The welfare of slow growing broiler genotypes reared in organic system

doi: 10.9755/ejfa.2015.04.026


INTRODUCTION
Under organic housing systems, chickens are faced with a rich environment and perform more behavioural repertories than in cages housing, all of which may improve animal welfare.Besides, they are subjected to various factors as well as infectious and parasitic diseases, social interactions and unfavourable climatic conditions that may expand both stress and fear reactions and depress wellbeing.As criteria for measuring levels of stress, welfare and fear in chickens is predicted to duration of tonic immobility (TI) and fl uctuating asymmetry (FA) (Campo et al., 2008;Dávila et al., 2011).
As it is known, the right and left sides of any morphological character are expected to be equal during growth or exhibit a similar growth in symmetric animals.Many factors such as genetically structures, rearing and the other environmental conditions of the animals are shaped the situation (Campo et al., 2005b;Mendeş, 2008).Environmental stress such as stocking density, lighting and feeding programs may affect developmental stability, thus, it can be seen increasing variation between individuals in the poultry housing systems (Mendeş, 2008;Møller et al., 1995;Møller et al., 1999).Housing systems and gender are important for chicken welfare.The morphology of two sides of a bilateral character largely develops under identical environmental conditions, alterations between right and left are presumed to refl ect developmental unstability.FA can be considered as deviations from perfect symmetry.It may benefi t in determining the suitability of breeding conditions as experienced by animals during their growing (Van Nuffel et al., 2007).FA has been claimed to be positively related to TI by Campo et al. (2000).On the other hand, such shortterm differences could contain principal information about changes in the environment of an individual.Bizeray et al. (2002) have reported that increased activity may potentially improve leg condition performance and reduce the level of fearfulness in birds.Tuyttens et al. (2008) stated that broilers from conventional farms reveal more FA than broilers from organic farms, and recommend that, in despite of the potentially raised up risk of immunological challenge, bird welfare is usually superior in organic farms as compared with conventional farms in Belgium.
The objective of this study is therefore to compare two slow-growing genotypes and sex reared broilers organically with regards to a wide variety of animal-related welfare indicators such as duration of the TI, a traditional measure of fearfulness in poultry; FA and relativite asymmetry (RA), a measure that has been reported to refl ect chronic stress and welfare status and some serum biochemical profi le.

MATERIALS AND METHODS
Two hundred and forty slow-growing chickens (mixed-sex) consisting of equal number of Hubbard S757 (S757) and Hubbard Grey Barred JA (GB-JA) strains were utilized for the investigation under organic system.In the study, day-old chicks were weighed, identified with a wing number and randomly allocated to two treatments with six replications in two-way ANOVA.The experiment was approved by the Ethics Committee of the Cumhuriyet University (20.06.2011/50).
There were twelve portable shelters (1.5 x 1.5 m), each containing 20 birds per replication with 10 birds/m 2 stocking density placed in each of the 100 m 2 grazing area.The research was carried out according to the principles and implementation of regulation on organic agriculture (OFL, 2010) published by the Republic of Turkey, Ministry of Food, Agriculture and Livestock.The experiment was ended at the end of the 14 th week.Birds were fed a three-phase organic diet ad-libitum: a starter diet (197 g crude protein (CP)/kg and 13.00 MJ of metabolizable energy (ME) per kg of diet) from 0 to 28 days; a grower diet (201 g/kg CP and 12.72 MJ of ME per kg of diet) from 29 to 81 days and a fi nisher diet (180 g/kg CP and 12.91 MJ of ME per kg of diet) from 82 to 98 days.Creating artifi cial poultry pasture, Lotus corniculatus (50%) and Bromus inermis (50%) are used by mixing (Eleroğlu et al., 2014a).
The eighteen male and eighteen female chickens from each group selected a total of 72 chickens were tested for TI.The TI reactions were examined in 6, 10 and 14 weeks old birds benefi ting from the wing numbers.The TI was induced by placing birds in a U-shaped wooden cradle covered with a cloth and restraining them for 15 seconds, as reported by Jones and Faure (1981).The duration of TI was recorded (i.e. the time until the bird stood up).If an attempt of induction was unsuccessful (no TI or TI lasting less than 10 s), the experimenter immediately resumed the induction procedure.If TI could not be induced after fi ve attempts, the bird was deemed not to be susceptible and its TI duration score was 0 s.If the bird did not stand after 10 min, a maximum score of 600 s was recorded for TI duration (Dávila et al., 2011;Campo and Prieto, 2009).In the present study, after TI tested, the responses of rectal temperatures (RT) of slow-growing broilers were measured.The RT was measured with a manual electronic thermometer (±0.1°C) in 6, 10 and 14 weeks by inserting into the rectum 3 cm in depth for each bird.Thermometer until it is fi xed measurement the chicken was gently handled.
The twelve male and twelve female slow-growing chickens from each group selected a total of 48 chickens were slaughtered and after tested for asymmetry measurements.FA and RA were used as measures for deviation from bilateral symmetry.The measured morphological traits were both right (R) and left (L) outer, middle, inner, and hind toe, and leg (metatarsus) lengths, and tarsometatarsus widths areas (A= length of the third phalanx of the mid toe, B= length of the fourth phalanx of the outer toe, C= length of the back toe, D= length of tarsometatarsus, E= width of tarsometatarsus at the spur, F= width at 1 cm above the spur of tarsometatarsus and G= width of tarsometatarsus at the joint with tibiotarsus).Right and left side values of a bird were taken during the same session.All bilateral 5 lengths and 2 tarsometatarsus widths were measured (Van Nuffel et al., 2007) in millimeter by using a digital caliper (to the nearest 0.01 mm).FA for a trait was defi ned by the unsigned or absolute differences between sides [|R-L|]; the unsigned value as an index of FA (equivalent to the mean deviation) was more appropriate for these data than indices using the variance of right minus left sides (Campo et al., 2005b).A series of steps was followed before identifying exhibited asymmetry as FA (normal distribution of signed right minus left differences with a mean of zero).RA was defi ned as the ratio of the absolute value of asymmetry (L-R) over bilateral traits: RA = (|L-R|/[(L+R)/2]) x 100 (Yang, 1998).
Before slaughter process, about 5 mL blood samples were collected from the experimental birds.At the ages of 98 days (48 birds) blood was collected by venipuncture of the wing vein (Vena cutanea ulnaris), kept on ice and transferred to the laboratory (Eleroğlu et al., 2014b).Serum was separated and used for biochemical assays.The concentration of serum glucose, cholesterol, total protein, uric acid, Ca, P, Na, K and Cl were measured, using commercial kits on an auto-analyzer (Technicon RA-1000).The statistical analysis was conducted using the SPSS 16.0 (Inc.Chicago.IL.USA) program.Treatment effects were considered to be signifi cant at P<0.05.Data were expressed as mean values with pooled standard errors (standard errors of the mean, SEM).

RESULTS
Mean values indicating the comparison of genotype and sex on the TI, number of tonic immobility induction (NTI) and RT are summarized in Table 1.
Slow-growing genotypes housed in organic system were similar duration of TI for 6 and 14 weeks.Likewise, the genotypes had no effect on the NTI at 6, 10 and 14 weeks.The TI had signifi cant difference between genotypes at 10 weeks (P<0.01).The average tonic immobility duration of S757 genotype was higher than that GB-JA genotype (67.53 vs. 44.79s) at 10 weeks.However, the observed difference between male and female in 14 weeks was signifi cant (P<0.05).
Table 2 is summarized the data concerning the FA and RA.There was not a signifi cant difference (P>0.05) in the FA and RA of A, B, C, D, E and F values between genotypes, sex and their interaction except FA value of G in terms of sex.Some serum blood parameters of two different slow-growing broiler genotypes reared organic system are summarized in Table 3.It has seen that genotypes and sex did not affect on serum glucose, total protein, Cl, Na, K, P, Ca levels, except uric acid (P>0.05).Cholesterol and uric acid has signifi cant differences between genotypes (P<0.01).It is seen that only FA of A is signifi cantly correlated with FA of B (P<0.05), whereas FA of E is signifi cantly correlated with FA of G (Table 4; P<0.05).Likewise, there is an association between the RA of A and RA of B (Table 4; P<0.05).

DISCUSSION
As can be seen from Table 1, slow-growing male broilers showed more fear stress than those female broilers (average TI 51.89 vs. 34.46s) at 14 weeks of age.Overall TI and NTI were similar (P>0.05) in genotypes and sex.Some study showed that genotypes had considerable variations in terms of TI (Campo et al., 2000).In the present study TI of slow-growing broilers had excessively lower (ranged 57.70 to 93.77 s) with outdoor access than those (ranged 158 to 398 s) of Campo et al. (2008), who tested six different Spanish breeds.Likewise, Prieto and Campo (2010) stated that TI found 99 s in White Leghorn reared with standard temperatures.
The result of present study showed that the responses of RT was not affected by genotypes, sex and their interaction (Table 1; P>0.01).RT is one of the most important physiological responses that refl ect the thermoregulation of animal body, and has been suggested to be an indicator of the level of heat stress in broiler chickens (Deeb and Cahaner, 1999).When the broiler chickens are exposed to high temperature, the RT will be elevated, because of the increased heat accumulation (Lin et al., 2004).Slowgrowing broilers are recognized to be less sensitive to heat (Washburn et al., 1980).Several researchers (Deeb and Cahaner, 2001;N'dria et al., 2007) stated that internal heat production in hot conditions in broilers is known to be higher than in slow-growing genotypes.However, broilers rectal temperature was higher under the hot condition, thus resulting in greater body temperature variation (N'dria et al., 2007).According to this result easily understood that the slow-growing broiler genotypes were not exposed to heat stress under organic system.The physiological reactions of the slow-growing broilers animals in terms of level of rectal temperature is in accordance with the results of N'dria et al. (2007) in similar study for the normal environmental temperature.
The degree of relative FA varied among traits.This variation among traits suggests the convenience of a mean RA from multiple traits as a reliable measure of developmental stability (Campo et al., 2000).Mean RA showed that genotypes had similar developmental stability.This fi nding agrees with Campo et al. (2005b) and Campo et al. (2000) who reported that the differences in FA and RA among genotypes were not signifi cant for leg length (metatarsus) in males and females under conventional systems.Females and males showed similar degrees of FA and RA in six morphological traits, whereas the sex differed for their degree of FA in G at 14 weeks of age.Males showed signifi cantly greater average FA and RA for G than females (1.55 vs. 0.75 and 3.66 vs. 1.59).
It has been displayed that females prefer males with symmetric sexual attributes (Møller, 1992), and there is evidence of natural selection for symmetrical attributes in poultry (Campo et al., 2005b).Sexual dimorphism with larger values for males than females was apparent in this trait.Therefore, this morphological trait could be taken into consideration as sexual trait determining the gender of adult birds.
This study has been unable to demonstrate that genotype effect was signifi cant for the RA of middle toe length, the mean value being greater in the Quail Castellana Silver (5.23) than in the Black Menorca (1.17) and Red-Barred Vasca (1.15) genotypes until 8 wk of age (mixed sexes) in conventional system reported by Campo and Prieto (2009).Previous researchers suggested that middle toe length asymmetry was a sensitive indicator of stress.On the other hand, Campo et al. (2000) suggested that RA measures did not provide a general tool to indicate fearful or stress susceptibility in birds and utilization of FA as a biological monitor of environmental and genetic stress may be useful only in extreme conditions.Moreover Campo et al. (2007) determined that birds exposing to continuous light were more stressed and fearful according to the results of measured FA and TI.Campo and Prieto (2009) suggested that the utilization of FA, TI as biological indicators of well-being, fear, and stress may be not useful in all extreme conditions, especially in those including pain.On the other hand Møller et al. (1999) reported that FA was positively correlated with the duration of TI in chickens that were experiencing environmental stress.Hence, according to the current research fi ndings, slow-growing broiler welfare indicators are similar to each other, resulted in an improvement in the greater the organic housing conditions.
Cholesterol and uric acid concentrations are ranged from 97.59 to 120.87 mg/dL and 3.67 to 5.56 mg/dL which are also in agreement with previous data reported by Silva et al. (2007) and Eleroğlu et al. (2011) who studied in conventional system.
In fact, it could be thought for the differences of serum level uric acid that GB-JA genotypes could not benefi t more from dietary protein, although supplying the equally dietary protein level for two genotypes during rearing period and a study (Szabo et al., 2005) found a direct relation between the amount of ingested protein and uric acid serum level.Rajman et al. (2006) also found higher uric acid levels in broiler breeders during the rearing phase, at 30 and 44 days of age, as compared to older breeders.
Average Cholesterol levels was significantly (P<0.01)higher in male than in female slow-growing broiler (112.86 vs. 101.20).The higher values of cholesterol in S757 genotype correspond to their low mobilization by tissues and to their intense synthesis by the liver (Szabo et al., 2005).Furthermore, the increase of cholesterol value could be related to the higher dietary energy supply.The importance of biochemical parameters as diagnostic tools and physiological indicators in birds has been documented (Eleroğlu et al., 2011;Öztürk et al., 1999;Albokhadaim, 2012).However, these parameters are greatly affected by sex, age and season (Silva et al., 2007).
There is no signifi cant correlation between overall TI and RT.This result is in agreement with these found by Campo et al. (2007) indicating that neither females nor males had signifi cant correlation coeffi cients between morphological characters and TI.This result is in disagreement with these found by Ghareeb and Böhm (2008) indicating the ease of capture rank was negatively correlated with the TI at week 5 (-0.364) and with the NTI at week 6 (-0.238) and suggested that birds TI and NTI had longer and higher.
Furthermore, the destitute of a strong correlation between the FA of other attributes showed that the level of FA in other attributes did not reverberate equally the quality of broilers.It is further known that the attributes could indicate high levels of genetic and phenotypic correlation in their means, notably morphological attributes between them and secondary sexual attributes between them, different attributes rarely showed much correlation in their level of FA (Campo et al., 2005a).On the contrary, Campo et al. (2000) analyzed that the correlation coeffi cient between mean RA of the different attributes and tonic immobility was positive and signifi cant in the Villafranquina females (r= 0.32; P < 0.05), emphasized that hens with a high level of morphological FA tended to have a high level of fearfulness.
Results indicate that slow-growing genotypes and sex were not negatively affected by the measures of stress, such as the FA and RA, TI and RT.As can be seen from the results of other research that organic rearing conditions positively affects the welfare of both slow-growing genotypes.
Moreover, further research would help to clearly defi ne the relative importance of welfare indicators in organic rearing slow-growing broilers, which are exposed to several factors including infectious and parasitic diseases, social interactions, and adverse climatic conditions.