A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 84 Use of semi-leafless peas (Pisum sativum L) in laying hen diets Erja Koivunen1, Petra Tuunainen1, Eija Valkonen2, Jarmo Valaja3 1Luke Natural Resources Institute Finland, Green Technology, Pig and Poultry Production, 31600 Jokioinen, Finland 2 Hankkija Oy, P.O. Box 390, 05801 Hyvinkää, Finland 3 Department of Agricultural Sciences, P.O. Box 28, University of Helsinki, 00014, Finland e-mail: erja.koivunen@luke.fi The study was conducted to evaluate an appropriate inclusion level of white-flowered semi-leafless green spring peas in diets for laying hens. Egg production and egg quality variables (specific weight, Haugh unit, shell strenght) were determined with 576 hens in a 52-week feeding experiment, which comprised of three feeding phases. The hens were offered one of the four cereal and soybean meal (SBM) based experimental diets. Peas were tested in proportions of 0, 100, 200 or 300 g kg-1 in the diet. Pea inclusion had no effects on production performance, feed consumption or feed conversion ratio (FCR) of the hens during the entire trial. The pea inclusion impaired FCR dur- ing the second feeding phase (p < 0.05) and increased birds’ live weight in a linear manner during the second and the third feeding phases (p < 0.05). Pea inclusion had no effects on egg quality. It can be concluded that at least 300 g kg-1 of the studied peas can be used in the diets of laying hens without negative effects on production per- formance or egg quality. Key words: egg production, egg quality, feed, laying hen, pea Introduction Imported soybean meal (SBM) is the main protein source used in poultry feed in Europe. In those climates, where soybean (Glycine max) cannot be produced or its production is not economical, there is a strong interest in maxi- mizing the use of locally produced protein sources, like peas (Pisum sativum L.), as a substitute for imported SBM. The use of domestic legumes like peas offers the possibility to improve self-sufficiency in protein-rich feedstuffs (Gatel 1994). In addition, to increase the production of locally produced protein sources is also a way to diver- sify northern cropping system dominated by cereals (Peltonen-Sainio et al. 2013). A lot of area is also favorable for crop based protein production from legumes (Peltonen-Sainio et al. 2013). Peas have an important role in the crop rotation due to their ability to fix nitrogen (Stoddard et al. 2009). Because of that, growing peas has a special function in organic farming (Stoddard et al. 2009). Pea supplies both energy and protein in poultry diets (Rodrigues et al. 2012). Gatel (1994) stated that pea protein is as rich in lysine as SBM protein. Pea protein contains a similar proportion of threonine, but less sulfur containing amino acids and tryptophan than SBM protein (Gatel 1994). Compared to cereals, pea is a good source of lysine, but the sulphur containing amino acids methionine and cysteine and also tryptophan are present at low levels in the protein of peas (Gatel 1994). However, considering the protein amino acid profile of cereals and peas, they complement each other well (Gatel 1994). In addition, shortages in the amino acid composition of peas are easy to compensate with feed grade crystalline amino acids in conventional poultry diets (Fru-Nji et al. 2007). The main anti-nutritional factors (ANF) present in the peas are protease inhibitors, lectins and tannins, which have an adverse effect on protein digestibility (Gatel 1994). Owing to the high variability in ANF within the pea cultivar it has been possible to improve their nutritional value by selective breeding (Gatel 1994). High levels of unprocessed peas at a level of 250 – 500 g kg-1 in a laying hen diet have been demonstrated to support good production (Ivusic et al. 1994, Perez-Maldonado et al. 1999, Fru-Nji et al. 2007). Fru-Nji et al. (2007) reported no differences in egg quality between diets that contained up to level of 500 g kg-1 of peas. Anderson (1979) and Ivusic et al. (1994) showed that diets containing 300 – 590 g kg-1 of peas had an adverse effect on egg shell quality. There is a need to evaluate the nutritive values of locally produced and currently available pea cultivars, and to find their optimal inclusion levels in poultry diets. The aim of this study was to find an appropriate inclusion lev- el of white-flowered semi-leafless green spring peas (cv. Karita) in SBM and cereal-based diets for laying hens. A further aim was to study the effects of dietary pea inclusion on specific weight, Haugh unit and shell strenght. Manuscript received December 2014 A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 85 Materials and methods Experimental animals and treatments A total of 576 Leghorn chickens (Lohmann Selected Leghorn, LSL Classic) aged 21 weeks were randomly assigned to 32 replicates, with six cages per replicate and three hens per conventional cage, offering 660 cm2 cage area per hen. The replicates were randomly assigned to four different dietary treatments, yielding eight replicates per treatment. During the trial, each photoperiod lasted 14.5 hours and scotoperiod 9.5 hours. The temperature in the hen house was kept at 20 °C. The study was approved by the Local Ethical Committee for Animal Experiments. A diet based on cereals and SBM served as control (Table 1). A variety of white-flowered semi-leafless green spring pea seeds cv. Karita (Lantmännen SW 1995) was included at 100 g kg-1, 200 g kg-1 and 300 g kg-1 of diet (18.1, 37.1 or 56.9% of soybean meal was replaced by peas). The experiment lasted 52 weeks (a whole laying period), and it comprised of three feeding phases and was divided to 13 four-week periods. The first feeding phase lasted for five periods (20 weeks) and second and third feeding phases lasted for four periods (both of them 16 weeks). The diets within the different feeding phases were aimed to formulate to contain equal amounts of crude protein, ly- sine, methionine, threonine, calcium and available phosphorus per MJ of AME using table values for feed ingre- dients published in the Finnish Feed Tables and Nutrient Requirements (Luke 2014) and to meet the nutrient re- quirements of LSL Classic hens (Lohmann 2010). The nutrient contents of diets were equalized with rapeseed oil, amino acids and monocalcium phosphate. The feed ingredients were ground in a roller mill (Gehl Company, West Bend, Wisconsin, USA). The feeds were mixed and cold-pelleted (Amandus Kahl Laborpresse 1175, Germany). Feed and water were available ad libitum throughout the experiment. Table 1. Composition of experimental diets (g kg -1) Experimental diets 21 – 41 weeks of age Experimental diets 41 – 57 weeks of age Experimental diets 57 – 73 weeks of age Control Pea inclusion g kg -1 Control Pea inclusion g kg -1 Control Pea inclusion g kg -1 100 200 300 100 200 300 100 200 300 Barley 258 232 207 181 287 258 231 202 330 298 276 244 Wheat 258 232 206 181 199 179 160 140 114 102 70 55 Oat 257 231 206 181 287 258 231 202 330 297 275 244 Soybean meal 116 95 73 50 116 94 71 49 116 94 72 50 Pea – 100 200 300 – 100 0 200 300 – 100 200 300 Rapeseed oil 1.0 1.1 1.0 – 1.0 1.1 – – – – – – Monocalcium phosphate 19 19 18 18 19 19 18 18 19 19 18 18 Limestone 81 80 80 80 81 80 80 80 81 80 80 80 Salt 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 Mineral premix1 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Vitamin premix2 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 DL-Methionine 1.1 1.5 1.5 1.5 1.1 1.5 1.5 1.5 1.1 1.2 1.3 1.4 L-Lysine 1.0 1.0 – – 1.0 1.0 – – 1.0 1.0 – – 1 Providing the following per kg of feed: Ca 0.6 g, Fe 25 mg, Cu 8 mg, Mn 50 mg, Zn 65 mg, I 0.5 mg, Se 0.2 mg 2 Providing the following per kg of feed: Ca 2.4 g, vitamin A 23.958 IU (retinol), vitamin D 3 5.476 IU, vitamin E 61.6 mg (α-tokopherol 56.1 mg), vitamin K 3 10.5 mg, vitamin B 1 4.8 mg, vitamin B 2 10.5 mg, vitamin B 6 7.4 mg, vitamin B 12 0.04 mg, biotin 0.4 mg, folic acid 1.3 mg, niacin 84.2 mg, pantothenic acid 21.1 mg, canthaxanthin 5.7 mg A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 86 Analytical and experimental procedures Feed samples were taken from every batch made and then pooled. The pooled samples were passed through a hammer mill fitted with a 1-mm mesh prior to analysis. Crude fat and ash contents were determined by standard methods (AOAC, 1990, methods 942.05 and 920.39). Crude fiber content was determined with a modified meth- od (AOAC method 962.09) using glass wool instead of ceramic filters. The nitrogen content was analyzed using a Leco FP 428 nitrogen analyser (Leco Corporation, St. Joseph, MI). The crude protein content was calculated by multiplying the nitrogen content by 6.25. Amino acid content (excluding tryptophan, which was not determined) was analyzed using accredited In-house method No. 5000 (EC 1998). Total (peptide bound and free) amino acid analysis was performed with Waters Finland MassTrak UPLC (Waters Corporation, Milford, USA) and the appli- cation was UPLC Amino Acid Analysis Solution®. The calcium and phosphorus concentrations were determined with an ICP emission spectrophotometer (Thermo Jarrel Ash-Baird, Franklin, MA; Luh Huang and Schulte 1985). Egg weight and number were recorded daily, and the mean production variables were calculated for each four-week period. The feed consumption was measured in each period. Mortality was recorded daily. Cumulative mortality was calculated at the end of the experiment. The hens were weighed when they were 21-, 41-, 56-, and 72 weeks old. Egg quality variables; specific weight, Haugh unit, shell strength were examined once per each feeding phase at the age of 36-, 54 and 68- weeks old. The egg quality variables were measured in eight eggs per replicate. The spe- cific weight was based on Archimedes’ principle for assessment of the specific gravity of eggs (Hamilton, 1982). Albumen height was measured with a digital tripod micrometer (York Electronic Centre, Technical Services and Supplies Limited, York, England) and converted to Haugh units. The shell-breaking force (shell strength) was meas- ured as compressive fracture force using an eggshell tester of the OTAL Precision Company Limited, Ottawa, ON, Canada (Hamilton 1982). Statistical analyses Production performance data was subjected to repeated-measures ANOVA using the GLM procedure of SAS (SAS Institute Inc., Cary, NC, USA) and the following model: Y ijk = µ + t i + δ i + p j + (p × t) ij + ε ijk , where Y ijk = observation, µ = the general mean, t i = the effect of the treatment (i = 1, …,4), δ i = the error term for the effect of the treatment i, p j = the effect of the period (j= 1,…,13), and ε ijk = the experimental error term. The egg quality variables, birds’ live weight, and - growth were analyzed using the following model: Y ij = µ + t i + ε ik , where Y ij = observation, µ = the general mean, t i = the effect of the treatment (i = 1, …,4), and ε ijk = the experimental error term. The treatment ef- fects for the three feeding phases were separated into three polynomial contrasts: the linear, quadratic and cubic effect of dietary pea inclusion (P linear , P quadratic , P cubic) . Because the cubic effect was not significant it was removed. In the current study, p ≤ 0.05 was considered to be significant. Results The diets within different feeding phases were from practical point of view similar in their nutrient content (Table 2). The experiment lasted 52 weeks (a whole laying period), and it comprised of three feeding phases and was divid- ed to 13 four-week periods. The first feeding phase lasted for five periods (20 weeks) and second and third feed- ing phases lasted for four periods (both of them 16 weeks). The diets within the different feeding phases were aimed to formulate to contain equal amounts of crude protein, lysine, methionine, threonine, calcium and avail- able phosphorus per MJ of AME using table values for feed ingredients published in the Finnish Feed Tables and Nutrient Requirements (Luke 2014) and to meet the nutrient requirements of LSL Classic hens (Lohmann 2010). The nutrient contents of diets were equalized with rapeseed oil, amino acids and monocalcium phosphate. The feed ingredients were ground in a roller mill (Gehl Company, West Bend, Wisconsin, USA). The feeds were mixed and cold-pelleted (Amandus Kahl Laborpresse 1175, Germany). Feed and water were available ad libitum through- out the experiment. A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 87 Nutrient content in feed ingredients to some extent varied during the experiment (52 weeks). Hence the diets were not totally isonitrogenonous and amino acid contents slightly varied. The pea cultivar used in the current study contained 217 g kg-1 DM crude protein (Table 3). AME = apparent metabolizable energy DM = dry matter 1 based on Finnish Feed tables and nutrient requirements (Luke 2014) Table 3. Analysed chemical composition of SBM and pea (g kg -1 DM), except DM1 SBM Pea DM, g kg-1 876 875 Crude protein 530 217 Crude fat 14.8 14.0 Crude fibre 40.7 55.4 Ash 71.2 33.8 Nitrogen-free extract 344 680 1 based on single analyses DM = dry matter SBM = soybean meal Table 2. Calculated and analyzed chemical composition of the experimental diets (g kg -1DM), except AME and DM Experimental diets 21 – 41 weeks of age Experimental diets 41 – 57 weeks of age Experimental diets 57 – 73 weeks of age Control Pea inclusion g kg -1 Control Pea inclusion g kg -1 Control Pea inclusion g kg -1 100 200 300 100 200 300 100 200 300 Calculated composition AME, MJ/kg 11.5 11.6 11.6 11.6 11.4 11.5 11.5 11.5 11.3 11.3 11.3 11.3 Crude protein 162.9 163.2 163.5 163.1 161.0 161.3 161.5 161.6 158.5 159.1 159.1 159.4 Lysine 8.2 8.7 8.6 8.7 8.2 8.7 8.3 8.7 8.3 8.8 8.4 8.8 Methionine 3.9 4.2 4.1 4.0 3.9 4.2 4.1 4.0 3.9 3.9 3.8 3.8 Methionine + cysteine 7.4 7.6 7.3 7.1 7.3 7.5 7.3 7.0 7.3 7.2 7.1 6.9 Threonine 5.9 6.0 6.1 6.2 5.9 6.0 6.1 6.1 5.9 6.0 6.1 6.2 Calcium 38.8 38.4 38.2 38.3 38.8 38.4 38.3 38.3 38.9 38.5 38.3 38.4 Phosphorus (available)1 4.7 4.8 4.6 4.7 4.7 4.8 4.6 4.7 4.7 4.8 4.7 4.7 Analyzed composition DM, g/kg 918.0 909.4 905.7 907.8 895.8 895.1 891.3 888.9 890.9 890.9 889.7 888.3 Crude protein 177.3 176.7 174.9 173.8 163.7 168.2 163.7 167.2 174.2 178.1 176.6 169.5 Crude fat 28.9 27.7 26.1 23.1 28.0 28.2 23.2 22.0 28.2 25.8 24.5 24.6 Crude fiber 59.8 48.6 52.2 51.8 59.2 63.6 55.8 62.8 66.1 65.4 40.8 62.2 Ash 136.4 132.6 129.9 133.6 115.1 128.7 138.6 124.1 120.7 132.0 129.0 130.1 Alanine 7.1 7.2 7.3 7.5 6.6 7.6 7.2 7.3 7.8 8.1 8.5 8.1 Arginine 9.8 10.5 10.5 11.2 10.4 11.5 12.1 11.6 11.5 13.1 12.2 11.7 Aspartic acid 13.9 15.4 15.3 16.3 13.0 15.6 17.0 15.9 15.8 17.1 17.7 18.2 Cysteine 3.5 3.5 3.3 3.3 3.8 3.8 3.4 3.8 3.7 4.1 3.8 3.1 Glutamic acid 41.4 41.3 39.1 37.3 34.6 36.7 38.1 35.3 41.1 41.6 40.8 39.1 Glycine 7.4 7.6 7.5 7.5 6.8 7.7 7.6 7.5 7.8 8.2 8.4 8.1 Histidine 4.3 4.3 4.3 4.1 4.2 4.5 4.1 4.3 4.4 4.8 4.6 4.2 Isoleucine 6.4 6.5 6.1 6.7 6.3 6.8 6.4 6.4 7.0 7.1 7.0 6.8 Leucine 12.6 12.6 12.7 12.3 12.8 13.5 12.9 13.1 13.8 14.4 14.1 13.3 Lysine 8.1 8.7 8.7 9.2 7.6 8.9 9.3 8.9 8.9 9.8 9.3 9.4 Methionine 3.5 4.2 3.8 3.9 3.6 3.7 3.8 3.6 3.5 4.1 4.0 3.5 Phenylalanine 8.4 8.5 8.2 8.3 8.0 8.8 8.1 8.4 9.3 9.5 9.4 8.9 Proline 13.5 12.2 11.7 10.8 12.2 11.7 10.9 11.5 11.9 14.1 12.7 9.6 Serine 8.1 8.5 8.3 8.4 7.6 9.2 8.9 8.2 9.5 9.7 9.6 8.9 Treonine 5.5 6.1 6.0 6.3 5.5 6.4 6.6 6.0 6.6 6.8 6.8 6.6 Valine 7.1 7.1 6.9 7.8 7.7 8.5 7.8 7.9 8.5 8.7 8.5 8.2 Calcium 43.8 41.3 39.3 42.1 33.6 37.4 41.5 36.5 36.1 39.8 39.1 39.1 Phosphorus 8.9 8.9 8.4 8.8 7.7 8.4 8.9 8.5 8.0 8.6 8.4 8.0 A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 88 Dietary pea inclusion had no effects on the production performance, feed consumption or feed conversion ratio (FCR) of the hens during the entire trial. The only significant difference among production performance variables stud- ied was a linear manner impaired FCR during the second feeding phase (41 – 57 weeks of age) (p < 0.05) (Table 4). Birds’ live weight increased in a linear manner along pea inclusion during the second and third feeding phases (41 – 57 and 57 – 73 weeks of age) (p < 0.05) (Table 5). 1 Values are means of 8 replicates per treatment and they represent the means of the values of 13, 5, 4 or 4 periods (4 weeks each) FCR = feed conversion ratio Table 4. The effects of dietary inclusion level of peas on laying hen egg production variables1 Pea inclusion, g kg -1 p-values Control 100 200 300 SEM plinear pquadratic Egg production, % 21 – 73 weeks of age 93.4 93.1 93.3 92.1 3.03 0.388 0.631 21 – 41 weeks of age 96.1 95.7 96.1 95.5 1.57 0.696 0.233 41 – 57 weeks of age 95.4 94.7 95.2 94.0 1.96 0.210 0.671 57 – 73 weeks of age 89.0 89.5 89.0 88.0 2.33 0.506 0.534 Egg weight, g 21 – 73 weeks of age 65.6 65.1 65.2 65.5 1.08 0.909 0.187 21 – 41 weeks of age 62.0 61.4 61.7 61.8 0.64 0.995 0.233 41 – 57 weeks of age 64.1 63.5 63.7 63.9 0.69 0.842 0.143 57 – 73 weeks of age 68.9 68.7 68.7 69.2 0.63 0.512 0.265 Egg mass production, g/hen per d 21 – 73 weeks of age 61.2 60.5 60.8 60.3 1.95 0.403 0.869 21 – 41 weeks of age 59.6 58.8 59.4 59.0 0.92 0.627 0.587 41 – 57 weeks of age 61.1 60.1 60.6 60.0 1.32 0.186 0.765 57 – 73 weeks of age 61.3 61.5 61.1 60.9 1.60 0.670 0.813 Feed consumption, g/hen per d 21 – 73 weeks of age 129 129 130 130 3.3 0.433 0.900 21 – 41 weeks of age 122 122 123 124 1.6 0.062 0.296 41 – 57 weeks of age 127 127 128 129 2.1 0.318 0.790 57 – 73 weeks of age 135 134 135 134 2.8 0.739 0.825 FCR, g of feed/g of egg 21 – 73 weeks of age 2.12 2.14 2.14 2.16 0.075 0.179 0.993 21 – 41 weeks of age 2.05 2.07 2.07 2.10 0.040 0.102 0.774 41 – 57 weeks of age 2.08 2.12 2.11 2.14 0.046 0.038 0.672 57 – 73 weeks of age 2.20 2.18 2.21 2.20 0.058 0.742 0.897 Cumulative mortality, % 21 – 73 weeks of age 3.47 3.47 9.03 4.86 1.911 0.179 0.245 Table 5. The effects of dietary inclusion level of peas on the mean live weight and change in live weight of laying hens1 Pea inclusion, g kg -1 p-values Control 100 200 300 SEM plinear pquadratic Live weight, g 21 weeks of age 1542 1550 1547 1578 9.0 0.145 0.593 41 weeks of age 1798 1809 1788 1829 12.8 0.302 0.239 56 weeks of age 1839 1868 1871 1893 16.1 0.037 0.796 72 weeks of age 1869 1915 1921 1935 18.5 0.027 0.391 Growth, g 21 – 41 weeks of age 256 258 241 251 9.2 0.357 0.695 41 – 56 weeks of age 41.0 60.0 84.0 64.0 11.10 0.058 0.088 56 – 72 weeks of age 31.0 47.0 49.0 42.0 9.90 0.431 0.239 1 Values are means of 8 replicates per treatment and represent the mean values A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 89 The egg quality variables studied; specific weight, Haugh unit and shell strength were similar among the all feed- ing treatments with the exception in a quadratic manner decreased specific weight along pea inclusion examined during the second feeding phase (41 – 57 weeks of age) (p < 0.05) (Table 6). Discussion Crude protein content of studied batch of peas (217 g kg-1 DM) was comparable with previous reports using the same pea variety (Partanen et al. 2001, Partanen et al. 2006). As expected the crude protein content of semi- leafless peas was lower than for instance reported for ordinary field peas (243 g kg-1 DM) (Partanen et al. 2001, Rodrigues et al. 2012). Protein content of peas is known to vary greatly between cultivar with a range from 181 to 436 g kg-1 DM (Gatel and Grosjean 1990). The average crude protein content of peas is lower than that of faba beans (300 g kg-1 DM) and lupins (340 g kg-1 DM) (Luke 2014), which are other potential home-grown grain leg- umes (Palander et al. 2006). In the current study the diet that included up to 300 g kg-1 of peas supported a good production. The egg produc- tion variables were comparable to earlier studies with high inclusion levels of peas (Castanon and Perez-Lanzac 1990, Ivusic et al. 1994, Perez-Maldonado et al. 1999, Fru-Nji et al. 2007). Compared with control diet Castanon and Perez-Lanzac (1990), Ivusic et al. (1994), Perez-Maldonado et al. (1999) and Fru-Nji et al. (2007) reported no significant difference in egg production variables, including up to 333 g kg-1, 445 g kg-1, 500 g kg-1 or 250 g kg-1 of peas (respectively). Castanon and Perez-Lanzac (1990) studied cull peas orginate from a surplus in the canning in- dustry, so the results of their study are not totally comparable with our results. In the diet that included up to 300 g kg-1 of peas, the protein from peas was able to replace approximately 44% of the protein from SBM. There are several other studies showing that SBM protein can be replaced by pea protein (Castanon and Perez-Lanzac 1990, Perez-Maldonado et al. 1999, Fru-Nji et al. 2007). However, the additional me- thionine was needed to avoid reduction in production performance, when peas were included to the diet in line with literature (Perez-Maldonado et al. 1999, Fru-Nji et al. 2007). However, the necessary amount of added methio- nine is dependent on the content of methionine in feed ingredients used and the crude protein content achieved. Based on the results of production performance and egg quality, peas had no adverse effect. This indicated that the studied pea cultivar did not contain harmful levels of ANF. This is in line with Smulikowska et al. (2001), who reported that the role of trypsin- and protease inhibitors in modern spring cultivars of pea are found to be less important. Seeds of coloured-flowered cultivars, which are rich in tannins are less effectively utilized by poultry than white-flowered ones (Smulikowska et al. 2001, Rodrigues et al. 2012). Table 6. The effects of dietary inclusion level of peas on egg quality variables1 Pea inclusion, g kg -1 p-values Control 100 200 300 SEM plinear pquadratic Specific weight 36 weeks of age 1.086 1.085 1.085 1.086 0.0006 0.608 0.386 54 weeks of age 1.086 1.085 1.085 1.086 0.0005 0.084 0.012 68 weeks of age 1.077 1.078 1.077 1.076 0.0006 0.444 0.209 Haugh unit 36 weeks of age 91.1 90.7 90.9 90.8 0.85 0.897 0.878 54 weeks of age 87.2 88.6 87.8 87.7 0.65 0.918 0.270 68 weeks of age 82.1 83.2 82.8 81.6 0.91 0.680 0.216 Shell strength, kg 36 weeks of age 3.70 3.88 3.85 3.81 0.111 0.596 0.328 54 weeks of age 3.59 3.65 3.60 3.45 0.076 0.172 0.174 68 weeks of age 3.14 2.98 3.06 3.06 0.066 0.848 0.460 1 Values are means of 8 replicates per treatment (each observation is a mean of 8 eggs per experimental unit) and represent the mean values. A G R I C U LT U R A L A N D F O O D S C I E N C E E. Koivunen et al. (2015) 24: 84–91 90 The linear increase in FCR and live weight with increasing pea inclusion during the second feeding phase (41 – 57 weeks of age) was unexpected and indicates that weight gain was prioritized over egg production during this period as feed intake remained unchanged. However, these findings remain unexplained. In agreement with the current results Ivusic et al. (1994), and Igbasan and Guenter (1997) reported no differences in mortality between the control and diets with pea inclusion. The dietary pea inclusion had a significant effect on specific weight, but from a practical point of view the differ- ence observed is irrelevant. Our results on the egg quality variables agree with the results of Anderson (1979) and Fru-Nji et al. (2007). Anderson (1979) found no significant differences in egg quality variables (albumen qual- ity, yolk colour and chemical composition) between control diet and diet included up to 300 g kg-1 of peas, but showed that pea inclusion (300 g kg-1) had an adverse effect egg shell quality. Fru-Nji et al. (2007) found no signifi- cant difference in egg quality variables (shell strength, shell fraction, yolk fraction, yolk index, yolk colour, albumen fraction, albumen index) in diets with up to 250 g kg-1 of peas. However, Ivusic et al. (1994) reported that feed- ing diets with 590 g peas per kg of feed resulted in eggs with thinner shells and with reduced yolk pigmentation. In conclusion, when diets are balanced with regards to their nutrient content at least 300 g kg-1 semi-leafless peas studied can be used in laying hen diets based on cereals and SBM, without negative effects on the production performance and egg quality. Acknowledgements The Ministry of Agriculture and Forestry of Finland supported this study. The authors would like to thank the staff of the Animal Production Research of MTT Agrifood Research Finland (Nowadays Luke Natural Resources Insti- tute Finland) for their professional input to this study. Erja Koivunen would like to thank the Agriculture Research Foundation of August Johannes and Aino Tiura and the Raisio Plc Research Foundation for providing grant to write this publication. Erja Koivunen would like to express acknowledgement to professor Jan Erik Lindberg for his help and critical review of the manuscript. References Anderson, K. 1979. Some conventional feedstuffs for laying hens, 1. Effects to production and chemical composition of eggs. Swed- ish Journal of Agricultural Research 9: 29–36. AOAC (1990) Official Methods of Analysis. Association of Official Analytical Chemists, Inc., Arlington, VA. 1298 p. Castanon, J.I.R. & Perez-Lanzac, J. 1990. 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Agricultural and Food Science 18: 191–205. Use of semi-leafless peas (Pisum sativum L) in laying hen diets Introduction Materials and methods Experimental animals and treatments Analytical and experimental procedures Statistical analyses Results Discussion Acknowledgements References