ABSTRACT
An experiment was undertaken in Haramaya University to find out the effect of replacing Soybean meal (SBM) by processed kidney bean (PKB) on egg quality parameters. To carry out the experiment, 180 white leghorn hens of similar initial body weight of 1121.17 g ± 24.92 and 6.5 months of age and 30 cocks were randomly distributed into five treatments using complete randomized design (CRD). Each treatment consisting 12 layers and 2 cocks was replicated three times. PKB replaced SBM at a rate of 0 (control), 25, 50, 75 and 100% for T1, T2, T3, T4 and T5, respectively. The optimum amount of biological and economic level of SBM (26%) recommended in layers’ ration in the Haramaya University poultry farm was used as a basis of replacement. Three eggs per replicate or 9 eggs per treatment were collected every two weeks to assess egg shell weight, shell thickness, albumen weight and height, Haugh unit and egg yolk weight and color. All qualitative egg quality parameters were analyzed by general logistic regression model while all quantitative egg quality parameters were analyzed by general linear model. The results showed no significant eggshell weight, albumin height, albumin weight, yolk height, yolk weight, and yolk diameter and yolk index among treatments. Yolk color of the layers fed T5 was significantly yellow compared to groups offered T1 and T2. It is concluded that PKB can replace SBM up to 75% (195 g/kg) without adverse effect on egg quality.
Key words: Egg weight, egg yolk, Haugh unit, shell thickness, yolk color
The demand for animal protein for human nutrition in the developing world is high due to the increase in population and the wide speared malnutrition (OECD-FAO, 2010). Animal production, particularly poultry play a major role in bridging the protein gap and food deficiency in developing countries where average daily consumption is far below recommended standards (Onyimonyi et al. 2009; OECD-FAO, 2010).
However, the productivity of animals in the developing regions is low. Hence, there is poor animal protein intake (Alli-Balogun et al. 2003). The contribution of intensive commercial poultry industry to the supply of poultry meat and eggs in most developing countries in general and in Ethiopia in particular, has been very low. The overall per capita consumption of egg and meat in Ethiopia is about 0.12 and 0.14 kg, respectively (USAID, 2010) and their contributions do not exceed 2 to 3% of the total animal protein consumption in the country (Alemu et al., 2009).
The profit from poultry production can be attained by minimizing feed cost which accounts for more than half of the total cost of production (Girma et al., 2012). Within the poultry industry, 75 to 80% of the total cost of production is attributed to feed costs. Of this, nearly 30% is due to supplying protein in the ration (Coon, 2002). Protein sources are especially limiting factors in poultry feed production in the tropics (Atawodi et al., 2008). Diseases, poor feeding, management practices, limited quantity and quality of standard feed are the major constraints limiting poultry production in Ethiopia (Taddelle et al., 2000). However, soybean production in the country is low and the price of the grain as well as the cake is extremely high.
It is suggested that evaluation and nutritional characterization of alternative protein ingredients that are locally available and relatively affordable to improve commercial poultry production and increase its efficiency is an urgent requirement (Kamalzadeh et al., 2008; Nalle et al., 2010; Ani and Okeke, 2011). Kidney bean is one of the neglected tropical legumes that can be used to fortify cereal-based diets. Elsewhere, it is a potential component of diets of pigs and poultry, because of its high protein content, energy and amino acids content that is similar to that of soybean except for a content level of methionine (Laurena et al., 1991; Okaka et al., 1992). However, this legume contain various biologically active compounds usually referred as anti-nutritional factors (ANFs) that may lead to reduced nutritive value compared to the predicted when consumed by animals and humans. Even though ANFs limit the use of raw kidney bean, various processing techniques reduce the effects. Several studies have indicated that heat processing (cooking and dry heating) increases the digestible nutrients available to young animals, especially chicken resulting in improved growth (Emiola and Ologhobo 2006). Despite the importance of PKB; in Ethiopia there is limited research so far undertaken on the effect replacement of SBM with kidney bean meal in white leghorn layer diets. To date, there is only one work that suggests 100% replacement of kidney bean for soybean (Sisay et al., 2015a). But this work was based on 10% (100 g/kg) of soybean, which is lower than the percentage of SBM in layers’ diet to meet the requirement for high production. Therefore, this experiment was carried out to assess the effect of replacment of SBM with PKB on egg quality.
Ingredients and experimental rations
The experiment was carried out at Haramaya University Poultry Farm, Ethiopia that located at 42° 3’ E longitude, 9° 26’N latitude and situated at an altitude of 1980 m above sea level. The area receives mean annual rainfall of 780 mm and average minimum and maximum temperatures 8 and 24°C respectively (Samuel, 2008). Corn grain (CG), wheat short (WS), soybean meal (SBM), noug seed cake (NSC), processed kidney bean (PKB), vitamin premix, limestone, and salt were used to formulate experimental diets.
To treat anti- nutritional factors, the kidney beans were cleaned, soaked in water for five hours, boiled for 1 hour at 100°C and dried under the sun until it is quite enough for grinding (Emiola et al.,2007; Sisay et al., 2015b). Firewood used as a source of heat energy. The temperature during boiling was roughly maintained at 100°C by adding or removing the wood into and out of fire by using thermometer to keep temperature roughly at 100°C. Corn grain, SBM, NSC, and PKB were ground to pass through a 2mm sieve before formulating the treatment rations at Haramaya University feed milling unit. Representative samples of CG, SBM, NSC and PKB were taken for chemical analysis before formulating the actual dietary treatments. The nutrient contents of each feed ingredient [dry matter (DM), crude protein (CP), ether extract (EE), crude fiber (CF), metabolizable energy (ME) and ash] were determined following the procedure of the AOAC (1990) were used to formulate the rations (Table 1). The experiment had five diets in which PKB replaced SBM at a rate of 0, 25, 50, 75 and 100% for T1, T2, T3, T4 and T5, respectively. The formulated diets contained 2800 to 2900 Kcal metabolizable energy (ME) per Kg of dry matter (DM) and 16 to 16.5% crude protein (CP) as recommended for layers (Leeson and Summers, 2001).
Management of experimental animals
The experimental house was partitioned into 15 pens with wire-mesh and covered with grass litter material of 10 cm depth. Before the commencement of the actual experiment, the experimental pens, watering equipments, feeding troughs and laying nests were disinfected, sprayed against external parasites and thoroughly cleaned. The birds were vaccinated against common poultry diseases. Initially 180 white leghorn layers and 30 cocks of mature white leghorn breeds of similar age (6.5 months) and weight (1121.17 g ± 24.92), obtained from the University’s poultry farm, were randomly assigned to the five dietary treatments as indicated in Table 1. Twelve layers and 2 cocks per treatment were assigned to five treatments. In a completely randomized design (CRD), each treatment was replicated three times.
Data collection and measurement
Egg quality parameters
Egg quality parameters were measured for each replicate. Three eggs per replicate were randomly sampled every two weeks for quality analysis. The total eggs used for quality analysis were 225 eggs (45 eggs per treatment). The sampled eggs were weighed and broken on flat mirror to examine shell thickness, shell weight, yolk diameter, yolk index, yolk color, yolk weight, yolk height, albumen weight and albumen height.
Egg shell, shell weight and shell thickness
The sampled eggs were broken and the shell was separated. The weight of the shell was measured by using sensitive balance. The shell was further broken into parts, the shell membrane manually removed, and the thickness at the pointed, blunt ends and middle of the egg were measured using a micrometer gauge. The mean value of the three measurements was taken as shell thickness of the eggs.
Albumin
Haugh unit (HU) is a measure of albumen quality (Keener et al.,2006). The albumen of the broken eggs was carefully separated from the yolk. Tripod micrometer was used to measure the albumen height. Albumen weight was measured by using sensitive balance. The HU was calculated by employing the following formula (Raji et al.,2009).
HU=100 log (H + 7.5 - 1.7W0.37)
Where, HU = Haugh unit, H = height of albumen and W = egg weight (grams) (Raji et al.,2009).
Yolk
After the separation of the yolk and albumen, yolk diameter and height were measured by tripod micrometer. Yolk weight was measured by using a sensitive balance. Yolk index was calculated as the ratio of yolk height to yolk diameter and the result was expressed as a percentage. After removing yolk membrane and taking yolk height, yolk weight, yolk diameter all yolk part was mixed. Then the yolk sample was placed on a piece of white paper and yolk color determined on Roche fan measurement strips as a color reference. The instrument has 1 to 15 strips representing pale to orange-yellow color (Vuillemiler, 1976).
Statistical analysis
Data on yolk color was analyzed by logistic regression; and all other parameters were statistically analyzed using the general linear model procedure of SAS 2008 version 9. 1. Differences between treatment means were separated using least significance difference (LSD). The general logistic regression model used was given as:
Nutrient composition of ingredients and the treatment
The results of the chemical analysis of ingredients used and nutritional composition of the diet for each treatment are given in Tables 2 and 3, respectively. The DM contents of PKB obtained in this study was slightly lower than reported by Marzo et al. (2002) (93.2%) and Audu and Aremu (2011) (96.8) but similar with Sisay et al. (2015a) (88.00) while CP contents were slightly higher than reported by Marzo et al. (2002), Audu and Aremu (2011), Emiola (2011), Sisay et al., (2015b) and Emiola and Ologhobo (2006) which were 20.9, 23.6, 24.7, 25.8 and 26.8%, respectively. The EE content of kidney bean was the same as that reported by Emiola (2011) while Sisay et al. (2015a) reported higher (4.69) content and the CP was higher than reported by Marzo et al. (2002). The CF content of kidney bean used in this study was comparable to that reported by Arija et al. (2006), Emiola (2011), Sai-Ut et al. (2009), Audu and Aremu, (2011) who reported 5.1, 5.0, 6.0, and 4.7%, respectively. The result of chemical composition of kidney been used in the present experiment showed comparable ME contents to that of 3342.2 and 3365 kcal/kg, reported by Ofongo and Ologhobo (2007) and Arija et al. (2006) respectively.
Quality of eggs
Shell weight and shell thickness
The shell thickness and shell weight means are presented in Table 4. Eggshell weight of hens fed PKB as a replacement for SBM was not significantly (P>0.05) different. However, the shell thickness of the layers fed control diet (no PKB) was significantly (P<0.05) lower compared to diet in which PKB fully replaced SBM which contrasts Sisay et al., (2015b) report that there is no (p>0.05) difference among treatments in egg shell thickness. This could be an attribute of egg sizes, since calcium content is not much different in magnitude between the treatments. In this case, the available calcium should be spread across the surface of the egg, thus the egg with large size tend to have a thinner eggshell. In agreement with the present finding, Butcher and Miles (2003) and Rajkumar et al. (2009) reported that smaller eggs have stronger shells than larger ones, since the limited amount of calcium needs to be deposited over all part of the shell evenly. In contrast to this finding, Gernat (2001), Iyayi and Taiwo (2003), Kwari et al. (2011) and Gheisari et al. (2011) replaced shrimp meal, mucuna seed meal and sorrel seed meal for soybean meal at different level as protein sources and found no significant effect on shell thickness.
Albumin weight, height and haugh unit
As shown in Table 4, there was no significant difference (P>0.05) in albumen weight and height, but Haugh unit (HU) of layer fed control diet was significantly (P<0.01) lower than hens fed diet containing PKB as a substitute for SBM. The difference in HU might be related to the decrease in the magnitude of the value of albumin height and increase in egg weight of the hens in the control group. Albumin height and egg weight have a direct and indirect contribution for the HU values, respectively in which the increase in albumin height increase the he HU and the increase in egg weight decrease HU. This is in line with the result demonstrated by Suk and Park (2001) that albumen weight is positively associated with egg weight and that of Mousavi et al. (2013) who reported independence of HU and albumen height from dietary CP level. Wu et al. (2007) Related HU to nutrients and stated that the HU of hens fed higher nutrient density was significantly lower than that of hens fed lower nutrient densities, probably because of the higher egg weight of hens fed the high nutrient density. Though HU is significant, it is within the recommended range (81.0 - 93.4) in all treatments, which implies no quality differences in egg between treatments. This concurs with the previous reports of Lewko and Gornowicz (2009) who reported a range of 70-100 for HU as an indication of good quality eggs.
Yolk height, weight, diameter and index
There was no significant (P>0.05) difference among dietary treatments in yolk height, weight, diameter and index (Table 4), this in agreement with Sisay et al. (2015a) finding. There is no any obvious trend in magnitude exhibited in these parameters indicating no significant relation with the amount of PKB included in the diet. Nutrition does not contribute directly to the yolk height, weight, diameter, and yolk index, but is influenced by the weight of the egg, which is dependent on the nutrients consumed by the birds. Since high egg weight was not observed among treatments, variations in yolk traits were also not observed among treatments. The present finding are in agreement with those of Kaya et al. (2011) who did not detect any difference among yolk height, weight and yolk index by substituting common vetch for SBM at different proportions.
Yolk color
The yolk color of the birds in T4 was significantly (P<0.05) different from the birds in T1 and T2 similar to that of the birds fed T3 and T4. The Roche color fan reading of the eggs were within the range of 1 to 6, in which the majority of the eggs had readings of two (29.3%), three (25.3%), four (21.3%), one (16.9%), five (6.7%) and six (0.4%) on percentage basis on Roche color fan (Table 5). Similarly the logistic regression results for yolk color showed significant difference (pr>chisq <0.0001 at α = 0.05) with Wald chi sq value of 85.2 among the treatments (Appendix Table 1). Furthermore logistic regression contrast rows estimation and testing results of yolk color in T 4 and T5 revealed that the improvement in yolk color as compared to group fed T1 and T2 (Appendix Table 2). The odd ratio value of T1 vs. T5, T2 vs.T5, T3 vs.T5 and T4 vs. T5 shows yolk color of T1, T2, T3 and T4 is one -third, two -fifth, three- fourth and seven -eighth as yellow as that of T5 respectively. This showed that the improvement of yolk color of the eggs increased with the level of PKB, which implies the richness of PKB in the beta- carotene compared to SBM. This agrees with that of Hassan (2013) who obtained more yellowish yolk than control diet as a result of incorporation of guar meal in the diets of layers. Contrary to this finding, Kaya et al. (2011) observed no difference in yolk color when Raw and Processed Common Vetch Seed (Vicia sativa) replaced SBM at 25%. Laudadio and Tufarelli (2010) Reported reduction in yolk color from 12.22 to 11.78 by feeding faba beans compared to SBM. The overall current study shown that the replacement of SBM by PKB has no any impact on all egg quality parameter as those indicating significant value is even within a range of quality egg, indicating that valuable replacement for both internal and external egg quality parameter.
The authors have not declared any conflict of interests.
REFERENCES
|
Alemu D, Degefe T, Ferede S, Nzietcheung S, Roy D (2009). Overview and Background Paper on Ethiopia's Poultry Sector: Relevance for HPAI Research in Ethiopia. International Food Policy Research Institute (IFPRI).
|
|
|
|
Alli-Balogun JK, Lakpini CAM, Alawa JP, Mohammed A, Nwanta JA (2003). Evaluation of cassava foliage as a protein supplement for sheep. Niger. J. Anim. Prod. 30(1):37-46.
Crossref
|
|
|
|
Ani AO, Okeke GC (2011). The Performance of Broiler Birds Fed Varying Levels of Roasted Pigeon pea (Cajanus cajan) Seed Meal. Pak. J. Nutr. 10 (11):1036-1040.
Crossref
|
|
|
|
AOAC (1990). Association of Official Analytical Chemist. Official Method of Analysis (13th ed). 15th ed. AOAC Arlington, Verginia, USA pp. 12-98.
|
|
|
|
Arija I, Centeno C, Viveros A, Brenes A, Marzo F, Illera JC, Silvan G (2006). Nutritional evaluation of raw and extruded kidney bean (Phaseolus vulgaris L. var. Pinto) in chicken diets. Poult. Sci. 85(4):635-644.
Crossref
|
|
|
|
Atawodi SE, Mari D, Atawodi JC, Yahaya Y (2008). Assessment of Leucaena leucocephala leaves as feed supplement in laying hens. Afr. J. Biotechnol. 7(3):317-321.
|
|
|
|
Audu SS, Aremu MO (2011). Effect of processing on chemical composition of red kidney bean (Phaseolus Vulgaris L.) Flour. Pak. J. Nutr. 10(11): 1069-1075.
Crossref
|
|
|
|
Butcher GD, Miles RD (2003) Factors causing poor pigmentation of brown shell eggs. University of Florida.
View
|
|
|
|
Coon CN (2002). Feeding egg-type replacement pullets. In: Commercial Chicken Meat and Egg Production. Bell DD, Weaver WD (Eds.). Cluwer Academic Publishers, Dordrecht, the Netherlands. pp. 267-285.
Crossref
|
|
|
|
Emiola IA, Ologhobo AD (2006). Nutritional assessment of raw and different processed Legume seed in Broiler ration. J. Anim. Vet. Adv. 5(2):96-101.
|
|
|
|
Emiola IA, Ologhobo AD, Gous RM (2007). Performance and histological responses of internal organs of broiler chickens fed raw, dehulled, and aqueous and dry-heated kidney bean meals. Poult. Sci. 86(6):1234-1240.
Crossref
|
|
|
|
Emiola IA (2011). Processed african yam bean (sphenostylis stenocarpa) in broiler feeding: performance characteristics and nutrient utilization. J. Environ. Issues Agric. Dev. Ctries 3(3):123-131.
|
|
|
|
Gernat AG (2001). The effect of using different levels of shrimp meal in laying hen diets. Poult. Sci. 80(5):633-636.
Crossref
|
|
|
|
Gheisari AA, Ghayor P, Eghbal-Saeid S, Toghyani M, Najafi AA (2011). Effect of Different Dietary Levels of Rapeseed Meal on Reproductive Performance of Iranian Indigenous Breeder Hens. Asian J. Anim. Vet. Adv. 6:62-70.
Crossref
|
|
|
|
Girma M, Tamir B, Dessie T (2012). Effects of replacing peanut seed cake with brewery dried yeast on laying performance, egg quality and carcass characteristics of rhode island red chicken. Int. J. Poult. Sci. 11:65-72.
Crossref
|
|
|
|
Hassan SM (2013). Effects of adding different dietary levels of guar meal on productive performance of laying hens. J. Cell Anim. Biol. 7(5):57-62.
Crossref
|
|
|
|
Iyayi EA, Taiwo VO (2003). The effect of rations incorporating mucuna (mucuna pruriens) seed meal on the performance of laying hens and broilers. Trop. Subtrop. Agro ecosyst. 1:239-246.
|
|
|
|
Kamalzadeh A, Rajabbaigy M, Kiasat A (2008). Livestock production systems and trends in livestock industry in Iran. J Agric. Soc. Sci. 4:183-188.
|
|
|
|
Kaya H, Celebi S, Macit M, Geyikoglu F (2011). The effects of raw and physical processed common vetch seed (Vicia sativa) on laying performance, egg quality, metabolic parameters and liver histopatology of laying hens. Asian-Australas. J. Anim. Sci. 24(10):1425-1430
Crossref
|
|
|
|
Keener KM, McAvoy KC, Foegeding JB, Curtis PA, Anderson KE, Osborne JA (2006). Effect of testing temperature on internal egg quality measurements. Poult. Sci. 85(3):550-555.
Crossref
|
|
|
|
Kwari ID, Diarra SS, Raji AO, Adamu SB (2011). Egg production and egg quality laying hens fed raw or processed sorrel (Hibiscus sabdariffa) seed meal. Agric. Boil. J. North Am. 2(4):616-621.
Crossref
|
|
|
|
Laudadio V, Tufarelli V (2010). Treated fava bean (Viciafaba var. minor) as substitute for soybean meal in ration of early phase laying hens: Egg-laying performance and egg quality. Poult. Sci. 89:2299-2303.
Crossref
|
|
|
|
Laurena A, Rodriguez F, Sabino MNG, Zamora AF, Mendoza EMT (1991). Amino acid composition, relative nutritive value and invitro protein digestibility of several Phillipine indigenous legumes. Plant Foods Hum. Nutr. 41:59-68.
Crossref
|
|
|
|
Leeson S, Summers JD (2001). The Nutrition of Chicken, 2nd ed. University Books, Guelph, Canada. 355 p.
|
|
|
|
Lewko L, Gornowicz E (2009). Egg albumen quality as affected by bird origin. J. Cent. Eur. Agric. 10(4):455-464.
|
|
|
|
Marzo F, Alonso R, Urdaneta E, Arricibita FJ, Ibá-ez F (2002). Nutritional quality of extruded kidney bean (Phaseolus vulgaris L. var. Pinto) and its effects on growth and skeletal muscle nitrogen fractions in rats. J. Anim. Sci. 80:875-879.
|
|
|
|
Mousavi SN, Khalaji S, Ghasemi-Jirdehi A, Foroudi F (2013). Investigation on the effects of dietary protein reduction with constant ratio of digestible sulfur amino acids and threonine to lysine on performance, egg quality and protein retention in two strains of laying hens. Italian J. Anim. Sci. 12(1):2.
Crossref
|
|
|
|
Nalle CL, Ravindran V, Ravindran G (2010). Evaluation of favba beans, white lupins and peas as protein source in broiler rations. Int. J. Poult. Sci. 9 (6):567-573.
Crossref
|
|
|
|
OECD-FAO (2010). OECD and Food and Agriculture Organization of the United Nations. OECD-FAO Agricultural book Outlook 2010. OECD Publishing. pp. 147-158.
|
|
|
|
Ofongo ST, Ologhobo AD (2007). Processed Kidney Bean (Phaseolus vulgaris) in Broiler Feeding: Performance Characteristics. Conf. Int. Agric. Res. Dev. P 6.
|
|
|
|
Okaka JC, Akobundu ENT, Okaka ANC (1992). Human Nutrition – An Intergrated Approach. Obio Press Ltd., Enugu pp. 182-220.
|
|
|
|
Onyimonyi AE, Olabode A, Okeke GC (2009) Performance and economic characteristics of broilers fed varying rationary levels of Neem leaf meal (Azadirachtaindica). Int. J. Poult. Sci. 8(3):256-259.
Crossref
|
|
|
|
Raji AO, Aliyu JJ, Igwebuike U, Chiroma S (2009). Effect of storage methods and time on egg quality traits of laying hens in a hot dry climate Eur. J. Agric. Biol. Sci. 4(4):1-7.
|
|
|
|
Rajkumar U, Sharma RP, Rajaravindra KS, Niranjan M, Reddy BLN, Bhattacharya TK, Chatterjee RN (2009). Effect of genotype and age on egg quality traits in naked neck chicken under tropical climate from India. Int. J. Poult. Sci. 8(12):1151-1155.
Crossref
|
|
|
|
Sai-Ut S, Ketnawa S, Chaiwut P, Rawdkuen S (2009). Biochemical and functional properties of proteins from red kidney,navy and adzuki beans. Asian J. Food Agro-Industry 2(04):493-504.
|
|
|
|
Samuel S (2008). The Epidemiology and management options of chocolate spot disease (Botrytis fabaesard) on faba bean (Viciafaba L.) in Northern Ethiopia. Ph.D Dissertation, Haramaya University, Ethiopia P 175.
|
|
|
|
Sisay FM, Mengistu UL, Getachew A (2014). Effects of replacing soybean meal with processed kidney bean meal (Phaseolus vulgaris) on egg production of white leghorn hens. World Appl. Sci. J. 32(9):1918-1926.
|
|
|
|
Sisay FM, Mengistu UL, Getachew A (2015a). Effects of Replacing Soybean Meal with Processed Kidney Bean Meal (Phaseolus vulgaris) on qualities of Eggs of White Leghorn Hens. Int. J. Agric. Sci. Res. 4(3):049-056.
|
|
|
|
Sisay FM, Mengistu UL, Getachew A (2015b). Effects of Replacing Soybean Meal with Processed Kidney Bean Meal (Phaseolus vulgaris) on egg fertility and chick quality of White Leghorn Hens. J. Adv. Vet. Anim. Res. 2(2):146-152.
|
|
|
|
Suk YO, Park C (2001). Effect of breed and age of hens on the yolk to albumen ratio in two different genetic stocks. Poult. Sci. 80:855-858.
Crossref
|
|
|
|
Tadelle D, Alemu Y, Peters KJ (2000). Indigenous chickens in Ethiopia: genetic potential and attempts at improvement. World's Poult. Sci. J. 56(01): 45-54.
Crossref
|
|
|
|
USAID (2010). Partnership for safe poultry in Kenya (PSPK) program regional poultry value chain analysis in Ethiopia P 26.
|
|
|
|
Vuillemiler JP (1976). The Roche yolk color fan –an an instrument of measuring color. Poult. Sci. 48:767-779.
Crossref
|
|
|
|
Wu G, Bryant MM, Gunawardana P, Roland Sr DA (2007). Effect of Nutrient Density on Performance, Egg Components, Egg Solids, Egg Quality, and Profits in Eight Commercial Leghorn Strains during Phase One. Poult. Sci. 86(4):691-697.
Crossref
|
