The effect of storage of cereal grain and enzyme supplementation on measurements of AME and broiler chick performance

Transcription

1 The effect of storage of cereal grain and enzyme supplementation on measurements of AME and broiler chick performance T. A. Scott 1, and A. B. Pierce 2 1 Pacific Agri-Food Research Center, Agassiz, British Columbia, Canada V0M 1A0 ( scottta@em.agr.ca); 2 United Grain Growers- Livestock Services Division, Box 50, Site 2 RR 2, Okotoks, Alberta, Canada T0L 1T0. Contribution no. 631, received 26 June 2000, accepted 22 December Scott, T. A. and Pierce, A.B The effect of storage of cereal grain and enzyme supplementation on measurements of AME and broiler chick performance. Can. J. Anim. Sci. 81: There is a concern that feeding newly harvested cereal grain results in poor performance in poultry. A broiler chick apparent metabolizable energy (AME) bioassay was used to measure changes in feeding value of wheat (n = 14), hulless (n = 10) and hulled (n = 14) barley with or without a commercial enzyme appropriate for wheat- or barley-based diets. In the broiler chick bioassay, four pens of six male broiler chicks were fed ad lib, from 4 to 17 d, diets containing 80% of a test cereal grain and a high-protein basal mixture containing 1% celite as an acid-insoluble ash marker. Each of the cereal-grain-based diets, with or without enzyme, was tested within 3 mo of harvest and again 6 mo later. With cereal grain storage there were consistent (P < 0.05) increases in feed intake (FI) between 4 and 17 d and body weight (BW) at 17 d of age with wheat-based diets fed with (12.5 and 16.9%, respectively, for FI and BW) or without (16.1 and 22.7%) enzyme. In hulless barley diets without enzyme, there was a significant improvement in BW (7.5%) with storage, while storage had a significant effect on FI and BW (2.9 and 6.3%, respectively) when fed with enzyme. For all other barley diets there was a positive effect of storage on FI and BW, but it was not significant. Feed conversion ratios decreased marginally (P > 0.05) with storage of cereal grain. AME of diets was improved within each period by enzyme supplementation. However, there were measurable decreases (P < 0.05) in AME with storage of cereal grains for the three cereal grains with enzyme supplementation (ranging from 3.2 to 8.2%). The r 2 of the above measurements for the different sources of cereal grain between storage periods ranged from 0.65 to 0.94, indicating that the relative ranking of the cereal grains, with respect to feeding value, remained similar during storage. Increases in FI with storage were not significantly related to the attempts of the broiler chicks, to maintain metabolizable energy (ME) intake. Therefore, this increases our concerns that factors in newly harvested cereal grains may exist and that they may limit voluntary feed intake and/or growth. Key words: Cereal grain storage, AME, broiler performance, wheat, barley Scott, T.A. et Pierce, A. B Effet du type de céréale, de la durée d entreposage et des suppléments enzymatiques sur la performance des poussins à griller et détermination de l EMA. Can. J. Anim. Sci. 81: L industrie des aliments pour animaux continue de se méfier des céréales récemment récoltées qui seraient responsables d une piètre performance chez les volailles. Toutefois, on dispose de peu de données pour étayer cette opinion. Un essai biologique basé sur la détermination de l énergie métabolisable apparente (EMA) chez des poussins à griller a été utilisé pour mesurer la valeur fourragère du blé (n = 14), de l orge à grains nus (n = 10) et de l orge vêtue (n = 14), avec ou sans ajout d une préparation enzymatique commerciale convenant aux régimes à base de blé ou d orge. Pour l essai biologique chez les poussins à griller, on a utilisé quatre cages renfermant six poulets à griller mâles recevant à volonté, pendant 4 à 17 jours, une ration renfermant 80 % d une céréale d essai et un mélange de base à haute teneur en protéines renfermant 1% de célite comme marqueur des cendres insolubles dans l acide. Chacun des régimes à base de céréale, avec ou sans enzymes, a fait l objet d un essai moins de 3 mois après la récolte de la céréale et 6 mois plus tard. L entreposage des céréales augmentait généralement la prise alimentaire (PA) (P < 0,05) chez les poussins de 4 à 17 jours et le poids corporel (PC) chez les poussins de 17 jours dans le cas des rations à base de blé avec ajout d enzymes (PA = 12,5% et PC = 16,9 %) ou sans ajout d enzymes (PA = 16,1% et PC = 22,7%). Dans les régimes à base d orge à grains nus sans enzymes, l entreposage se traduisait par une amélioration significative du PC de 7,5%, mais pas de la PA, alors que la présence d enzyme dans ce cas se traduisait par une amélioration significative de la PA de 2,9% et du PC de 6,3%. Pour tous les autres régimes à base d orge, on a observé un effet positif, mais non significatif, sur la PA et le PC. L indice de consommation diminuait légèrement (P > 0,05) avec l entreposage des céréales. Les suppléments d enzymes amélioraient l EMA des régimes à chaque période. Toutefois, il y avait une diminution mesurable (P < 0,05) de l EMA avec l entreposage des céréales dans le cas des trois types de céréales supplémentées aux enzymes (de 3,2% à 8,2%). Les valeurs de r 2 pour les mesures susmentionnées pour les différentes sources de céréales entre les périodes d entreposage étaient comprises entre 0,71 et 0,94, ce qui indique que le classement relatif des céréales en ce qui concerne leur valeur alimentaire reste le même après entreposage. En outre, cela indique que des facteurs dans les céréales récemment récoltées peuvent réduire de façon significative la prise volontaire d aliments et la croissance qui en résulte. Mots clés: Entreposage des céréales, EMA, performance des poussins à griller, blé, orge Abbreviations: AME, apparent metabolizable energy; BW, body weight; E+, with enzyme supplementation; E, no enzyme supplementation; FI, feed intake; ME, metabolizable energy; NSP, non- starch polysaccharide; TME, true metabolizable energy 237

2 238 CANADIAN JOURNAL OF ANIMAL SCIENCE Feedmill nutritionists in western Canada have concerns regarding new crop syndrome, which results in compromised performance when poultry are fed diets formulated with recently harvested cereal grains (A. Pierce, personal observation). The limited reports regarding the impact of newly harvested cereal grain on poultry performance are contradictory. Brufau et al. (1993) and Bartov (1996) reported no impact on the performance of poultry when fed newly harvested barley or corn. Huyghebaert and Schöner (1999) reported that storage of eight newly harvested wheat samples for 5 mo did not affect the ME levels measured, nor did storage change the relative rank for ME, or the individual wheat sample response to enzyme supplementation. However, Fuente et al. (1998) reported that a newly harvested barley was not as well utilized by broilers, and young (10 d of age), as compared to older (30 d of age) broilers were negatively impacted for a longer time after the grain was harvested. These reports did not indicate changes of ad libitum feed intake and performance due to storage of cereal grain. Waters and Choct (1998) indicated that the nutritive value of cereal grains for poultry generally changes during storage. These authors attributed this change to degradation of the viscous non-starch polysaccharides (NSP). Degradation of NSP would lower digesta viscosity and result in an improvement in performance, similar to that experienced when diets are supplemented with NSP degrading enzymes (Bedford 1996). This is supported by observations that betaglucan levels of barley decreased with storage (Hesselman et al. 1981; Brufau et al. 1993). Pomeranz (1974) reported that long-term storage of cereal grain resulted in a decrease in fat content of the cereal grain, and an increase in free fatty acids, both factors that would be expected to reduce the energy availability of the cereal grain. Fuente et al. (1998) demonstrated that AME measurements using young broiler chicks were improved with storage of one source of freshly harvested barley. They recommended that freshly harvested barley be stored longer (minimum 10 wk) for very young broilers (less than 10 d of age) than for older (30 d of age) broilers, where a minimum storage of 3 wk was indicated. Of significance in their study, with respect to interpretation of ME measurements, TME measurements (using adult cockerels) of the same barley and storage times failed to demonstrate any differences in ME levels with storage. Variability in feeding value of western Canadian wheat and barley sources has been measured by bioassay (Scott et al. 1998a,b). Variation in AME of wheat- or barley-based diets was significantly reduced with enzyme supplementation, indicating that low AME cereal grains generally benefit more from enzyme supplementation than high AME cereal grains. Scott et al. (1998c) reported that the relationship between broiler performance (growth, feed intake, and feed conversion) and AME values was low. This lack of relationship leads to the supposition that other factors, besides dietary AME level, exist and reduce the broiler s voluntary intake of feed, and hence, growth rate. This study attempts to qualify if changes in cereal grains (wheat, hulled and hulless barley) during storage (within Table 1. Geographical distribution of cereal grain types tested in bioassay series within 3 mo of harvest and again 6 mo later Samples tested Barley Geographical location Wheat Hulled Hulless Okanagan Valley, British Columbia Edmonton, Alberta Ste-Anne, Manitoba Lethbridge, Alberta Olds, Alberta Total mo of harvest and again 6 mo later) significantly impact cereal grain ME content and/or broiler performance (growth, voluntary feed intake and feed conversion). A total of 38 different cereal grains forming 80% of a test-diet with or without supplementation with an appropriate commercial enzyme were evaluated. MATERIAL AND METHODS Cereal Grain, Storage Treatments, Diets, and Bioassay Fourteen hulled barley, 10 hulless barley and 14 wheat samples were tested in a broiler chick bioassay (Scott et al. 1998a), with or without a commercial source of enzyme, within 3 mo of harvest and again 6 mo later. Approximately 100 kg each of different sources of cereal grains were gathered from five locations in western Canada by feed mill personnel shortly after harvest. The cereal grain sources were identified by geographical location and class of cereal grain (i.e., wheat, hulled or hulless barley) and shipped to the Pacific Agri-Food Research Centre for bioassay evaluation (Table 1). All research protocols are pre-approved by the PARC Animal Care Committee in compliance with guidelines of the Canadian Council on Animal Care. Bioassay evaluation of feeding values for the 38 cereal grains (with or without enzyme), was completed in three initial bioassay series, each of 17 d duration, in the autumn/winter of Approximately 6 mo later a second bioassay of the same samples, in similar series allocations, was completed. A control wheat and hulled barley (unknown date of harvest, but maintained in storage for more than 12 mo before the start of the study) were fed in each bioassay series with or without an appropriate NSP enzyme. The control cereal grains were included to evaluate variation between bioassay series due to chick quality, environment, etc. The variation in broiler chick performance and AME measurements for common control samples, tested in each series, was small (less than 3%); and variation was not parallel with storage period. Therefore, based on response measured for control samples, the data for test cereal grains was not adjusted, and the variation was assumed to be random. The data for control samples was not included in subsequent analysis for effect of storage. Specifics of the bioassay have been published elsewhere (Scott et al. 1998a). Briefly, 45 to 50 kg of test cereal grain

3 SCOTT AND PIERCE EFFECT OF CEREAL GRAIN STORAGE ON BROILERS 239 are ground (3.6-mm screen) and mixed [80% cereal grain: 20% basal, containing 1.1% (by weight of complete diet) acid insoluble ash marker for digestibility determinations]. This diet is then split, one portion maintained as-is, the other portion supplemented with 0.10% enzyme (Avizyme-1100 for barley and Avizyme-1300 for wheat were supplied by Finnfeeds Int., PO Box 777, Marlborough, Wiltshire SN8 1XN, UK) appropriate for the type of cereal in the diet. The diets were fed ad libitum to four replicate cages of six male broiler chicks from 4 to 17 d of age. During the feeding period (4 to 17 d) broiler performance was monitored and expressed as feed intake (g bird 1 d 1 ) between 4 and 17 d, body weight (g) at 17 d, and feed:gain between 4 and 17 d. At 16 d, clean stainless steel collection trays were placed under each cage and excreta from the birds was collected for 24 h. A sub-sample of clean (i.e., free of obvious feathers and feed contaminants) excreta was collected in 250-mL plastic specimen cups, weighed, freeze-dried and reweighed, to determine excreta dry matter. Finely ground samples of diets and excreta were analysed for dry matter, acid insoluble ash, and GE by bomb calorimetry. These measurements were used to determine the AME of the diet (kcal ME kg 1 diet). Since the present study is a comparison of performance and digestibility, the AME determination was not corrected for nitrogen to reflect the AME of the complete diet with respect to performance. Statistical Analysis Data for each class of cereal grain (i.e., wheat, hulled and hulless barley), with or without enzyme, were analysed separately for the effect of storage time. Because sample numbers from each geographical location were small and the actual cultivars of each cereal grain were inconsistent, it was felt that analysis for differences in location effects would be confounded. Therefore, cereal grain sources, regardless of location, were assumed to be independent. Initial statistical analysis did not demonstrate any noteworthy enzyme and storage time interactions; therefore, the analyses were performed using the General Linear Models (GLM) procedure within each cereal type (with or without enzymes) for the main effect of storage time, with random error (between sources of specific cereals and between-cage variables) the error term (SAS Institute, Inc. 1993). Significant treatment effects are assumed to be P RESULTS AND DISCUSSION There were no changes in 1000-kernel weight (g) during the 6 mo storage of the 14 barley, 10 hulless barley and 14 wheat samples. However, there were decreases in moisture content of hulless barley (12.8 versus 11.9% moisture) and wheat (13.7 versus 12.8%) samples during storage. Overall, the broiler chick performance and AME determinations for the samples of wheat, hulled and hulless barley, were typical of measurements obtained with the young broiler chick bioassay (Scott et al. 1998a) (Table 2). There was a positive response to enzyme supplementation for all measurements except for feed intake of wheat-based diets. Only for excreta dry matter (collected at 16 d of age) for hulled barley was there a storage time-by-enzyme interaction. Six months of storage of the newly harvested cereal grain samples and enzyme supplementation of diets, compared with diets without enzyme, generally resulted in changes in excreta dry matter, BW at 17 d of age, and FI between 4 and 17 d. No changes in feed conversion ratio with storage were detected, except for wheat without enzyme, where storage resulted in a 4.5% improvement (i.e., lower) in feed conversion ratio. Average AME of diets with enzyme, but not without enzyme, were significantly decreased by storage of cereal grain. This is contrary to the effect of storage reported by Fuente et al. (1998) with one sample of barley. Huyghebaert and Schöner (1999) could not identify any change in AME level, or change in relative rank of AME level of eight wheat sources fed with or without enzyme, following storage for 5 mo. Fuente et al. (1998) and Huyghebaert and Schöner (1999) did not measure the birds response to diets with or without enzyme. Excreta dry matter decreased with storage of all cereal grains, with or without enzyme, except for hulless barley without enzyme (P = 0.09). Excreta dry matter is an indication of the viscous nature of digesta, since high NSP diets are implicated in the production of wet droppings (Bedford 1996). Thus, lower excreta dry matter would indicate that digesta viscosity was increased when cereal grain had been stored. Enzyme supplementation significantly increased excreta dry matter at both storage times (Table 2). Digesta viscosity was measured on only the wheat-based diets, with or without enzyme supplementation (data not included), and showed a decrease with storage time (24.8 vs centipoids at 0 and 6 mo storage, respectively) for diets without enzymes. Viscosity of digesta of wheat-based diets with enzymes also decreased with storage (5.2 vs. 3.7 centipoids at 0 and 6 mo storage, respectively), but this difference was not significant. In the present study, the measurements of reduced digesta viscosity in wheat-based diets after storage do not support the decreased excreta dry matter measurements. However, the decrease in viscosity measured with wheatbased diets supports the work by others (Hessleman et al. 1981; Brufau et al. 1993; Fuente et al. 1998) who observed that beta-glucan levels of stored barley decreased and resulted in lower viscosity measurements of cereal grain extracts or digesta from birds fed these diets. The discrepancy between measurements of viscosity and excreta moisture due to storage is difficult to explain. One explanation may relate to higher water consumption due to seasonal conditions, although brooding room temperatures were maintained at normal levels for all six bioassay series regardless of outside conditions. Another explanation may relate to the effect of storage on cereal grain factor(s) affecting the voluntary intake of the diet and/or water, that may, in turn, impact the excreta dry matter. Water consumption was not monitored. Changes in FI by birds fed all diets (with or without enzyme) were positively influenced by storage of cereal grain in this study, although the difference was not always significant. Studies of this type are unavoidably confounded by differences in source of birds and environment. However,

4 240 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 2. Broiler chick performance (between 4 and 17 d of age) and AME z of enzyme supplementation y of 38 cereal grains evaluated within 3 mo of harvest (0 mo) and again 6 mo (6 mo) later Post-harvest Hulled barley x Hulless barley x Wheat x storage time (mo) E+ w E w E+ E E+ E Excreta dry matter (%) (24 h collection at 16 d of age) 0 mo 39.6 ± ± ± ± ± ± mo 31.4 ± ± ± ± ± ± 0.52 % change Storage, effect (P) ** ** ** 0.09 ** ** Live body weight (g) 17 d of age 0 mo 414 ± ± ± ± ± ± mo 440 ± ± ± ± ± ± 2.8 % change Storage, effect (P) ** ** ** Feed intake (g bird 1 d 1 ) from 4 to 17 d of age 0 mo 40.7 ± ± ± ± ± ± mo 41.9 ± ± ± ± ± ± 0.44 % change Storage, effect (P) ** ** ** Feed conversion ratio (g feed: g body weight) 0 mo 1.53 ± ± ± ± ± ± mo 1.52 ± ± ± ± ± ± % Change Storage, effect (P) * AME (kcal kg 1 diet, DM basis) based on excreta collected for 24 h at 16 d of age 0 mo 3120 ± ± ± ± ± ± 38 6 mo 3020 ± ± ± ± ± ± 53 % Change Storage, effect (P) ** 0.51 * 0.43 ** 0.44 z The only significant (P < 0.05) interaction for storage time and enzyme was for excreta dry matter of hulled barley. y The only significant effect of enzyme supplementation was for feed intake of wheat-based diets. x There were 14, 10 and 14 samples of hulled barley, hulless barley and wheat fed with or without an appropriate NSP enzyme to four groups of six male broilers from 4 to 17 d of age. w E+ indicates diets were fed with appropriate enzyme; E indicates diets were fed without enzyme supplementation. *,** Significant at P < 0.05 and P < 0.01, respectively. as indicated earlier, two control cereal grains (with and without enzyme) were measured in each series. The variation in measurements for control samples did not indicate that variation due to storage of newly harvested grain was due to variation in chick quality, environment, etc., between the three bioassay series. The variation with storage for individual test cereal grains (with or without enzyme), and wheat in particular, indicates that there are factors in newly harvested grain that impact poultry performance (Fig. 1). Variations in measurement of feed value of cereal grains, particularly when these measurements include determination of performance, can be compromised by a number of factors. In earlier studies conducted over a 2-yr period, we measured the feeding value of 104 sources of wheat fed with or without enzyme (Scott et al. 1998a). Each year, two common control samples of wheat were tested in each assay series. Based on measurements on control samples, the interassay variability was small for broiler ad libitum feed intake, feed:gain and diet AME content (CV < 8 %). This suggests that there was no need to use repeated measurements on control samples and covariate analyses for correcting observations on test cereal grains across bioassay series. Variation in the change in FI with storage of each source of wheat, hulled and hulless barley is presented in Fig. 1. Overall, FI of broilers fed wheat- and barley-based diets increased with storage. However, FI measurements for barley were more variable and, for some barley samples, storage reduced FI. Changes in palatability of cereal grain, regardless of nutrient value of a diet, were indicated to be of importance in comparing the feeding value of cereal grain (Scott et al. 1998c). Digesta viscosity has been reported (Bedford 1996) to reduce food passage rate, which would have some impact on FI. This would likely be important only for those diets that were not supplemented with an enzyme, as the enzymesupplemented diets were considered to have low digesta viscosity. Factors that impact water consumption also impact food consumption. Hence, if there is a palatability factor in recently harvested cereal grain that may limit water intake (and increase excreta dry matter), it would also be expected to result in reduced FI. The wheat-based diets were measured in the first of the three bioassay series (i.e., they were the most recently harvested). This may be important as the largest differences in

5 SCOTT AND PIERCE EFFECT OF CEREAL GRAIN STORAGE ON BROILERS 241 Fig. 1. The change (%) in feed intake measured within 3 mo of harvest and again 6 mo later for individual samples of hulled barley (n = 14), hulless barley (n = 10) and wheat (n = 14) fed with and without an appropriate NSP enzyme.

6 242 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 3. Correlation coefficients (r 2 ) between the same measurements on broiler chicks fed cereal grain samples collected within 3 mo of harvest and again 6 mo later (enzyme treatments combined) All Hulless samples Barley barley Wheat Number of diets Excreta DM (24 h collection at 16 d) Live body weight N/S at 17 d of age Feed intake 4 to d of age Feed conversion ratio to 17 d of age AME based on excreta collected at 16 d broiler performance measured for the cereal grains were for wheat, and may indicate that the changes occurring in cereal grain with storage may be relatively rapid. This is supported by Fuente et al. (1998) who indicated that 3 wk storage was required for a barley sample before use in older broilers (> 30 d) and 10 wk storage for younger (< 10 d) broilers. In the present study, due to logistics of sample collection, transport time and diet inclusion, there could have been a 12 to 14 wk imposed storage of newly harvested grain before all samples were tested. One concern with regard to measurement of different cereal grains for feeding value relates to how the effect of storage impacts the relative ranking of samples for feeding value. We estimated this by determining the correlation coefficients for the parameters measured within 3 mo of harvest and again after 6 mo storage for all diets, and then for each type of cereal grain (enzyme treatments combined) (Table 3). Overall, the correlation coefficients between the same trait measured before and after storage were relatively high (ranging from 0.65 for AME to 0.91 for feed:gain), indicating that the relative rankings of the cereal grains only change minimally with storage. However, for the wheat-based diets the correlation coefficients were not as high. The rankings between wheat-based diets (with or without enzyme) for body weight measured at 0 and 6 mo storage were not significantly related. Again, this may demonstrate that changes in newly harvested grain may occur rapidly or that the type of cereal grain (i.e., wheat vs. barley) may be important. In the current study, the 38 test cereal grains were fed for 13 d before excreta samples were collected to determine AME. During that 13-d period, voluntary feed intake, growth and feed:gain were monitored. As discussed earlier, there may be other factors, besides soluble NSP levels of cereal grains, that limit voluntary FI and the broiler s subsequent growth rate. This is emphasised by the lower relationship (r 2 ) between AME of a diet and the broiler s growth when fed the diet ad libitum (Table 4). At both 0 and 6 mo storage, the strongest relationship with body weight at 17 d of age is voluntary FI (r 2 = 0.94). Although, one would not necessarily expect AME to be related to growth, it should be highly correlated with FI, and this was not the case, which is consistent with other studies (Scott et al. 1998c). Although determination of storage effects is confounded by the use of different birds and uncontrolled changes in environment, this discussion is based on the bioassay measurements of 76 different diets (38 cereal grains 2 enzyme treatments) before and after storage. Of significant note was an average increase in voluntary FI with storage, equal to 4% for hulled and hulless barley-based diets and 14% for wheat-based diets. The data also lead to speculation that changes in cereal grain after harvest, which impact voluntary FI, may be relatively rapid as indicated by the differences noted with storage of the wheat (measured in the first series after harvest and after storage), as compared with barley samples (measured 1 and 2 mo after harvest and again 6 mo later). This is supported by Fuente et al (1998), based on one barley sample, and their conclusion that storage for 3 wk was of sufficient duration to result in improved digestibility for broilers over 30 d of age. It is important to determine those factors in cereal grain that impact the bird s voluntary intake, which will directly impact the bird s ability to reach its genetic potential for growth rate. Based on these results for 38 cereal grains fed with or without enzyme, the feed milling industry s concern that feeding newly harvested cereal grains wheat in particular Table 4. Correlation coefficients (r 2 ) between measurements of broiler chick performance (4 to 17 d of age) and AME when fed 76 wheat, and hulled and hulless barley diets with or without enzyme measured within 3 mo of harvest and 6 mo later 16 d excreta Body wt at Feed intake Feed:gain DM 17 d (g) (g bird 1 d 1 ) ratio AME Within 3 mo of harvest 16 d excreta DM Body weight 17 d (g) Feed intake (g bird 1 d 1 ) Feed:gain ratio AME 1.00 Repeated 6 mo later 16 d excreta DM N/S Body weight at 17 d Feed intake 4 17 d N/S Body weight 17 d (g) Feed intake (g bird 1 d 1 ) 1.00

7 SCOTT AND PIERCE EFFECT OF CEREAL GRAIN STORAGE ON BROILERS 243 to broilers reduces growth performance is justified. However, this reduction in performance cannot be attributed to AME content of the newly harvested cereal grain, but rather to the existence of unknown factors that limit the broiler chicks voluntary feed intake and growth rate. Carefully controlled studies need to be developed to determine if the variation in negative effects of newly harvested grain is influenced by crop year (i.e., growing and harvest conditions) and source (i.e., cultivar). These studies should be combined with simultaneous determination of cereal chemistry, and near infra-red spectroscopy to identify causative relationships. If relationships are identified, then studies are required to determine if they can be manipulated so that broiler chick performance in the field is maintained at high and consistent levels. ACKNOWLEDGEMENTS The authors gratefully acknowledge the financial support of the British Columbia Chicken Marketing Board, Livestock Services Division, United Grain Growers Ltd., and Agriculture and Agri-Food Canada. We would also like to thank E. Ritson and members of UniFeed Inc. for their assistance in obtaining cereal grain samples. The poultry staff of the Pacific Agri-Food Research Centre are also thanked for their dedication and hard work in maintaining the birds and collecting and analysing samples. Bartov, I Effect of storage duration on the nutritional value of corn kernels for broiler chicks. Poult. Sci. 75: Bedford, M. R The effect of enzymes on digestion. J. Appl. Poult. Res. 5: Brufau, J., Francesch, M., Pérez-Vendrell, A. M. and Esteve- García, E Effects of post-harvest storage on nutritive value of barley in broilers. Pages in Proc. of the 1st Symposium on Enzymes in Animal Nutrition, Kartause Ittingen, Switzerland. Fuente, J. M., Perez de Ayala, P., Flores, A. and Villamide, M. J Effect of storage time and dietary enzyme on the metabolizable energy and digesta viscosity of barley-based diets for poultry. Poult. Sci. 77: Hesselman, K., Elwinger, K., Nilsson, M. and Thomke, S The effect of β-glucanase supplementation, stage of ripeness and storage treatment of barley in diets fed to broiler chickens. Poult. Sci. 60: Huyghebaert, G. and Schöner, F. J Influence of storage and addition of enzyme on metabolisable energy content of wheat. 1. Impact of storage and enzyme addition. Arch. Geflügelkd. 63: Pomeranz, Y Biochemical, functional, and nutritive changes during storage. Pages in C. M. Christensen, ed. Storage of cereal grains and their products. American Association of Cereal Chemists, St. Paul, MN. SAS Institute, Inc SAS user s guide: Statistics. SAS Institute, Cary, NC. Scott, T. A., Silversides, F. G., Classen, H. L., Swift, M. L., Bedford M. R. and Hall, J. W. 1998a. A broiler chick bioassay for measuring the feeding value of wheat and barley in complete diets. Poult. Sci. 77: Scott, T. A., Silversides, F. G., Classen, H. L., Swift M. L. and Bedford, M. R. 1998b. Comparison of sample source (excreta or ileal digesta) and age of broiler chick on measurement of apparent digestible energy of wheat and barley. Poult. Sci. 77: Scott, T. A., Silversides, F. G., Classen, H. L., Swift, M. L. and Bedford, M. R. 1998c. Prediction of the performance of broiler chicks from apparent metabolizable energy and protein retention values obtained using a broiler chick bioassay. Can. J. Anim. Sci. 79: Waters, D. L. E. and Choct, M A simple method for the measurement of endogenous beta-glucanase activity in wheat. Page 204 in Proc. Australian Poultry Science Symposium, Sydney University Press, Sydney, NSW, Australia.

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