Production and Egg Quality as Influenced by Mash or Crumbled Diets Fed to Laying Hens in an Aviary System

Production and Egg Quality as Influenced by Mash or Crumbled Diets Fed to Laying Hens in an Aviary System A. WAHLSTRÖM, 1 R. TAUSON, and K. ELWINGER Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, S-755 97 Uppsala, Sweden ABSTRACT Effects of feeding a crumbled diet compared consumption per kilogram egg mass produced (collectable with a mash diet on laying performance and egg quality of two hybrids of laying hens, a total of 3,204 birds, kept in an aviary system from 20 to 80 wk of age, were investigated. The two diets had the same composition and calculated nutrient content. Two hybrids, Lohmann Selected Leghorn (LSL) and SLU-1329 (a two-line cross of Leghorn Rhode Island Red), were housed in six pens each of an aviary system with groups of 269 and 265 birds, respectively. There was a total of three replicates per treatment (diet hybrid). Birds fed the mash diet compared with those fed the crumbled diet had a significantly higher proportion of misplaced eggs, inferior feed conversion ratio (FCR), and higher energy misplaced eggs included). The latter birds had higher body and egg weight, suggesting a higher nutritive value for the crumbled diet. Higher egg mass production and a more intensive yolk color were also found for the birds fed the crumbled diet compared with the mash diet. Hybrid affected production and egg quality traits the most. The LSL also showed significantly higher excreta DM compared with SLU-1329. Interactions between diets and hybrids were found regarding the proportion of misplaced eggs, dirty eggs, egg weight, and FCR. Some of the interactions may indicate other genetic and nutritional factors affecting bird performance in aviary systems more than is normally seen in cages. (Key words: heat treatment, mash, crumbled pellets, diets, layer) 1999 Poultry Science 78:1675 1680 INTRODUCTION Numerous reports have been published over the years comparing the effects of various heat treatments of feed on layer performance. Most of these studies have been conducted in cages. However, as alternative housing systems have been developed during recent years, such as high-intensity aviaries, it is also important to study possible dietary effects in birds kept under these new conditions. Laying hens fed mash diets compared with pelleted diets resulted in lower feed consumption and body weight (Morris, 1947; Jensen and McGinnis, 1952; Black et al., 1958). Jensen and McGinnis (1952) also found that birds receiving mash diets lost weight. In comparison with crumbled diets, Leghorn hens fed mash diets had lower feed consumption and body weight (Pepper et al., 1968). However, Hamilton and Proudfoot (1995) found that body weight at 20 wk of age was higher for Leghorns receiving mash diets compared with those receiving pellets and crumbled pellet diets, but, at 70 wk, this difference had disappeared. Those authors also reported that egg production was higher when feeding mash compared with crumbled pellets and pelleted diets, whereas other authors have reported unchanged or small changes in egg production for mash and pelleted diets (Morgan and Heywang, 1941; Jensen and McGinnis, 1952; Black et al., 1958; McCracken et al., 1996). Laying hens (Savory and Hetherington, 1997) and chickens (Jensen et al., 1962; Savory, 1974) fed mash diets spent more time eating than those given pelleted diets. This increased feeding time has been suggested by Savory (1974) as an explanation why pelleted diets are more efficiently converted than mash diets, which may imply higher body weight. The literature is rather unclear regarding effects of feed structure on bird mortality (Morgan and Heywang, 1941; Black et al., 1958; Hamilton and Proudfoot, 1995). Previous studies with birds fed mash and pelleted diets (Jensen and McGinnis, 1952; Black et al., 1958; McCracken et al., 1996) or mash and crumbled diets (Hamilton and Proudfoot, 1995) have not revealed any obvious effect on egg weight. Furthermore, few experiments have focused on the effects of heat treatment of feed mixtures on egg quality parameters. However, Jensen and McGinnis (1952) reported a limited increase in yolk color intensity Received for publication February 16, 1999. Accepted for publication July 26, 1999. 1 To whom correspondence should be addressed: Annsofie. Wahlstrom@huv.slu.se Abbreviation Key: AA = amino acid; CF = crude fat; FCR = feed conversion ratio; LSL = Lohmann Selected Leghorn; SLU-1329 = twoline Cross, Leghorn Rhode Island Red. 1675

1676 WAHLSTRÖM ET AL. when feeding pelleted compared with mash diets. Hamilton and Proudfoot (1995) were unable to observe significant effects when comparing mash, crumbled pellets, and pelleted diets with regard to albumen quality (Haugh units) and frequency of blood-spotted eggs. The compulsory introduction in Sweden of heat treatment of all poultry feed mixtures (Statens Jordbruksverk, 1993) to prevent salmonella contamination has led to reports on increased problems with wet excreta and dirty eggs. Also, under experimental conditions, a tendency toward wetter droppings when laying hens are fed pelleted diets compared with mash diets has been shown (McCracken et al., 1996). The effects of viscosity and DM content of excreta may be of greater importance when the birds are kept in floor than in cage systems, as the hens are in closer contact with the excreta. Considerable variation among hybrids in production performance and egg quality has been demonstrated in several studies (e.g., Al Bustany and Elwinger, 1987; Abrahamsson et al., 1995). However, there are only few reports on the reactions of different hybrids to heat treatment of diets, although Morris (1947) was unable to observe any difference when comparing hybrids of laying hens fed mash or pelleted diets. The objective of this study was to compare a crumbled diet with a mash diet with regard to their effects on laying performance and egg quality traits of two hybrids of laying hens kept in an aviary system. MATERIALS AND METHODS Birds and Housing System The experiment included 1,614 Lohmann Selected Leghorn (LSL) hens and 1,590 SLU-1329 hens [a two-line cross of Leghorn Rhode Island Red (Liljedahl and Weyde, 1980)]. From 1 d of age, the birds were reared under the same conditions with feed and water supplied on raised slatted floors with high perches. From 5 wk, they also had access to litter between the slatted areas. At 16 wk, the pullets were transferred to the laying house. There they were housed in 12 identical pens of an aviary system, including litter (wood shavings), single nests, and three welded wire tiers with nipple drinkers. The two lower tiers had flat chain feeders, and the top resting tier had only perches (Abrahamsson and Tauson, 1995). Each of six pens housed 269 LSL birds, and six other pens each housed 265 SLU-1329 birds. Each pen measured 3.0 to 5.8 m, which allowed 15.5 and 15.3 hens per m 2 floor area, respectively, for the two genotypes. During rearing, the birds were vaccinated against Marek s disease, coccidiosis, and avian encephalomyelitis. Diets and Feeding The pullets were fed a commercial grower diet of crumbled pellets without coccidiostats until 17 wk. From 17 to 18 wk, they were given one of the two experimental Ingredients TABLE 1. Composition of the experimental diets Barley 366.8 Wheat 250.0 Oats 100.0 Wheat bran 30.0 Alfalfa meal 30.0 Soybean meal 80.0 Fish meal 20.0 Animal fat 20.0 Vitamins 1 10.0 Limestone 79.0 NaCl 2.0 Dicalcium phosphate 10.0 DL-Methionine 1.5 Lysine HCl 0.7 (g per kg feed) 1 Vitamin mix provided the following (per kg feed): vitamin A, 15,000 IU; vitamin D 3, 2,500 IU; vitamin E, 50.0 mg; vitamin B 1, 2.50 mg; vitamin B 2, 6.00 mg; vitamin B 3, 40.0 mg; vitamin B 6, 4.50 mg; vitamin B 12, 2.5 10 2 mg; biotin, 0.20 mg; vitamin K 3, 3.00 mg; folic acid, 1.50 mg; pantothenic acid, 1.50 mg; choline, 800 mg; iodine, 1.0 mg; selenium, 0.15 mg; manganese, 60 mg; zinc, 40 mg; copper, 8.0 mg; and iron, 80.0 mg. diets with identical composition (Table 1). The two dietary treatments, mash or crumbled pellets, were randomly distributed among the hybrids and pens, giving a total of three replicates per treatment, hybrid feed structure. Cereals included in the diets were ground using a hammer mill with a 5-mm sieve. No heat treatment was carried out on the mash diet. Prior to entering the die, the crumbled diet was exposed to approximately 80 C in a steam conditioner for 20 to 30 s. The outlet temperature from the pelleter die was approximately 80 C. The pellets were finally crumbled down to 2- to 3-mm pieces. Within 7 to 8 min after pelleting, the crumbled pellets had been cooled to a temperature of around 20 C. The contents of CP, DM, and ash were analyzed at each feed delivery, resulting in 14 and 19 samples of the mash and crumbled diets, respectively. Analyses of crude fat (CF) were performed on three pooled samples per diet. Dry matter, CP, CF, and ash were determined according to Jennische and Larsson (1990), similar to AOAC (1984) procedures. Carbohydrates (glucose, fructose, sucrose, fructans, and starch) were analyzed on three pooled samples per diet using an enzymatic method described by Larsson and Bengtsson (1983) and Boehringer Mannheim (1989). Amino acids (AA) were analyzed on one pooled sample from each diet collected during the entire experimental period, according to the European Commission (1977, 1979). Analyzed nutrient contents of the diets are shown in Table 2. Recording of Data All data were collected per pen. The study consisted of the period between 20 and 80 wk. Egg production (includes the number of collectable eggs not laid in the nests, called misplaced eggs), feed intake, and mortality were recorded daily. All dead birds were autopsied at the National Veterinary Institute, Uppsala, Sweden. Egg weight was recorded once weekly. Proportions of cracked

EFFECTS OF HEAT TREATMENT OF DIETS ON EGG PRODUCTION 1677 TABLE 2. Analyzed nutrient content of diets (mean ± SD) Analyzed nutrient content Nutrient contents Mash Crumbled pellets ME, MJ/kg 10.41 1 ± 0.19 10.36 1 ± 0.06 (g/kg feed) Ash 131 ± 12 129 ± 14 DM 909 ± 5 908 ± 8 CP 157 ± 4.1 156 ± 4.7 Cysteine 3.2 2.9 Methionine 4.1 4.0 Lysine 7.5 7.2 Arginine 8.7 8.6 Crude fat 42 ± 1.5 44 ± 3.1 Glucose 0.8 ± 0.4 0.6 ± 0.2 Fructose 0.3 ± 0.3 0.1 ± 0.3 Sucrose 14.9 ± 1.4 15.4 ± 1.5 Fructans 8.6 ± 0.9 9.6 ± 0.1 Starch 379 ± 13 374 ± 6 Sodium 1.5 ± 0.2 1.2 ± 0.2 Calcium 44.3 ± 2.5 41.0 ± 4.6 Phosphorus 6.0 ± 0.3 5.8 ± 0.3 1 The ME was calculated according to the EEC-model; ME = (0.1551 CP) + (0.3431 crude fat) + (0.1669 starch) + 0.1301 sucrose). (candled) and dirty eggs were recorded at a commercial egg packing plant on seven evenly distributed occasions, each based on the accumulated production of 2 successive d. Albumen height (measured on a millimeter-scale), albumen DM content (dried at 105 C), yolk color (a Roche color fan was used for visual comparison to determine the yolk color), shell weight, and deformation (using a load of 500 g at 32 wk and the Canadian Egg Shell Tester, 2 operating a load of 1 kg at 53 and 73 wk) were recorded. Blood and meat spots were visually determined after cracking 20 eggs from each pen at 32, 54, and 72 wk. Albumen height was also measured on 20 eggs from each pen collected at the same time, following storage for 30 d at +8 C. Dry matter content in fresh excreta samples collected from the manure belts was determined at 32, 53, and 73 wk (Jennische and Larsson, 1990). Live weight was recorded at 35 and 55 wk on 40 randomly selected birds from each pen, providing a total of 120 birds per treatment (diet hybrid) on each occasion. Statistical Analysis Statistical analyses were carried out using the GLM and the MIXED procedure (where an effect of age was included) of SAS (SAS Institute, 1996). Before analysis, traits given in proportions of mortality, misplaced eggs, cracked and dirty eggs, and blood and meat spots were subjected to arcsin transformation (Snedecor and Cochran, 1968). Results are generally presented as least squares means values based on the statistical model used. Feed consumption, live weight, production performance, and mortality were analyzed with the following statistical model: 2 Otal Precision Company Limited, Ottawa, Ontario, Canada K1G 3N3. Y ijk = µ + α i + β j + (αβ) ij + e ijk. Regarding interior egg quality and excreta DM, age and age interactions with diets and hybrids were also considered. Interactions were excluded from the final model used if not found significant (P > 0.1): Y ijlm = µ + α i + β j + γ l + (αβ) ij + (αγ) il + (βγ) jl + d ijm pl e ijlm where Y ijkl and Y ijlm = response variable; µ = overall mean; α i = fixed effect of hybrid (i = 1, 2); β j = fixed effect of diet (j = 1, 2); γ l = effects of age (l = 1, 2, 3); (αβ) ij,(αγ) il, and (βγ) jl = effects of interactions; d ijm = random effect of group; and e ijk and e ijlm = random variation. RESULTS Feed Intake, Production Performance, Exterior Egg Quality, and Live Weight Results on feed and nutrient intake, production performance, exterior egg quality, mortality, and live weight are presented in Table 3. The proportions of misplaced eggs and dirty eggs were lower when feeding the crumbled diet compared with the mash diet (P < 0.01 and P < 0.05, respectively). Egg weight (P < 0.001), egg mass production per hen per day, and kilogram egg mass per hen housed (P < 0.05) were higher when feeding the crumbled diet compared with the mash diet. Birds fed the former diet also had a better feed conversion ratio (FCR; P < 0.01) and a lower calculated energy intake per kilogram egg mass produced (P < 0.01). Live weight was higher for birds fed the crumbled diet than for those fed the mash diet (P < 0.05). Hybrid affected all traits significantly except mortality. Thus, LSL hens consumed more feed, resulting in higher daily intake of calculated energy, CP, and AA (P < 0.05). The LSL hens also had a lower proportion of misplaced (P < 0.01), dirty, and cracked eggs compared with SLU- 1329 hens (P < 0.001). Laying percentage and egg mass production were higher for LSL than for SLU-1329 hens, whereas egg weight was lower (P < 0.001). The LSL birds had better FCR (P < 0.001) and consumed less calculated energy per kilogram egg mass (P < 0.001). The SLU-1329 birds were heavier than LSL birds at 35 (P < 0.01) and 55 wk (P < 0.001). Interactions (diet hybrid) were found in the proportions of misplaced and dirty eggs (P < 0.05 and P < 0.01, respectively) and egg weight (P < 0.001). The SLU-1329 hens had significantly more misplaced and dirty eggs when they were fed mash diets compared with crumbled pellets, whereas these parameters in LSL hens were unaffected by diet. Egg weight in SLU-1329 birds was not affected by diet, but, in LSL birds, the egg weight increased when the hens were fed the crumbled diet. An interaction between diet and hybrid was also found in FCR, i.e., LSL birds did not show significantly different FCR depending on diet, whereas SLU-1329 birds had

1678 WAHLSTRÖM ET AL. TABLE 3. Feed consumption, production performance, exterior egg quality, mortality, and live weight (least squares means) Experimental diets P Mash Crumbled pellets Diets Hybrids Interactions LSL SLU-1329 LSL SLU-1329 (D) (H) (D H) Daily feed intake, g/hen 115.6 111.2 117.0 112.0 0.54 0.02 0.86 Daily energy intake (ME), MJ/hen 1.20 1.16 1.21 1.16 0.76 0.03 0.87 Daily protein intake, g/hen 18.1 17.5 18.2 17.4 0.98 0.03 0.87 Daily methionine + cysteine intake, g/hen 0.83 0.80 0.81 0.77 0.06 0.03 0.91 Daily lysine intake, g/hen 0.87 0.83 0.84 0.81 0.07 0.03 0.91 Laying, % 84.6 63.4 84.8 69.7 0.06 0.001 0.08 Misplaced eggs, 1 % 9.2 25.1 6.4 10.8 0.01 0.01 0.05 Dirty eggs. 1 % 5.7 13.5 6.5 8.2 0.02 0.001 0.01 Cracked eggs, 1 % 3.6 7.7 3.7 7.4 0.95 0.001 0.71 Egg weight, g 62.3 c 67.3 a 63.5 b 67.3 a 0.001 0.001 0.001 Daily egg mass production, g/hen 52.7 42.7 53.9 46.9 0.03 0.001 0.17 Egg mass production, kg/hen housed 21.4 17.5 21.9 19.2 0.04 0.001 0.22 Mortality, 1 % of hen housed 4.2 4.0 4.3 4.0 0.92 0.79 0.93 Feed conversion ratio, kg/kg egg 2.19 c 2.61 a 2.17 c 2.39 b 0.01 0.001 0.01 ME per kg egg, MJ/ kg egg 22.8 c 27.2 a 22.5 c 24.8 b 0.002 0.001 0.01 Live weight at 35 wk, kg 1.68 1.76 1.73 1.82 0.02 0.01 0.67 Live weight at 55 wk, kg 1.74 1.90 1.83 1.94 0.02 0.001 0.31 a c Values within rows with no common sueprscript differ (P < 0.05). 1 Presented as mean values instead of least squares means because of the arcsin transformation. improved FCR when fed the crumbled compared with the mash diet. Interior Egg Quality and Excreta Dry Matter Content As shown in Table 4, albumen DM content was lower, and the yolk pigmentation was more intensive, when feeding the crumbled diet compared with the mash diet (P < 0.05 and P < 0.001, respectively). The LSL hens had higher albumen height, both in fresh eggs and after 30 d of storage (P < 0.001), higher albumen DM content (P < 0.05), as well as higher shell percentage (P < 0.01). The SLU-1329 hens had more pigmented yolk than LSL hens (P < 0.001). Other egg quality traits were not found to be significantly affected by diet or hybrid. Age affected most traits except for albumen height after 30 d of storage and incidence of blood spots. Generally, inferior egg quality (P < 0.001) was shown at 73 wk with regard to albumen height, albumen DM, shell percentage, and shell deformation. Albumen height was also affected by an interaction between age and diet (data not presented; P < 0.01; 7.7, 8.3, and 7.0 mm for the mash diet and 7.8, 7.7, and 7.0 mm for the crumbled diet at 32, 53, and 73 wk, respectively). Hybrid and age interacted regarding albumen DM (data not presented; P < 0.01; 12.3, 11.9, and 11.6% for LSL hens and 11.8, 11.8, and 11.7% for SLU-1329 hens at 32, 53, and 73 wk, respectively). Meat spots increased with age (P < 0.001). Yolk color was also affected by age (P < 0.001). There was also an interaction between diet and age regarding yolk color (data not presented; P < 0.01; 5.9, 6.8, and 6.5 points for TABLE 4. Interior egg quality and excreta DM (least squares means) Experimental diets Age P Mash Crumbled pellets Diets Hybrids Age Interaction LSL SLU-1329 LSL SLU-1329 32 wk 53 wk 73 wk (D) (H) (A) tested Albumen height (Ah), mm 8.6 6.8 8.4 6.6 7.8 8.0 7.0 0.13 0.001 0.001 D A, 0.01 Ah at 30 d of storage, mm 5.6 4.9 5.6 4.8 5.2 5.3 5.2 0.76 0.001 0.19 NS 1 Albumen DM, % 11.9 11.9 11.9 11.6 12.0 11.8 11.6 0.03 0.04 0.001 H A, 0.01 Yolk color, points 6.2 6.6 6.9 7.2 6.3 7.0 6.8 0.001 0.001 0.001 D A, 0.01 Shell percentage, % 9.1 8.9 9.1 8.9 9.4 9.1 8.5 0.82 0.01 0.001 NS Deformation, 2 10 2 mm 2.1 2.1 2.1 2.2 2.1...... 0.15 0.19 Deformation, 3 10 2 mm 7.8 7.6 7.5 7.6... 7.3 8.1 0.34 0.60 0.001 NS Blood spots, 4 % 2.2 5.0 4.0 5.7 4.5 2.5 5.5 0.52 0.21 0.28 NS Meat spots, 4 % 3.9 2.8 3.9 5.1 1.2 3.3 7.2 0.43 0.87 0.001 NS Excreta DM, % 23.9 22.3 23.4 22.1 23.0 23.7 22.1 0.28 0.01 0.001 NS 1 P > 0.05. 2 Values from analysis performed at 32 wk of age. 3 Values from analyses performed at 53 and 73 wk of age. 4 Presented as mean values instead of least squares means because of the arcsin transformation.

EFFECTS OF HEAT TREATMENT OF DIETS ON EGG PRODUCTION 1679 the mash diet and 6.8, 7.2, and 7.0 points for the crumbled diet at 32, 53, and 73 wk, respectively). As shown in Table 4, the excreta DM content was affected by hybrid and age (P < 0.01 and P < 0.001, respectively); SLU-1329 birds had lower DM content in their excreta than LSL hens. Lower DM contents were found in excreta from older birds (73 wk). No significant interactions between diet and hybrid were found. DISCUSSION Daily feed intake was not significantly affected by diet, which is in contrast to several other reports (e.g., Jensen and McGinnis, 1952; Black et al., 1958). The lack of difference in feed intake in our study may be explained by the use of crumbled diets in comparison with intact pellets, which were used in most other studies. However, in a more recent study, McCracken et al. (1996) reported lower intake of DM when layers were fed mash diets compared with crumbled or intact pellets. In our study, when calculating the daily DM intake, the difference between the mash and the crumbled pellet diet was very limited, 103.1 and 104.0 g per hen, respectively. The lack of difference in daily feed intake between the crumbled and mash diets might also be an effect of the housing system. Average feed intake was similar in the present study compared with an earlier experiment using the same hybrids in the same housing system (Wahlström et al., 1998b). However, feed intake was higher for hybrids when hens were housed in single cages but fed the crumbled and the mash diets; thus there was no significant difference in feed intake between the two diets, although the intake of the latter diet was lower and the difference greater than in the present study (Wahlström et al., 1998a). Other studies, mostly conducted in cages, have shown a higher feed intake for birds fed crumbled or pelleted diets compared with mash diets (e.g., Jensen and McGinnis, 1952; Black et al., 1958; Pepper et al., 1968). The lower average feed intake and the lack of difference between the diets in the present study may indicate that birds fed the crumbled diet had a lower feed intake than expected and, consequently, had more time to explore the areas in the pens (e.g., resting areas, nests, or litter floor area) than birds fed the mash diet. This hypothesis might partly be supported by Savory (1974) and Savory and Hetherington (1997), who showed that birds fed mash diets vs pelleted diets spent more time eating (e.g., had less time for exploring their environment). As a result of this, birds fed the mash diets may also have spent more time on the two lower wire tiers (with feeders) than those given the crumbled pellet diet. This conclusion is supported by, or may also possibly explain, the higher proportion of misplaced eggs, mainly laid on the two lower tiers, in these groups. Higher body and egg weights were observed for birds fed the crumbled diet despite no difference in feed intake between diets. The steam pelleting process might have enhanced the nutritive value, as suggested by Pepper et al. (1968) and Savory (1974). In a metabolic trial testing the same diets and hybrids as in the present study, a higher digestibility of crude fat in the crumbled diet was found (Wahlström et al., 1998a). This difference in the diets also might have increased the availability of linoleic acid, thus resulting in heavier eggs (e.g., Scragg et al., 1987). Egg weight in LSL birds increased when they were fed the crumbled diet compared with the mash diet, whereas no such effect was found for SLU-1329 hens. This result might indicate a genetically higher production capacity in LSL hens, implying that these birds would benefit more than SLU-1329 hens from a higher nutritive value in the crumbled diet than in the mash diet. Eating of misplaced eggs was observed among SLU- 1329 hens, which might have influenced feed and energy intake considerably as well as the number of collectable eggs, and also explain the significant effects on FCR. Using energy requirement models presented by Emmans (1974), the daily energy intake would be slightly less (approximately 3%) for SLU-1329 than for LSL, which is in accordance with results in the present study. However, in earlier experiments with similar dietary energy density and birds housed in aviaries (Wahlström et al., 1998b), SLU-1329 birds had a laying percentage over the same production period of around 70 (including 21% misplaced eggs). This finding indicates that some eggs were missing, especially in groups fed the mash diet in the present study, which only recorded a laying percentage of 63. In accordance with other studies (Abrahamsson and Tauson, 1995; Wahlström et al., 1998b), a higher proportion of misplaced eggs resulted in a higher proportion of dirty eggs, as it did for SLU-1329 hens in the present study. Mortality was not affected by diet, which is in agreement with both earlier and more recent reports [e.g., Morgan and Heywang (1941) and Hamilton and Proudfoot (1995)]. The yolk pigmentation was more intensive when feeding the crumbled diet compared with the mash diet, which agrees with Jensen and McGinnis (1952). Oxycarotenoid pigments of feedstuffs (i.e., lucerne meal) are known to oxidize and lose their pigmenting effect when exposed to high temperature (Karunajeewa et al., 1984). However, as the digestibility of CF was higher in the crumbled diet than in the mash diet (Wahlström et al., 1998a), the absorption of fat-soluble carotenoids might have increased (Belyavin and Marangos, 1989). The crumbled diet had a slightly lower content of lysine, although the analysis was only carried out on one sample per diet. This reduction might have resulted in a lower lysine intake for birds fed the crumbled diet, especially the SLU- 1329 hens, and might explain the lower albumen DM content in these groups, as also reported by Al Bustany and Elwinger (1987). However, Al Bustany and Elwinger had a larger variation in lysine intake (0.46 to 0.87% dietary lysine) than in our study. The SLU-1329 birds, compared with LSL birds, had a lower shell percentage, which explains the increased proportions of cracked eggs, in agreement with Al Bustany and Elwinger (1987) and Wahlström et al. (1998b). As expected, there were hybrid differences and differences caused by the birds age in several interior egg quality parameters, in agreement with

1680 WAHLSTRÖM ET AL. Al Bustany and Elwinger (1987). The proportions of blood and meat spots in the eggs were rather high (2 to 6%), possibly because of cracking the eggs instead of only candling them before analysis. Comparing the diets, there was no significant difference in excreta DM content, which agrees with Wahlström et al. (1998a) but disagrees with McCracken et al. (1996). The latter authors also included heat-treated mash in their comparison. However, excreta DM was affected by hybrid, which agrees with Wahlström et al. (1998a). Differences in behavior, such as different stress levels or drinking activities, might have contributed to the DM content in the excreta, although this was not studied in this experiment. In conclusion, genotype generally had greater impact than feed structure on production, feed consumption, and egg quality. However, this study illustrates the importance of certain nutritional and genetical factors affecting bird performance in aviary systems. Also other traits, such as number of dirty eggs, FCR, and egg weight, were found to be affected by an interaction between hybrid and diet. ACKNOWLEDGMENTS The National Board of Agriculture and the Swedish Farmers Foundation for Agricultural Research are thanked for financial support. The authors are also grateful to Sigvard Thomke, Swedish University of Agricultural Sciences, Uppsala, Sweden, for valuable comments on the manuscript. REFERENCES Abrahamsson, P., and R. Tauson, 1995. Aviary systems and conventional cages for laying hens. Effects on production, egg quality, health and birds location in three hybrids. Acta Agric. Scand. Sect. A, Anim. Sci. 45:191 203. Abrahamsson, P., R. Tauson, and M. C. Appleby, 1995. Performance of four hybrids of laying hens in modified and conventional cages. Acta Agric. Scand. Sect. A, Anim. Sci. 45:286 296. Al Bustany, Z., and K. Elwinger, 1987. Shell and interior quality and chemical composition of eggs from hens of different strains and ages fed different dietary lysine levels. Acta Agric. Scand. 37:175 187. Association of Official Analytical Chemists, 1984. Official Methods of Analysis, 14th rev. ed. AOAC, Washington, D.C. Belyavin, C. G., and A. G. Marangos, 1989. Natural products for egg yolk pigmentation. Pages 47 68 in: Recent Development in Poultry Nutrition. 1. Poultry Nutrition. D.J.A. Cole and W. Haresign, eds. Anchor Press Ltd., Tiptree, Essex, Great Britain. Black, D.J.G., R. C. Jennings, and T. R. Morris, 1958. The relative merits of pellets and mash for laying stock. Poultry Sci. 37:707 722. Boehringer Mannheim, 1989. Methods of biochemical analysis and food analysis. Using test-combinations. Pages 46 50 in: Boehringer Mannheim GmbH. Biochemica, Sandhofer Straße 116, 6800 Mannheim 31, Germany. Emmans, G. C., 1974. The effects of temperature on the performance of laying hens. Pages 79 90 in: Energy Requirements of Poultry. T. R. Morris and B. M. Freeman, eds. British Poultry Science Ltd., Edinburgh. European Commission, 1977. EEC dir. 77/101/EEC. Council directive of 23 November 1976. On the marketing of straight feedingstuffs. European Commission, 1979. EEC dir. 79/373/EEC. Council directive of 2 April 1979. On the marketing of compound feedingstuffs. Hamilton, R.M.G., and F. G. Proudfoot, 1995. Effects of ingredient particle size and feed form on the performance of Leghorn hens. Can. J. Anim. Sci. 75:109 144. Jennische, P., and K. Larsson, 1990. Traditionella svenska analysmetoder för foder och växtmaterial. Rapport 60. SLL, Uppsala, Sweden. [in Swedish] Jensen, L. S., and J. McGinnis, 1952. A comparison of feeding pelleted and unpelleted diets containing different levels of alfalfa to laying hens. Poultry Sci. 31:307 310. Jensen, L. S., L. H. Merrill, C. V. Reddy, and J. McGinnis, 1962. Observations on eating patterns and rate of food passage of birds fed pelleted and unpelleted diets. Poultry Sci. 41:1414 1419. Karunajeewa, H., R. J. Hughes, M. W. McDonald, and F. S. Shenstone, 1984. A review of factors influencing pigmentation of egg yolks. World s Poultry Sci. 40:52 65. Larsson, K., and S. Bengtsson, 1983. Bestämning av lättillgänliga kolhydrater i växtmaterial Method no 22. SLL, Uppsala, Sweden. [in Swedish] Liljedahl, L.-E., and C. Weyde, 1980. Scandinavian selection and crossbreeding experiment with laying hens. II. Results from the Swedish part of experiment. Acta Agric. Scand. 30:237 260. McCracken, K. J., A. McAllister, and R. Johnston, 1996. Effects of processing of layer diets on food intake, excreta production and performance. Br. Poult. Sci. 37:S61 S62. Morgan, R. B., and B. W. Heywang, 1941. A comparison of a pelleted and unpelleted all-mash diet for laying chickens. Poultry Sci. 20:62 65. Morris, L., 1947. Pelleted and unpelleted mash for laying hens. Poultry Sci. 26:122 125. Pepper, W. F., J. D. Summers, S. J. Slinger, and G. C. Ashton, 1968. Effect of steam pelleting on the performance of hens fed various laying diets. Can. J. Anim. Sci. 48:229 234. SAS Institute, 1996. SAS System for Windows, Release 6.12 TS Level 0200. SAS Institute, Inc., Cary, NC. Savory, C. J., 1974. Growth and behaviour of chicks fed on pellets or mash. Br. Poult. Sci. 15:281 286. Savory, C. J., and J. D. Hetherington, 1997. Effects of plastic anti-pecking devices on food intake and behaviour of laying hens fed on pellets or mash. Br. Poult. Sci. 38:125 131. Scragg, R. H., N. B. Logan, and N. Geddes, 1987. Response of egg weight to the inclusion of various fats in layers diets. Br. Poult. Sci. 28:15 21. Snedecor, G. W., and W. G. Cochran, 1968. Statistical Methods, 6th rev. ed. The Iowa State Univ. Press, Ames, IA. Statens Jordbruksverk, 1993. Statens Jordbruksverks föreskrifter om foder. SJVFS 1993:177, M39, O39. Statens Jordbruksverk, 551 82 Jönköping, Sweden. [in Swedish] Wahlström, A., K. Elwinger, and S. Thomke, 1998a. Total tract and ileal nutrient digestibility of a diet fed as mash or crumbled pellets to two laying hybrids. Feed Sci. Technol. 77:229-239. Wahlström, A., R. Tauson, and K. Elwinger, 1998b. Effects on production performance and egg quality when feeding different oats/wheat ratios to two hybrids of laying hens kept in aviaries. Acta Agric. Scand. Sect. A, Anim. Sci. 48:243 249.