Bull Vet Inst Pulawy 54, 43-48, 2010
NUTRITIONAL EFFICIENCY OF GENETICALLY-MODIFIED INSECT RESISTANT CORN (MON 810) AND GLYPHOSATE-TOLERANT SOYBEAN MEAL (ROUNDUP READY) FOR BROILERS SYLWESTER ŚWIĄTKIEWICZ, MAŁGORZATA ŚWIĄTKIEWICZ, JERZY KORELESKI, AND KRZYSZTOF KWIATEK1 Department of Animal Nutrition and Feed Science, National Research Institute of Animal Production, 32-083 Balice, Poland
[email protected] 1 Department of Hygiene of Animal Feedingstuffs, National Veterinary Research Institute, 24-100 Pulawy, Poland
[email protected] Received for publication October 21, 2009
Abstract The aim of this study was to evaluate the effect of genetically-modified (GM) insect-resistant corn (MON 810) and glyphosate-tolerant GM soybean meal (Roundup Ready, MON 40-30-2), used as the main dietary components for broilers, on the performance parameters, results of slaughter analysis, and the chemical composition of the breast muscles. In a 42-d floor pen experiment, Ross 308 broilers were fed corn-soybean meal diets. In the experiment, a randomised complete block design was used with 4 dietary treatments. Each treatment was divided into 4 replicates (pens) of 40 birds. All the experimental diets met the requirements of broilers; they were all isonitrogenous and isoenergetic, and contained non-modified corn and soybean meal (group I), non-modified corn and GM soybean (group II), GM corn and non-modified soybean meal (group III), or GM corn and GM soybean meal (group IV), respectively. The nutrient composition of Bt corn and its non-modified isogenic counterpart (parental line) revealed no major differences. The final live weight, average daily weight gain, feed intake, feed conversion (feed:gain ratio), and mortality rate did not differ statistically across the dietary treatments. No statistical differences (P>0.05) were also found in the results of slaughter analysis (carcass yield, meat yield, abdominal fat pad, and relative weight of the liver, gizzard, and spleen) and chemical composition of the breast muscles. It was concluded that insect-resistant GM corn (MON 810) and soybean meal produced from glyphosate-tolerant GM soybean (Roundup Ready) are nutritionally equivalent to conventional feeds and can be used as components of broiler diets with no adverse effect on performance indices.
Key words: broilers, genetically-modified feeds, animal performance, meat yield. The presence of genetically-modified (GM) plants, i.e. plants containing a DNA construct (transgen), originating from foreign organism, in the genome, is increasing in the crops available on feed market. The most widespread GM plants are those developed for protection against insects and herbicide tolerance. Almost all extracted soybean meal available on the European feed market is produced from GM Roundup Ready (RR) plants. RR soybean was developed by inserting a gene isolated from the Agrobacterium sp. CP4 strain of soil bacterium, expressing 5enolpyruvylshikimate-3-phosphate synthase in plant. This enzyme confers glyphosate, an active ingredient in herbicide (Roundup), tolerance upon plants. The land area devoted to GM corn cultivation in the European countries has increased in recent years. In 2008, this increase was also noted in Poland (10). The transgenic corn (MON 810) grown in Europe was modified by the
integration of gene isolated from the Bacillus thuringensis soil bacterium, in order to produce the insecticidal Cry1A(b) protein. Cry1A(b) acts specifically against certain Lepidoptera and confers insect resistance with respect to the European corn borer (Ostrinia numbilatis), the primary corn pest in the Europe, and one, which causes major production losses and makes the plants more susceptible to secondary infection by Fusarium sp. mould. Although GM plants have been used as feed for years and a number of studies have proved their nutritional safety for animals (8, 19, 20), they still give rise to public discussion. The main concern is the potential and unknown effect of transgenic DNA and expressed protein on animals and, indirectly, through products made from animals fed GM crops, on humans. Since rapidly growing broilers are especially sensitive to the composition of their diet and any nutrient deficiency
44 or presence in the feed of harmful substances quickly leads to a reduced growth rate, they provide a useful model for determining potential and unintended effects arising from transgenic plants. The aim of this study was to evaluate the nutritional efficiency of transgenic Bt corn grain (event MON 810) and glyphosate-tolerant soybean meal (Roundup Ready) used as the main dietary components for broilers, by determining their effects on performance parameters, the results of slaughter analysis, and the chemical composition of the breast muscles.
Material and Methods Animals and housing. A total of 640 sexed Ross 308, one-day-old broilers, with an average initial body weight of 42 g, were obtained from a commercial hatchery. For the first 42 d of life, the chickens were kept in pens set on a concrete floor covered with wood shavings, in an environmentally-controlled room containing individual pen lamps and a ventilation system. The pen dimensions were 1.60 × 2.00 m, equalling 3.20 m2 total floor space and 0.08 m2 per bird. A continuous 24-h lighting programme was used. During the experiment, feed and water were available for ad libitum consumption. The environmental conditions were similar for all treatments (pens). The Local Krakow Ethics Committee for Experiments with Animals approved all the experimental procedures relating to the use of live animals. Experiment design and experimental diets. For the experiment, a randomised complete block design with four dietary treatments was used: I – (control) nonmodified corn and soybean meal, II – non-modified corn
and GM soybean meal, III – GM corn and non-modified soybean meal, IV – GM corn and GM soybean meal. Each treatment was divided into four replicates (pens) of 40 birds (20 male and 20 female chickens). The test GM corn grain was obtained from plants, which contained the Bt gene, expressing Cry1A(b) protein (YieldGard, MON 810), geneticallymodified for protection against the European corn borer (Ostrinia numbilatis). The test soybean meal was produced from glyphosate-tolerant plants (Roundup Ready, MON-40-30-2). A non-modified isogenic parental line of corn (DKC 3420) and non-modified commercial soybean meal were used as controls. In the case of corn, the environmental conditions of growth were the same for both lines. The broilers were fed mash, corn-soybean, starter diets for the first 21 d and grower-finisher diets for the next 21 d. The nutrient content of the diets was calculated in accordance with the chemical composition of raw feedstuffs and the metabolisable energy value, on the basis of equations taken from European Tables (11). The chemical composition of the corn and soybean meal components was determined by conventional methods (2). Amino acids were analysed in acid hydrolysates, after initial peroxidation of sulphur amino acids, in colour reaction with the ninhydrin reagent, using a Beckman-System Gold 126 AA automatic analyser. Calcium content was determined by flame atomic absorption spectrophotometry, and phosphorus content by the colorimetric method (2). All the diets were formulated to meet the nutrient requirements of growing broilers (17) and to contain the same amount of crude protein, metabolisable energy, lysine, methionine, calcium, and available phosphorus (Table 1).
Table 1 The composition and nutrient content of experimental diets (%)
Conventional corn
56.47
Starter (1-21 d) Group Group II III 54.20 -
GM corn (MON 810)
-
-
56.52
Conventional soybean meal GM soybean meal (RR) Rapeseed oil Limestone Monocalcium phosphate NaCl DL-Methionine (99%) Vitamin-mineral premix1 Nutrient contents Metabolisable energy, MJ/kg Crude protein Lys Met Ca Total P Available P
36.9 2.50 1.70 1.40 0.30 0.23 0.50
39.0 2.70 1.70 1.37 0.30 0.23 0.50
36.85 2.50 1.70 1.40 0.30 0.23 0.50
Item
1
Group I
12.5 22 1.20 0.55 0.94 0.70 0.43
60.25
Grower (22-42 d) Group Group III Group IV II 58.54 -
54.25
-
-
60.30
58.64
38.95 2.70 1.70 1.37 0.30 0.23 0.50
32.0 3.60 1.75 1.30 0.30 0.21 0.50
33.45 3.90 1.75 1.26 0.30 0.21 0.50
31.95 3.60 1.75 1.30 0.30 0.21 0.50
33.40 3.85 1.75 1.26 0.30 0.21 0.50
Group IV -
Group I
13.0 20 1.15 0.52 0.92 0.70 0.40
The premix provided per 1 kg of starter (grower) diet: vitamin A – 135,000 IU (12,000 IU); vitamin D3 - 3,500 IU (3,250 IU); vitamin E – 45 mg (40 mg); vitamin K3 – 3 mg (2.25 mg); vitamin B1, 3.25 mg (2 mg); vitamin B2 - 7.5 mg (7.25 mg); vitamin B6 - 5 mg (4.25 mg); vitamin B12 - 0.0325 mg (0.03 mg); Ca-pantotenate - 15 mg (12 mg); niacin – 45 mg (40 mg); folic acid - 1.5 mg (1 mg); choline chloride –600 mg (450 mg); Mn - 100 mg (100 mg); Zn – 75 mg (65 mg); Fe - 67.5 mg (65 mg); Cu - 17.5 mg (15 mg); I - 1 mg (0.8 mg); S - 0.275 mg (0.25 mg), Co - 0.4 mg (0.4 mg).
45 Measurements. The chickens were observed regularly, on a twice-daily basis, in terms of general health. Individual body weight was registered at 1, 21, and 42 d; feed intake (FI) was recorded for 1–21 and 22–42 d, and mortality was registered. Body weight gain (BWG) and feed conversion efficiency (feed to gain ratio, FCE), adjusted for the weight of the dead birds, were calculated for each of the experimental periods (age 1 to 21 d, 22 to 42 d, and 1 to 42 d). The performance efficiency index (PI) was calculated on the basis of BWG, FCE, and mortality, using the following equation: PI = [body weight (kg) x survivability (%)/age (42 d) x FCE (kg)] x 100. At the end of the experiment, and after 12 h of starvation, 24 broilers (12 cockerels and 12 hens) were chosen from each group and decapitated. The mass of the cooled carcasses and edible giblets was estimated and the carcass, breast muscles, and abdominal fat yields were calculated, as well as the relative weights of the liver, gizzard, and spleen. Skinless samples of the breast muscles were collected from the carcasses and their dry matter, crude protein, and fat content were analysed (2). Statistical analysis. The data were subjected to a one-way factorial analysis of variance. The
significance of differences between the means of treatment was determined using Duncan’s multiple range test, with the differences being considered significant at P≤0.05. The statistical analyses were performed with Statistica 5.0 PL software (Statsoft Inc.).
Results The evaluation of the basal nutrients, minerals, and amino acids in grains of Bt corn (MON 810), and its non-modified isogenic counterpart (parental line) in the content analysed, revealed no major differences (Table 2). In the case of the soybean meals used in the study, the differences were higher; however, the values obtained for both meals were comparable and within the standard range. The mortality rate during the first 21 d averaged 1.78%; from 22 to 42 d - 1.68%; for the entire feeding period - 3.46%, ranging from 2.56% to 4.68% across dietary treatments (Table 3). In both experimental periods, mortality was random across treatments and the remaining birds were in good health.
Table 2 The chemical composition of corn grains and soybean meals used in experiment (g/kg, ‘as is’ basis) Item Dry matter Crude protein
Corn grain
Soybean meal
Conventional
GM (MON 810)
Conventional
GM (MON 40-30-2)
862 76.7
863 77.5
877 479
886 457
Crude fat
340
345
20.4
32.2
Crude fibre
18.8
18.7
36.6
42.8
Crude ash
13.0
12.4
57.0
63.1
Starch
637
628
40.8
35.4
Calcium
0.10
0.10
2.72
3.53
Phosphorus
2.87
2.83
6.44
7.01
Methionine
1.49
1.51
6.42
7.54
Lysine
2.35
2.52
28.9
29.2
Cystine
1.59
1.61
6.23
7.00
Threonine Tryptophan
2.69 0.40
2.66 0.44
17.5 5.15
18.5 7.63
Arginine
3.11
3.28
32.9
33.3
Valine
3.54
3.59
21.2
21.2
Isoleucine
2.49
2.50
23.2
20.6
Leucine
9.05
9.13
36.5
36.4
Phenyloalanine
3.51
3.54
23.6
22.9
Tyrosine
1.69
1.79
17.3
17.3
Histidine
2.33
2.35
12.0
12.5
Aspartic acid
5.59
5.49
57.1
50.5
Serine
3.00
3.20
21.6
22.4
Proline
6.14
5.99
23.5
21.6
46 Table 3 The performance of broilers fed either conventional or GM corn and soybean meal in diets
Live weight (g) 21 d 42 d Average daily body weight gain (g) 1–21 d 22–42 d 1–42 d Feed intake (g) 1–21 d 22–42 d, 1–42 d, Feed conversion efficiency (g/g) 1–21 d 22–42 d 1–42 d Mortality (%) 1–21 d 22–42 d 1–42 d Production Index 1-42 d, points 1
Treatment groups1 I II
III
IV
Statistical analysis (P level) SEM
789 2,456
783 2,464
793 2,459
787 2,472
0.9 0.974
4.5 11.6
37.4 79.4 58.9
37.0 80.1 59.1
37.6 79.3 59.0
37.2 80.3 59.3
0.9 0.853 0.973
0.225 0.423 0.283
1,145 3,235 4,380
1,143 3,235 4,378
1,157 3,261 4,418
1,155 3,274 4,429
0.856 0.872 0.845
6.09 18.9 23.0
1.534 1.94 1.815
1.545 1.926 1.808
1.542 1.958 1.829
1.55 1.943 1.821
0.956 0.884 0.934
0.009 0.013 0.011
2.38 1.78 4.16
0.6 1.98 2.58
2.38 1.18 3.56
1.78 1.78 3.56
0.39 0.467 0.894
0.406 0.39 0.305
309
313
309
312
0.941
2.76
I – non-modified corn and soybean meal, II – non-modified corn and GM soybean meal, III – GM corn and non-modified soybean meal, IV – GM corn and GM soybean meal
Table 4 The results of slaughter analysis and the chemical composition of breast muscles in broilers fed either conventional or GM corn and soybean meal in diets
Slaughter analysis Carcass yield, % of body weight Breast muscles, % of carcass Abdominal fat pad, % of carcass Liver, % of body weight Gizzard, % of body weight Spleen, % of body weight Breast muscles analysis (%) Dry matter Protein Fat 1
Treatment groups1 I II
III
IV
Statistical analysis P level SEM
77.1 26.5 1.83 2.05 1.18 0.164
77.9 26.4 1.95 1.91 1.17 0.152
77.7 26.1 1.98 2.03 1.19 0.150
77.8 26.8 1.94 1.94 1.17 0.143
0.187 0.417 0.698 0.404 0.695 0.664
0.141 0.157 0.047 0.035 0.019 0.005
25.5 23.5 1.08
25.3 23.5 1.01
25.5 23.7 1.04
25.4 23.8 1.02
0.888 0.626 0.643
0.087 0.071 0.020
I – non-modified corn and soybean meal, II – non-modified corn and GM soybean meal, III – GM corn and non-modified soybean meal, IV – GM corn and GM soybean meal
In every experimental group, good performance indices were obtained (Table 3). The mean live weight of the chickens, averaged across all the dietary treatments, was 788 g at 21 d and 2,463 g at 42 d; daily BWG was 37.3 g (1–21 d), 79.8 g (22–42 d), and 59.1 g (1–42 d); FI was 1,150 g (1–21 d), 3,251 g (22–42 d), and 4,401 g (1–42 d); FCE was 1.543 g/g (1–21 d), 1.942 g/g (22–42 d) and 1.818 g/g (1–42 d); and production index was 311 points (1–42 d). No statistical differences (P>0.05) were observed in any of the
performance parameters across dietary treatments. BWG, FI, and FCE for the first (1-21 d), second (22-42 d), and entire (1-42 d) rearing period were comparable for birds fed diets containing non-transgenic or transgenic feeds, and the performance indices obtained were, in general, similar to industry norms for broilers. No statistically confirmed differences were noted in either carcass variable measurements or the relative weights of the liver, gizzard, and spleen (Table 4). The mean carcass yield, expressed as a percentage of
47 live weight, and averaged across all dietary treatments, was 77.6%, the meat yield (as percentage of carcass weight) was 26.5%, and the abdominal fat pad (as percentage of carcass weight) was 1.93%. All the carcass measurements determined were similar for broilers fed diets containing either transgenic or nontransgenic corn and soybean meal. There were also no statistically-confirmed differences (P>0.05) between the treatments in respect to the chemical composition of the breast muscles, i.e. for dry matter, crude protein, and fat content (Table 4).
Discussion In our study, the chemical composition of GM (MON810) corn grain and its isogenic counterpart was similar. For comparison, Rossi et al. (16) found some numerical differences for protein, fat, and crude fibre content in MON 810 and non-modified, isogenic corns produced at the same farm; however, they indicated that the variability of nutrient contents in both lines were within the normally expected range. Based on detailed chemical analyses (proximate analyses, amino acids, fatty acids, and anti-nutrient content), McCann et al. (13) and Padgette et al. (15) reported that the composition of soybean seeds and processed fractions genetically-modified for glyphosate tolerance (event 4030-2 and 61-67-1) were comparable to the non-modified seeds and fractions of conventional soybean. To date, studies evaluating the nutritional value and safety of transgenic Bt corn and glyphosate-tolerant soybean meal have not demonstrated any negative effect of these feeds on broiler performance and carcass variables. For example, our results are consistent with the study conducted by Rossi et al. (16), who observed no differences for body weight gain, feed intake, or feed conversion when broilers were fed a diet containing either 50%-60% Bt corn (MON 810), or non-modified near isogenic corn. The results of the experiment with Bt 176 corn (other event, genetically-modified for protection against the European corn borer), also showed no differences in body weight gain and the majority of carcass measurements, as compared to broilers fed the control (non-modified) corn (1, 5); however, the chickens which had consumed the transgenic diet exhibited better feed conversion ratios and higher Pectoralis minor breast muscle yield (5). The authors of the publication cited above (5) indicated that these differences could not be directly attributed to corn source, but showed an absence of any detrimental effects associated with diets produced using transgenic Bt corn. No unintended effects of transgenic insect-protected corn on broiler performance were found when the Bt 11 hybrid was used as the main dietary component (4). Moreover, Aulrich et al. (3) reported no differences in dietary metabolisable energy content where broilers were fed transgenic either Bt or conventional corn (50% of the diet). In a series of experiments, Taylor et al. (22-25) studied the nutritional efficiency of different lines of genetically-modified corn for broilers. Similarly to our
results, they showed, in a 42-d experiment with chickens, that a diet with transgenic corn expressing Cry1A(b) protein (MON 810) had no negative effect on final body weight, feed conversion, and carcass yield (23). In their subsequent experiments (22, 24, 25), they observed no differences in performance indices, as compared to the control group, when broilers were fed diets containing transgenic corn, expressing Cry3Bb1 protein, modified for corn rootworm protection (event MON 863), corn expressing Cry1A(b) and CP4 EPSPS proteins, modified simultaneously for European corn borer protection and herbicide tolerance (event MON 810 x NK 603), corn expressing Cry3Bb1 and CP4 EPSPS proteins, modified for corn rootworm protection and herbicide tolerance (MON 88017), or corn expressing Cry1A(b), Cry3Bb1, and CP4 EPSPS proteins, modified simultaneously for European corn borer protection, corn rootworm protection, and herbicide tolerance (MON 88017 x MON 810). The lack of differences in the performance of broilers fed a diet containing transgenic corn that was observed in the different experiments is consistent with the compositional evaluation of Bt corn, which reveals no major differences in chemical composition in comparison to its non-modified, conventional counterpart. The number of studies comparing the performance of broilers fed a diet formulated with transgenic glyphosate-tolerant (Roundup Ready) and those fed non-modified soybean meal is limited. Similarly to our results, Hammond et al. (9) found no differences in body weight gain, feed intake, feed conversion, mortality, and meat yield when broilers were fed a diet containing approximately 30% of soybean meal produced from either GM glyphosatetolerant (MON 40-30-2) or non-modified, isogenic plants. Likewise, soybean meal produced from other glyphosate-tolerant soybean lines (MON 8978, DP356O43-5) were nutritionally equivalent to their nonmodified, conventional counterparts in broilers diets (14, 21). An absence of adverse effect produced by glyphosate-tolerant soybean seeds or extracted meal was also observed in performance parameters for pigs (7), dairy cows (9), and fish (6, 9, 18). Moreover, the results of Kan and Hartnell (12) study showed no differences in the performance of broilers fed soybean meal derived from GM insect-protected soybean (expressing Cry1Ac protein) and those fed commercial, non-modified varieties. On the basis of the results obtained, it can be concluded that insect-resistant GM corn ((MON 810) and soybean meal produced from glyphosate-tolerant GM soybean (Roundup Ready, MON 4030-2) are nutritionally equivalent to non-modified corn and soybean meal and can be used as feed components in broiler diets with no negative effect on tperformance, survivability, carcass yield measurements, or breast muscle composition.
48
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