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The Passage of Oat and Other Feed Residues Through the Adult Cockerel1
The Passage of Oat and Other Feed Residues Through the Adult Cockerel1 I. R. SIBBALD Animal Research Institute, Agriculture Canada, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6 (Received for publication July 9, 1979)
1980 Poultry Science 59:2136-2144 INTRODUCTION
The movement of feed residues through the alimentary canal of the chicken has been a subject of investigation for more than fifty years (Sibbald, 1979a). The term "rate of passage" (ROP) is widely used to describe such movement but it is, perhaps, a misnomer and its definition has varied among authors. The passage of feed residues is better described by three parameters: the time between ingestion and the excretion of the first residue, the appearance time (AT); the time between ingestion and the excretion of the last residue, the clearance time (CT); and the time between ingestion of a unit of feed and the excretion of the median residue, the passage time (PT). Clearance time is important in bioassays such as those for true metabolizable energy and true available amino acids (Sibbald, 1976, 1979b). In such assays birds are starved to empty their alimentary canals of feed residues. A known amount of feed is placed in the crop and the resulting residues are collected quantitatively. The duration of the excreta collection period must be sufficient to ensure that all feed residues are voided (>CT). If the collection period is too short (
1 Contribution Institute.
number
864
Animal
There is a lack of information concerning those characteristics of a feedingstuff which determine its CT. Fiber and mineral content may be involved, but the relationships seem to be complex (Sibbald, 1979a). Other factors affecting CT include the duration of starvation prior to feed input, the time of feeding, the amount of feed input, and the physical form of the feed (Sibbald, 1979a). When two feedingstuffs differ in CT they usually differ in so many other characteristics that it is impossible to identify the causative factor(s). For example, ground yellow corn and dehydrated alfalfa differ in CT and in a multiplicity of other factors which include: crude protein, crude fiber, ether extract, mineral content, and saponin content (NAS, 1971); bulk density, particle size distribution and water binding capacity. In a recent experiment, a sample of oats was found to have a CT greater than 24 hr (Sibbald, 1980b). Earlier work showed other samples to have CT less than 24 hr (Sibbald, 1979a). It, therefore, seemed appropriate to use oats, varying greatly in proximate composition, to identify the variables affecting CT. Three experiments were conducted. In the final experiment the excretion of wheat, dehydrated alfalfa, and fish meal residues was compared with that of oat residues to determine if the same variables affected CT.
Research
MATERIALS AND METHODS
Three experiments were made with adult, 2136
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ABSTRACT Three experiments were made with adult White Leghorn cockerels to study the passage of feed residues through the alimentary canal. The birds were starved for 24 hr and then force-fed known quantities of feedingstuffs. Excreta were collected quantitatively at 2 hr intervals during the light periods, dried, and weighed. In the first two experiments the birds received 12 hr of light daily while in the third experiment continuous light was used. Residues of oats fed at levels ranging from 6 to 30 g/bird appeared in the excreta within 2 hr and continued to be voided for 52 hr. The rate and duration of residue output were functions of residue input; this was true for, wheat, fish meal, and dehydrated alfalfa as well as oats. For practical purposes the clearance times were substantially less than 52 hr for most of the inputs studied. (Key words: appearance time, clearance time, time of passage, definitions, excreta, oats, hull-less oats, wheat, fish meal, dehydrated alfalfa)
PASSAGE OF FEED RESIDUES
treatment groups. Treatments 1 to 6 involved inputsof0,6, 12, 18, 24, and 30g, respectively, of oats (Sample 4) marked with stained particles and cold pelleted. Treatments 7, 8, and 9 were 24 g of wheat, 18 g of fish meal, and 12 g of dehydrated alfalfa, respectively, all fed as pellets. The oats were ground and passed through a series of sieves. Particles which passed through a #12 sieve but which were retained by a #30 sieve were removed and stained with basic fucsin as described by Castle (1956). The stained particles were added back to a portion of the recombined sieve fractions to produce a concentration of 1% by weight. The sieving step was introduced to avoid the cooking of fines, which tend to inhibit filtration. Each excreta sample from each bird fed oats was weighed and then made into a slurry with water. Each slurry was poured onto a piece of cheesecloth stretched over an embroidery hoop. The cheesecloth was washed with a stream of water, and the number of stained particles (<5, >5, <10, >10) remaining on the cloth was noted. No attempt was made to measure a passage time, as was done by Sibbald (1979c), because of the confounding effect of the metabolic plus endogenous wastes (Sibbald, 1979a). RESULTS AND DISCUSSION The physical and chemical characteristics of the oats are described in Table 1. Before grinding there were large differences in bulk densities and 1,000 kernel weights, but there is no reason to believe that they had a direct
TABLE 1. Physical and chemical characteristics of the oats Sample no.
1
2
3
4
5
6
Variety Bulk density (kg/hl) b 1000 kernels (g) b Gross energy (kcal/g) Dry matter (%) Ether extract (%) Crude fiber (%) Crude protein (N X 6.25%) Ash (%) Calcium (%) Phosphorus (%)
Vicar* 65.7 21.6 4.30 88.3 5.94
Garry 58.0 27.6 4.19 89.6 4.72
Kelsey 51.5 31.0 4.22 89.9 5.64
Scott 44.5 33.6 4.18 88.8 3.92
Condor 39.9 27.7 4.14 88.5 4.75 11.4
Garry 32.9 29.0 4.20 90.2 3.45 15.6 10.8 3.50 .139 .424
This is a hull-less variety. Measured prior to grinding.
1.9
16.0 1.85 .088 .415
7.5
13.6 2.95 .066 .349
8.1
12.4 3.12 .088 .261
9.5
12.8 2.70 .099 .373
9.6
3.25 .050 .513
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White Leghorn cockerels of the Kentville Control strain drawn from a single population. The birds were individually housed in wire cages in a windowless room with continuous access to fresh water. In the first two experiments the birds received 12 hr of light daily (0600 to 1800 hr); in the third experiment the birds were acclimatized to and received continuous light. The birds were starved for 24 hr, starting at 0800 hr, and were then weighed and force-fed the appropriate ration. Excreta voided were collected quantitatively at 2 hr intervals during the light periods for 52 hr. The excreta samples were frozen, dried in a forced-draft air oven at 80 C for 18 hr, and weighed. Experiment 1. Six samples of ground oats were each fed to six randomly selected cockerels; the input was 30 g/bird. Subsamples of the oats were assayed for proximate composition (AOAC, 1975) and gross energy. Cumulative dry matter excretion was measured for each bird. Experiment 2. Three samples of ground oats, selected on the basis of residue yield from those used in Experiment 1, were each fed at two levels of six randomly selected birds. The levels of input were calculated to yield amounts of excreta dry matter similar to those resulting from 30 g of low and high fiber oats (Samples 1 and 6). The two levels were 30 and 56, 21 and 38, and 16 and 30 g/bird of oat Samples 1, 4, and 6, respectively. Experiment 3. Four birds, from the middle weight range of the population were assigned to each of nine treatments. The selection was made to minimize variation within the smaller
2137
SIBBALD
2138
Y = 16.02+ Y=
2.26 X 2
1.82 + 16.40 X2
The correlation coefficients were r Y x ,
=
-859
and r w . = .796 both at 32 DF; the multiple YX2 correlation coefficient R Y . X J X J = .860 was similar to r Y X , and reflects the close correlation between crude fiber and ash ( r x x .904 at 4DF). There was variation among the crude protein values of the oats, but partial correlations with protein were no better than the simple correlations described above. No pair of the parameters listed in Table 1 could account for more of the variation than crude fiber alone. While crude fiber and ash largely determined the weight of feed residues voided, the other indigestible constituents should not be neglected. During the first 2 hr after feeding, the excreta outputs were similar among the six groups. Differences then developed, indicating the appearance of oat residues, but it was not until 22 hr postfeeding that the final pattern of excreta output was established. From 22 to 52 hr the amount of excreta increased with the crude fiber and ash content of the oats, suggesting that the CT might increase with the amount of residues to be voided. Mean dry matter output during the final 2 hr ranged from .22 to .45 g. There were no distinct trends associated with crude fiber input or with
TABLE 2. Mean cumulative dry matter excretion (Experiment I) expressed as weight and as a percentage of the total
Sample Input /bird no.
No. of observations
Time after feed input (hr) 2
8
6
4
10
22
24
26
(g) 1 2 3
30 30 30
6 6 6
Mean (g)
.65
SEM
.140
Mean (g)
.67
SEM
.135
Mean (g)
.47
SEM
.096
4
30
5
Mean (g)
.43
SEM
.042
5
30
6
Mean (g)
.45
SEM
.077
Mean (g)
.40
SEM
.037
6
1 2 3 4 5 6
30
30 30 30 30 30 30
5
6 6 6 5 6 5
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
5.8 4.6 2.9 2.6 2.7 1.9
1.50 .134 1.33 .188 1.24 .107 1.77 .192 2.10 .254 1.28 .164 13.5 9.0 7.6
10.9 12.4 6.2
2.07 .220 1.86 .330 1.96 .197 2.73 .380 3.43 .457 2.33 .358 18.6 12.7 12.0 16.8 20.3 11.2
3.04 .328 2.94 .531 2.98 .282 4.06 .561 4.94 .561 3.87 .327 27.3 20.0 18.2 25.0 29.3 18.6
3.63 .353 3.81 .600 4.06 .303 4.85 .742 5.76 .594 5.01 .404 32.6 25.9 24.8 29.8 34.2 24.1
7.49 6.72 .381 .343 9.12 7.80 1.205 1.110 9.42 7.91 .687 .709 8.51 9.66 .826 .812 8.82 10.04 .689 .691 9.81 10.99 .948 1.057 60.3 53.1 48.4 52.3 52.3 47.2
67.2 62.1 57.6 59.4 59.5 52.8
7.99 .276 9.86 1.209 10.45 .644 10.38 .901 10.80 .634 12.40 1.153 71.7 67.1 63.9 63.8 64.0 59.6
(continued)
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effect on CT. Gross energy and dry matter values were similar between grains, and although ether extract and ash values varied relatively, the absolute amounts were not very different. The major differences among the oats were in crude fiber and crude protein content. The mean initial body weights were 2.3 5, 2.37, and 2.38 in Experiments 1, 2, and 3, respectively. Analysis of variance demonstrated that the differences among treatment means, within an experiment, were not significant (P>.05). Experiment I. Data describing the cumulative dry matter excretions are presented in Table 2. Single birds in groups fed oats 4 and 6 regurgitated; data obtained from them are omitted from the table. The amount of excreta voided from 0 to 52 hr (Y) increased with the inputs (g/bird) of crude fiber ( X t ) and ash (X 2 ). Linear regression analyses produced the following equations:
2139
PASSAGE OF FEED RESIDUES TABLE 2. (continued) Mean cumulative dry matter excretion (Experiment 1) expressed as weight and as a percentage of the total
Sample Input /bird no.
No. of observa tions
Time after feed input (hr) 28
30
32
34
46
48
50
8.40 .198 10.51 1.210 11.34 .635 11.10 .979 11.58 .612 13.15 1.207
8.64 .186 11.07 1.225 12.06 .582 11.70 1.006 12.29 .613 13.90 1.220
8.90 .170 11.52 1.114 12.89 .600 12.34 1.034 13.01 .557 14.82 1.138
9.15 .242 11.96 1.085 13.28 .550 12.77 1.006 13.46 .611 15.93 1.095
10.28 .284 13.54 1.004 14.99 .675 15.04 .780 15.50 .507 18.77 .909
10.56 .328 14.04 .998 15.62 .704 15.42 .813 16.10 .510 19.66 .876
10.92 .400 14.30 .983 16.03 .722 15.98 .810 16.52 .483 20.35 .833
75.4 71.5 69.4 68.3 68.7 63.2
77.6 75.4 73.8 72.0 72.9 66.8
79.9 78.4 78.8 75.9 77.2 71.2
82.1 81.4 81.2 78.5 79.8 76.6
92.3 92.2 91.7 92.5 91.9 90.2
94.8 95.6 95.5 94.8 95.5 94.5
98.0 97.3 98.0 98.3 98.0 97.8
52
(g) 1
30
6
Mean (g) SEM
30
6
Mean (g)
3
30
6
Mean (g)
4
30
5
Mean (g)
5
30
6
Mean (g)
6
30
5
SEM SEM SEM SEM
Mean (g) SEM
1 2 3 4 5 6
30 30 30 30 30 30
6 6 6 5 6 5
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
52 hr excreta output. Analysis of variance showed that treatment differences were not significant (P>.05). There were significant (P<.01) differences among treatments in the amount of excreta voided during the final 4 and 6 hr periods. Most of the difference during the final 4 hr was due to the relatively large excreta output of the birds fed oat sample 6. This was the most fibrous sample and produced the greatest quantity of residues. It is probable that most of the excreta produced by the other five groups consisted of metabolic and endogenous wastes. Excreta outputs during the final 6 hr tended to parallel the 52 hr excreta outputs. These observations support the hypothesis that CT is largely determined by the quantity of residues to be voided. Experiment 2. The second experiment was designed to test the above hypothesis. Samples of oats 1, 4, and 6 were fed at two levels (Table 3) estimated to yield amounts of residues equivalent to those from 30 g of oats 1 and 6, respectively. Assuming that birds fed 30, 21, and 16 g of oats 1, 4, and 6, respectively, produced equal amounts of excreta, then each oat should have the same CT.
100.0 100.0 100.0 100.0 100.0 100.0
The mean cumulative dry matter excretions, expressed in absolute amounts and percentages, are displayed in Table 3. Data describing 8 of the original 36 birds were discarded because of either regurgitation (2) or crop impaction at 48 hr (6). The latter was a major problem throughout the experiment. Large differences in the rate of excreta output were noticed early in the experiment. The crops of the birds were palpated 24 hr after force-feeding and lumps of feed were detected in 12 birds. Birds of all treatments were affected, but the problem was most severe among the high residue input groups. The distribution of the impactions was as follows: oats 6, 30 g, 4; oats 6, 16 g, 1; oats 1, 56 g, 2; oats 1, 30 g, 1; oats 4, 38 g, 2; oats 4, 21 g, 2. The crops were palpated again at the conclusion of the experiment, and lumps of feed were detected in six birds; several other birds may have had feed residues in their crops, but they could not be detected by palpation. The cumulative excreta outputs at 52 hr differed between the high and low levels of input (P<.01) and also between oats (P<.01). Apparently the residue output from oat sample 1 was overestimated, because at the high level
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2
11.14 .386 14.69 .999 16.35 .736 16.26 .774 16.86 .470 20.80 .828
2140
SIBBALD particularly when reference was made to the cumulative total output. Experiment 3. One of the difficulties associated with the first two experiments was the continuity of the data caused by the interruption of the dark periods. Recently, Squibb and Collier (1979) suggested that the movement of materials through the alimentary tract should be more uniform under continuous light. For these two reasons it was decided to conduct the experiment under continuous illumination. In an attempt to avoid crop impaction all feedingstuffs were pelleted; this was successful. Of the 20 birds fed oats, 10 excreted stained particles within 2 hr of feeding; in only one bird was the appearance delayed until the third excreta collection. There was no clear evidence that AT was related to the amount of the input. Stained particles were excreted by 17 birds during the final 2 hr (50 to 52 hr postfeeding) of the experiment, but the concentrations were low and most birds had several prior excretions in which stained particles were not detected. The postpeak output of particles may be likened to continuous dilution with ever decreasing amounts being voided for an indefinite period. Balch (1950) and Castle (1956)
TABLE 3. Mean cumulative dry matter excretion (Experiment 2) expressed as weight and as a percentage of the total
Sample Input no. /bird
No. of observations
Time after feed input (hr) 4
2
6
10
8
22
24
26
(g) 1 4 6 1 4 6
1 4 6 1 4 6
30 21 16 56 38 30
30 21 16 56 38 30
6 5 4 5 3 5
6 5 4 5 3 5
Mean (g)
.36
SEM
.128
Mean (g)
.70
SEM
.175
Mean (g)
.28
SEM
.027
Mean (g)
.38
SEM
.133
Mean (g)
.70
SEM
.099
Mean (g)
.65
SEM
.113
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
3.2 4.9 2.0 2.2 3.5 3.3
1.21 .262 1.58 .307 1.49 .242 1.86 .238 1.74 .339 1.71 .544 10.9 11.1 10.9 10.8 8.7 8.6
2.02 .335 2.94 .252 2.58 .417 2.72 .263 2.86 .624 2.98 .707 18.3 20.7 18.9 15.7 14.2 15.0
2.84 .524 3.70 .311 3.80 .477 4.03 .535 4.19 .794 4.11 .963 25.7 26.0 27.9 23.3 20.9 20.6
3.76 .617 4.29 .405 4.72 .458 5.05 .562 5.22 .824 5.09 1.073 34.0 30.2 34.6 29.2 26.0 25.6
7.02 6.27 7.38 .727 .750 .758 6.96 7.82 8.74 .615 .698 .518 8.16 9.04 9.76 .675 .604 .581 9.11 10.55 11.70 .643 .647 .563 9.18 10.57 11.49 .959 1.084 1.142 9.97 11.18 12.18 2.002 2.200 2.281 56.7 48.9 59.9 52.6 45.8 50.1
63.5 55.0 66.3 61.0 52.7 56.2
66.7 61.5 71.6 67.6 57.3 61.2 (continued)
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of input, the 52 hr excreta output was substantially less than from the high inputs of oats 4 and 6 (17.3 cf 20.1 and 19.9g). One difficulty in estimating inputs required to produce a particular output is that excreta consist of feed residues and metabolic plus endogenous wastes; unless these can be partitioned such estimates are unlikely to be accurate. Agreement between experiments was satisfactory. In Experiments 1 and 2, 30 g of oats 1 yielded 11.14 and 11.06 g of excreta dry matter, respectively; comparable data for 30 g of oats 6 were 20.80 and 19.91 g. As in the first experiment, excreta outputs of the six groups were similar during the first 4 hr, although the high input groups produced slightly more excreta than the low input groups. By 6 hr postfecding, there was a distinct difference between the high and low groups which continued throughout the experiment. During the final 2 hr, the birds on the high inputs voided more excreta than those on the low inputs (P<.01), but there were no significant differences among oats within input levels. This suggests that the high input was associated with a greater CT and provides support for the hypothesis. Examination of data for other time periods tended to confirm this interpretation
2141
PASSAGE OF FEED RESIDUES TABLE 3. (continued) Mean cumulative dry matter excretion (Experiment 2) expressed as weight and as a percentage of the total
Sample Input /bird no.
No. of observa tions
Time after feed input (hr) 28
30
32
34
46
48
50
7.84 .673 9.53 .445 10.37 .492 12.47 .483 12.48 1.057 13.11 2.260
8.18 .655 10.07 .547 10.89 .444 13.15 .441 13.40 1.008 13.86 2.160
8.45 .656 10.64 .481 11.23 .431 13.68 .422 14.12 .875 14.54 2.040
8.76 .607 11.08 .450 11.43 .445 14.13 .384 14.83 .664 15.09 2.059
10.24 .538 12.90 .412 12.82 .574 16.14 .524 18.29 .743 18.02 1.469
10.57 .560 13.45 .448 13.10 .587 16.56 .564 19.08 .499 18.76 1.418
10.84 .568 13.78 .446 13.38 .598 16.83 .568 19.47 .610 19.30 1.438
70.9 67.0 76.1 72.1 62.2 65.8
74.0 70.8 79.9 76.0 66.8 69.6
76.4 74.8 82.4 79.1 70.4 73.0
79.2 77.9 83.8 81.7 73.9 75.8
92.6 90.7 94.0 93.3 91.2 90.5
95.6 94.6 96.1 95.7 95.1 94.2
98.0 96.9 98.2 97.3 97.0 96.9
52
(g) 1
30
6
Mean (g) SEM
Mean (g)
21
5
6
16
4
Mean (g)
1
56
5
Mean (g)
4
38
3
Mean (g)
6
30
5
SEM SEM SEM SEM
Mean (g) SEM
1 4 6 1 4 6
30 21 16 56 38 30
6 5 4 5 3 5
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
observed a similar effect in work with ruminants and, in some calculations, discounted the "tails" of cumulative excretion curves. The absolute CT for oats under the conditions of this experiment was greater than 52 hr; however, for practical purposes it was much less, as will be shown. The mean cumulative excreta dry matter data were arranged in the same manner as the data of Table 2. This revealed that within 4 hr postfeeding the excreta outputs of birds on treatments 1 to 6 increased with the oat input. To test this the cumulative excreta dry matter values for each bird on each of the six treatments at each time postfeeding were regressed on the oat inputs. The results are summarized in Table 4. The correlation coefficients increased for 24 hr and then remained relatively constant. The intercepts were estimates of the metabolic plus endogenous excreta outputs and were similar to the mean values of the negative control birds on which they were regressed: Y = .952 X = .069; r = .998 at 24 DF. The regression coefficients were estimates of the amount of residues voided per gram of oat input. The coefficients increased in a curvilinear manner, suggesting that the residues were excreted rapidly during the first 18 hr postfeed-
100.0 100.0 100.0 100.0 100.0 100.0
ing and then at a diminishing rate; this is compatible with the concept of continuous dilution. However, the effect is complicated, because in addition to changes in time there were differences in the oat inputs, and excreta outputs, between treatment groups. The cumulative data suggest that birds which received the most oats took the most time to void the oat residues; this accentuated the curvilinearity of the regression coefficients. Within 4 hr of feeding, the cumulative dry matter excretions tended to reflect the 52 hr outputs. To test this, the cumulative excreta dry matter values for each bird on each of the treatments at each time postfeeding were regressed on the 52 hr cumulative excreta outputs. The results are presented for treatments 1 to 6 and 1 to 9 in Table 4. The correlation coefficients increased rapidly with the time after feeding and confirmed the linearity of the relationships. The regression coefficients increased in a curvilinear manner approaching unity as time progressed. The most interesting results of the analyses are the intercepts which decreased rapidly until 18 hr postfeeding and then began to increase. The changes suggest that in absolute terms, the cumulative excreta outputs for the treatments were similar for the
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4
11.06 .562 14.22 .490 13.63 .634 17.30 .554 20.06 .647 19.91 1.293
2142
SIBBALD TABLE 4. Relationships between cumulative dry matter excretion (Y), air dry oat input and total excreta output (X2) Regression of Y on x. Treatments 1 to 6 f
YX! (22 df)
Intercept
coef
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52
.305 .844 .882 .926 .932 .954 .953 .958 .962 .964 .972 .978 .981 .981 .980 .981 .979 .984 .983 .983 .983 .982 .982 .983 .980 .979
-.031 .934 1.200 1.410 1.618 1.846 1.988 2.127 2.380 2.646 2.863 3.048 3.190 3.449 3.612 3.866 4.091 4.330 4.548 4.802 5.025 5.282 5.485 5.688 5.909 6.094
.063 .052 .114 .169 .222 .245 .265 .283 .301 .304 .311 .319 .325 .327 .333 .335 .339 .346 .347 .349 .352 .350 .353 .353 .357 .359
Reg
Regression of Y on X2 Treatments 1 to 6 r
YX 2 (22 df) .157 .829 .861 .908 .916 .936 .937 .948 .948 .952 .967 .977 .983 .984 .988 .992 .993 .997 .997 .998 .998 .998 .999 .999 1.000
first few hours (2 to 4) and then diverged until about 18 hr postfeeding when they started to converge and assume parallel relationships. A bird receiving a large quanitity of a feed excreted the residues more rapidly and over a longer period than a bird receiving less of the same feed. The approach to parallel relationships was observed in earlier experiments and can be seen in the figures of Sibbald (1979a). The results of the analyses for treatments 1 to 6 are similar to those for treatments 1 to 9, suggesting that the relationships discussed above were not limited to oats but applied to a variety of feedingstuffs. The excreta output data were rearranged to permit examination of changes during the concluding periods of the experiment. There were differences in excreta outputs among treatments, but during the final 16 hr of the experiment they were small. Analyses of variance were made of the data for all treatments for each period prior to completion. During the final 36 hr there were no significant
Regression of Y on X 2 Treatments 1 to 9
Inter cept
coef
YX 2 (34 df)
.372 .108 -.570 -1.237 -1.861 -1.996 -2.191 -2.392 -2.373 -2.200 -2.158 -2.150 -2.130 -1.918 -1.891 -1.714 -1.584 -1.443 -1.257 -1.059 -.882 -.615 -.455 -.252 -.144
.011 .141 .303 .451 .590 .654 .710 .763 .806 .820 .844 .869 .888 .895 .914 .924 .936 .954 .958 .966 .974 .971 .978 .978 .994
.288 .663 .729 .831 .880 .903 .925 .937 .945 .951 .968 .973 .976 .985 .988 .991 .993 .996 .997 .998 .998 .998 .999 .999 1.000
Reg
r
Inter cept
coef
.214 .159 -.057 -.649 -1.333 -1.687 -2.191 -2.422 -2.363 -2.261 -2.313 -2.238 -2.235 -2.036 -1.941 -1.780 -1.623 -1.435 -1.301 -1.084 -.876 -.649 -.502 -.368 -.176
.026 .129 .245 .388 .537 .621 .715 .773 .809 .827 .860 .878 .897 .906 .919 .929 .940 .954 .965 .969 .973 .976 .983 .991 .997
Reg
(P>.05) differences among treatments; during the final 38 hr, there was a significant effect (P<.05), and this became highly significant (P<.01) for the remaining time periods (40 to 52 hr). Multiple range tests confirmed that excreta outputs increased with oat inputs (treatments 1 to 6). Analysis of variance may have lacked the sensitivity to detect trends in excreta outputs between treatments in the final phases of the experiment. Therefore, it was decided to apply linear regression analysis in much the same manner as shown in Table 4. The excreta dry matter outputs of all birds for a particular time period were regressed on their total 52 hr outputs. The results are summarized for treatments 1 to 6 and 1 to 9 in Table 5. Most of the correlation coefficients are significant, but it is apparent that excreta output during the final hours of the experiment bore little relationship to the cumulative 52 hr output. The intercepts tend to mirror those of Table 4. The
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Hours after feeding
(X,),
PASSAGE OF FEED RESIDUES
2143
TABLE 5. Relationships between excreta outputs in periods prior to completion and total excreta output Time to completion of experiment (h)
Treatments 1 to 9 Reg
r
(22 df)
Intercept
coef
(34 df)
Intercept
coef
.273 .459 .412 .484 .419 .518 .484 .511 .500 .544 .510 .549 .562 .569 .575 .566 .581 .678 .741 .815 .846 .935 .968 .994 .996
.144 .193 .455 .615 .882 1.059 1.257 1.443 1.584 1.714 1.891 1.918 2.130 2.150 2.156 2.200 2.373 2.392 2.191 1.996 1.861 1.237 .507 -.108 -.199
.0064 .0245 .0215 .0289 .0261 .0339 .0415 .0460 .0635 .0764 .0863 .1053 .1123 .1306 .1565 .1802 .1935 .2366 .2904 .3458 .4097 .5492 .6971 .8594 .9694
.108 .287 .317 .395 .380 .435 .417 .477 .476 .498 .496 .504 .464 .508 .529 .541 .563 .618 .698 .788 .847 .921 .957 .986 .995
.176 .282 .502 .649 .876 1.084 1.301 1.435 1.623 1.780 1.939 2.036 2.235 2.238 2.311 2.261 2.363 2.422 2.190 1.687 1.333 .694 .057 -.160 -.160
.0029 .0146 .0168 .0238 .0267 .0310 .0350 .0462 .0597 .0710 .0814 .0937 .1034 .1222 .1400 .1728 .1911 .2272 .2852 .3786 .4631 .6124 .7554 .8706 .9617
regression coefficients indicate that only a small quantity of excreta were voided during the final phases of the experiment. The first experiment involved feeding equal weights of six samples of oats which, during the 52 hr excreta collection period, yielded different quantities of excreta. There was evidence that oat residues were voided within 6 hr postfeeding and that the CT was 50 hr or less. It appeared that the CT was a function of the amount of residues to be voided. The findings of the second experiment were distorted to some degree by the problem of crop impaction, but the AT appeared to be less than 6 hr. The birds which received the most residues excreted them at a greater rate over a longer period than the birds which received lesser amounts. The CT was not established, but for the high residue inputs it appeared to exceed 52 hr. The final experiment was conducted under continuous light, which permitted excreta collection every 2 hr. By the use of stained particles it was found that AT was less than 2 hr and CT was more than 5 2 hr. However, the amounts of feed
Reg
residues voided in the latter hours of the experiment were small. Confirmed was the finding that rate and duration of residue output is a function of residue input. The relationship held not only for oats but also for wheat, fish meal, and dehydrated alfalfa. There may, be various other factors which affect the passage of feed residues, but the results indicate residue input to be a primary determinant. The AT can be measured with some degree of confidence by the use of stained particles. The absolute CT can be determined by the same procedure; however, if the birds receive a single input of feed, as in these experiments, they could die of starvation before the CT is reached. For purposes of the TME, TAAA, and similar bioassays, the CT may be defined as the time after feeding at which subsequent residue output is too small to have a measurable effect on the data obtained. In Table 4 it is shown that 1 g of oats yielded .319, .346, and .353 g of residues at 24, 36, and 48 hr after feeding, respectively. A TME bioassay based on a 24 hr excreta collection, as originally suggested
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2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Treatments 1 to 6 r
2144
SIBBALD
ACKNOWLEDGMENT The autlior wishes to thank S. Tobin for her able technical assistance. REFERENCES Association of Official Analytical Chemists, 1975.
Official methods of analysis. 12th ed. AOAC, Washington, DC. Balch, C. C , 1950. Factors affecting the utilization of food by dairy cows. 1. The rate of passage of food through the digestive tract. Brit. J. Nutr. 4:361-388. Castle, E. J., 1956. The rate of passage of foodstuffs through the alimentary tract of the goat. 1. Studies on adult animals fed hay and concentrates. Brit. J. Nutr. 1 0 : 1 5 - 2 3 . National Academy of Sciences, 1971. Atlas of nutritional data on United States and Canadian feeds. Nat. Acad. Sci. Washington, DC. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:303—308. Sibbald, I. R., 1979a. Passage of feed through the adult rooster. Poultry Sci. 58:446-459. Sibbald, I. R., 1979b. A bioassay for available amino acids and true metabolizable energy in feedingstuffs. Poultry Sci. 58:668-673. Sibbald, 1. R., 1979c The effect of the duration of the excreta collection period on the true metabolizable energy vales of feedingstuffs with slow rates of passage. Poultry Sci. 58:896— 899. Sibbald, I. R., 1979d. Effect of level of feed input, dilution of test material and duration of excreta collection on true metabolizable energy values. Poultry Sci. 58:1325-1329. Sibbald, I. R., 1980a. The clearance time and rate of passage of feed residues. Poultry Sci. 59:374— 377. Sibbald, I. R., 1980b. The effects of dietary cellulose and sand on the combined metabolic plus endogenous energy and amino acid outputs of adult cockerels. Poultry Sci. 59:836-844. Squibb, R. L., and G. H. Collier, 1979. Feeding behavior of chicks under three lighting regimes. Poultry Sci. 58:641-645.
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(Sibbald, 1976), would underestimate the energy excretion and give an inflated TME value. Bioassays have demonstrated this for oats and for several other feedingstuffs which yield large amounts of residues (Sibbald, 1979c,d; 1980b). The results of the present experiments indicate that TME assays for some oats should use excreta collection periods greater than 24 hr; for very fibrous oats a 48 hr collection should be adequate. The measurement of PT was not attempted in the present work, but it is a parameter of interest, particularly under conditions of ad libitum feeding. Castle (1956) calculated a PT (R) which was defined as the sum of the times for 10% increments of cumulative excreta output, from 5 to 95%, divided by 10; this effectively removed the problem of prolonged CT. The same approach was used in poultry by Sibbald (1980a). The median time might be a good estimate of PT if the cumulative excretion curve is symmetrical, but this in infrequent. There are many ways to define and estimate PT; consequently, it is important that the terminology be clearly defined. The term "rate of passage" is imprecise and can be misleading.
1980 Poultry Science 59:2136-2144 INTRODUCTION
The movement of feed residues through the alimentary canal of the chicken has been a subject of investigation for more than fifty years (Sibbald, 1979a). The term "rate of passage" (ROP) is widely used to describe such movement but it is, perhaps, a misnomer and its definition has varied among authors. The passage of feed residues is better described by three parameters: the time between ingestion and the excretion of the first residue, the appearance time (AT); the time between ingestion and the excretion of the last residue, the clearance time (CT); and the time between ingestion of a unit of feed and the excretion of the median residue, the passage time (PT). Clearance time is important in bioassays such as those for true metabolizable energy and true available amino acids (Sibbald, 1976, 1979b). In such assays birds are starved to empty their alimentary canals of feed residues. A known amount of feed is placed in the crop and the resulting residues are collected quantitatively. The duration of the excreta collection period must be sufficient to ensure that all feed residues are voided (>CT). If the collection period is too short (
1 Contribution Institute.
number
864
Animal
There is a lack of information concerning those characteristics of a feedingstuff which determine its CT. Fiber and mineral content may be involved, but the relationships seem to be complex (Sibbald, 1979a). Other factors affecting CT include the duration of starvation prior to feed input, the time of feeding, the amount of feed input, and the physical form of the feed (Sibbald, 1979a). When two feedingstuffs differ in CT they usually differ in so many other characteristics that it is impossible to identify the causative factor(s). For example, ground yellow corn and dehydrated alfalfa differ in CT and in a multiplicity of other factors which include: crude protein, crude fiber, ether extract, mineral content, and saponin content (NAS, 1971); bulk density, particle size distribution and water binding capacity. In a recent experiment, a sample of oats was found to have a CT greater than 24 hr (Sibbald, 1980b). Earlier work showed other samples to have CT less than 24 hr (Sibbald, 1979a). It, therefore, seemed appropriate to use oats, varying greatly in proximate composition, to identify the variables affecting CT. Three experiments were conducted. In the final experiment the excretion of wheat, dehydrated alfalfa, and fish meal residues was compared with that of oat residues to determine if the same variables affected CT.
Research
MATERIALS AND METHODS
Three experiments were made with adult, 2136
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ABSTRACT Three experiments were made with adult White Leghorn cockerels to study the passage of feed residues through the alimentary canal. The birds were starved for 24 hr and then force-fed known quantities of feedingstuffs. Excreta were collected quantitatively at 2 hr intervals during the light periods, dried, and weighed. In the first two experiments the birds received 12 hr of light daily while in the third experiment continuous light was used. Residues of oats fed at levels ranging from 6 to 30 g/bird appeared in the excreta within 2 hr and continued to be voided for 52 hr. The rate and duration of residue output were functions of residue input; this was true for, wheat, fish meal, and dehydrated alfalfa as well as oats. For practical purposes the clearance times were substantially less than 52 hr for most of the inputs studied. (Key words: appearance time, clearance time, time of passage, definitions, excreta, oats, hull-less oats, wheat, fish meal, dehydrated alfalfa)
PASSAGE OF FEED RESIDUES
treatment groups. Treatments 1 to 6 involved inputsof0,6, 12, 18, 24, and 30g, respectively, of oats (Sample 4) marked with stained particles and cold pelleted. Treatments 7, 8, and 9 were 24 g of wheat, 18 g of fish meal, and 12 g of dehydrated alfalfa, respectively, all fed as pellets. The oats were ground and passed through a series of sieves. Particles which passed through a #12 sieve but which were retained by a #30 sieve were removed and stained with basic fucsin as described by Castle (1956). The stained particles were added back to a portion of the recombined sieve fractions to produce a concentration of 1% by weight. The sieving step was introduced to avoid the cooking of fines, which tend to inhibit filtration. Each excreta sample from each bird fed oats was weighed and then made into a slurry with water. Each slurry was poured onto a piece of cheesecloth stretched over an embroidery hoop. The cheesecloth was washed with a stream of water, and the number of stained particles (<5, >5, <10, >10) remaining on the cloth was noted. No attempt was made to measure a passage time, as was done by Sibbald (1979c), because of the confounding effect of the metabolic plus endogenous wastes (Sibbald, 1979a). RESULTS AND DISCUSSION The physical and chemical characteristics of the oats are described in Table 1. Before grinding there were large differences in bulk densities and 1,000 kernel weights, but there is no reason to believe that they had a direct
TABLE 1. Physical and chemical characteristics of the oats Sample no.
1
2
3
4
5
6
Variety Bulk density (kg/hl) b 1000 kernels (g) b Gross energy (kcal/g) Dry matter (%) Ether extract (%) Crude fiber (%) Crude protein (N X 6.25%) Ash (%) Calcium (%) Phosphorus (%)
Vicar* 65.7 21.6 4.30 88.3 5.94
Garry 58.0 27.6 4.19 89.6 4.72
Kelsey 51.5 31.0 4.22 89.9 5.64
Scott 44.5 33.6 4.18 88.8 3.92
Condor 39.9 27.7 4.14 88.5 4.75 11.4
Garry 32.9 29.0 4.20 90.2 3.45 15.6 10.8 3.50 .139 .424
This is a hull-less variety. Measured prior to grinding.
1.9
16.0 1.85 .088 .415
7.5
13.6 2.95 .066 .349
8.1
12.4 3.12 .088 .261
9.5
12.8 2.70 .099 .373
9.6
3.25 .050 .513
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White Leghorn cockerels of the Kentville Control strain drawn from a single population. The birds were individually housed in wire cages in a windowless room with continuous access to fresh water. In the first two experiments the birds received 12 hr of light daily (0600 to 1800 hr); in the third experiment the birds were acclimatized to and received continuous light. The birds were starved for 24 hr, starting at 0800 hr, and were then weighed and force-fed the appropriate ration. Excreta voided were collected quantitatively at 2 hr intervals during the light periods for 52 hr. The excreta samples were frozen, dried in a forced-draft air oven at 80 C for 18 hr, and weighed. Experiment 1. Six samples of ground oats were each fed to six randomly selected cockerels; the input was 30 g/bird. Subsamples of the oats were assayed for proximate composition (AOAC, 1975) and gross energy. Cumulative dry matter excretion was measured for each bird. Experiment 2. Three samples of ground oats, selected on the basis of residue yield from those used in Experiment 1, were each fed at two levels of six randomly selected birds. The levels of input were calculated to yield amounts of excreta dry matter similar to those resulting from 30 g of low and high fiber oats (Samples 1 and 6). The two levels were 30 and 56, 21 and 38, and 16 and 30 g/bird of oat Samples 1, 4, and 6, respectively. Experiment 3. Four birds, from the middle weight range of the population were assigned to each of nine treatments. The selection was made to minimize variation within the smaller
2137
SIBBALD
2138
Y = 16.02+ Y=
2.26 X 2
1.82 + 16.40 X2
The correlation coefficients were r Y x ,
=
-859
and r w . = .796 both at 32 DF; the multiple YX2 correlation coefficient R Y . X J X J = .860 was similar to r Y X , and reflects the close correlation between crude fiber and ash ( r x x .904 at 4DF). There was variation among the crude protein values of the oats, but partial correlations with protein were no better than the simple correlations described above. No pair of the parameters listed in Table 1 could account for more of the variation than crude fiber alone. While crude fiber and ash largely determined the weight of feed residues voided, the other indigestible constituents should not be neglected. During the first 2 hr after feeding, the excreta outputs were similar among the six groups. Differences then developed, indicating the appearance of oat residues, but it was not until 22 hr postfeeding that the final pattern of excreta output was established. From 22 to 52 hr the amount of excreta increased with the crude fiber and ash content of the oats, suggesting that the CT might increase with the amount of residues to be voided. Mean dry matter output during the final 2 hr ranged from .22 to .45 g. There were no distinct trends associated with crude fiber input or with
TABLE 2. Mean cumulative dry matter excretion (Experiment I) expressed as weight and as a percentage of the total
Sample Input /bird no.
No. of observations
Time after feed input (hr) 2
8
6
4
10
22
24
26
(g) 1 2 3
30 30 30
6 6 6
Mean (g)
.65
SEM
.140
Mean (g)
.67
SEM
.135
Mean (g)
.47
SEM
.096
4
30
5
Mean (g)
.43
SEM
.042
5
30
6
Mean (g)
.45
SEM
.077
Mean (g)
.40
SEM
.037
6
1 2 3 4 5 6
30
30 30 30 30 30 30
5
6 6 6 5 6 5
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
5.8 4.6 2.9 2.6 2.7 1.9
1.50 .134 1.33 .188 1.24 .107 1.77 .192 2.10 .254 1.28 .164 13.5 9.0 7.6
10.9 12.4 6.2
2.07 .220 1.86 .330 1.96 .197 2.73 .380 3.43 .457 2.33 .358 18.6 12.7 12.0 16.8 20.3 11.2
3.04 .328 2.94 .531 2.98 .282 4.06 .561 4.94 .561 3.87 .327 27.3 20.0 18.2 25.0 29.3 18.6
3.63 .353 3.81 .600 4.06 .303 4.85 .742 5.76 .594 5.01 .404 32.6 25.9 24.8 29.8 34.2 24.1
7.49 6.72 .381 .343 9.12 7.80 1.205 1.110 9.42 7.91 .687 .709 8.51 9.66 .826 .812 8.82 10.04 .689 .691 9.81 10.99 .948 1.057 60.3 53.1 48.4 52.3 52.3 47.2
67.2 62.1 57.6 59.4 59.5 52.8
7.99 .276 9.86 1.209 10.45 .644 10.38 .901 10.80 .634 12.40 1.153 71.7 67.1 63.9 63.8 64.0 59.6
(continued)
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effect on CT. Gross energy and dry matter values were similar between grains, and although ether extract and ash values varied relatively, the absolute amounts were not very different. The major differences among the oats were in crude fiber and crude protein content. The mean initial body weights were 2.3 5, 2.37, and 2.38 in Experiments 1, 2, and 3, respectively. Analysis of variance demonstrated that the differences among treatment means, within an experiment, were not significant (P>.05). Experiment I. Data describing the cumulative dry matter excretions are presented in Table 2. Single birds in groups fed oats 4 and 6 regurgitated; data obtained from them are omitted from the table. The amount of excreta voided from 0 to 52 hr (Y) increased with the inputs (g/bird) of crude fiber ( X t ) and ash (X 2 ). Linear regression analyses produced the following equations:
2139
PASSAGE OF FEED RESIDUES TABLE 2. (continued) Mean cumulative dry matter excretion (Experiment 1) expressed as weight and as a percentage of the total
Sample Input /bird no.
No. of observa tions
Time after feed input (hr) 28
30
32
34
46
48
50
8.40 .198 10.51 1.210 11.34 .635 11.10 .979 11.58 .612 13.15 1.207
8.64 .186 11.07 1.225 12.06 .582 11.70 1.006 12.29 .613 13.90 1.220
8.90 .170 11.52 1.114 12.89 .600 12.34 1.034 13.01 .557 14.82 1.138
9.15 .242 11.96 1.085 13.28 .550 12.77 1.006 13.46 .611 15.93 1.095
10.28 .284 13.54 1.004 14.99 .675 15.04 .780 15.50 .507 18.77 .909
10.56 .328 14.04 .998 15.62 .704 15.42 .813 16.10 .510 19.66 .876
10.92 .400 14.30 .983 16.03 .722 15.98 .810 16.52 .483 20.35 .833
75.4 71.5 69.4 68.3 68.7 63.2
77.6 75.4 73.8 72.0 72.9 66.8
79.9 78.4 78.8 75.9 77.2 71.2
82.1 81.4 81.2 78.5 79.8 76.6
92.3 92.2 91.7 92.5 91.9 90.2
94.8 95.6 95.5 94.8 95.5 94.5
98.0 97.3 98.0 98.3 98.0 97.8
52
(g) 1
30
6
Mean (g) SEM
30
6
Mean (g)
3
30
6
Mean (g)
4
30
5
Mean (g)
5
30
6
Mean (g)
6
30
5
SEM SEM SEM SEM
Mean (g) SEM
1 2 3 4 5 6
30 30 30 30 30 30
6 6 6 5 6 5
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
52 hr excreta output. Analysis of variance showed that treatment differences were not significant (P>.05). There were significant (P<.01) differences among treatments in the amount of excreta voided during the final 4 and 6 hr periods. Most of the difference during the final 4 hr was due to the relatively large excreta output of the birds fed oat sample 6. This was the most fibrous sample and produced the greatest quantity of residues. It is probable that most of the excreta produced by the other five groups consisted of metabolic and endogenous wastes. Excreta outputs during the final 6 hr tended to parallel the 52 hr excreta outputs. These observations support the hypothesis that CT is largely determined by the quantity of residues to be voided. Experiment 2. The second experiment was designed to test the above hypothesis. Samples of oats 1, 4, and 6 were fed at two levels (Table 3) estimated to yield amounts of residues equivalent to those from 30 g of oats 1 and 6, respectively. Assuming that birds fed 30, 21, and 16 g of oats 1, 4, and 6, respectively, produced equal amounts of excreta, then each oat should have the same CT.
100.0 100.0 100.0 100.0 100.0 100.0
The mean cumulative dry matter excretions, expressed in absolute amounts and percentages, are displayed in Table 3. Data describing 8 of the original 36 birds were discarded because of either regurgitation (2) or crop impaction at 48 hr (6). The latter was a major problem throughout the experiment. Large differences in the rate of excreta output were noticed early in the experiment. The crops of the birds were palpated 24 hr after force-feeding and lumps of feed were detected in 12 birds. Birds of all treatments were affected, but the problem was most severe among the high residue input groups. The distribution of the impactions was as follows: oats 6, 30 g, 4; oats 6, 16 g, 1; oats 1, 56 g, 2; oats 1, 30 g, 1; oats 4, 38 g, 2; oats 4, 21 g, 2. The crops were palpated again at the conclusion of the experiment, and lumps of feed were detected in six birds; several other birds may have had feed residues in their crops, but they could not be detected by palpation. The cumulative excreta outputs at 52 hr differed between the high and low levels of input (P<.01) and also between oats (P<.01). Apparently the residue output from oat sample 1 was overestimated, because at the high level
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2
11.14 .386 14.69 .999 16.35 .736 16.26 .774 16.86 .470 20.80 .828
2140
SIBBALD particularly when reference was made to the cumulative total output. Experiment 3. One of the difficulties associated with the first two experiments was the continuity of the data caused by the interruption of the dark periods. Recently, Squibb and Collier (1979) suggested that the movement of materials through the alimentary tract should be more uniform under continuous light. For these two reasons it was decided to conduct the experiment under continuous illumination. In an attempt to avoid crop impaction all feedingstuffs were pelleted; this was successful. Of the 20 birds fed oats, 10 excreted stained particles within 2 hr of feeding; in only one bird was the appearance delayed until the third excreta collection. There was no clear evidence that AT was related to the amount of the input. Stained particles were excreted by 17 birds during the final 2 hr (50 to 52 hr postfeeding) of the experiment, but the concentrations were low and most birds had several prior excretions in which stained particles were not detected. The postpeak output of particles may be likened to continuous dilution with ever decreasing amounts being voided for an indefinite period. Balch (1950) and Castle (1956)
TABLE 3. Mean cumulative dry matter excretion (Experiment 2) expressed as weight and as a percentage of the total
Sample Input no. /bird
No. of observations
Time after feed input (hr) 4
2
6
10
8
22
24
26
(g) 1 4 6 1 4 6
1 4 6 1 4 6
30 21 16 56 38 30
30 21 16 56 38 30
6 5 4 5 3 5
6 5 4 5 3 5
Mean (g)
.36
SEM
.128
Mean (g)
.70
SEM
.175
Mean (g)
.28
SEM
.027
Mean (g)
.38
SEM
.133
Mean (g)
.70
SEM
.099
Mean (g)
.65
SEM
.113
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
3.2 4.9 2.0 2.2 3.5 3.3
1.21 .262 1.58 .307 1.49 .242 1.86 .238 1.74 .339 1.71 .544 10.9 11.1 10.9 10.8 8.7 8.6
2.02 .335 2.94 .252 2.58 .417 2.72 .263 2.86 .624 2.98 .707 18.3 20.7 18.9 15.7 14.2 15.0
2.84 .524 3.70 .311 3.80 .477 4.03 .535 4.19 .794 4.11 .963 25.7 26.0 27.9 23.3 20.9 20.6
3.76 .617 4.29 .405 4.72 .458 5.05 .562 5.22 .824 5.09 1.073 34.0 30.2 34.6 29.2 26.0 25.6
7.02 6.27 7.38 .727 .750 .758 6.96 7.82 8.74 .615 .698 .518 8.16 9.04 9.76 .675 .604 .581 9.11 10.55 11.70 .643 .647 .563 9.18 10.57 11.49 .959 1.084 1.142 9.97 11.18 12.18 2.002 2.200 2.281 56.7 48.9 59.9 52.6 45.8 50.1
63.5 55.0 66.3 61.0 52.7 56.2
66.7 61.5 71.6 67.6 57.3 61.2 (continued)
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of input, the 52 hr excreta output was substantially less than from the high inputs of oats 4 and 6 (17.3 cf 20.1 and 19.9g). One difficulty in estimating inputs required to produce a particular output is that excreta consist of feed residues and metabolic plus endogenous wastes; unless these can be partitioned such estimates are unlikely to be accurate. Agreement between experiments was satisfactory. In Experiments 1 and 2, 30 g of oats 1 yielded 11.14 and 11.06 g of excreta dry matter, respectively; comparable data for 30 g of oats 6 were 20.80 and 19.91 g. As in the first experiment, excreta outputs of the six groups were similar during the first 4 hr, although the high input groups produced slightly more excreta than the low input groups. By 6 hr postfecding, there was a distinct difference between the high and low groups which continued throughout the experiment. During the final 2 hr, the birds on the high inputs voided more excreta than those on the low inputs (P<.01), but there were no significant differences among oats within input levels. This suggests that the high input was associated with a greater CT and provides support for the hypothesis. Examination of data for other time periods tended to confirm this interpretation
2141
PASSAGE OF FEED RESIDUES TABLE 3. (continued) Mean cumulative dry matter excretion (Experiment 2) expressed as weight and as a percentage of the total
Sample Input /bird no.
No. of observa tions
Time after feed input (hr) 28
30
32
34
46
48
50
7.84 .673 9.53 .445 10.37 .492 12.47 .483 12.48 1.057 13.11 2.260
8.18 .655 10.07 .547 10.89 .444 13.15 .441 13.40 1.008 13.86 2.160
8.45 .656 10.64 .481 11.23 .431 13.68 .422 14.12 .875 14.54 2.040
8.76 .607 11.08 .450 11.43 .445 14.13 .384 14.83 .664 15.09 2.059
10.24 .538 12.90 .412 12.82 .574 16.14 .524 18.29 .743 18.02 1.469
10.57 .560 13.45 .448 13.10 .587 16.56 .564 19.08 .499 18.76 1.418
10.84 .568 13.78 .446 13.38 .598 16.83 .568 19.47 .610 19.30 1.438
70.9 67.0 76.1 72.1 62.2 65.8
74.0 70.8 79.9 76.0 66.8 69.6
76.4 74.8 82.4 79.1 70.4 73.0
79.2 77.9 83.8 81.7 73.9 75.8
92.6 90.7 94.0 93.3 91.2 90.5
95.6 94.6 96.1 95.7 95.1 94.2
98.0 96.9 98.2 97.3 97.0 96.9
52
(g) 1
30
6
Mean (g) SEM
Mean (g)
21
5
6
16
4
Mean (g)
1
56
5
Mean (g)
4
38
3
Mean (g)
6
30
5
SEM SEM SEM SEM
Mean (g) SEM
1 4 6 1 4 6
30 21 16 56 38 30
6 5 4 5 3 5
Mean Mean Mean Mean Mean Mean
(%) (%) (%) (%) (%) (%)
observed a similar effect in work with ruminants and, in some calculations, discounted the "tails" of cumulative excretion curves. The absolute CT for oats under the conditions of this experiment was greater than 52 hr; however, for practical purposes it was much less, as will be shown. The mean cumulative excreta dry matter data were arranged in the same manner as the data of Table 2. This revealed that within 4 hr postfeeding the excreta outputs of birds on treatments 1 to 6 increased with the oat input. To test this the cumulative excreta dry matter values for each bird on each of the six treatments at each time postfeeding were regressed on the oat inputs. The results are summarized in Table 4. The correlation coefficients increased for 24 hr and then remained relatively constant. The intercepts were estimates of the metabolic plus endogenous excreta outputs and were similar to the mean values of the negative control birds on which they were regressed: Y = .952 X = .069; r = .998 at 24 DF. The regression coefficients were estimates of the amount of residues voided per gram of oat input. The coefficients increased in a curvilinear manner, suggesting that the residues were excreted rapidly during the first 18 hr postfeed-
100.0 100.0 100.0 100.0 100.0 100.0
ing and then at a diminishing rate; this is compatible with the concept of continuous dilution. However, the effect is complicated, because in addition to changes in time there were differences in the oat inputs, and excreta outputs, between treatment groups. The cumulative data suggest that birds which received the most oats took the most time to void the oat residues; this accentuated the curvilinearity of the regression coefficients. Within 4 hr of feeding, the cumulative dry matter excretions tended to reflect the 52 hr outputs. To test this, the cumulative excreta dry matter values for each bird on each of the treatments at each time postfeeding were regressed on the 52 hr cumulative excreta outputs. The results are presented for treatments 1 to 6 and 1 to 9 in Table 4. The correlation coefficients increased rapidly with the time after feeding and confirmed the linearity of the relationships. The regression coefficients increased in a curvilinear manner approaching unity as time progressed. The most interesting results of the analyses are the intercepts which decreased rapidly until 18 hr postfeeding and then began to increase. The changes suggest that in absolute terms, the cumulative excreta outputs for the treatments were similar for the
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4
11.06 .562 14.22 .490 13.63 .634 17.30 .554 20.06 .647 19.91 1.293
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SIBBALD TABLE 4. Relationships between cumulative dry matter excretion (Y), air dry oat input and total excreta output (X2) Regression of Y on x. Treatments 1 to 6 f
YX! (22 df)
Intercept
coef
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52
.305 .844 .882 .926 .932 .954 .953 .958 .962 .964 .972 .978 .981 .981 .980 .981 .979 .984 .983 .983 .983 .982 .982 .983 .980 .979
-.031 .934 1.200 1.410 1.618 1.846 1.988 2.127 2.380 2.646 2.863 3.048 3.190 3.449 3.612 3.866 4.091 4.330 4.548 4.802 5.025 5.282 5.485 5.688 5.909 6.094
.063 .052 .114 .169 .222 .245 .265 .283 .301 .304 .311 .319 .325 .327 .333 .335 .339 .346 .347 .349 .352 .350 .353 .353 .357 .359
Reg
Regression of Y on X2 Treatments 1 to 6 r
YX 2 (22 df) .157 .829 .861 .908 .916 .936 .937 .948 .948 .952 .967 .977 .983 .984 .988 .992 .993 .997 .997 .998 .998 .998 .999 .999 1.000
first few hours (2 to 4) and then diverged until about 18 hr postfeeding when they started to converge and assume parallel relationships. A bird receiving a large quanitity of a feed excreted the residues more rapidly and over a longer period than a bird receiving less of the same feed. The approach to parallel relationships was observed in earlier experiments and can be seen in the figures of Sibbald (1979a). The results of the analyses for treatments 1 to 6 are similar to those for treatments 1 to 9, suggesting that the relationships discussed above were not limited to oats but applied to a variety of feedingstuffs. The excreta output data were rearranged to permit examination of changes during the concluding periods of the experiment. There were differences in excreta outputs among treatments, but during the final 16 hr of the experiment they were small. Analyses of variance were made of the data for all treatments for each period prior to completion. During the final 36 hr there were no significant
Regression of Y on X 2 Treatments 1 to 9
Inter cept
coef
YX 2 (34 df)
.372 .108 -.570 -1.237 -1.861 -1.996 -2.191 -2.392 -2.373 -2.200 -2.158 -2.150 -2.130 -1.918 -1.891 -1.714 -1.584 -1.443 -1.257 -1.059 -.882 -.615 -.455 -.252 -.144
.011 .141 .303 .451 .590 .654 .710 .763 .806 .820 .844 .869 .888 .895 .914 .924 .936 .954 .958 .966 .974 .971 .978 .978 .994
.288 .663 .729 .831 .880 .903 .925 .937 .945 .951 .968 .973 .976 .985 .988 .991 .993 .996 .997 .998 .998 .998 .999 .999 1.000
Reg
r
Inter cept
coef
.214 .159 -.057 -.649 -1.333 -1.687 -2.191 -2.422 -2.363 -2.261 -2.313 -2.238 -2.235 -2.036 -1.941 -1.780 -1.623 -1.435 -1.301 -1.084 -.876 -.649 -.502 -.368 -.176
.026 .129 .245 .388 .537 .621 .715 .773 .809 .827 .860 .878 .897 .906 .919 .929 .940 .954 .965 .969 .973 .976 .983 .991 .997
Reg
(P>.05) differences among treatments; during the final 38 hr, there was a significant effect (P<.05), and this became highly significant (P<.01) for the remaining time periods (40 to 52 hr). Multiple range tests confirmed that excreta outputs increased with oat inputs (treatments 1 to 6). Analysis of variance may have lacked the sensitivity to detect trends in excreta outputs between treatments in the final phases of the experiment. Therefore, it was decided to apply linear regression analysis in much the same manner as shown in Table 4. The excreta dry matter outputs of all birds for a particular time period were regressed on their total 52 hr outputs. The results are summarized for treatments 1 to 6 and 1 to 9 in Table 5. Most of the correlation coefficients are significant, but it is apparent that excreta output during the final hours of the experiment bore little relationship to the cumulative 52 hr output. The intercepts tend to mirror those of Table 4. The
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Hours after feeding
(X,),
PASSAGE OF FEED RESIDUES
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TABLE 5. Relationships between excreta outputs in periods prior to completion and total excreta output Time to completion of experiment (h)
Treatments 1 to 9 Reg
r
(22 df)
Intercept
coef
(34 df)
Intercept
coef
.273 .459 .412 .484 .419 .518 .484 .511 .500 .544 .510 .549 .562 .569 .575 .566 .581 .678 .741 .815 .846 .935 .968 .994 .996
.144 .193 .455 .615 .882 1.059 1.257 1.443 1.584 1.714 1.891 1.918 2.130 2.150 2.156 2.200 2.373 2.392 2.191 1.996 1.861 1.237 .507 -.108 -.199
.0064 .0245 .0215 .0289 .0261 .0339 .0415 .0460 .0635 .0764 .0863 .1053 .1123 .1306 .1565 .1802 .1935 .2366 .2904 .3458 .4097 .5492 .6971 .8594 .9694
.108 .287 .317 .395 .380 .435 .417 .477 .476 .498 .496 .504 .464 .508 .529 .541 .563 .618 .698 .788 .847 .921 .957 .986 .995
.176 .282 .502 .649 .876 1.084 1.301 1.435 1.623 1.780 1.939 2.036 2.235 2.238 2.311 2.261 2.363 2.422 2.190 1.687 1.333 .694 .057 -.160 -.160
.0029 .0146 .0168 .0238 .0267 .0310 .0350 .0462 .0597 .0710 .0814 .0937 .1034 .1222 .1400 .1728 .1911 .2272 .2852 .3786 .4631 .6124 .7554 .8706 .9617
regression coefficients indicate that only a small quantity of excreta were voided during the final phases of the experiment. The first experiment involved feeding equal weights of six samples of oats which, during the 52 hr excreta collection period, yielded different quantities of excreta. There was evidence that oat residues were voided within 6 hr postfeeding and that the CT was 50 hr or less. It appeared that the CT was a function of the amount of residues to be voided. The findings of the second experiment were distorted to some degree by the problem of crop impaction, but the AT appeared to be less than 6 hr. The birds which received the most residues excreted them at a greater rate over a longer period than the birds which received lesser amounts. The CT was not established, but for the high residue inputs it appeared to exceed 52 hr. The final experiment was conducted under continuous light, which permitted excreta collection every 2 hr. By the use of stained particles it was found that AT was less than 2 hr and CT was more than 5 2 hr. However, the amounts of feed
Reg
residues voided in the latter hours of the experiment were small. Confirmed was the finding that rate and duration of residue output is a function of residue input. The relationship held not only for oats but also for wheat, fish meal, and dehydrated alfalfa. There may, be various other factors which affect the passage of feed residues, but the results indicate residue input to be a primary determinant. The AT can be measured with some degree of confidence by the use of stained particles. The absolute CT can be determined by the same procedure; however, if the birds receive a single input of feed, as in these experiments, they could die of starvation before the CT is reached. For purposes of the TME, TAAA, and similar bioassays, the CT may be defined as the time after feeding at which subsequent residue output is too small to have a measurable effect on the data obtained. In Table 4 it is shown that 1 g of oats yielded .319, .346, and .353 g of residues at 24, 36, and 48 hr after feeding, respectively. A TME bioassay based on a 24 hr excreta collection, as originally suggested
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2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Treatments 1 to 6 r
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SIBBALD
ACKNOWLEDGMENT The autlior wishes to thank S. Tobin for her able technical assistance. REFERENCES Association of Official Analytical Chemists, 1975.
Official methods of analysis. 12th ed. AOAC, Washington, DC. Balch, C. C , 1950. Factors affecting the utilization of food by dairy cows. 1. The rate of passage of food through the digestive tract. Brit. J. Nutr. 4:361-388. Castle, E. J., 1956. The rate of passage of foodstuffs through the alimentary tract of the goat. 1. Studies on adult animals fed hay and concentrates. Brit. J. Nutr. 1 0 : 1 5 - 2 3 . National Academy of Sciences, 1971. Atlas of nutritional data on United States and Canadian feeds. Nat. Acad. Sci. Washington, DC. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:303—308. Sibbald, I. R., 1979a. Passage of feed through the adult rooster. Poultry Sci. 58:446-459. Sibbald, I. R., 1979b. A bioassay for available amino acids and true metabolizable energy in feedingstuffs. Poultry Sci. 58:668-673. Sibbald, 1. R., 1979c The effect of the duration of the excreta collection period on the true metabolizable energy vales of feedingstuffs with slow rates of passage. Poultry Sci. 58:896— 899. Sibbald, I. R., 1979d. Effect of level of feed input, dilution of test material and duration of excreta collection on true metabolizable energy values. Poultry Sci. 58:1325-1329. Sibbald, I. R., 1980a. The clearance time and rate of passage of feed residues. Poultry Sci. 59:374— 377. Sibbald, I. R., 1980b. The effects of dietary cellulose and sand on the combined metabolic plus endogenous energy and amino acid outputs of adult cockerels. Poultry Sci. 59:836-844. Squibb, R. L., and G. H. Collier, 1979. Feeding behavior of chicks under three lighting regimes. Poultry Sci. 58:641-645.
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(Sibbald, 1976), would underestimate the energy excretion and give an inflated TME value. Bioassays have demonstrated this for oats and for several other feedingstuffs which yield large amounts of residues (Sibbald, 1979c,d; 1980b). The results of the present experiments indicate that TME assays for some oats should use excreta collection periods greater than 24 hr; for very fibrous oats a 48 hr collection should be adequate. The measurement of PT was not attempted in the present work, but it is a parameter of interest, particularly under conditions of ad libitum feeding. Castle (1956) calculated a PT (R) which was defined as the sum of the times for 10% increments of cumulative excreta output, from 5 to 95%, divided by 10; this effectively removed the problem of prolonged CT. The same approach was used in poultry by Sibbald (1980a). The median time might be a good estimate of PT if the cumulative excretion curve is symmetrical, but this in infrequent. There are many ways to define and estimate PT; consequently, it is important that the terminology be clearly defined. The term "rate of passage" is imprecise and can be misleading.