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Efficiency of Feed Utilization and Rate of Feed Passage Through the Digestive System1
Efficiency of Feed Utilization and Rate of Feed Passage Through the Digestive System 1 K. W. WASHBURN Department of Poultry Science, The University of Georgia, Livestock-Poultry Building, Athens, Georgia 30602 (Received for publication April 23, 1990)
1991 Poultry Science 70:447-452 INTRODUCTION
The rate at which feed passes through the digestive tract of pigs appears to be related to the amount of energy derived from the diet (Maner et al, 1962; Kass et al, 1980). For chickens, dietary factors that influence efficiency of feed utilization influence the feed passage rate (FPR) through the digestive system. These include carbohydrates (Monson et al, 1950), sugars (Stokstad et al, 1953), and dietary fats (Mateos and Sell, 1981; Mateos et al, 1982). These studies have led to the conclusion that the FPR through the digestive tract should be an important factor influencing the amount of energy derived from the diet. However, in these studies on FPR, the actual efficiency of feed utilization was not determined. Comparing feed-restricted broilers with fullfed broilers, it has been observed that for the week of full feeding after removal from the restricted feeding program, consumption was greater but the gain less than for birds on a continuous full feeding program. This results in a decreased efficiency of feed utilization. A possible explanation for this decreased effi-
Supported by state and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia.
ciency is that the feed restriction affected FPR immediately after returning to full feeding. The primary objective of the present experiment was to determine the relationship of efficiency of feed utilization and feed restriction to rate of passage of feed through the digestive system. A secondary objective was to evaluate three different methods of measuring FPR. MATERIALS AND METHODS
General Procedure The relationship of efficiency of feed utilization to FPR through the digestive system was studied. This was done by comparing strains and sexes differing in efficiency, correlating individual variation in efficiency with FPR, and observing the effects on FPR of restricted feeding regimes that affect efficiency. Management Chickens to be tested were grown in floor pens until 24 days of age at which time they were placed in the individual cage and feeding system described by Guill and Washburn (1972). At 4 wk of age, the collection of body weight, consumption, and feed utilization efficiency data was initiated after removing individual chickens that did not adjust to the cage and
447
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
ABSTRACT The relationship of efficiency of feed utilization determined by the feed conversion ratio (FCR) to the rate of feed passage through the digestive system of juvenile chickens was studied and three different methods of measuring feed passage rate (FPR) were evaluated. The FPR did not differ between sexes that had different FCR, nor did it differ between commercial broiler strains that differed in FCR. Feed restriction did not affect FPR. There was little correlation between FCR and FPR in any of the groups evaluated and the FPR was similar for high- and low-FCR groups. There was some evidence for increased FPR in birds grown at 32.2 C compared with those grown at 26.7 C. Similar results were obtained for FPR whether the tracer dye was given in the feed, or in a gelatin capsule, or no tracer dye was used. Repeatability of FPR obtained on the same individuals at different ages was very low. (Key words: feed passage rate, feed efficiency, broilers, feed restriction, ambient temperature)
448
WASHBURN
feeding system (i.e., little or no feed consumption). Efficiency of feed utilization was determined as the feed conversion ratio (FCR). The chickens were fed the standard University of Georgia starter ration (23% protein; 3,120 kcal/ kg ME) until 24 days of age and the finisher (21.2% protein; 3,256 kcal/kg ME) thereafter. Continuous lighting was used. Determination of Feed Passage Rate
2
Day-Glo Color Corp., Cleveland, OH 44103.
Trial 1 Fifty-four males and 54 females from each of four commercial broiler strains were divided into two experimental groups, full-fed and restricted. The full-fed group was allowed full access to feed from 4 to 8 wk of age. The restricted group was allowed full access to feed on Weeks 4 to 5 and 6 to 7, and access to feed was restricted on alternate days during Weeks 5 to 6 and 7 to 8. Consumption decreased during Weeks 5 to 6 and 7 to 8, and body weight decreased 18 and 13% for these periods, respectively. Body weights and consumption were recorded and FCR calculated weekly. Feed passage rate was determined at 6 and 8 wk of age. An analysis of variance and Duncan's separation of means within ages with sex (1 df), strain (3 df), and feeding regimen (1 df) as main effects, and their interactions were used to determine significance of difference between groups in FCR and FPR. Trial 2 The relationship of FPR with feed intake and FCR was studied in more detail. The general procedure and the method of feed restriction was the same as previously described. Males of a commercial broiler strain were used. The feed restriction periods were from 4 to 5 and 6 to 7 wk of age with ad libitum feeding during 5- to 6-wk and 7- to 8-wk periods. Feed passage rate was determined at 5,6,7, and 8 wk of age. Analysis of variance within ages with feeding regimen (1 df) as a main effect and Duncan's separation of means were used to determine significance of differences between groups. Trial 3 Males and females of commercial broiler Strains A and B (103 or 104 males and females of each strain) were grown under the standard management procedure previously described. All birds were given ad libitum access to feed. Weight gain and feed consumption were determined and FCR calculated over the 4- to 8-wk period. Three methods of measuring FPR were tested using the same birds during the 38 to 49 days of age period, hi Method 1 (Ml), gelatin
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
The FPR was considered as the first appearance of a fluorescent dye after a 12-h restriction followed by a 30-min refeeding period. Cherry and Siegel (1978) have measured both time of first appearance and complete clearance of the tracer. However, most studies (Hillerman et al., 1953; Tuckey et al., 1958; Wilson et al, 1980; Mateos and Sell, 1981; Mateos etal., 1982) used time to first appearance as an indicator of FPR, considering it to be a reliable index. Jensen et al. (1962) plotted the distribution from first appearance to complete disappearance and found that the concentration of the marker followed a normal distribution. The accuracy of visually determining the first appearance of the tracer in the excreta is enhanced if the digestive tract is emptied before the tracer is administered. The restriction times used in various studies have been quite variable, ranging from 2 to 32 h. However, the duration of the starvation period has little affect on TME values (Sibbald, 1976), and a high correlation coefficient between the amount of excreta voided and length of restriction time was reported by Sibbald (1979). Because the results of Sibbald (1979) indicated that birds were voiding excreta at a constant rate (with no feed residues) at 10 h following feed removal, the 12-h period of restriction before administering the tracer was chosen in the present study. The following procedure was used: 1) feed access was restricted for 12 h; 2) birds were returned to feed and each was given a gelatin capsule containing .03 g of fluorescent dye,2 which eliminates the accuracy problems associated with visually scoring the most commonly used tracers, ferric oxide and chromic oxide; 3) dropping pans were cleaned and visually monitored at 15-min intervals, or less, for the first appearance of the dye in the excreta for a maximum time of 300 min. In a small number of individuals, the excreta from the test feeding did
not contain dye or took longer than 300 min so the number of individuals on which data are reported was less than the number of birds tested.
449
EFFICIENCY AND FEED PASSAGE RATE TABLE 1. Feed conversion ratio (FCR) and feed passage rate (FPR) of different strains, sexes, and feeding regimens (Trial J)
Source of variation
FPR, 6 wk
FCR, 7 to 8 wk
FPR, 8 wk
(g:g)
(min)
(g:g)
(min)
2.37" 2.43" 2.62" 2.68" 2.74" 2.34 b 2.41 b 2.69"
228" 228" 228" 218* 208" 227" 225" 217"
2.31" 2.27" 2.03b 2.18b 2.14" 2.19" 2.06b 2.33"
237" 226" 224" 210" 232" 218" 226" 224"
a,b Means in a column within strains, sexes, or feeding regimen with no common superscripts are significantly different (PS.05).
capsules containing .03 g of fluorescent dye were given as a marker after a 30-min period of feeding. In Method 2 (M2), the birds were given access to feed containing .2 g dye per pound (454 g) of feed. In Method 3 (M3), the birds were given access to feed containing no dye. In all methods, access to feed had been restricted for the previous 12 h. The FPR was considered as the minutes to the first appearance of solid dye-colored excreta in Methods 1 and 2 and of solid excreta in Method 3. An analysis of variance and Duncan's separation of means with methods (2 df), strain (1 df), and sex (1 df) as main effects, and their interactions were used to determine significance of differences. Correlations were obtained for the FPR values derived by the three methods and between FPR obtained by the three methods and performance traits. The individuals were grouped into high FCR groups and low FCR groups (25% of the population in each grouping) and their FPR compared. Trial 4 The observation that the correlation between the FPR obtained on the same individuals by the three methods was not high indicated study on the repeatability of the measure was needed. The known effect of high environmental temperature on consumption and personal observation (i.e., aborted trial) that attempts to obtain FPR in birds moved from a relatively cooler environment to a hotter one were unsuccessful, suggested it would be desirable to obtain the repeatability estimates in both a normal and relatively hot environ-
mental temperature. Data on FCR were also collected in this trial so that correlations between FCR and FPR could be determined. Fifty-five males of a single broiler strain were placed in each of two rooms using the individual cage system as previously described. Temperature of one room was maintained at approximately 26.7 C from 3 to 7 wk and another room was maintained at 32.2 C from 3 to 7 wk of age. Individual consumption, gain, and FCR were obtained at weekly intervals from 3 to 7 wk of age. Feed passage rate was determined on all birds at 4,5, 6, and 7 wk of age by the methods previously described. Correlations were obtained within temperature treatments for the 3 to 7 wk FCR and the mean FPR for the 3- to 7-wk period. Repeatability values were calculated for FPR within the environmental temperatures using the formula R = "Vv/Vw + "*E described by Becker (1975), where 7 ^ = M S w - MSfl/ki with ki denoting the number of measurements per individual; MSw denoting the mean squares within; and MS E the mean squares for environment. An analysis of variance and Duncan's separation of means with temperature (1 df), age (3 df), and their interaction were used to test for statistical significance of differences. RESULTS
Trials 1 and 2 The results presented in Table 1 (Trial 1) and Table 2 (Trial 2) indicate a lack of association between FPR through the digestive system and
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
Strain A B C D x Restricted group x Full-fed group x Male x Female
FCR, 5 to 6 wk
450
WASHBURN
TABLE 2. Effect of feed restriction on feed conversion ratio (FCR) and feed passage rate (FPR) (Trial 2) FCR1 Age (wk) 4 to 5 to 6 to 7 to
n
R
5 110 6 110 7 101 8 75
FFR
FF
R
(g:g) 2.19 s2 2.28* 2.13' 1.91b 1.45b2 1.72' 2.83' 2.32b
166' 177' 213' 188'
FF (min) 174' 175* 209' 185'
efficiency of feed utilization. These results also indicate that the restriction of feed used in the present study did not affect the FPR. Consequently, changes in FPR of the digestive system do not appear to be the reason for the differences sometimes observed in efficiency of restricted and full-fed groups. In Trial 1 the FPR was not significantly different between strains even when the strains differed significantly in FCR (Table 1). There was no significant difference between males and females in FPR although they differed significantly in FCR. The FPR was not significantly different between full-fed groups and groups whose consumption had been restricted the previous week, and there were no trends toward higher or lower FPR for the two feeding regimens (compared with the full-fed group the restricted group had lower FPR at 6 wk, but higher FPR at 8 wk). The phenotypic correlations between FPR and FCR were low and nonsignificant (.14 for the 5- to 6-wk data and .09 for the 7- to 8-wk data).
Trial 3 Data presented in Table 3 indicate that the three methods (dye in gelatin capsules, dye in feed, or no dye) gave comparable results. Although the differences are statistically significant, they are small and comparable to differences observed between repeated measures on the same individual using the same technique. The coefficient of variation was less in the no dye method. The labor required for using the dye in the capsule method is much greater than the other methods and it is more difficult to keep accurate individual time records. The no dye method appears to be the method of choice if individual cages are used and the dropping pans are easily observed as they were in the facility used in this experiment. The correlations between the different methods, although statistically significant (PS.01) were in the low (.19) to moderate (.37) range. The correlations between methods for males and females, respectively, were as follows: Ml and M2, .26 and .19; Ml and M3, .37 and .24; and M2 and M3, .20 and .20. Differences between the methods were consistent for both sexes and for both strains. There were no significant differences in FPR between the two broiler strains. Strain B was a significantly faster growing strain that consumed significantly more feed, yet differences between the strains in FCR were not significant (Table 4). There were also no significant differences in FPR between males and females that differed in FCR. There were no significant correlations of FPR obtained by any of the three methods with gain or consumption (Table S).
TABLE 3. Feed passage rate in minutes of broiler strains and sexes obtained by three methods (Trial 3) Strain A
Strain B
Method
Male
Female
x
Male
Female
x
x
(CV)
1 2 3
214 200 218
209 205 218
212 202 218
216 206 218
210 205 219
213 205 218
212' 203 b 218°
(19.6) (18.3) (13.5)
:
Means for methods with no common superscripts are significantly different (P£.05).
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
a b - Means for FCR or FPR between restricted and full-fed groups within ages with no common superscripts are significantly different (P<.05). R = group restricted from 4 to 5 and 6 to 7 wk and fullfed from 5 to 6 and 7 to 8 wk; FF = group receiving feed ad libitum from 4 to 8 wk. 2 Period of restricted feeding.
In Trial 2, the FPR was obtained at the end of the full-fed periods as well as the restricted periods. There were no significant differences in FPR between restricted and full-fed groups at any of the weekly periods of restriction or full feeding, although the FCR differed between groups (Table 2).
451
EFFICIENCY AND FEED PASSAGE RATE
TABLE 4. Consumption, gain, and feed conversion ratio (FCR) for broiler strains and sexes (Trial 3) Gain
Consumption Strain
Male
Female
A B x
1,936 2,141 2,041"
(g) 1,653 l,879 u 1.764b
958 1,036 999"
1,789" 2,012" 1,901
FCR
Female
Male
— (g) 759 860 808 b
Male 855 b 950" 903
Female -
2.03 2.08 2.05 b
2.11" 2.14"
"•"Means with no common superscripts are significantly different (P<.05).
Trial 4 The FPR was significantly higher in the birds grown at 32.2 C than in those grown at 26.7 C when analyzed over the 4-wk period of determination (Table 6). Means for the 32.2 C environment were consistently higher than those of die 26.7 C environment, but differences were significant only for values obtained at 5 wk of age. There were significant differences in FPR for the different ages, but there was no evidence of increasing or decreasing FPR with age. Repeatability of FPR was very low in both temperature regimens (R = .056 for 26.7 C and .0003 for 32.2 Q , and there was no significant correlation of 4- to 7-wk FCR with die mean FPR in either regimen (.11 in 26.7 C and .09 in 32.2 C). TABLE 5. Correlation of three methods (Ml, M2, M3) of measuring feed passage rate to performance traits of gain, consumption (Cons), and feed conversion ratio (FCR) (Trial 3) Females
Males Trait
Ml
M2
M3
Ml
M2
M3
Gain Cons FCR
-.09 .02 .15*
.08 .13 .08
-.16 .01 .22**
-.08 -.08 .03
.11 -.01 -.12
.00 -.08 -.08
*K.05. **PS.01.
DISCUSSION
It has been hypothesized that a slower FPR through die digestive system could increase the utilization of feed in tiiree ways: 1) increasing die time nutrients are in contact wiui absorptive cells, which should increase nutrient absorption; 2) altering die microbial population mat could affect the utilization of nutrients; and 3) influencing feed intake. It has also been hypotiiesized mat a faster FPR could be associated with increased utilization of feed if me FPR is considered an indicator of die efficiency of die digestive system. These conclusions were derived from studies on FPR in which efficiency of feed utilization was not determined. The results of the present study in which FPR and FCR were determined on die same individuals suggest mat neitiier of die hypouieses concerning die association of FPR and efficiency is valid, ratiier die FPR (of young chickens receiving a normal diet) does not affect efficiency at all. There is some inconclusive evidence tiiat feed intake may influence FPR. Sibbald (1979) TABLE 6. Feed passage rate (FPR) obtained at 4 to 7 wk from individuals maintained in two temperature environments (Trial 4)
Age
26.7 C
(wk) 4 5 6 7
207 235 209 181
X
208 b
± ± ± ±
Environmental temperature 325 C
22" 27 b 39" 24"
212 267 212 188
± ± ± ±
23" 29" 47" 28"
209y 25 l x 203? 185z
223*
*^*Means between environments within ages with no common superscripts are significantly different (K.05). ^y^Means for ages with no common superscripts are significantly different (PS.05). 'Means of individuals ± SD.
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There was some evidence of a positive correlation of FPR determined by Methods 1 and 3 with FCR in die males. Aldiough statistically significant, the correlations were low (.15 and .22). If the mean correlation over both sexes and three methods (y= .05) is considered the most reliable, then there was no correlation of FPR with FCR. There was no difference in FPR between the individuals classified into high-FCR (213 min) or low-FCR (210 min) groupings, aldiough the groups differed significantly in FCR (2.25 for the high-FCR group and 1.99 for the low-FCR group).
452
WASHBURN
values are normally expected at younger than at older ages. In the present study the restriction of feed at various ages affected the FCR and had a confounding affect on the association of age on FCR. Li addition, during the 1st wk (youngest age), the process of adjusting to the cages may result in decreased growth and consumption, resulting in abnormal FCR values. REFERENCES Becker, W. A., 1975. Manual of Quantitative Genetics. 3rd edition. Washington State University, Pullman, WA. Cherry, J. A., and P. B. Siegel, 1978. Selection for body weights at eight weeks of age. 15. Feed passage and intestinal size of normal and dwarf chicks. Poultry Sci. 57:336-340. Guill, R. A., and K. W. Washburn, 1972. Cages and feed troughs for individual broiler feed consumption experiments. Poultry Sci. 51:1229-1233. HUlerman, J. P., F. H. Kratzer, and W. O. Wilson, 1953. Feed passage through chickens and turkeys and some regulating factors. Poultry Sci. 32:332-335. Jensen, L. S., L. M. Merrill, C. V. Reddy, and J. McGinnis, 1962. Observations on eating patterns and rate of feed passage of birds fed pelleted and unpelleted diets. Poultty Sci. 41:1414-1419. Kass, M. L., P. J. Van Soest, W. G. Pond, B. Lewis, and R. E. McDowell, 1980. Utilization of dietary fiber from alfalfa by growing swine. I. Apparent digestibility of diet components in specific segments of the gastrointestinal tract J. Anim. Sci. 50:175-191. Maner, J. H., W. G. Pond, J. K. Loosli, and R. S. Lowery, 1962. Effect of isolated soybean protein and casein on the gastric pH and rate of passage of feed residues in baby pigs. J. Anim. Sci. 21:49-52. Mateos, G. F., and J. L. Sell, 1981. Influence of fat and carbohydrate source on rate of feed passage of semipurified diets for laying hens. Poultry Sci. 60: 2114-2119. Mateos, G. G., J. A. Sell, and J. A. Eastwood, 1982. Rate of feed passage transit time as influenced by supplemental fat Poultry Sci. 61:94-100. Monson, W. J., L. S. Dietrich, and C. A. Elvhjem, 1950. Studies on the effect of different carbohydrates on chick growth. Proc. Soc. Exp. Biol. Med. 75: 256-259. Sibbaid, I. R., 1976. The effect of the duration of starvation of the assay bird on true metabolizable energy values. Poultry Sci. 55:1578-1579. Sibbaid, I. R., 1979. Passage of feed through the adult rooster. Poultry Sci. 58:446-459. Stokstad, FX.R., T. M. Jukes, and W. L. Williams, 1953. Growth promoting effect of aureomycin on various types of diets. Poultry Sci. 31:1054-1058. Tuckey, R., B. E. March, and J. Biely, 1958. Diet and the rate of feed passage in the growing chick. Poultry Sci. 37:786-792. Wilson, E. K., F. W. Pierson, P. Y. Hester, R. L. Adams, and W. J. Stadelman, 1980. The effects of high environmental temperature on feed passage time and performance traits of White Peking ducks. Poultry Sci. 59:2322-2330.
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
found that when using a force-feeding system, the rate of dry matter excretion of adult White Leghorn males was increased as larger amounts of feed were force-fed. Wilson et al. (1980) reported that restriction of feed intake of Peking ducks for 6 h resulted in a reduction in FPR compared with full-fed ducks. In the present study there was no relationship of restriction of feed or amount of feed consumption to FPR. There is some evidence that high (29.4 C) environmental temperature may cause an increase in FPR of Peking ducks (Wilson et al, 1980) although HUlerman et al. (1953) found no difference in the FPR of chickens maintained at 15.6 or 32.2 C. In the present study there was some evidence for increased FPR in birds raised at higher temperatures, but the differences were not consistent. Li the few studies in which the FPR was repeatedly measured on the same birds, considerable variation was observed and variability was decreased if first appearance of the marker was calculated by averaging data obtained for four periods. A large variability between means obtained on the same birds at different periods, relatively high coefficients of variations, and moderate correlation and low repeatabilities between measures on the same individual were obtained in the present study. Therefore, repeated measures appear to be essential in studies involving FPR. Confounding of time of measuring with treatments and small sample size may lead to invalid conclusions. No differences in FPR between males and females were observed in the current study. In the study of Cherry and Siegel (1978) the less efficient females had a higher FPR than males. Li the present study there were no significant differences in FPR between different commercial broiler strains. Cherry and Siegel (1978) reported that the FPR was significantly higher in males of a high body weight line than in males of the low weight line. In females the opposite (but not significant) results were obtained. Therefore, if FPR values for sexes are combined, there was little difference between the lines in FPR. The dw (dwarfing) gene, which is known to affect efficiency of feed utilization, did not significantly influence FPR in the study of Cherry and Siegel (1978). The FCR did not follow the expected increase with chronological ages. Lower FCR
1991 Poultry Science 70:447-452 INTRODUCTION
The rate at which feed passes through the digestive tract of pigs appears to be related to the amount of energy derived from the diet (Maner et al, 1962; Kass et al, 1980). For chickens, dietary factors that influence efficiency of feed utilization influence the feed passage rate (FPR) through the digestive system. These include carbohydrates (Monson et al, 1950), sugars (Stokstad et al, 1953), and dietary fats (Mateos and Sell, 1981; Mateos et al, 1982). These studies have led to the conclusion that the FPR through the digestive tract should be an important factor influencing the amount of energy derived from the diet. However, in these studies on FPR, the actual efficiency of feed utilization was not determined. Comparing feed-restricted broilers with fullfed broilers, it has been observed that for the week of full feeding after removal from the restricted feeding program, consumption was greater but the gain less than for birds on a continuous full feeding program. This results in a decreased efficiency of feed utilization. A possible explanation for this decreased effi-
Supported by state and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia.
ciency is that the feed restriction affected FPR immediately after returning to full feeding. The primary objective of the present experiment was to determine the relationship of efficiency of feed utilization and feed restriction to rate of passage of feed through the digestive system. A secondary objective was to evaluate three different methods of measuring FPR. MATERIALS AND METHODS
General Procedure The relationship of efficiency of feed utilization to FPR through the digestive system was studied. This was done by comparing strains and sexes differing in efficiency, correlating individual variation in efficiency with FPR, and observing the effects on FPR of restricted feeding regimes that affect efficiency. Management Chickens to be tested were grown in floor pens until 24 days of age at which time they were placed in the individual cage and feeding system described by Guill and Washburn (1972). At 4 wk of age, the collection of body weight, consumption, and feed utilization efficiency data was initiated after removing individual chickens that did not adjust to the cage and
447
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
ABSTRACT The relationship of efficiency of feed utilization determined by the feed conversion ratio (FCR) to the rate of feed passage through the digestive system of juvenile chickens was studied and three different methods of measuring feed passage rate (FPR) were evaluated. The FPR did not differ between sexes that had different FCR, nor did it differ between commercial broiler strains that differed in FCR. Feed restriction did not affect FPR. There was little correlation between FCR and FPR in any of the groups evaluated and the FPR was similar for high- and low-FCR groups. There was some evidence for increased FPR in birds grown at 32.2 C compared with those grown at 26.7 C. Similar results were obtained for FPR whether the tracer dye was given in the feed, or in a gelatin capsule, or no tracer dye was used. Repeatability of FPR obtained on the same individuals at different ages was very low. (Key words: feed passage rate, feed efficiency, broilers, feed restriction, ambient temperature)
448
WASHBURN
feeding system (i.e., little or no feed consumption). Efficiency of feed utilization was determined as the feed conversion ratio (FCR). The chickens were fed the standard University of Georgia starter ration (23% protein; 3,120 kcal/ kg ME) until 24 days of age and the finisher (21.2% protein; 3,256 kcal/kg ME) thereafter. Continuous lighting was used. Determination of Feed Passage Rate
2
Day-Glo Color Corp., Cleveland, OH 44103.
Trial 1 Fifty-four males and 54 females from each of four commercial broiler strains were divided into two experimental groups, full-fed and restricted. The full-fed group was allowed full access to feed from 4 to 8 wk of age. The restricted group was allowed full access to feed on Weeks 4 to 5 and 6 to 7, and access to feed was restricted on alternate days during Weeks 5 to 6 and 7 to 8. Consumption decreased during Weeks 5 to 6 and 7 to 8, and body weight decreased 18 and 13% for these periods, respectively. Body weights and consumption were recorded and FCR calculated weekly. Feed passage rate was determined at 6 and 8 wk of age. An analysis of variance and Duncan's separation of means within ages with sex (1 df), strain (3 df), and feeding regimen (1 df) as main effects, and their interactions were used to determine significance of difference between groups in FCR and FPR. Trial 2 The relationship of FPR with feed intake and FCR was studied in more detail. The general procedure and the method of feed restriction was the same as previously described. Males of a commercial broiler strain were used. The feed restriction periods were from 4 to 5 and 6 to 7 wk of age with ad libitum feeding during 5- to 6-wk and 7- to 8-wk periods. Feed passage rate was determined at 5,6,7, and 8 wk of age. Analysis of variance within ages with feeding regimen (1 df) as a main effect and Duncan's separation of means were used to determine significance of differences between groups. Trial 3 Males and females of commercial broiler Strains A and B (103 or 104 males and females of each strain) were grown under the standard management procedure previously described. All birds were given ad libitum access to feed. Weight gain and feed consumption were determined and FCR calculated over the 4- to 8-wk period. Three methods of measuring FPR were tested using the same birds during the 38 to 49 days of age period, hi Method 1 (Ml), gelatin
Downloaded from http://ps.oxfordjournals.org/ at New York University on February 18, 2015
The FPR was considered as the first appearance of a fluorescent dye after a 12-h restriction followed by a 30-min refeeding period. Cherry and Siegel (1978) have measured both time of first appearance and complete clearance of the tracer. However, most studies (Hillerman et al., 1953; Tuckey et al., 1958; Wilson et al, 1980; Mateos and Sell, 1981; Mateos etal., 1982) used time to first appearance as an indicator of FPR, considering it to be a reliable index. Jensen et al. (1962) plotted the distribution from first appearance to complete disappearance and found that the concentration of the marker followed a normal distribution. The accuracy of visually determining the first appearance of the tracer in the excreta is enhanced if the digestive tract is emptied before the tracer is administered. The restriction times used in various studies have been quite variable, ranging from 2 to 32 h. However, the duration of the starvation period has little affect on TME values (Sibbald, 1976), and a high correlation coefficient between the amount of excreta voided and length of restriction time was reported by Sibbald (1979). Because the results of Sibbald (1979) indicated that birds were voiding excreta at a constant rate (with no feed residues) at 10 h following feed removal, the 12-h period of restriction before administering the tracer was chosen in the present study. The following procedure was used: 1) feed access was restricted for 12 h; 2) birds were returned to feed and each was given a gelatin capsule containing .03 g of fluorescent dye,2 which eliminates the accuracy problems associated with visually scoring the most commonly used tracers, ferric oxide and chromic oxide; 3) dropping pans were cleaned and visually monitored at 15-min intervals, or less, for the first appearance of the dye in the excreta for a maximum time of 300 min. In a small number of individuals, the excreta from the test feeding did
not contain dye or took longer than 300 min so the number of individuals on which data are reported was less than the number of birds tested.
449
EFFICIENCY AND FEED PASSAGE RATE TABLE 1. Feed conversion ratio (FCR) and feed passage rate (FPR) of different strains, sexes, and feeding regimens (Trial J)
Source of variation
FPR, 6 wk
FCR, 7 to 8 wk
FPR, 8 wk
(g:g)
(min)
(g:g)
(min)
2.37" 2.43" 2.62" 2.68" 2.74" 2.34 b 2.41 b 2.69"
228" 228" 228" 218* 208" 227" 225" 217"
2.31" 2.27" 2.03b 2.18b 2.14" 2.19" 2.06b 2.33"
237" 226" 224" 210" 232" 218" 226" 224"
a,b Means in a column within strains, sexes, or feeding regimen with no common superscripts are significantly different (PS.05).
capsules containing .03 g of fluorescent dye were given as a marker after a 30-min period of feeding. In Method 2 (M2), the birds were given access to feed containing .2 g dye per pound (454 g) of feed. In Method 3 (M3), the birds were given access to feed containing no dye. In all methods, access to feed had been restricted for the previous 12 h. The FPR was considered as the minutes to the first appearance of solid dye-colored excreta in Methods 1 and 2 and of solid excreta in Method 3. An analysis of variance and Duncan's separation of means with methods (2 df), strain (1 df), and sex (1 df) as main effects, and their interactions were used to determine significance of differences. Correlations were obtained for the FPR values derived by the three methods and between FPR obtained by the three methods and performance traits. The individuals were grouped into high FCR groups and low FCR groups (25% of the population in each grouping) and their FPR compared. Trial 4 The observation that the correlation between the FPR obtained on the same individuals by the three methods was not high indicated study on the repeatability of the measure was needed. The known effect of high environmental temperature on consumption and personal observation (i.e., aborted trial) that attempts to obtain FPR in birds moved from a relatively cooler environment to a hotter one were unsuccessful, suggested it would be desirable to obtain the repeatability estimates in both a normal and relatively hot environ-
mental temperature. Data on FCR were also collected in this trial so that correlations between FCR and FPR could be determined. Fifty-five males of a single broiler strain were placed in each of two rooms using the individual cage system as previously described. Temperature of one room was maintained at approximately 26.7 C from 3 to 7 wk and another room was maintained at 32.2 C from 3 to 7 wk of age. Individual consumption, gain, and FCR were obtained at weekly intervals from 3 to 7 wk of age. Feed passage rate was determined on all birds at 4,5, 6, and 7 wk of age by the methods previously described. Correlations were obtained within temperature treatments for the 3 to 7 wk FCR and the mean FPR for the 3- to 7-wk period. Repeatability values were calculated for FPR within the environmental temperatures using the formula R = "Vv/Vw + "*E described by Becker (1975), where 7 ^ = M S w - MSfl/ki with ki denoting the number of measurements per individual; MSw denoting the mean squares within; and MS E the mean squares for environment. An analysis of variance and Duncan's separation of means with temperature (1 df), age (3 df), and their interaction were used to test for statistical significance of differences. RESULTS
Trials 1 and 2 The results presented in Table 1 (Trial 1) and Table 2 (Trial 2) indicate a lack of association between FPR through the digestive system and
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Strain A B C D x Restricted group x Full-fed group x Male x Female
FCR, 5 to 6 wk
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TABLE 2. Effect of feed restriction on feed conversion ratio (FCR) and feed passage rate (FPR) (Trial 2) FCR1 Age (wk) 4 to 5 to 6 to 7 to
n
R
5 110 6 110 7 101 8 75
FFR
FF
R
(g:g) 2.19 s2 2.28* 2.13' 1.91b 1.45b2 1.72' 2.83' 2.32b
166' 177' 213' 188'
FF (min) 174' 175* 209' 185'
efficiency of feed utilization. These results also indicate that the restriction of feed used in the present study did not affect the FPR. Consequently, changes in FPR of the digestive system do not appear to be the reason for the differences sometimes observed in efficiency of restricted and full-fed groups. In Trial 1 the FPR was not significantly different between strains even when the strains differed significantly in FCR (Table 1). There was no significant difference between males and females in FPR although they differed significantly in FCR. The FPR was not significantly different between full-fed groups and groups whose consumption had been restricted the previous week, and there were no trends toward higher or lower FPR for the two feeding regimens (compared with the full-fed group the restricted group had lower FPR at 6 wk, but higher FPR at 8 wk). The phenotypic correlations between FPR and FCR were low and nonsignificant (.14 for the 5- to 6-wk data and .09 for the 7- to 8-wk data).
Trial 3 Data presented in Table 3 indicate that the three methods (dye in gelatin capsules, dye in feed, or no dye) gave comparable results. Although the differences are statistically significant, they are small and comparable to differences observed between repeated measures on the same individual using the same technique. The coefficient of variation was less in the no dye method. The labor required for using the dye in the capsule method is much greater than the other methods and it is more difficult to keep accurate individual time records. The no dye method appears to be the method of choice if individual cages are used and the dropping pans are easily observed as they were in the facility used in this experiment. The correlations between the different methods, although statistically significant (PS.01) were in the low (.19) to moderate (.37) range. The correlations between methods for males and females, respectively, were as follows: Ml and M2, .26 and .19; Ml and M3, .37 and .24; and M2 and M3, .20 and .20. Differences between the methods were consistent for both sexes and for both strains. There were no significant differences in FPR between the two broiler strains. Strain B was a significantly faster growing strain that consumed significantly more feed, yet differences between the strains in FCR were not significant (Table 4). There were also no significant differences in FPR between males and females that differed in FCR. There were no significant correlations of FPR obtained by any of the three methods with gain or consumption (Table S).
TABLE 3. Feed passage rate in minutes of broiler strains and sexes obtained by three methods (Trial 3) Strain A
Strain B
Method
Male
Female
x
Male
Female
x
x
(CV)
1 2 3
214 200 218
209 205 218
212 202 218
216 206 218
210 205 219
213 205 218
212' 203 b 218°
(19.6) (18.3) (13.5)
:
Means for methods with no common superscripts are significantly different (P£.05).
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a b - Means for FCR or FPR between restricted and full-fed groups within ages with no common superscripts are significantly different (P<.05). R = group restricted from 4 to 5 and 6 to 7 wk and fullfed from 5 to 6 and 7 to 8 wk; FF = group receiving feed ad libitum from 4 to 8 wk. 2 Period of restricted feeding.
In Trial 2, the FPR was obtained at the end of the full-fed periods as well as the restricted periods. There were no significant differences in FPR between restricted and full-fed groups at any of the weekly periods of restriction or full feeding, although the FCR differed between groups (Table 2).
451
EFFICIENCY AND FEED PASSAGE RATE
TABLE 4. Consumption, gain, and feed conversion ratio (FCR) for broiler strains and sexes (Trial 3) Gain
Consumption Strain
Male
Female
A B x
1,936 2,141 2,041"
(g) 1,653 l,879 u 1.764b
958 1,036 999"
1,789" 2,012" 1,901
FCR
Female
Male
— (g) 759 860 808 b
Male 855 b 950" 903
Female -
2.03 2.08 2.05 b
2.11" 2.14"
"•"Means with no common superscripts are significantly different (P<.05).
Trial 4 The FPR was significantly higher in the birds grown at 32.2 C than in those grown at 26.7 C when analyzed over the 4-wk period of determination (Table 6). Means for the 32.2 C environment were consistently higher than those of die 26.7 C environment, but differences were significant only for values obtained at 5 wk of age. There were significant differences in FPR for the different ages, but there was no evidence of increasing or decreasing FPR with age. Repeatability of FPR was very low in both temperature regimens (R = .056 for 26.7 C and .0003 for 32.2 Q , and there was no significant correlation of 4- to 7-wk FCR with die mean FPR in either regimen (.11 in 26.7 C and .09 in 32.2 C). TABLE 5. Correlation of three methods (Ml, M2, M3) of measuring feed passage rate to performance traits of gain, consumption (Cons), and feed conversion ratio (FCR) (Trial 3) Females
Males Trait
Ml
M2
M3
Ml
M2
M3
Gain Cons FCR
-.09 .02 .15*
.08 .13 .08
-.16 .01 .22**
-.08 -.08 .03
.11 -.01 -.12
.00 -.08 -.08
*K.05. **PS.01.
DISCUSSION
It has been hypothesized that a slower FPR through die digestive system could increase the utilization of feed in tiiree ways: 1) increasing die time nutrients are in contact wiui absorptive cells, which should increase nutrient absorption; 2) altering die microbial population mat could affect the utilization of nutrients; and 3) influencing feed intake. It has also been hypotiiesized mat a faster FPR could be associated with increased utilization of feed if me FPR is considered an indicator of die efficiency of die digestive system. These conclusions were derived from studies on FPR in which efficiency of feed utilization was not determined. The results of the present study in which FPR and FCR were determined on die same individuals suggest mat neitiier of die hypouieses concerning die association of FPR and efficiency is valid, ratiier die FPR (of young chickens receiving a normal diet) does not affect efficiency at all. There is some inconclusive evidence tiiat feed intake may influence FPR. Sibbald (1979) TABLE 6. Feed passage rate (FPR) obtained at 4 to 7 wk from individuals maintained in two temperature environments (Trial 4)
Age
26.7 C
(wk) 4 5 6 7
207 235 209 181
X
208 b
± ± ± ±
Environmental temperature 325 C
22" 27 b 39" 24"
212 267 212 188
± ± ± ±
23" 29" 47" 28"
209y 25 l x 203? 185z
223*
*^*Means between environments within ages with no common superscripts are significantly different (K.05). ^y^Means for ages with no common superscripts are significantly different (PS.05). 'Means of individuals ± SD.
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There was some evidence of a positive correlation of FPR determined by Methods 1 and 3 with FCR in die males. Aldiough statistically significant, the correlations were low (.15 and .22). If the mean correlation over both sexes and three methods (y= .05) is considered the most reliable, then there was no correlation of FPR with FCR. There was no difference in FPR between the individuals classified into high-FCR (213 min) or low-FCR (210 min) groupings, aldiough the groups differed significantly in FCR (2.25 for the high-FCR group and 1.99 for the low-FCR group).
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values are normally expected at younger than at older ages. In the present study the restriction of feed at various ages affected the FCR and had a confounding affect on the association of age on FCR. Li addition, during the 1st wk (youngest age), the process of adjusting to the cages may result in decreased growth and consumption, resulting in abnormal FCR values. REFERENCES Becker, W. A., 1975. Manual of Quantitative Genetics. 3rd edition. Washington State University, Pullman, WA. Cherry, J. A., and P. B. Siegel, 1978. Selection for body weights at eight weeks of age. 15. Feed passage and intestinal size of normal and dwarf chicks. Poultry Sci. 57:336-340. Guill, R. A., and K. W. Washburn, 1972. Cages and feed troughs for individual broiler feed consumption experiments. Poultry Sci. 51:1229-1233. HUlerman, J. P., F. H. Kratzer, and W. O. Wilson, 1953. Feed passage through chickens and turkeys and some regulating factors. Poultry Sci. 32:332-335. Jensen, L. S., L. M. Merrill, C. V. Reddy, and J. McGinnis, 1962. Observations on eating patterns and rate of feed passage of birds fed pelleted and unpelleted diets. Poultty Sci. 41:1414-1419. Kass, M. L., P. J. Van Soest, W. G. Pond, B. Lewis, and R. E. McDowell, 1980. Utilization of dietary fiber from alfalfa by growing swine. I. Apparent digestibility of diet components in specific segments of the gastrointestinal tract J. Anim. Sci. 50:175-191. Maner, J. H., W. G. Pond, J. K. Loosli, and R. S. Lowery, 1962. Effect of isolated soybean protein and casein on the gastric pH and rate of passage of feed residues in baby pigs. J. Anim. Sci. 21:49-52. Mateos, G. F., and J. L. Sell, 1981. Influence of fat and carbohydrate source on rate of feed passage of semipurified diets for laying hens. Poultry Sci. 60: 2114-2119. Mateos, G. G., J. A. Sell, and J. A. Eastwood, 1982. Rate of feed passage transit time as influenced by supplemental fat Poultry Sci. 61:94-100. Monson, W. J., L. S. Dietrich, and C. A. Elvhjem, 1950. Studies on the effect of different carbohydrates on chick growth. Proc. Soc. Exp. Biol. Med. 75: 256-259. Sibbaid, I. R., 1976. The effect of the duration of starvation of the assay bird on true metabolizable energy values. Poultry Sci. 55:1578-1579. Sibbaid, I. R., 1979. Passage of feed through the adult rooster. Poultry Sci. 58:446-459. Stokstad, FX.R., T. M. Jukes, and W. L. Williams, 1953. Growth promoting effect of aureomycin on various types of diets. Poultry Sci. 31:1054-1058. Tuckey, R., B. E. March, and J. Biely, 1958. Diet and the rate of feed passage in the growing chick. Poultry Sci. 37:786-792. Wilson, E. K., F. W. Pierson, P. Y. Hester, R. L. Adams, and W. J. Stadelman, 1980. The effects of high environmental temperature on feed passage time and performance traits of White Peking ducks. Poultry Sci. 59:2322-2330.
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found that when using a force-feeding system, the rate of dry matter excretion of adult White Leghorn males was increased as larger amounts of feed were force-fed. Wilson et al. (1980) reported that restriction of feed intake of Peking ducks for 6 h resulted in a reduction in FPR compared with full-fed ducks. In the present study there was no relationship of restriction of feed or amount of feed consumption to FPR. There is some evidence that high (29.4 C) environmental temperature may cause an increase in FPR of Peking ducks (Wilson et al, 1980) although HUlerman et al. (1953) found no difference in the FPR of chickens maintained at 15.6 or 32.2 C. In the present study there was some evidence for increased FPR in birds raised at higher temperatures, but the differences were not consistent. Li the few studies in which the FPR was repeatedly measured on the same birds, considerable variation was observed and variability was decreased if first appearance of the marker was calculated by averaging data obtained for four periods. A large variability between means obtained on the same birds at different periods, relatively high coefficients of variations, and moderate correlation and low repeatabilities between measures on the same individual were obtained in the present study. Therefore, repeated measures appear to be essential in studies involving FPR. Confounding of time of measuring with treatments and small sample size may lead to invalid conclusions. No differences in FPR between males and females were observed in the current study. In the study of Cherry and Siegel (1978) the less efficient females had a higher FPR than males. Li the present study there were no significant differences in FPR between different commercial broiler strains. Cherry and Siegel (1978) reported that the FPR was significantly higher in males of a high body weight line than in males of the low weight line. In females the opposite (but not significant) results were obtained. Therefore, if FPR values for sexes are combined, there was little difference between the lines in FPR. The dw (dwarfing) gene, which is known to affect efficiency of feed utilization, did not significantly influence FPR in the study of Cherry and Siegel (1978). The FCR did not follow the expected increase with chronological ages. Lower FCR