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Effects of Increasing Dietary Levels of Full-Fat Canola on Performance, Nutrient Retention, and Bone Mineralization
Effects of Increasing Dietary Levels of Full-Fat Canola on Performance, Nutrient Retention, and Bone Mineralization S. LEESON, J. O. ATTEH, and J. D. SUMMERS Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario NIG 2WI (Received for publication May 29, 1986) ABSTRACT Day-old male broiler chickens were fed diets containing 0, 5, 10, 15, or 20% raw, ground, full-fat canola for a period of three weeks. Increasing the dietary proportion of full-fat canola significantly reduced feed intake (P<.05) and weight gain (P<.01), without altering feed:gain ratio. Diet had no significant effect on protein retention although there was a significant decrease in fat retention with an increase in dietary levels of full-fat canola (P<.01). This was accompanied by a significant decrease in metabolizable energy (P<.01). Increasing the proportion of dietary full-fat canola significantly reduced the concentration of soap in the digesta (P<.05) and excreta (P<.01). There was no significant effect of the dietary treatments on calcium or phosphorus retention. There was also no effect of the dietary full-fat canola on bone ash, bone calcium, or phosphorus content. (Key words: full-fat canola, broilers, performance, bone minerals) 1987 Poultry Science 6 6 : 8 7 5 - 8 8 0 INTRODUCTION
Full-fat canola, which contains approximately 40% oil and 20% protein (Summers and Leeson, 1985) is a potentially valuable feedstuff for chickens. However, widespread use of fullfat canola is not in practice due mainly to the pricing of edible oil and the fact that variable results have been recorded of its use as a feedstuff. Leslie and Summers (1972) reported a decrease in feed intake and egg production with an increase in dietary proportion of raw rapeseed. Olomu et al. (1975) observed that inclusion of 20% raw or autoclaved full-fat rapeseed in diets of broiler chicks resulted in a significant decrease in fat and energy retention, and an increase in the size of the thyroid gland. Summers et al. (1982) also reported that 17.5% or more full-fat canola in diets of broilers lowered both body weight gain and feed intake, although feed efficiency was similar to that of broilers fed a control diet. Shen et al. (1983) showed that if the seeds were finely ground, or if the seeds were steam pelleted in order to rupture the coat, good results with up to 20% whole canola seed could be expected. Fat utilization may be part of the problem associated with diets supplemented with raw full-fat canola. One of the major problems that affects dietary fat utilization is the formation of insoluble soaps between dietary fatty acids and minerals (Whitehead et al., 1971; Hakansson, 1975; Atteh and Leeson, 1983, 1984). March and MacMillan (1979) reported that addition of
5% erucic acid to diets with 5% corn oil increased soap formation. Also, utilization of a mixture of corn oil and erucic acid was lower than that of corn oil alone whether fed in combination with soybean meal or rapeseed meal (March and MacMillan, 1979). The study reported herein was undertaken to investigate the effects of inclusion of graded proportion of dietary full-fat canola on soap formation in the intestine and its effect on performance, nutrient retention, and bone mineralization in broiler chickens. MATERIALS AND METHODS
One hundred and sixty day-old male broiler chickens were housed in electrically heated battery brooders and fed the experimental diets shown in Table 1. The five experimental mash diets, which were calculated to be isonitrogenous [23% crude protein (CP)] and isoenergetic [3200 kcal metabolizable energy (ME)], contained 0, 5, 10, 15, or 20% dietary full-fat canola that had been ground with a commercial hammer mill. Calculated dietary calcium and available phosphorus were .9 and .4%, respectively, in all diets. Each diet was tested with four replicate cages of eight chicks, with diets and water available ad libitum during a trial period that lasted 3 weeks. A nutrient retention study using chromic oxide as a marker was undertaken with this same set of chicks when they were 2 weeks old. Excreta samples were collected over a 72 hr
875
LEESON ET AL.
876
TABLE 1. Percentage diet ccimposition Diet Ingredient Corn Basal1 Soybean meal (48%) Full-fat canola Corn gluten meal DL-Methionine Lysine HC1 Calcium phosphate Limestone Animal-vegetable blend fat Alfafloc (cellulose) Sand Total Analyzed nutrient content Crude protein, % Crude fat, % Calcium, % Total phosphorus, %
2
1
43.00 6.60 30.50
3
4
5
6.83
42.50 6.60 28.30 5.00 6.83
42.00 6.60 26.07 10.00 6.83
41.25 6.60 23.92 15.00 6.83
.04 .06
.03 .06
.02 .07
.02 .08
1.62 1.36 7.77
1.62 1.30 5.77
1.61 1.30 3.70
1.60 1.30 1.70
39.30 6.60 20.00 20.00 8.50 .12
1.60 1.24
.84
.62
.40
.18
1.38
1.37
1.40
1.52
2.64
100.00
100.00
100.00
100.00
100.00
24.63 9.44
25.50 9.11
25.02 9.01
25.38 9.10
.89 .73
.91 .72
25.57 8.97 1.01
.91 .79
.98 .81
.73
'Contained: barley, 5%; iodized salt (.011% Col), .25%; chromic oxide, .30%; corn starch, .30%; mineral-vitamin premix, .75% (provides per kilogram of diet: vitamin A, 8,000 IU; vitamin D 3 , 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, .25 mg; pantothenic acid, 11.0 mg; vitamin B 1 2 , 13 Mg; niacin, 26 mg; choline, 900 mg; vitamin K (menadione sodium bisulfite complex), 1.5 mg; folic acid, 1.5 mg; biotin, .25 mg; santoquin (antioxidant), 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg).
period and freeze dried prior to grinding and chemical analysis. Feed consumption and body weight gain were determined at the conclusion of the 3-week trial. Four chicks from each replicate were then killed by cervical dislocation and the body cavity immediately exposed and contents of the small intestine flushed out. Digesta from the small intestine of chicks within a replicate were pooled, freeze dried, and subsequently used to determine the soap concentration of the gut contents. The left tibia of two chicks per replicate was removed and cleaned of adhering flesh, dried at 100 C for 48 hr, defatted using Soxhlet extraction apparatus (Varian, Georgetown, Ontario, Can.), and dried again prior to dry ashing at 600 C overnight. Feed and excreta samples were ashed at 550 C overnight for mineral and chromium analysis. Chemical Analysis. Nitrogen in feed and excreta was determined by the Kjeldahl procedure (Kjel-foss automatic, Model 16310, Fisher Scientific, Toronto, Ontario, Can.), and gross energy determined by adiabatic oxygen bomb calorimetry (Parr, Model 1241, Parr Instruments, IL). Ash samples from feed, excreta, and bone were digested using the method of Association of Official Analytical Chemists (AOAC, 1980) for preparation of
sample solutions of inorganic materials for atomic absorption spectrophotometry. The resulting solutions were transferred into 100 ml volumetric flasks and made up to volume with strontium chloride (1.5% w/v). The solutions were then analyzed for calcium using a Techtron atomic absorption spectrophotometer (Model AA4, Varian, Georgetown, Ontario, Can.) and phosphorus using a Technicon auto analyzer (Model AA2, Technicon, Montreal, Quebec, Can.). Chromium in feed and excreta samples was determined using the method of Fenton and Fenton (1979). Total glycerides and fatty acids in feed, contents of the small intestine (digesta), and excreta were determined by petroleum ether extraction using Soxhlet apparatus. To estimate the proportion of fatty acids in the digesta and excreta that was present as soap, the method of fat determination described by Atteh and Leeson (1985) was used. Methyl esters were analyzed for component fatty acids using gas-liquid chromatography (Varian, Model 2100, Georgetown, Ontario, Can.) according to the method of AOAC (1980). A 5 ft X 0.08 in column of 5% DEGS PS on 100/120 mesh Supelcoport (Fisher Scientific, Toronto, Ontario, Can.) was used forthechromatograph.
DIETARY FULL-FAT CANOLA ON PERFORMANCE
Data were subjected to analysis of variance (Statistical Analysis System, 1982). Significant differences among treatments were determined using the protected Duncan's multiple range test (Duncan, 1955). RESULTS AND DISCUSSION
Performance. Increasing the dietary percent of full-fat canola above 10% significantly reduced feed intake (P<.05) and average body weight gain (P<.01) relative to birds fed the control diet (Table 2). However, there was no significant effect of dietary treatments on feed:gain ratio or mortality. These results are congruent with earlier observations (Leslie and Summers, 1972; Clement and Renner, 1977; Summers et al., 1982) showing a decrease in feed intake and weight gain with increasing dietary amounts of full-fat canola. There is no apparent explanation for the decrease in feed intake with increased dietary proportions of ground full-fat canola. The ME values of diets with a high proportion of full-fat canola were lower than that of the control diet (Table 3) and as such would be expected to actually result in increased feed intake compared with controls. The decrease in feed intake with increased dietary full-fat canola could be associated with the problem of palatability or undesirability of the diets. There was no indication of ingredient selection or rejection within the mash diets. Summers et al. (1982) reported that artificial coloring of diets containing high levels of full-fat canola resulted in increased feed intake. Nutrient Retention and Soap Formation. There was no significant effect of increasing dietary amounts of full-fat canola on protein,
877
calcium, or phosphorus retention (Table 3). Although a decrease in fat retention and diet ME with increased canola (P<.01) was observed, there was also a decrease in soap concentration in the digesta (P<.05) and the excreta (P<.01) as the level of dietary full-fat canola increased. The decrease in fat retention and ME level of the diet observed in this study may explain earlier observations (Olomu et al., 1975; Clement and Renner, 1977; Summers et al., 1982) of the detrimental effects on performance with high dietary levels of full-fat canola. However, results are somewhat at variance from those of Shen etal. (1983). One of the major assets of full-fat canola as a feedstuff is its high fat content. However, results of the present study and from literature cited suggest that chickens may not make maximum utilization of this fat. Birds fed diets with 20% full-fat canola retained only about 50% of the dietary fat. This result is similar to the observation of Summers et al. (1982) who indicated that birds offered diets containing 17.5% full-fat canola retained 46% of the dietary fat. As mentioned previously, the formation of insoluble soaps involving fatty acids and minerals can lead to reduced fat retention (Hakansson, 1975; Sibbald and Price, 1977; Kussaibati et al., 1983; Atteh and Leeson, 1983, 1984). In this instance formation of soap due to the presence of erucic acid (March and MacMillan, 1979) was not of significance because the sample of canola used contained little of this fatty acid (Table 4). Soap formation does not seem to be a problem limiting fat retention in the present study, as indicated by the fact that excreta soap concentration decreased with an increase in dietary full-fat
TABLE 2. Effects of increasing dietary full-fat canola on performance of broiler chicks from day-old to 3 weeks of age
Dietary level of full-fat canola
Daily feed intake
Body weight gain (0 to 3 weeks)
Feed intake: body weight gain ratio
43.lc 42.9bc 402abc 38.5 a b 37.1 a 3.2
587.1 B 597.1 B 570.0 B 491.1A 477.8 A 45.3
1.54 1.54 1.48 1.65 1.65 0.1
(%) 0 5 10 15 20 Standard deviation
Means within a column with different superscripts are significantly different (P<.05). A,B Means within a column with different superscripts are significantly different (P<.01).
LEESON ET AL.
878
TABLE 3. Effects of dietary levels of full-fat canola on apparent nutrient retention by broiler chicks, metabolizable energy (ME) of diets, and soap formation Dietary level of full-fat canola
Crude protein
Calcium
Phosphorus
Fat
ME
Digesta soap concentration 1
Fecal soap concentration 2
45.8 C 33.2 B 27.0 A 24.0 A 24.0 A
30.8 C 20.3 b 13.6 a 12.5 a 12. l a
4.1
4.1
(kcal/g) 0.0 5.0 10.0 15.0 20.0 Standard deviation
d
53.0 47.6 48.3 49.5 51.8
57.6 48.2 54.7 65.8 49.2
34.4 29.1 32.4 30.1 34.2
73.8 64.2 C 61.9 C 55.9 b 49.8 a
2.7
5.5
3.5
3.5
3.26 c 3.14 b 3.01 a 3.03 a 2.99 a 0.05
a—d Means within a column with different superscripts are significantly different (P<.05). A—C Means within a column with different superscripts are significantly different (P-C01). 1
Small Intestine Digesta Ether Extract II (acid-ether) as proportion of Extracts I plus II (ether + acid-ether).
2
Fecal Ether Extract II (acid-ether) as proportion of Extracts I plus II (ether + acid-ether).
canola (Table 3). Calculation of absolute daily excreta soap indicates there is a lesser quantity produced when birds are fed with 20% canola (.2 g) than with the control diet (.31 g). In most cases, about half of the soap that was formed during digestion was subsequently absorbed. Thus, close to 90% of unabsorbed fat was present in nonsoap form for birds consuming diets with 20% full-fat canola, compared to about 70% for the control diet. This is congruent with earlier reports (March and MacMillan, 1979) showing that birds fed a diet containing rapeseed excreted less soap than did those fed a soybeanbased diet. The nonsignificant effect of the dietary canola level on calcium retention is congruent with the observation above, that soap formation was not a problem related to limited fat retention. Changes in the fatty acid profile of the dietary fat as it progressed through the digestive tract are shown in Table 4. The fatty acid profiles of the nonsoap fat in both the digesta and excreta were similar to the fatty acid composition of the diets. However, the fatty acid profiles of soap fat in the digesta and excreta showed a substantial increase in saturated and a decrease in proportion of unsaturated fatty acids. The fatty acid profile of the soap fat content of the excreta, when compared with the fatty acid profile of the soap fat in the digesta, indicates that substantial amounts of soap formed by oleic and linoleic acid Diets 1 and 2 were subsequently absorbed. This is congruent with earlier findings (Boyd et
al., 1932; Atteh and Leeson, 1984) showing that the soaps of these fatty acids are utilized. However, with an increase in dietary levels of full-fat canola above 5%, there was little change in the concentration of unsaturated fatty acids in the soap fat of the excreta relative to that in the digesta. The decrease in soap concentration in the contents of the gut and in the excreta accompanying an increase in dietary proportion of full-fat canola probably relates to changes in dietary fatty acids. Atteh and Leeson (1984, 1985) showed that saturated fatty acids accounted for a large proportion of soap formation because of their low absorbability. The proportion of dietary palmitic and stearic acids decreases with an increase in proportion of dietary full-fat canola. This would explain why an increase in dietary full-fat canola resulted in a significant decrease in soap formation. Bone Ash and Minerals. There was no significant effect of increasing dietary proportions of full-fat canola on bone ash and bone calcium or phosphorus content. Bone ash content averaged 40%, while calcium and phosphorus represented approximately 31 and 15% respectively of this ash. The lack of difference in calcium and phosphorus retention would explain the nonsignificant effect of dietary treatments on bone mineralization. As most of the soaps that were formed in the gut were subsequently absorbed, no detrimental effect of increasing dietary proportions of full-fat canola was observed on bone mineralization.
40.4 27.4
5.0
34.9 24.8
2.6
16 0 18 0 18 18 18 22
3.2
6.7
7.9
.2
10.9
15.3
17.5
16 0 18 0 18 1 18 2 18 3 22 1
.40
.6
6.4
44.8 27.1 1.0
8.4
49.9 28.2
8.5 1.2
Fatty acid profile of diets (%)
1.2
9.5
52.4 29.5
5.7 0.5
10
15
1.1
7.0
47.4 26.9
8.8 4.0
1.3
8.0
49.5 27.4
7.1 3.0
15.6 10.0 40.5 24.7 5.2 .7
2.0 .4
6.8 1.0
8.6 8.9
51.2 26.5
48.7 26.2
9.3 1.4
53.7 26.4
5.1 1.5
6.4 2.3
9.2
1.3
8.5
51.1 27.5
5.7 2.0
20
4.5
Fatty acid make-up of nonsoap fat in excreta (%)
1.2
5.6
44.6 27.0
5.7
11.4
Fatty acid make-up of nonsoap fat in digesta (%)
19.30 12.7 33.9 28.2
1.0
3.8
34.4 33.7
8.5
14.6
0
5
20
Full-fat canola level (%)
10
15
5
__ 0
Fatty acid chain length:double bonds
Full-fat canola level (%)
TABLE 4. Changes in fatty acid profiles of dietary fat during digestion in broi fed diets with supplemental full-fat canola
LEESON ET AL.
880
The study indicates that inclusion of dietary full-fat canola above 10% is detrimental to the performance of broiler chicks. The detrimental effect of high dietary amounts of full-fat canola is associated with a decrease in feed intake and an inability to retain dietary fat. Soap formation during the process of digestion plays a minimal role in such reduced fat retention.
ACKNOWLEDGMENT
This work was supported by the Canola Council of Canada and the Ontario Ministry of Agriculture and Food. REFERENCES Association of Official Analytical Chemists, 1980. Pages 21, 447 in: Official Methods of the Association of Official Analytical Chemists, Assoc. Off. Anal. Chem., Washington, DC. Atteh, J. O., and S. Leeson, 1983. Effects of dietary fatty acids and calcium levels on performance and mineral metabolism of broiler chickens. Poultry Sci. 62:24122419. Atteh, J. O., and S. Leeson, 1984. Effects of dietary saturated and unsaturated fatty acids and calcium levels on performance and mineral metabolism of broiler chicks. Poultry Sci. 63:2252-2260. Atteh, J. 0 . , and S. Leeson, 1985. Influence of age, dietary cholic acid and calcium levels on performance, utilization of free fatty acids and bone mineralization in broilers. Poultry Sci. 64:1959-1971. Boyd, S. F., C. L. Crum, and J. F. Lyman, 1932. The absorption of calcium soaps and the relation of dietary fat to calcium utilization in the white rat. J. Biol. Chem. 95:29-41. Clement, H.,andR. Renner, 1977. Studies of the utilization
of high and low erucic acid rapeseed oils by the chick. J. Nutr. 107:251-260. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1—42. Fenton, T. W., and M. Fenton, 1979. An improved procedure for determination of chromic oxide in feed and feces. Can. J. Anim. Sci. 59:631-634. Hakansson, J., 1975. The effect of fat on calcium, phosphorus and magnesium balances in chicks. Swed. J. Agric. Res. 5:145-157. Kussaibati, R., B. Leclerq, and J. Guillaume, 1983. Effects of calcium, magnesium and bile salts on apparent metabolizable energy and digestibility of lipids, starch and proteins in growing chicks. Ann. Zootech. (Paris) 32:7-20. Leslie, A. J., and J. D. Summers, 1972. Feeding value of rapeseed for laying hens. Can. J. Anim. Sci. 52:563566. March, B. E., and C. MacMillan, 1979. Excretion of soap fatty acids by chicks fed diets of different composition. Poultry Sci. 58:1246-1249. Olomu, J. M., A. R. Robblee, D. R. Clandinin, and R. T. Hardin, 1975. Utilization of full-fat rapeseed and rapeseed meals in rations for broiler chicks. Can. J. Anim. Sci. 55:461-469. Shen, H., J. D. Summers, and S. Leeson, 1983. The influence of steam pelleting and grinding on the nutritive value of canola rapeseed for poultry. Anim. Feed Sci. Technol. 8:303-311. Sibbald, I. R., and K. Price, 1977. The effects of dietary inclusion and of calcium on the true metabolizable energy value of fat. Poultry Sci. 56:2070-2078. Statistical Analysis Systems (SAS), 1982. SAS User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Summers, J. D., and S. Leeson, 1985. Page 10 in: Poultry Nutrition Handbook. Univ. Guelph, Guelph, Ont., Can. Summers, J. D., H. Shen, and S. Leeson, 1982. The value of canola seed in poultry diets. Can. J. Anim. Sci. 62:861-868. Whitehead, C. C , W. A. Dewar, and J. N. Downie, 1971. Effect of dietary fat on mineral retention in the chick. Br. Poult. Sci. 12:249-254.
Full-fat canola, which contains approximately 40% oil and 20% protein (Summers and Leeson, 1985) is a potentially valuable feedstuff for chickens. However, widespread use of fullfat canola is not in practice due mainly to the pricing of edible oil and the fact that variable results have been recorded of its use as a feedstuff. Leslie and Summers (1972) reported a decrease in feed intake and egg production with an increase in dietary proportion of raw rapeseed. Olomu et al. (1975) observed that inclusion of 20% raw or autoclaved full-fat rapeseed in diets of broiler chicks resulted in a significant decrease in fat and energy retention, and an increase in the size of the thyroid gland. Summers et al. (1982) also reported that 17.5% or more full-fat canola in diets of broilers lowered both body weight gain and feed intake, although feed efficiency was similar to that of broilers fed a control diet. Shen et al. (1983) showed that if the seeds were finely ground, or if the seeds were steam pelleted in order to rupture the coat, good results with up to 20% whole canola seed could be expected. Fat utilization may be part of the problem associated with diets supplemented with raw full-fat canola. One of the major problems that affects dietary fat utilization is the formation of insoluble soaps between dietary fatty acids and minerals (Whitehead et al., 1971; Hakansson, 1975; Atteh and Leeson, 1983, 1984). March and MacMillan (1979) reported that addition of
5% erucic acid to diets with 5% corn oil increased soap formation. Also, utilization of a mixture of corn oil and erucic acid was lower than that of corn oil alone whether fed in combination with soybean meal or rapeseed meal (March and MacMillan, 1979). The study reported herein was undertaken to investigate the effects of inclusion of graded proportion of dietary full-fat canola on soap formation in the intestine and its effect on performance, nutrient retention, and bone mineralization in broiler chickens. MATERIALS AND METHODS
One hundred and sixty day-old male broiler chickens were housed in electrically heated battery brooders and fed the experimental diets shown in Table 1. The five experimental mash diets, which were calculated to be isonitrogenous [23% crude protein (CP)] and isoenergetic [3200 kcal metabolizable energy (ME)], contained 0, 5, 10, 15, or 20% dietary full-fat canola that had been ground with a commercial hammer mill. Calculated dietary calcium and available phosphorus were .9 and .4%, respectively, in all diets. Each diet was tested with four replicate cages of eight chicks, with diets and water available ad libitum during a trial period that lasted 3 weeks. A nutrient retention study using chromic oxide as a marker was undertaken with this same set of chicks when they were 2 weeks old. Excreta samples were collected over a 72 hr
875
LEESON ET AL.
876
TABLE 1. Percentage diet ccimposition Diet Ingredient Corn Basal1 Soybean meal (48%) Full-fat canola Corn gluten meal DL-Methionine Lysine HC1 Calcium phosphate Limestone Animal-vegetable blend fat Alfafloc (cellulose) Sand Total Analyzed nutrient content Crude protein, % Crude fat, % Calcium, % Total phosphorus, %
2
1
43.00 6.60 30.50
3
4
5
6.83
42.50 6.60 28.30 5.00 6.83
42.00 6.60 26.07 10.00 6.83
41.25 6.60 23.92 15.00 6.83
.04 .06
.03 .06
.02 .07
.02 .08
1.62 1.36 7.77
1.62 1.30 5.77
1.61 1.30 3.70
1.60 1.30 1.70
39.30 6.60 20.00 20.00 8.50 .12
1.60 1.24
.84
.62
.40
.18
1.38
1.37
1.40
1.52
2.64
100.00
100.00
100.00
100.00
100.00
24.63 9.44
25.50 9.11
25.02 9.01
25.38 9.10
.89 .73
.91 .72
25.57 8.97 1.01
.91 .79
.98 .81
.73
'Contained: barley, 5%; iodized salt (.011% Col), .25%; chromic oxide, .30%; corn starch, .30%; mineral-vitamin premix, .75% (provides per kilogram of diet: vitamin A, 8,000 IU; vitamin D 3 , 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, .25 mg; pantothenic acid, 11.0 mg; vitamin B 1 2 , 13 Mg; niacin, 26 mg; choline, 900 mg; vitamin K (menadione sodium bisulfite complex), 1.5 mg; folic acid, 1.5 mg; biotin, .25 mg; santoquin (antioxidant), 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg).
period and freeze dried prior to grinding and chemical analysis. Feed consumption and body weight gain were determined at the conclusion of the 3-week trial. Four chicks from each replicate were then killed by cervical dislocation and the body cavity immediately exposed and contents of the small intestine flushed out. Digesta from the small intestine of chicks within a replicate were pooled, freeze dried, and subsequently used to determine the soap concentration of the gut contents. The left tibia of two chicks per replicate was removed and cleaned of adhering flesh, dried at 100 C for 48 hr, defatted using Soxhlet extraction apparatus (Varian, Georgetown, Ontario, Can.), and dried again prior to dry ashing at 600 C overnight. Feed and excreta samples were ashed at 550 C overnight for mineral and chromium analysis. Chemical Analysis. Nitrogen in feed and excreta was determined by the Kjeldahl procedure (Kjel-foss automatic, Model 16310, Fisher Scientific, Toronto, Ontario, Can.), and gross energy determined by adiabatic oxygen bomb calorimetry (Parr, Model 1241, Parr Instruments, IL). Ash samples from feed, excreta, and bone were digested using the method of Association of Official Analytical Chemists (AOAC, 1980) for preparation of
sample solutions of inorganic materials for atomic absorption spectrophotometry. The resulting solutions were transferred into 100 ml volumetric flasks and made up to volume with strontium chloride (1.5% w/v). The solutions were then analyzed for calcium using a Techtron atomic absorption spectrophotometer (Model AA4, Varian, Georgetown, Ontario, Can.) and phosphorus using a Technicon auto analyzer (Model AA2, Technicon, Montreal, Quebec, Can.). Chromium in feed and excreta samples was determined using the method of Fenton and Fenton (1979). Total glycerides and fatty acids in feed, contents of the small intestine (digesta), and excreta were determined by petroleum ether extraction using Soxhlet apparatus. To estimate the proportion of fatty acids in the digesta and excreta that was present as soap, the method of fat determination described by Atteh and Leeson (1985) was used. Methyl esters were analyzed for component fatty acids using gas-liquid chromatography (Varian, Model 2100, Georgetown, Ontario, Can.) according to the method of AOAC (1980). A 5 ft X 0.08 in column of 5% DEGS PS on 100/120 mesh Supelcoport (Fisher Scientific, Toronto, Ontario, Can.) was used forthechromatograph.
DIETARY FULL-FAT CANOLA ON PERFORMANCE
Data were subjected to analysis of variance (Statistical Analysis System, 1982). Significant differences among treatments were determined using the protected Duncan's multiple range test (Duncan, 1955). RESULTS AND DISCUSSION
Performance. Increasing the dietary percent of full-fat canola above 10% significantly reduced feed intake (P<.05) and average body weight gain (P<.01) relative to birds fed the control diet (Table 2). However, there was no significant effect of dietary treatments on feed:gain ratio or mortality. These results are congruent with earlier observations (Leslie and Summers, 1972; Clement and Renner, 1977; Summers et al., 1982) showing a decrease in feed intake and weight gain with increasing dietary amounts of full-fat canola. There is no apparent explanation for the decrease in feed intake with increased dietary proportions of ground full-fat canola. The ME values of diets with a high proportion of full-fat canola were lower than that of the control diet (Table 3) and as such would be expected to actually result in increased feed intake compared with controls. The decrease in feed intake with increased dietary full-fat canola could be associated with the problem of palatability or undesirability of the diets. There was no indication of ingredient selection or rejection within the mash diets. Summers et al. (1982) reported that artificial coloring of diets containing high levels of full-fat canola resulted in increased feed intake. Nutrient Retention and Soap Formation. There was no significant effect of increasing dietary amounts of full-fat canola on protein,
877
calcium, or phosphorus retention (Table 3). Although a decrease in fat retention and diet ME with increased canola (P<.01) was observed, there was also a decrease in soap concentration in the digesta (P<.05) and the excreta (P<.01) as the level of dietary full-fat canola increased. The decrease in fat retention and ME level of the diet observed in this study may explain earlier observations (Olomu et al., 1975; Clement and Renner, 1977; Summers et al., 1982) of the detrimental effects on performance with high dietary levels of full-fat canola. However, results are somewhat at variance from those of Shen etal. (1983). One of the major assets of full-fat canola as a feedstuff is its high fat content. However, results of the present study and from literature cited suggest that chickens may not make maximum utilization of this fat. Birds fed diets with 20% full-fat canola retained only about 50% of the dietary fat. This result is similar to the observation of Summers et al. (1982) who indicated that birds offered diets containing 17.5% full-fat canola retained 46% of the dietary fat. As mentioned previously, the formation of insoluble soaps involving fatty acids and minerals can lead to reduced fat retention (Hakansson, 1975; Sibbald and Price, 1977; Kussaibati et al., 1983; Atteh and Leeson, 1983, 1984). In this instance formation of soap due to the presence of erucic acid (March and MacMillan, 1979) was not of significance because the sample of canola used contained little of this fatty acid (Table 4). Soap formation does not seem to be a problem limiting fat retention in the present study, as indicated by the fact that excreta soap concentration decreased with an increase in dietary full-fat
TABLE 2. Effects of increasing dietary full-fat canola on performance of broiler chicks from day-old to 3 weeks of age
Dietary level of full-fat canola
Daily feed intake
Body weight gain (0 to 3 weeks)
Feed intake: body weight gain ratio
43.lc 42.9bc 402abc 38.5 a b 37.1 a 3.2
587.1 B 597.1 B 570.0 B 491.1A 477.8 A 45.3
1.54 1.54 1.48 1.65 1.65 0.1
(%) 0 5 10 15 20 Standard deviation
Means within a column with different superscripts are significantly different (P<.05). A,B Means within a column with different superscripts are significantly different (P<.01).
LEESON ET AL.
878
TABLE 3. Effects of dietary levels of full-fat canola on apparent nutrient retention by broiler chicks, metabolizable energy (ME) of diets, and soap formation Dietary level of full-fat canola
Crude protein
Calcium
Phosphorus
Fat
ME
Digesta soap concentration 1
Fecal soap concentration 2
45.8 C 33.2 B 27.0 A 24.0 A 24.0 A
30.8 C 20.3 b 13.6 a 12.5 a 12. l a
4.1
4.1
(kcal/g) 0.0 5.0 10.0 15.0 20.0 Standard deviation
d
53.0 47.6 48.3 49.5 51.8
57.6 48.2 54.7 65.8 49.2
34.4 29.1 32.4 30.1 34.2
73.8 64.2 C 61.9 C 55.9 b 49.8 a
2.7
5.5
3.5
3.5
3.26 c 3.14 b 3.01 a 3.03 a 2.99 a 0.05
a—d Means within a column with different superscripts are significantly different (P<.05). A—C Means within a column with different superscripts are significantly different (P-C01). 1
Small Intestine Digesta Ether Extract II (acid-ether) as proportion of Extracts I plus II (ether + acid-ether).
2
Fecal Ether Extract II (acid-ether) as proportion of Extracts I plus II (ether + acid-ether).
canola (Table 3). Calculation of absolute daily excreta soap indicates there is a lesser quantity produced when birds are fed with 20% canola (.2 g) than with the control diet (.31 g). In most cases, about half of the soap that was formed during digestion was subsequently absorbed. Thus, close to 90% of unabsorbed fat was present in nonsoap form for birds consuming diets with 20% full-fat canola, compared to about 70% for the control diet. This is congruent with earlier reports (March and MacMillan, 1979) showing that birds fed a diet containing rapeseed excreted less soap than did those fed a soybeanbased diet. The nonsignificant effect of the dietary canola level on calcium retention is congruent with the observation above, that soap formation was not a problem related to limited fat retention. Changes in the fatty acid profile of the dietary fat as it progressed through the digestive tract are shown in Table 4. The fatty acid profiles of the nonsoap fat in both the digesta and excreta were similar to the fatty acid composition of the diets. However, the fatty acid profiles of soap fat in the digesta and excreta showed a substantial increase in saturated and a decrease in proportion of unsaturated fatty acids. The fatty acid profile of the soap fat content of the excreta, when compared with the fatty acid profile of the soap fat in the digesta, indicates that substantial amounts of soap formed by oleic and linoleic acid Diets 1 and 2 were subsequently absorbed. This is congruent with earlier findings (Boyd et
al., 1932; Atteh and Leeson, 1984) showing that the soaps of these fatty acids are utilized. However, with an increase in dietary levels of full-fat canola above 5%, there was little change in the concentration of unsaturated fatty acids in the soap fat of the excreta relative to that in the digesta. The decrease in soap concentration in the contents of the gut and in the excreta accompanying an increase in dietary proportion of full-fat canola probably relates to changes in dietary fatty acids. Atteh and Leeson (1984, 1985) showed that saturated fatty acids accounted for a large proportion of soap formation because of their low absorbability. The proportion of dietary palmitic and stearic acids decreases with an increase in proportion of dietary full-fat canola. This would explain why an increase in dietary full-fat canola resulted in a significant decrease in soap formation. Bone Ash and Minerals. There was no significant effect of increasing dietary proportions of full-fat canola on bone ash and bone calcium or phosphorus content. Bone ash content averaged 40%, while calcium and phosphorus represented approximately 31 and 15% respectively of this ash. The lack of difference in calcium and phosphorus retention would explain the nonsignificant effect of dietary treatments on bone mineralization. As most of the soaps that were formed in the gut were subsequently absorbed, no detrimental effect of increasing dietary proportions of full-fat canola was observed on bone mineralization.
40.4 27.4
5.0
34.9 24.8
2.6
16 0 18 0 18 18 18 22
3.2
6.7
7.9
.2
10.9
15.3
17.5
16 0 18 0 18 1 18 2 18 3 22 1
.40
.6
6.4
44.8 27.1 1.0
8.4
49.9 28.2
8.5 1.2
Fatty acid profile of diets (%)
1.2
9.5
52.4 29.5
5.7 0.5
10
15
1.1
7.0
47.4 26.9
8.8 4.0
1.3
8.0
49.5 27.4
7.1 3.0
15.6 10.0 40.5 24.7 5.2 .7
2.0 .4
6.8 1.0
8.6 8.9
51.2 26.5
48.7 26.2
9.3 1.4
53.7 26.4
5.1 1.5
6.4 2.3
9.2
1.3
8.5
51.1 27.5
5.7 2.0
20
4.5
Fatty acid make-up of nonsoap fat in excreta (%)
1.2
5.6
44.6 27.0
5.7
11.4
Fatty acid make-up of nonsoap fat in digesta (%)
19.30 12.7 33.9 28.2
1.0
3.8
34.4 33.7
8.5
14.6
0
5
20
Full-fat canola level (%)
10
15
5
__ 0
Fatty acid chain length:double bonds
Full-fat canola level (%)
TABLE 4. Changes in fatty acid profiles of dietary fat during digestion in broi fed diets with supplemental full-fat canola
LEESON ET AL.
880
The study indicates that inclusion of dietary full-fat canola above 10% is detrimental to the performance of broiler chicks. The detrimental effect of high dietary amounts of full-fat canola is associated with a decrease in feed intake and an inability to retain dietary fat. Soap formation during the process of digestion plays a minimal role in such reduced fat retention.
ACKNOWLEDGMENT
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