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Poult Sci 2007. 86:2152-2161
© 2007 Poultry Science Association
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METABOLISM AND NUTRITION

Broiler Performance and Carcass Characteristics When Fed Diets Containing Lysine Maize (LY038 or LY038 x MON 810), Control, or Conventional Reference Maize

D. M. Lucas*,1, M. L. Taylor*, G. F. Hartnell*, M. A. Nemeth*, K. C. Glenn* and S. W. Davis{dagger}

* Monsanto Company, St. Louis, MO 63167; and {dagger} Colorado Quality Research, Wellington, CO 80549

1 Corresponding author: donald.m.lucas{at}monsanto.com


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
Lysine maize (Zea mays), LY038, was developed through the application of modern biotechnology to accumulate free Lys in the germ portion of maize grain and provide an alternative to direct addition of supplemental Lys to poultry diets. Maize LY038 x MON 810 was produced by conventional breeding of LY038 with MON 810, which provides the corn plant protection against feeding damage from the European corn borer. A 42-d broiler feeding study (10 pens of 10 male Cobb x Cobb 500 broilers/treatment) was conducted to compare the feeding value of grain from LY038 or LY038 x MON 810 to that of a conventional control (similar genetic background to the test maize) and 5 conventional maize hybrids. The LY038 and LY038 x MON 810 maize-based diets and control and conventional reference maize-based diets supplemented with L-Lys HCl were formulated to a Lys level below that required for optimal bird performance, whereas all other essential amino acids were present at levels, relative to Lys, above those required for optimal bird performance [1.05% and 0.90% total Lys (as-fed) for d 0 to 21 and d 21 to 42, respectively]. Total Lys level in control and reference maize-based diets without supplemental L-Lys HCl was formulated to be 0.079% lower than supplemented diets. Weight gain, feed efficiency, and carcass yield and composition of broilers fed diets containing LY038 or LY038 x MON 810 were not different (P > 0.05) from that of broilers fed L-Lys HCl-supplemented diets and were superior (P ≤ 0.05) to that of broilers fed conventional maize diets without supplemental L-Lys HCl. Both broiler performance and carcass data demonstrate that the bioefficacy of the incremental Lys in LY038 or LY038 x MON 810 grain was not different from that of Lys in conventional maize diets supplemented with L-Lys HCl. Thus, LY038 and LY038 x MON 810 can be considered as wholesome as and more nutritious than conventional maize due to its higher-than-average Lys content.

Key Words: broiler performance • carcass quality • Corynebacterium glutamicum-derived lysine feedback insensitive dihydrodipicolinate synthase • cordapA • lysine • maize


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
Maize (Zea mays)-soybean meal-based broiler diets formulated to include animal protein products, corn gluten meal, or other protein supplements low in Lys are characteristically deficient in Lys and require Lys supplementation for optimal bird performance and carcass characteristics (NRC, 1994; Kidd et al., 1998; Corzo et al., 2002, 2006). The development of Lys maize (LY038) through the application of biotechnology provides an alternative to direct addition of supplemental Lys to poultry diets by increasing the amount of Lys in maize grain.

Lysine maize (hereafter called LY038 or LY038 x MON 810) was developed by stably integrating into the maize genome the cordapA coding sequence under the control of the maize Glb1 promoter to direct the expression of the Corynebacterium glutamicum-derived Lys feedback insensitive dihydrodipicolinate synthase (cDHDPS) protein predominantly in the germ portion of maize kernels (Belanger and Kriz, 1991; Falco et al., 1995; Galili, 2002). The introduction of the cordapA gene into maize results in the production of maize grain with higher-than-average Lys content, relative to conventional maize, and improved nutritional value for use as a feed ingredient in broiler diets. The LY038 was conventionally bred with MON 810, which produces the Cry1Ab protein from Bacillus thuringiensis ssp. kurstaki strain HD-1, protecting against feeding damage from the European corn borer (Ostrinia numbilalis). The resulting combined-trait maize, LY038 x MON 810, is protected from feeding damage by the European corn borer and produces grain with higher-than-average Lys content, relative to conventional maize. Results from past broiler studies (Taylor et al., 2003a,b,c; Flachowsky et al., 2005) have shown that inclusion of MON 810 grain in broiler diets had no meaningful negative effect on broiler performance or carcass characteristics compared with those of broilers fed conventional maize grain-based diets.

This study was designed to evaluate performance and carcass characteristics of broilers fed diets containing LY038 or LY038 x MON 810 compared with that of broilers fed control or conventional reference corn-based diets formulated to a Lys level below that required for optimal bird performance, whereas all other essential amino acids were present at levels, relative to Lys, above those required for optimal bird performance (NRC, 1994; Emmert and Baker, 1997). The bioefficacy of the incremental Lys in LY038 and LY038 x MON 810 was assessed by comparing responses of broilers fed diets containing LY038 and LY038 x MON 810 with those of broilers fed control and conventional reference maize diets formulated with and without supplemental crystalline Lys (L-Lys HCl). L-Lysine HCl has been reported to be approximately 100% bioavailable for broilers (Sibbald and Wolynetz, 1985; Nelson et al., 1986; Izquierdo et al., 1988; Neme et al., 2001). All diets were formulated to the same nutrient specifications with the exception of the intended difference in Lys concentration. L-Lysine HCl was added to the Lys-supplemented diets to provide a dietary Lys concentration equivalent to that of diets containing LY038 and LY038 x MON 810 grain. Observation of bird performance and health throughout the study provided a basis for assessing the wholesomeness of diets containing LY038 and LY038 x MON 810 grain compared with L-Lys HCl-supplemented control or conventional reference maize grain-based diets.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 REFERENCES
 
Broilers and Housing
This study was conducted in accordance with the principles and guidelines for the care and use of agricultural animals in research (FASS, 1999) and, as applicable, in compliance with FDA (1979) and EPA (1983) good laboratory practice regulations. Male broiler chickens of a high-yielding commercial strain (Cobb x Cobb 500, Cobb-Vantress Hatchery, Cleveland, GA) were obtained at 1 d of age. Broilers were vaccinated for Marek’s disease at the hatchery and for Newcastle disease and infectious bronchitis upon arrival at the test site. The broilers were randomly assigned to clean pens with concrete floors (1.5 x 0.9 m, providing approximately 0.09 m2 of floor space per bird, excluding feeder space), containing 10 to 13 cm of unused wood shavings in an environmentally controlled building with incandescent lighting. Incandescent lighting was provided for 23 to 24 h/d for approximately the first 4 d and for 10 to 16 h for the remainder of the study. The target room temperature was 34°C at the start of the study and was gradually decreased to a target room temperature of 23°C from d 30 through the remainder of the study. Water and feed were available for ad libitum consumption throughout the study via 5 automatic nipple drinkers and a hanging tube feeder (43-cm diameter) in each pen. A chick feeder tray was placed in each pen for the first 6 d. Environmental conditions (floor space, temperature, lighting, bird density, and feeder and waterer space) were similar for all treatments.

Experimental Design
Eight maize sources (LY038, LY038 x MON 810, a conventional control with similar genetic background to the test maize, and 5 conventional reference hybrids) were used to formulate 14 diets. Grain from multiple conventional reference maize hybrids was included to demonstrate the range of broiler performance and carcass characteristics observed for diets containing different commercially available reference maize hybrids under the conditions of this feeding study. Control and 5 reference maize grain sources were formulated into diets with and without supplemental L-Lys HCl. Targeted Lys concentration of the respective control and reference maize diets, with and without L-Lys HCl supplementation, differed by 0.079 percentage units. The 14 dietary treatments were assigned in a randomized complete block design to 10 blocks of 14 pens. Each dietary treatment was offered to 10 pens of 10 birds each (100 birds/treatment, a total of 1,400 birds). An additional 2 chicks were placed in each pen initially (total of 12 birds/pen) to compensate for early chick mortality during the first 7 d posthatch. At d 7, the group size was standardized to 10 broilers/pen. The initial criterion for d-7 bird removal was slow growth, followed by random selection for the majority of birds removed.

Maize Grain
The LY038, LY038 x MON 810, control [LY038(-)], and 1 conventional reference grain (DKC61-42) were produced in Maui County, Hawaii, during the 2004–2005 growing season. The other 4 conventional reference grain sources included in this study (Pfister 2730, Asgrow RX772, DKC62-15, and Pioneer 34M94) were produced in Warren County, Illinois, in 2004. Mycotoxin (Romer Laboratories, Union, MO) and pesticide residue (Covance Laboratories, Madison, WI) analyses were conducted on each corn grain source before initiation of the study to verify that the levels were below the limits of concern for broiler performance. Proximate [CP (955.04 and 979.09), crude fat (960.39 and 948.22), crude fiber (962.09), ash (942.05), and moisture (926.08 and 925.09)] and amino acid (982.30) and analyses (Covance Laboratories) were performed on the grain according to methods of AOAC International (2005). Carbohydrate values were calculated by difference using the fresh weight-derived data [% carbohydrates = 100% – (% protein + % fat + % moisture + % ash)].

Diets
Diets were formulated based on the nutrient analyses for specific lots of LY038, LY038 x MON 810, conventional control [LY038(-)], and conventional reference maize fed in this study (Table 1Go). A crumbled starter diet (59% wt/ wt maize, as fed) was fed from d 0 to 21 (Table 2Go), and a pelleted grower-finisher diet (66% wt/wt maize, as fed) was fed from d 21 to 42 (Table 3Go). Diets containing LY038 or LY038 x MON 810 and diets containing control [LY038(-)] or conventional reference maize supplemented with L-Lys HCl were targeted to contain 1.05 and 0.90% total Lys, as-fed basis, for the starter and grower-finisher phases, respectively. The diets containing control [LY038(-)] or conventional reference grain and not supplemented with L-Lys HCl were targeted to contain approximately 0.97 and 0.82% total Lys for the starter and grower-finisher phases, respectively. Based on results of previously published studies (Kidd et al., 1998; Labadan et al., 2001; Corzo et al., 2002, 2006) and the results of a preliminary experiment using the same strain of birds and test facility utilized for the current study, the selected target dietary Lys concentrations were expected to be in a range in which bird performance and carcass parameters would be sensitive to a change in dietary Lys concentration. Lysine levels in all diets were below the NRC (1994) requirements and the Illinois ideal Lys:amino acid ratios (Emmert and Baker, 1997), so the broilers would be growth-responsive to changes in dietary Lys quantity and availability. The amount of L-Lys HCl added to the diets requiring Lys was determined based on the difference between the amount provided by the maize, soybean meal, and corn gluten meal and the desired level of total dietary Lys. Methionine, Cys, Arg, Trp, and Thr were formulated to meet or exceed 105% of the Illinois ideal Lys:amino acid ratio based on 1.05 and 0.90% Lys levels for the starter and grower-finisher diets, respectively. This assured that Lys would be the first limiting amino acid in all study diets. A coccidiostat, salinomycin (Sacox, Intervet Inc., Millsboro, DE), was included in all diets at a level of 50 g/ton. Diets were analyzed (University of Missouri, Experiment Station Chemical Laboratories, Columbia, MO) to confirm nutrient composition (Tables 2Go and 3Go).


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  		Table 1. Proximate (%) and amino acid (mg/g) composition1 of LY038, LY038 x MON 810, control LY038(-), and conventional reference maize (as-fed basis)
 

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  		Table 2. Starter diet formulation and nutrient composition (as-fed basis)1
 

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  		Table 3. Grower-finisher diet formulation and nutrient composition (as-fed basis)1
 
Measurements
Broilers were examined twice daily for general health. All broilers that died and those euthanized due to their unhealthy condition were weighed and necropsied. The probable cause of death or reason for removal was documented. Broilers were weighed by pen at d 0, 21, and 42 and individually before processing at study termination (d 43, 44, or 45). Weight gain (g) and feed intake (g) were determined for d 0 to 21, d 21 to 42, and d 0 to 42 intervals allowing calculation of feed efficiency (adjusted gain:feed, g:g) by pen for the same intervals based on total weight of surviving broilers in the pen adjusted for weight gain of any broilers that died or were culled during the study. At study termination, all surviving birds were processed to determine carcass yield and meat composition. Fat pad measurements were taken for each bird. Moisture, protein, and fat analyses (University of Missouri, Experiment Station Chemical Laboratories) were conducted on skinless breast and thigh meat samples from 1 randomly selected broiler per pen.

Statistical Analyses
Statistical analyses were conducted on performance (live weight, feed consumption, and adjusted feed efficiency for d 0 to 21, d 21 to 42, and d 0 to 42 intervals) and carcass [chilled carcass and fat pad weight (g and % live wt) and breast, thigh, drum, and wing weight (g and % chilled wt)] measurements, as well as moisture, protein, and fat values for breast and thigh meat. Statistical analysis (ANOVA) was carried out using a linear mixed model procedure (PROC MIXED) of SAS version 9.1 (SAS Online Doc, SAS Institute Inc., Cary, NC).

The statistical model included effects of treatment and block, with the experimental unit being the pen. The main effect of diet was tested, and if the overall F-test for the diet effect was significant (P ≤ 0.05), the following mean value contrasts were made at the 5% level of significance: (1 and 2) LY038 and LY038 x MON 810 diets, respectively, vs. the control [LY038(-)] diet without supplemental Lys; (3 and 4) LY038 and LY038 x MON 810 diets, respectively, vs. the control [LY038(-)] diet with supplemental Lys; and (5) the population of control [LY038(-)] and reference hybrid diets without supplemental Lys vs. the population of control [LY038(-)] and reference hybrid diets with supplemental Lys.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
REFERENCES
 
General Observations
Grain Characterization.
Mycotoxin and pesticide levels in all maize grain lots used in this study were below the limits of concern for broiler performance (data not shown). Aflatoxins B1, B2, G1, and G2 were below the limit of detection of 1.0 ppb, and levels of fumonisins B1, B2, and B3 in the grain ranged from not detectable to 4.9 ppm. All pesticide values were below the assay limits of detection: organophosphates (0.050 ppm), organonitrogens (0.500 ppm), organochlorinates (0.200 ppm), and N-methylcarbamates (0.100 ppm).

Diet Analytics.
The targeted Lys levels for the diets containing LY038 and LY038 x MON 810 as well as control and reference maize diets supplemented with L-Lys HCl were 1.05 and 0.90% in the starter and grower-finisher diets, respectively. The measured Lys levels in the LY038 and LY038 x MON 810 diets averaged 1.08 and 1.03% for the starter diet and 0.89 and 0.91% for the grower-finisher diet (Tables 2Go and 3Go, respectively). Control and reference maize diets supplemented with Lys ranged from 1.05 to 1.13% (average 1.08%) for the starter diets and ranged from 0.87 to 0.92% (average 0.89%) for the grower-finisher diets. Differences in Lys levels between control and reference maize diets with and without supplemental Lys were targeted to be 0.079% for both starter and grower-finisher diets. The measured differences in Lys levels between diets with and without supplemental Lys ranged from 0 to 0.12% (average 0.07%) for the starter diets and from 0.04 to 0.09% (average 0.06%) for the grower-finisher diets. Based on the bird performance results obtained in this study, the formulated Lys levels, supported by detailed feed preparation records, most likely reflect the actual Lys level in the diets more accurately than the measured Lys levels presented in Tables 2Go and 3Go.

Broiler Health.
The birds in all groups were in good health throughout the study based on twice daily pen observations. During the first 7 d of the study, chick mortality was low (total of 8 birds, 0.5%, due to bacterial infection) and unrelated to treatment. Similarly, mortality from d 7 to 42 was low and unrelated to treatment, averaging 1.1% and ranging from 0 to 2% across all treatments (data not shown).

Responsiveness of the Test System to Change in Dietary Lys
The growth responsiveness of broilers to Lys was demonstrated by measured differences (P ≤ 0.05) in rate of weight gain and feed efficiency of broilers fed diets containing control and conventional reference maize supplemented with Lys compared with their nonsupplemented Lys-deficient counterparts for d 0 to 21, d 21 to 42, and d 0 to 42 (Table 4Go). Carcass yield measurements (chilled carcass, fat pad, breast, drum, and wing weight, but not thigh weight) as well as meat composition (moisture and protein, but not fat, content of breast and thigh meat) responded (P ≤ 0.05) to a calculated 0.079% Lys addition to starter and grower-finisher diets containing lower total Lys content than required for optimal bird performance and carcass quality. Increased BW and improved feed efficiency with Lys addition to Lys-deficient diets has been reported by numerous investigators (Kidd et al., 1998; Labadan et al., 2001; Corzo et al., 2002, 2006). These results are also consistent with results of a preliminary experiment with male Cobb x Cobb 500 strain commercial broilers in the same test facility used for the current study that yielded the following optimal dietary Lys concentrations (as-fed basis) for respective growth phases (diets) and parameter responses: 1) for d 0 to 21 (starter diet), 1.22% for weight gain and 1.38% for feed efficiency; 2) for d 21 to 42 (grower diet), 0.87% for weight gain and 1.04% for feed efficiency and 0.92 and 0.95% for breast yield (g and % chilled carcass, respectively); and 3) for d 42 to 56 (finisher diet), 0.96% for weight gain, 0.97% for feed efficiency, and 0.90 and 0.96% for breast yield (g and % chilled carcass, respectively).


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  		Table 4. Response of broilers fed control LY038(-) or conventional reference maize-based diets with (+L) or without (NL) supplemental L-Lys HCl1
 
Performance and Carcass Quality
Performance means and SEM for diets formulated with LY038 or LY038 x MON 810, or control [LY038(-)] and each of 5 reference maize hybrids, each with and without supplemental L-Lys HCl, are summarized for d 0 to 21, d 21 to 42, and d 0 to 42 in Table 5Go. The bioefficacy of the incremental Lys in LY038 and LY038 x MON 810 was demonstrated by weight gain and feed efficiency improvements (P ≤ 0.05) for both the starter and grower-finsher phases and the entire test period for broilers fed diets containing LY038 or LY038 x MON 810 vs. diets containing either the control or conventional reference maize not supplemented with L-Lys HCl (Table 5Go). Growth rate and feed efficiency observed for broilers fed diets containing LY038 or LY038 x MON 810 were not different (P > 0.05) from those of broilers fed highly bioavailable L-Lys HCl-supplemented control or conventional reference maize-based diets for both the starter and grower-finsher phases and the entire test period.


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  		Table 5. Performance of broilers fed LY038, LY038 x MON 810, and control LY038(-) and commercial maize-based diets with (+L) or without (NL) supplemental Lys1
 
Carcass yield and meat (skinless breast and thigh) composition data for birds fed diets formulated with LY038 or LY038 x MON 810, or control [LY038(-)] and each of 5 conventional reference maize hybrids, each with and without supplemental L-Lys HCl, are summarized in Table 6Go. The weight and percentage (with exception of % thigh) of broiler carcass components increased (P ≤ 0.05) when the control and reference maize diets formulated with Lys as the limiting amino acid were supplemented with L-Lys HCl. Bioefficacy of the incremental Lys in LY038 and LY038 x MON 810 grain [present as free Lys as compared with essentially all the Lys in conventional maize that is present as protein-incorporated Lys (see total and free Lys content of each grain source fed in this study in Table 1Go)] was demonstrated by improved (P ≤ 0.05) yield of total chilled carcass and parts, including breast, drums, and wings, but not thighs (Table 6Go), for birds fed LY038 or LY038 x MON 810 compared with birds that received control or reference maize Lys-deficient diets without Lys supplementation. Further evidence of the bioefficacy of Lys in LY038 and LY038 x MON 810 grain is shown by the similar (P > 0.05) weight, percentage, and chemical composition (% protein, fat, and moisture in skinless breast and thigh tissues) of measured carcass components from birds fed LY038 or LY038 x MON 810 vs. those of birds fed control or reference maize diets supplemented with L-Lys HCl (Table 6Go).


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  		Table 6. Carcass characteristics of broilers fed LY038, LY038 x MON 810, and control LY038(-) and commercial corn-based diets with (L+) and without (NL) supplemental Lys1
 
Relatively small changes in growth rate, feed efficiency, and carcass measurements as a result of a change in nutritional or health status can be detected in the fast-growing broiler. Assessment of facility historical data using a similar experimental design (Taylor et al., 2003a,b,c) indicates treatment differences of approximately 4% in broiler weight gain and 2% in feed conversion would be identified as significant (P ≤ 0.05).

The bioefficacy and bioavailability of the incremental Lys expressed in LY038 and LY038 x MON 810 grain was demonstrated by the lack of difference (P > 0.05) in performance and carcass measurements of birds fed diets formulated with LY038 or LY038 x MON 810 compared with the performance and carcass measurements for birds fed diets containing either the control or conventional reference maize at the same inclusion rate as LY038 and supplemented with L-Lys HCl. Enhanced growth, feed efficiency, and carcass yield due to the increased level of available Lys in LY038 and LY038 x MON 810 grain were demonstrated by the superior (P ≤ 0.05) performance of broilers fed diets containing LY038 or LY038 x MON 810 compared with that of broilers fed control or conventional reference grain diets without supplemental Lys but otherwise identical in composition. No unexpected effects on bird performance or health were observed with the feeding of LY038 or LY038 x MON 810 grain. Therefore, LY038 and LY038 x MON 810 can be considered as wholesome as conventional maize when fed to poultry and more nutritious than conventional due to its higher-than-average Lys content, relative to conventional maize.

Received for publication February 26, 2007. Accepted for publication June 15, 2007.


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 ABSTRACT
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 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
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Belanger, F. C., and A. L. Kriz. 1991. Molecular basis for allelic polymorphism of the maize Globulin-1 gene. Genetics 129:863–872.[Abstract]

Corzo, A., W. A. Dozier III, and M. T. Kidd. 2006. Dietary lysine needs of late-developing heavy broilers. Poult. Sci. 85:457–461.[Abstract/Free Full Text]

Corzo, A., E. T. Moran Jr., and D. Hoehler. 2002. Lysine need of heavy broiler males applying the ideal protein concept. Poult. Sci. 81:1863–1868.[Abstract/Free Full Text]

Emmert, J. L., and D. H. Baker. 1997. Use of the ideal protein concept for precision formulation of amino acid levels in broiler diets. J. Appl. Poult. Res. 6:462–470.[Abstract/Free Full Text]

EPA. 1983. 40 CFR Part 160. Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Environ. Prot. Agency, Washington, DC.

Falco, S. C., T. Guida, M. Locke, J. Mauvals, C. Sanders, R. T. Ward, and P. Webber. 1995. Transgenic canola and soybean seeds with increased lysine. Biotechnology (N. Y.) 13:577–582.[Medline]

FASS. 1999. Guidelines for the Care and Use of Agricultural Animals in Research and Teaching, 1st rev. Fed. Anim. Sci. Soc., Savoy, IL.

FDA. 1979. 21 CFR Part 58. Good Laboratory Practice Regulations for Nonclinical Laboratory Studies. Food Drug Admin., Washington, DC.

Flachowsky, G. A., A. Chesson, and K. Aulrich. 2005. Animal nutrition with feeds from genetically modified plants. Arch. Anim. Nutr. 59:1–40.[Web of Science][Medline]

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Izquierdo, O. A., C. M. Parsons, and D. H. Baker. 1988. Bioavailability of lysine in L-lysine HCl. J. Anim. Sci. 66:2590–2597.[Abstract/Free Full Text]

Kidd, M. T., B. J. Kerr, K. M. Halpin, G. W. McWard, and C. L. Quarles. 1998. Lysine levels in starter and grower-finisher diets affect broiler performance and carcass traits. J. Appl. Poult. Res. 7:351–358.[Abstract/Free Full Text]

Labadan, M. C., Jr., K. N. Hsu, and R. E. Austic. 2001. Lysine and arginine requirements of broiler chickens at two- to three-week intervals to eight weeks of age. Poult. Sci. 80:599–606.[Abstract/Free Full Text]

Nelson, T. S., L. K. Kirby, and J. T. Halley. 1986. Digestibility of crystalline amino acids and the amino acids in corn and poultry blend. Nutr. Rep. Int. 34:903–906.[Web of Science]

Neme, R., L. Albino, H. Rostagno, R. Rodrigueiro, and R. Nunes. 2001. True digestibility of lysine HCl and lysine Sulfate determined with cecectomized adult roosters. Rev. Bras. Zootec. 30:1531–1535.

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Sibbald, I. R., and M. S. Wolynetz. 1985. The bioavailability of supplementary lysine and its effect on the energy and nitrogen excretion of adult cockerels fed diets diluted with cellulose. Poult. Sci. 64:1972–1975.[Web of Science][Medline]

Taylor, M. L., G. F. Hartnell, S. G. Riordan, M. A. Nemeth, K. Karunanandaa, B. George, and J. D. Astwood. 2003a. Comparison of broiler performance when fed diets containing grain from Roundup Ready (NK603), YieldGard x Roundup Ready (MON 810 x NK603), non-transgenic control, or commercial corn. Poult. Sci. 82:443–453.[Abstract/Free Full Text]

Taylor, M. L., G. F. Hartnell, S. G. Riordan, M. A. Nemeth, K. Karunanandaa, B. George, and J. D. Astwood. 2003b. Comparison of broiler performance when fed diets containing grain from YieldGard (MON 810), YieldGard x Roundup Ready (GA21), nontransgenic control, or commercial corn. Poult. Sci. 82:823–830.[Abstract/Free Full Text]

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