedlot finishing: (approximate days in feedlot)
Trial 1 Edroy, Texas; 195 days.
Trial 2 Brooksville, Florida; 230 days.
Trial 3 Edroy, Texas; 180 days.
aParaboceptol, Cutter Laboratories, Inc., Berkley, Calif.
bBovibac 1, Fort Dodge Laboratories, Inc., Fort Dodge, Iowa.
cLevasole, Pitman Moore, Inc., Washington Crossing, N.J.
dCo-Ral, Chemagro Corp., Kansas City, Missouri.
eConcentration per cc: A-500,000 I.U., D2-75,000 I.U., E-50 I.U., Burns Phar-
maceuticals, Oakland, Calif.
Each trial included two nutritional-management treatments
which were: 1) calves shipped directly to the feedlot at weaning,
and 2) calves preconditioned with feed 3 to 4 weeks after wean-
ing at the ranch, then shipped to the feedlot.
The preconditioned calves were fed at the preconditioning lot
of Lykes Bros. Inc., near Brighton, Florida. The preconditioning
supplements were formulated with ingredients typically found
in a feedlot ration (Table 2). Urea was added to adapt the
rumen of calves to urea since this ingredient was used in the
During preconditioning calves were started on greenchopped
pangola digitgrass (Digitaria decumbens Stent.) and 2 pounds
of supplement per head daily. The quantity of supplement was
increased over a 10 to 14 day period until calves were consuming
an average of 10 pounds per head per day. Pangolagrass green-
Table 2. Percent composition of rations
and feedlot finishing.
fed during preconditioning
1 2 3
Dried citrus pulp
Vitamin A (30,000 I.U./gm)
Feedlot finishing rations
Dried citrus pulp
aCalves were fed hay during the first 7 to 14 days in the feedlot, until a full
feed of concentrate was consumed with no apparent problems.
bGrain varied between milo and corn in trials 1 and 3, depending upon cost.
Corn was used in Trial 2.
cSupplement consisted of urea, soybean meal and cottonseed meal, fortified
with minerals and vitamins.
chop was offered ad libitum throughout the preconditioning
period. Intake of pangolagrass was not measured.
The preconditioning pens provided approximately 200 square
feet of space per calf. The pens had an earthen floor, concrete
feed bunks, and open water troughs, and were partially covered
to protect feed bunks from rain.
One-half of the calves in each nutritional-management treat-
ment were not medicated except for calfhood vaccinations
(blackleg-leptospirosis-malignant edema) which all calves re-
ceived at 4 to 6 months of age. One-half of the calves were
medicated with the following biologicals: infectious bovine rhi-
notracheitis (IBR), parainfluenza-3 (PI-3), leptospirosis, mixed
bacterin bovine formula 1, levamisol hydrochloride (drench-
wormer), coumaphos (pour-on grubicide), and vitamin ADE
Calves in trials 1 and 2 were medicated approximately 30
days preweaning and in trial 3 at weaning.
Calves in trials 1 and 3 were shipped by truck approximately
1,500 miles (30 hours) to Lykes Feedyard at Edroy, Texas for
finishing. Calves in trial 2 were trucked approximately 125 miles
to Lykes Feedyard at Brooksville, Florida for finishing. Both
feedlots were typical finishing facilities with several thousand
head capacity. Calves were fed in lots by nutritional-manage-
ment treatment groups. Steers and heifers in trial 3 were also
fed in separate lots. Sick animals in each lot were isolated from
the other calves and medicated until healthy. Feedlot rations are
presented in Table 2.
Calves were weighed at weaning, at the end of the precon-
ditioning period, upon arrival at the feedlot, and at the end of
the feedlot finishing period. Feed intake, except for pangola-
grass greenchop, was recorded for each nutritional-management
treatment group. Data were recorded for disease incidence
(number animals medicated), number of times animals were
medicated (some animals medicated 2 or more days), and death
loss. Slaughter and carcass evaluation data were collected on the
For statistical analyses the data were handled as four sepa-
rate trials because heifers and steers used in trial 3 were fed
separately. All data were analyzed by analysis of variance of a
2 x 2 x 4 factorial design (11). The factors were two nutritional-
management treatments, two medication treatments, and four
trials. Two separate analyses were conducted: 1) individual ani-
mal data with disproportionate subclass numbers for intransit
weight loss, feedlot rate of gain, and carcass information; 2)
group data for feed efficiency, death loss, disease incidence, and
RESULTS AND DISCUSSION
Preconditioning at the Ranch
The performance of calves during the 3 to 4 week precon-
ditioning period is presented in Table 3. During this period the
average daily gain over all trials was 0.92 pound per calf. A
gain of approximately 1 pound per calf per day is considered
average for a postweaning feeding period of this length (1, 4).
During the first few days after weaning, calves lose 10 to 20
pounds (9). After this stress period, calves gain 2 to 3 pounds
per day and regain their original weaning weight in 7 to 14 days.
If calves were fed for longer periods (45 to 60 days), the aver-
age rate of gain over the entire preconditioning period would be
greatly improved (4). The calf feeder must be critical of reports
that show high rates of gain (2 to 4 pounds per day) during a
short postweaning period because the starting weights may
have been taken after calves were shrunk 1 or more days while
It is important to note the death of two calves due to respi-
ratory disease during the preconditioning period in trial 2. This
is an added risk that must be realized in preconditioning calves.
The mortality was calculated to be 1% over the 3 trials of this
There was no difference in the performance or mortality of
non-medicated and medicated calves during the postweaning
period (Table 3). One calf in the non-medicated treatment group
(trial 2) was not shipped to the feedlot because of sickness, but
this calf later regained its health.
Cost and returns
Using feed intake data and standard costs for feeding cattle,
an estimated cost of preconditioning is presented in Table 4. The
Table 3. Performance of weaned calves during preconditioning with
feed 21 to 27 days prior to shipment to feedlot.
Trial 1 Trial 2 Heifers Steers
Number animals 50 48abe 39d 59d
No. days preconditioned 21 24 27 27
Weaning wt., Ibs. 497 473 421 496
Shipping wt., Ibs. 522 497 446 512
Preconditioning gain, Ibs. 25 24 25 16
Avg. daily gain, lbs. 1.19 0.96 0.93 0.59
Feed/animal, Ibs.e 174 208 220 220
Feed/animal/day, Ibs. 8.3 8.3 8.1 8.1
Death loss 0 2 0 0
Medication cost, S/calf 0 1.70 0 0
BY MEDICATION TREATMENT
Number animals 97bed 98d
No. days preconditioned 25 25
Weaning wt., Ibs. 478 472
Shipping wt., Ibs. 500 493
Preconditioning gain, Ibs. 22 21
Avg. daily gain, Ibs. 0.88 0.84
Death loss 1 1
aSeveral calves in this trial showed signs of sickness thus all calves were
medicated with 5cc of Tylan 200, 10cc of Terramysin and Sodium Sulfa-
methazine (0.1 Ib/calf first day and 0.05 Ib. for 3 subsequent days).
bTwo calves selected for this study could not be found when calves were
gathered for weaning.
cOne calf was sick at the end of the preconditioning period and was not
shipped to the feedlot. This calf later recovered.
dOne calf died of heat exhaustion at weaning and was considered unrelated
eMixed concentrate only. The quantity of pangolagrass greenchop, also fed,
was not measured.
total cost of $21.00 per head for preconditioning is in agreement
with other estimates for a similar preconditioning procedure
(3, 7). Feed cost was the most expensive item and would prob-
ably be higher in south Florida, relative to other areas, because
of reliance on imported feed ingredients.
On some ranches, calves might be preconditioned with sup-
plement to perennial grass pasture. Feeding on pasture could
Table 4. Estimated costs and returns from preconditioning a 500 Ib.
calf for 25 days postweaning.
Mixed ration (205 Ibs. @ $110/ton) 11.28
Greenchop (50 Ibs. of dry matter @ $40/ton) 1.00
Medication (vaccines, wormer, grub control, etc.) 1.50
Labor (working calves for medication) 0.50
Feeding, facilities, and labor ($0.15/head/day) 3.75
Interest ($192 value/calf @ 8%/annum) 1.05
Death loss (1%, with calves valued at $192) 1.92
Total cost of preconditioning 21.00
Value of calf at weaning
(500 Ibs. 4% pencil shrink @ $40/cwt) 192.00
Value of calf after preconditioning
(525 Ibs. 4% pencil shrink @ $40/cwt) 201.60
Gross returns to preconditioning 9.60
Cost of preconditioning 21.00
Net returns to preconditioning -11.40
Selling price required for preconditioned
calves to break even,-$/cwt
Calf value at weaning ($192) + preconditioning cost ($21)
Selling weight of preconditioned calf (5.04 cwt)
reduce preconditioning cost by supplying inexpensive forage and
eliminating expensive confinement facilities. However, feeding
on pasture for a 3 to 4 week period may not greatly reduce sup-
plement cost. Newly weaned calves must rely heavily on concen-
trate feeds for adequate weight gain. In other studies (9),
weaned calves grazed on St. Augustinegrass pasture and fed
5 pounds of concentrate per head daily showed no weight gain
during a 4-week postweaning period. When concentrate intake
was 8 pounds per head daily, average daily weight gain was ap-
proximately 1 pound per head per day during a 4-week post-
Estimated returns from preconditioning calves weighing 500
pounds at weaning are shown in Table 4. If a $40 per cwt price
for feeder calves is assumed and calves are sold on a live weight
minus a 4% pencil shrink basis, a negative return of $11.40 per
calf would be realized from preconditioning. To recover precon-
ditioning expenses the calf would have to be sold at a $2.26 per
cwt premium above the prevailing price for feeder calves.
Effect of nutritional-management treatments
Results on feedlot performance of calves by nutritional-
management treatment are presented in Table 5. Calves precon-
ditioned with feed lost more weight while in transit to the
feedlot than calves shipped at weaning, 11.1% and 8.5%, re-
spectively (P<0.01). This additional weight loss averaged 13
pounds for a 500-pound calf. This negative aspect of precondi-
tioning is important to the feeder calf buyer. A 13-pound ship-
ping weight loss with a $40 cwt feeder calf price would cost
$5.20 per calf.
Calves preconditioned with feed at the ranch gained faster
in the feedlot than calves shipped at weaning (P<0.01). Rate of
gain was 6% and 11% faster for preconditioned calves in trials
1 and 2, respectively, but only a small difference was observed
between treatments in trial 3. Faster gaining calves require less
time to reach slaughter weight and with feedlot overhead cost
ranging from $0.10 to $0.20 per head per day, cost savings
would be considerable with a 5% to 10% faster rate of gain.
There was no difference for feed efficiency between treat-
ments during the feedlot period. Preconditioned calves required
less feed per pound of gain in trial 1 (0.57 pounds) and 2 (0.23
pounds), but more feed per pound of gain in both the heifer
(0.79 pounds) and steer (0.17 pounds) lots in trial 3.
The most pronounced treatment effect was on animal sick-
ness in the feedlot. Actual death loss for non-preconditioned
calves shipped at weaning was 7 of 298 calves (2.3%), with no
death loss of calves preconditioned with feed at the ranch
(P<0.01). Similar results were observed in the data for number
of calves treated for sickness (P<0.05). The number and cost
of medications appeared higher for calves shipped at weaning
than for preconditioned calves, but this difference was not sig-
As a result of feedlot diseases, death losses are the most
costly. In addition to calf investment cost, feed and overhead
costs (approximately $1 per head per day) prior to death of the
calf must be accounted for. Of the calves lost, the average time
of death after entering the feedlot was 28 days for the animals
in this study.
Effect of medication treatments
Medicated calves gained slightly faster than did non-medi-
cated calves except for heifers in trial 3. Also, medicated calves
had a slightly higher dressing percentage, but these differences
were not significant (Table 6).
There was no difference between non-medicated and medi-
cated calves in death losses and disease incidence in the feedlot.
These results are in agreement with previous investigations
which were unable to demonstrate that vaccinating calves sev-
eral weeks prior to shipment reduced feedlot sickness (7, 10).
Effect of preconditioning on feedlot finishing cost
Estimated savings in feedlot finishing derived from precon-
ditioning are presented in Table 7. The reduced time in the feed-
lot (faster gain), reduced death loss, and lower medication cost
of preconditioned calves would result in a savings of $7.36 per
animal fed. However, if the feedlot operator purchased calves
on their ranch weight, the higher shipping weight loss of pre-
conditioned calves (valued at $5.20) reduces savings to $2.43
Economic Summary of Calf Preconditioning
An overall summary of costs and returns of calf precondi-
tioning is presented in Table 7. Savings in feedlot finishing costs
($7.36) derived from calf preconditioning were inadequate in
view of preconditioning expense ($11.40) and higher shipping
weight loss of preconditioned calves ($5.20). The negative re-
turn from time of weaning of $8.97 indicates that calf precon-
ditioning is not an economically sound management procedure.
A large number of calves produced in Florida and the south-
east are much lighter (200 to 300 pounds) than the calves used
in this study. Most "light weight" calves come from small
ranches and are sold through auction sales. Several surveys have
shown that disease incidence and mortality rate in the feedlot
was higher for auction calves than for calves shipped direct
from the ranch to the feedlot (1, 2). This type calf would prob-
ably benefit more from preconditioning than those calves used
in the present study.
SUMMARY AND CONCLUSIONS
A study consisting of 3 trials with 496 animals measured the
effect of preconditioning calves at weaning on calf performance.
Two nutritional-management treatments included: 1) calves
Table 5. Effect of preconditioning weaned calves with feed prior to shipment to the feedlot on performance and sick-
ness during the subsequent feedlot period.
Calves shipped at weaning Calves preconditioned with feed
Trial 3 Trial 3 of treatment
Trial 1 Trial 2 Heifers Steers Trial 1 Trial 2 Heifers Steers difference
Number animals 100 100 40 60' 50 45 39 59
Shipping weight (Fla.), Ibs. 511 476 406 456 522 497 446 512
Weight, Ibs. 46 13 41 55 57 27 62 72
Percent 9.0 2.7 10.1 12.1 10.9 5.4 13.9 14.1
Feedlot arrival wt., Ibs. 466 463 365 401 465 470 384 440
Feedlot final wt., Ibs." 961 852 728 821 960 853 692 814
Feedlot gain, Ibs. 495 389 363 420 495 383 308 374
Days in feedlot 198 246 191 191 187 219 166 166
Avg. daily gain, Ibs. 2.50 1.58 1.90 2.20 2.65 1.75 1.86 2.25
Feed/lb. of gain, Ibs. 8.10 9.61 8.25 7.27 7.53 9.38 9.04 7.44 NS
(per 100 head)
Death loss 1.0 2.0 0 6.7 0 0 0 0
No. animals medicated 18 4 38 32 10 2 5 12
No. medications 83 15 148 183 36 24 10 27 NS
Medication cost, $ 93.19 23.13 142.25 210.66 44.00 36.29 8.97 41.53 NS
Dressing % 61.5 58.9 60.3 60.1 61.1 58.7 59.7 59.5 NS
Quality grade Good Good Good Good Good Good Good Good NS
aNS = non-significant, = P < 0.05, and = P < 0.01.
"One calf foundered during 9th week in feedlot and was sold for slaughted.
cBecause of chronic sickness and poor performance one steer sold for slaughter after
dFinal feedlot weight based on hot carcass weight with a 60% dress.
14 weeks in feedlot.
Table 6. Effect of medication treatment of calves on performance and sickness during the subsequent feedlot period.
Non-medicated Medicated Sign
Trial 3 Trial 3 of treatment
Trial 1 Trial 2 Heifers Steers Trial 1 Trial 2 Heifers Steers differencea
Trial 1 Trial 2 Heifers Steers Trial 1 Trial 2 Heifers Steers
Shipping weight (Fla.), Ibs.
Feedlot arrival wt., Ibs.
Feedlot final wt., Ibs."
Feedlot gain, Ibs.
Days in feedlot
Avg. daily gain, Ibs.
(per 100 head)
No. animals medicated
Medication cost, $
58.6 59.9 59.8
Good Good Good
61.5 59.1 60.1 60.0
Good Good Good Good
a b c e]See respective footnotes on Table 5.
Table 7. Summary of estimated cost and returns derived from pre-
conditioning a 500 pound calf.
Net returns to preconditioning
at the ranch (from Table 4) -11.40
Cost of higher weight loss
from ranch to feedlot --5.20
Savings during feedlot finishing
Less time in feedlotb 1.50
Reduced death losse 5.28
Reduced medication cost" 0.85
Total Savings in feedlot 7.63
Total returns from time of weaninge -8.97
aA 13 lb. higher in transit shrink assuming calves were purchased on ranch
weight less 4% pencil shrink and a $40 per cwt calf price.
bBased on a 200 day feedlot period, 5% faster rate of gain, and $0.15 per
head per day feedlot overhead cost.
cDeath loss reduced 2.3 percent and calves fed 28 days (@$1 per head per
day) prior to death.
dTaken from Table 5.
eSavings in feedlot ($7.63), less cost of shipping weight loss (-$5.20), less
net returns to preconditioning at the ranch (-$11.40).
weaned and shipped to the feedlot without treatment and 2)
calves preconditioned with feed 3 to 4 weeks postweaning at the
ranch, then shipped to the feedlot. Two medication treatments,
each involving one-half of the calves in the nutritional-manage-
ment treatments, included: 1) calves not medicated, and 2)
calves medicated prior to shipment to the feedlot.
During preconditioning calves consumed an average of 8.2
pounds of supplemental feed per head per day in addition to
pangolagrass greenchop which was offered free-choice. Average
gain was 0.92 pounds per calf per day. There was no difference
in the performance of non-medicated and medicated calves dur-
ing the ranch feeding period. Two calves (1% of total) died
while being fed at the ranch.
Calves fed at the ranch postweaning had a higher weight
loss while in transit from the ranch to the feedlot than calves
shipped at weaning (P<0.01). The higher weight loss would
average 13 pounds for a 500-pound calf.
In the feedlot, those calves previously fed at the ranch had
a faster rate of gain (P<0.01), a lower death loss (P<0.01),
and less disease incidence (P<0.05) than did calves shipped at
weaning. Calves shipped at weaning had a higher dressing per-
cent at slaughter, but differences were small and non-significant.
There were no significant differences in the feedlot perfor-
mance of non-medicated and medicated calves; however, medi-
cated calves tended to have a faster rate of gain and a higher
From the results of this study the following conclusions are
1) When calves are fed 3 to 4 weeks postweaning at the
ranch, weight gains alone may not offset feed and over-
head cost. A $2.00 to $2.50 per cwt premium price might
be required to cover preconditioning expenses.
2) The higher shipping shrink of calves preconditioned with
feed would be a disadvantage to the feeder calf buyer if
purchase price is determined on a ranch weight, standard
pencil shrink basis.
3) Preconditioning calves with feed prior to shipment will
improve rate of gain, reduce sickness, and reduce death
loss in the feedlot. It is doubtful that the resulting cost
savings in the feedlot will offset the premium price re-
quired for preconditioned calves to recover precondition-
4) Results strongly suggest that disease incidence in the
feedlot is dependent upon the previous management of
feeder calves, and that vaccination of calves at the ranch
is not 100% effective for preventing disease incidence in
1. Algeo, J. 1967. Feeding calves prior to shipment. Proc. Precon-
ditioning Seminar, Okla. State Univ., Stillwater, Okla., p. 69-72.
2. Bristol, R. F. '1967. Preconditioning of feeder cattle prior to inter-
state shipment. Proc. Preconditioning Seminar, Okla. State Univ.,
Stillwater, Okla., p. 62-65.
3. Doane's Agricultural Report. 1969. Preconditioning feeder cattle.
32 (No. 16-5):255-56.
4. Eng, K. E. 1968. Preconditioning-who should do it? Feedstuffs.
40' (No. 37):26-27.
5. Herrick, J. B. 1967. Preconditioning feeder cattle. Proc., Precon-
ditioning Seminar, Okla. State Univ., Stillwater, Okla. p. 4-8.
6. Herrick, J. B. 1969. Preconditioning, its national status. J. Amer.
Vet. Med. Assoc. 154:1163-65.
7. Meyer, K. R., J. W. Judy, Jr., and J. H. Armstrong. 1970. Economic
analysis of feeder calf preconditioning program. J. Amer. Vet. Med.
8. Meyerholz, G. W. 1971. Preconditioning feeder calves. Vet. Sci.
Fact Sheet 10, Univ. of Fla., IFAS, Coop. Ext. Serv., Gainesville.
9. Pate, F. M., and J. R. Crockett. 1973. Effect of limited creep feeding
beef calves on post weaning performance. Univ. of Fla., IFAS AREC
Belle Glade Res. Rpt. EV-1973-3.
10. Schipper, I. A. 1972. A review of shipping fever prophylactics and
therapy. Anim. Nutr. Health. 27 (No. 9):5-8.
11. Snedecor, G. W. '1956. Statistical Methods. Iowa State College
Press, Ames, Iowa.
The authors wish to express their appreciation to Lykes
Brothers, Inc., Tampa, Florida, for supplying the cattle, facil-
ities, and management used to conduct these studies.