THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
407
A NEW TECHNIQUE FOR LIMITED FEEDING
EXPERIMENTS
WISE BURROUGHS and W. E. CARROLL
University of I||~nois
Ellis and Zellar (2) have reported that limiting the swine ration resulted in greater feed utilization even though the maintenance requirements were increased as a result of a longer feeding period. Pigs individually fed one-half, three-fourths, and full-fed rations consisting at
different times principally of corn, peanuts, and wheat, required less
feed per unit of live-weight gain with practically every decrease in
feed consumption. Carcass analyses indicated only slight differences in
the amount of fat (energy) stored whether the pigs were fed a full
ration or less.
Contrasted with Ellis and Zellar's work are a number of feedlot
trials (3, 6, 8, 11, 12) in which limiting the feed intake to approximately
one-half of a full feed increased significantly the feed cost of gain made.
In Similar experiments feeding a three-fourths ration did not greatly
increase the fed costs of the gains made, but did produce carcasses of
a lower grade. In an Ohio trial (11) slightly less feed was required
for 100 pounds gain when the ration was reduced from a full-feed to a
three-fourths feed. In two similar Cornell experiments (12) the same
results wer~ obtained. Two Oregon tests (8) showed little difference between full and limited feeding; one favored the former and the other
the latter. Likewise in Michigan trials (6), limiting the daily feed intake
slightly had little effect on feed requirements.
Because the results of the group feeding trials differed from those obtained by Ellis and Zellar with pigs fed individually, further study of
the problem, using a slightly different technique, appeared desirable.
The method of feeding used was a modification of the paired-feeding
technique. Twenty-four select pigs were divided into 12 pairs according
to litter, sex, and body weight. During the first two weeks, one member
of each pair was full-fed by hand twice daily and the pairmate was given
three-fourth as much total feed. Following this period the limited-fed
pig was given three-fourths as much feed as his full-fed brother received
when the latter was of a comparable weight. The rationing was based on
weekly body weights and food consumption. First, the full-fed pig's
average daily feed during each successive week was plotted against his
liveweight at the beginning of each respective weeL A second curve,
based upon three-fourths these amounts of feed, was plotted against these
same liveweights. The pair-mate pig on limited feed was then fed in
408
THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
accordance with the second curve. Regardless of the weight of the limitedfed pig on any weigh day his average daily feed for the week following
could be read directly from the graph.
From the beginning of the test until the pigs weighed 100 pounds,
the feed mixture used contained ground corn, 74.5 parts; tankage, 14.0
parts; soybean oilmeal, 7.0 parts; alfalfa meal, 4.0 parts; salt, 0.5 part.
Between live weights of 100 and 200 pounds the corn was increased to
80.5 and the tankage and soybean oilmeal were decreased to 10 and 5
parts respectively. The other ingredients remained unchanged.
The pigs were started on feed in the spring of 1936 and carried to
individual weights of 200 lbs. Each pig was slaughtered and carcass
grades and measurements were taken. In addition, carcasses from two
pairs of pigs were submitted to chemical analysis. T h e live-weights, gains
and feed consumptions are given in Table 1.
TABLE 1--LIVE WEIGHT GAINS AND FEED UTILIZATION
Pair
No.
1
2
3
4
5
6
7
8
9
10
11
12
Aver.
Feed
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Full
Limited
Initial
weight
lbs.
Final
weight
lbs.
Days
51
47
54
56
65
64
71
66
65
64
49
50
52
52
56
56
58
59
58
57
57
62
54
52
58
57
202
200
197
196
200
197
202
201
199
195
199
198
202
197
202
201
199
199
202
201
196
199
196
199
200
199
161
232
125
168
132
175
139
175
125
182
132
196
149
189
125
149
125
149
112
163
168
197
125
161
135
178
Average
daily
gain
lbs.
.94
.66
1.14
.83
1.02
.76
.94
.77
1.07
.72
1.14
.76
1.01
.77
1.17
.97
1.13
.94
1.29
.88
.83
.70
1.14
.91
1.07
.81
Total
feed
lbs.
Feed per
100 lbs.
gain
lbs.
523
638
474
480
488
487
465
476
479
523
478
544
491
492
491
439
464
428
458
512
498
470
465
467
481
496
346
417
331
343
361
366
355
353
357
399
319
367
327
340
337
303
329
306
318
356
358
343
328
318
339
351
THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
409
O n the average, the limited-fed pigs required 43 days longer to reach
market weight than did those that were full-fed. The average daily gains
were almost exactly in proportion to the level of feed intake. T h e average
feed eaten for 100 pounds of gain slightly favored full-feeding but the
difference was not statisticaly significant, as five of the twelve pairs favored
the limited-fed pigs. These results are more nearly in agreement with the
several feed-lot experiments referred to above than with the findings of
Ellis and Zellar.
The average carcass grades and measurements are summarized in
Table 2.
TABLE 2--CARCASS MEASUREMENTS
Full,fed
pigs
Dressing percent................................................................
Carcass Grade ....................................................................
1st, sacral vertebra ................................
Fat over Loin
(inches)
77.3
good-1.2
13th, thoracic vertebra ..........................
1st, thoracic vertebra..............................
Average ..................................................
1.0
1.6
1.3
Snout to rear toe....................................
Snout to 1st, thoracic vertebra............
Length
(inches)
1st, thoracic vertebra to H-bone ............
H-bone to rear toe ................................
Depth of chesl (inches) ................................................
Width of chest (inches) ................................................
Circumference of fore leg (inches) ................................
72.9
17.6
31.4
24.4
14.0
11.1
6.0
limitedfed pigs
78.0
good-1.0
0.9
1.5
1.1
73.6
18.1
30.8
25.2
13.2
11.0
6.0
N o differences were noted in either the dressing percentage or the
carcass grade of the two groups of hogs. T h e fat covering over the loin,
however, was somewhat greater on the full-fed animals. T h e limited-fed
hogs were slightly longer though not quite as deep as those that had been
full-f~d. N o differences were noted in the width measurements nor in
the circumference of the fore leg.
T h e chemical analyses
live-weight basis in T a b l e
and mineral matter were
fat and consequently the
higher in the carcasses of
of two pairs of pigs are summarized on the
3. Differences in percentages of crude protein
neither consistent nor significant. T h e average
dry matter and gross energy were noticeably
the full-fed pigs. These data, though much too
410
THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
meager for positive interpretation, are in good agreement with the carcass
measurements.
TABLE 3--CHEMICAL ANALYSIS
(Live weight basis)
Live
weight
lbs.
Dry
matter
%
Crude
fat
%
Gross
energy
cal/gm.
Crude
protein
%
Mineral
matter
%
llA
Aver,
202
196
199
46.9
5"0.8
48.9
Full,fed
25.1
27.9
26.5-
316534153290
15-.2
14.3
14.7
2.8
3.0
2.9
1B
llB
Aver.
200
199
200
46.3
39.1
42.7
Limited-fed
25-.2
19.7
22.5-
3088
2691
2890
14.514.7
14.6
3.2
2.7
3.0
Pig
No.
IA
Discussion
These results did not conclusively prove the merits of one type of
feeding over the other with respect to present market demands. That the
limited-fed hogs in this trial carried less fat but graded as high as the
full-fed animals is a step in the right direction though this point is in
need of more extensive observations. The fact that the limited-fed hogs
required 43 days longer to reach market weight and yet did not consume additional amounts of feed per unit of gain, merits some consideration. At least four factors may conceivably have operated to produce this
result.
First, the pigs on limited feed intake may have digested their feed
more completely than those on full feed. In the second place the basal
metabolism may have been reduced by the limited ration, thus permitting
a greater proportion of the feed to be used for the production of gain
than under conditions of maximum feed intake. A third possibility is that
the pigs fed the restricted ration actually utilized the available nutrients
more efficiently than the other pigs. Finally there is the possibility that
the gain produced under limited feeding required enough less nutrient
material for its production, than was required by the full-fed pi~s, to
provide maintenance for the extra period.
Contrary to results with steers, swine have been shown to digest their
feed equally well whether the allowance is a maintenance ration or a
full feed (1, 9).
Satisfactory data with swine are not available to indicate the effect of
different levels of feed intake on basal metabolism. Hamilton (7) was
THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
411
able to lower the basal metabolism of rats by limiting the feed intake.
Some 2~ years ago Dietrich (la) advanced the idea of a "factor of
waste" established in pigs by liberal feeding but did not exist, to the
same degree at any rate, in pigs fed less liberally. Dietrich's data were
not extensive and the idea gradually lost support.
In an attempt to determine whether the combined factors of metabolism
were influential in favoring the results obtained with the limited-fed
pigs, the following calculations were made. The total metabolizable energy
of the ration fed the two pairs of pigs whose carcasses were analyzed
was estimated from the values obtained by Mitchell and Hamilton (9)
with a similar ration. The maintenance requirements were estimated
from Deighton's (see 9) basal metabolism figures and an additional factor
of 20% for voluntary activity. This value appears reasonably accurate
since the maintenance value obtained is slightly below the metabolizable
energy requirements for maintenance as found by the Illinois workers.
The energy stored was determined directly. By adding the energy stored
and the estimated energy usd for maintenance, dividing by the total
metabolizable energy, and multiplying by 100, the metabolizable energy
net available was computed.
TABLE 4--THE INFLUENCE OF FEEDING ON THE METABOLIZABLE
ENERGY NET A V A I L A B L E
Total *
Energy **
metabolizable required
energy
for
consumed maintenance
therms
therms
Full.fed
Limited-fed
647.7
703.6
264.1
348.2
Energy
stored
therms
Total
net
energy
therms
238.0
201.6
502.1
~49.8
Metabolizable
energy
net
available
%
78
78
* Calculated on basis of 1.27 therms per pound of ration as found with similar
ration by Mitchell and Hamilton, Illinois Bulletin 323.
** Basal metabolism plus 20% increment for incidental activity.
The data in Table 4 lend little support to the suggestion that limiting
the ration of swine within the limits of this test brings about greater
metabolic efficiency in the use of nutrients. Pigs therefore appear to differ
from steers in this respect (4, 5, 10).
The data in Table 3 indicate that the gain made by the limitedfed pigs really did carry less energy than that produced by the fuI1 ration
and can, therefore, rightly be expected to have required less feed for its
production. This saving appears from the limited data at hand to be
sufficient to offset the feed necessary for the longer maintenance period of
the limited-fed pigs.
412
THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
Conclusions
1. Limiting the swine ration to three-fourths of a full-feed did not
materially lower the amount of feed required to put on a unit of
body weight. Limited-fed animals were not as well finished, however,
as were those that were full-fed.
2. The apparent equality of feed costs per unit of gain at the two
levels of feeding appears to be the result of two compensating factors;
namely, body composition and maintenance requirements, rather than
factors of digestion and metabolism.
3. The assumption that individual feeding trials lead to results of doubtful practical interpretation does not appear to be well founded. The
present study is in full agreement with the group feeding trials thus
far carried out on limited swine rations.
Literature Cited
1. Dietrich, Wm., 1899. On the food requirements of the pig for maintenance
and for gain. Wis. Agr. Exp. Sta. 16th Ann. Rpt. 1899, pp. 31-43.
la. Dietrich, Wm., 1912. Swine. p. 149. Sanders Publishing Co., Chicago.
2. Ellis, N. R., and T. H. Zellar, 1934. E~ect of quantity and kinds of feed on
economy of gains and body composition of hogs. U. S. D. A. Tech. Bul. 413.
3. Ferrin, E. F., and M. A. McCarty, 1928. Shall growing pigs be full fed?
Minn. Agr. Exp. Sta. Bull. 248.
4. Forbes, E. B., W. W. Braman, and M. Kriss, with the collaboration of C.
D. Jeffries, R. W. Swift, R. B. French, R. C. Miller, and C. V. Smyth, 1928.
The energy metabolism of cattle in relation to the plane of nutrition. Jour.
Agric. Res. 37, 253,300.
5. Forbes, E. B., W. W. Braman, and M. Kriss, with the collaboration of R.
W. Swift, R. B. French, C. V. Smythe, P. S. Williums and H. H. Williums,
1930. Further studies of the energy metabolism of cattle in relation to the
plane of nutrition. Journ. Agric. Res. 40, 37-78.
6. Freeman, V. A., 1936. Limited rations for pigs. Mich. Quarterly Bul. Vol.
17, 95,98.
7. Hamilton, T. S. 1939. The growth, activity and composition of rats fed diets
balanced and unbalanced with respect to protein. J. Nutr. 17, q6~.
8. Lindgrin, H. A., A. W. Oliver, and E. L. Potter. Types of hogs marketed
and consumer demand in Oregon. Oregon Agr. Exp. Sta. Bul. 297.
9. Mitchell, H. H., and T. S. Hamilton, 1929. Swine type studies. Ill. The
energy and protein requirements of growing swine and the utilization of feed
energy in growth. III. Bul. 323.
10. Mitchell, H. H., T. S. Hamilton, F. J. McClure, W. T. Haines, Jessie R.
Beadles, and H. P. Morris, 1932. The effect of the amount of feed consumed
by cattle on the utilization of its energy content. Jour. of Agric. Res. 45,
163,191.
11. Robison, W. L., 1920. Full and limited feeding of fall pigs. Ohio Agr. Exp.
Sta. Monthly Bul. 5, 27~,280.
12. Saint-Pierre, J. M., F. B. Morrison, and J. P. Willman, 1934. The relative
efficiency of limited and full-feeding for fattening pigs in dry lot. Proc.
Amer. Soc. An. Prod. 101,104.