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Article

Sustainable Production Potential of Indigenous Gerze Chickens Under Free-Range and Feed-Restriction Strategies

by
Elif Cilavdaroğlu
Department of Animal Science, Faculty of Agriculture, Ondokuz Mayıs University, 55139 Samsun, Türkiye
Sustainability 2026, 18(12), 6192; https://doi.org/10.3390/su18126192
Submission received: 25 May 2026 / Revised: 8 June 2026 / Accepted: 10 June 2026 / Published: 16 June 2026
(This article belongs to the Special Issue Sustainable Animal Production and Livestock Practices)
Versions Notes

Abstract

This study evaluated the effects of intensive indoor, free-range, and free-range feed-restricted rearing strategies on the growth performance, carcass traits, and meat quality of indigenous Gerze chickens. A total of 252 one-day-old chicks were allocated to three treatments: free-range (FR), free-range feed-restricted (FRR), and intensive indoor-reared (IN) groups. Outdoor access and Skip-a-Day feed restriction began at 8 weeks of age, and birds were reared until 16 weeks. At slaughter, 16 chickens per group, balanced by sex, were selected for carcass and meat-quality analyses. Although the IN group showed higher live weights at several intermediate ages, final body weight did not differ significantly between the FR and IN groups, whereas FRR birds had lower final body weight. Feed conversion ratio and cumulative feed consumption did not differ among groups, but these pen-level results should be interpreted cautiously. The IN group had a higher dressing percentage and abdominal fat ratio, whereas edible giblet ratios were greater in the FR and FRR groups. Free-range rearing affected selected meat-quality traits, including lower leg L* and a* values and higher pH values. These findings provide production-oriented evidence that Gerze chickens may be suitable for local free-range systems, while Skip-a-Day feed restriction requires further evaluation.

1. Introduction

Modern intensive poultry production systems have been developed to maximize growth rate, feed efficiency, and carcass yield; however, these systems are increasingly discussed in relation to animal welfare, product quality, and sustainability concerns [1,2,3]. In such systems, chickens are typically housed indoors under controlled environmental and management conditions, and highly selected fast-growing chickens are commonly fed high-energy diets to promote rapid growth [1,2,3]. Despite their high productivity and economic efficiency, intensive rearing may restrict the expression of natural behaviours and has raised concerns regarding animal welfare and health.
In parallel, consumer interest has increasingly shifted toward poultry products obtained from welfare-friendly, more natural, and locally differentiated production systems. Product quality, animal welfare, and production transparency have become important considerations in consumer preferences. There is a growing demand for poultry meat with lower growth intensity. Many consumers perceive free-range systems as being more welfare-friendly and producing meat with better sensory quality [1,2,3]. Free-range and outdoor-access systems are generally more compatible with slow-growing genotypes because these birds require longer growing periods and may be better suited to systems that allow movement and natural behaviour [1,3]. In such systems, access to outdoor areas or pasture may influence activity, feed-seeking behaviour, carcass composition, and meat quality, although the magnitude of these effects depends on genotype, age, diet, stocking density, and management conditions [2,4,5]. The slaughter age of slow-growing chickens generally ranges from 56 to 84 days, but it may extend to 100–120 days in indigenous genotypes [3,6]. Although the relatively slow growth and lower productivity of local chickens may limit their use in conventional commercial production, indigenous breeds remain important for smallholder farming, local food systems, genetic diversity, and adaptation to variable environmental conditions [6,7]. Therefore, evaluating native genotypes under alternative rearing systems is important for production planning, genetic-resource conservation, and the development of locally adapted poultry systems. For local meat-type chickens, achieving live weights of approximately 1200–1400 g within about 100 days has been considered a practical production target [8]. The Gerze chicken, an indigenous Turkish breed, was officially recognised in 2004 and has been protected since 1995. It is a dual-purpose breed characterized by a V-shaped comb, black feathers, and white skin. It exhibits moderate growth rates and produces white eggs [9]. Despite its importance as a native genetic resource, studies on the growth performance, carcass traits, and meat quality of Gerze chickens remain limited. Recent studies have begun to characterize different aspects of this breed, including incubation-related postnatal growth and stress physiology [10], growth and carcass performance under intensive conditions [8], and the effects of alternative feeding strategies on carcass and meat-quality characteristics [11]. Together, these studies indicate that information on the productive potential of Gerze chickens is increasing but remains limited. In a previous intensive-rearing study, Gerze chickens reached 1686 g at 20 weeks of age, with an FCR of approximately 4.5 [8]. In the same study, the mean live weight at 14 weeks exceeded 1200 g, which is considered acceptable for indigenous chickens [8]. These findings suggest that Gerze chickens may have potential for local meat production; however, their response to free-range rearing and feed-restriction strategies has not yet been sufficiently documented.
The sustainable use of indigenous chickens depends on management practices that balance production performance, resource use, animal welfare, and conservation of local genetic resources [7,12]. Therefore, the present study evaluated the growth performance, feed efficiency, carcass traits, and meat quality of Gerze chickens reared under intensive indoor and free-range conditions. In addition, a Skip-a-Day feed-restriction strategy was applied within the free-range system to assess its effects on feed-use efficiency and production traits during the later growing period.

2. Materials and Methods

2.1. Ethical Approval and Study Location

The study was conducted at the Ondokuz Mayıs University Agricultural Faculty Research Farm. All experimental procedures were approved by the Ondokuz Mayıs University Animal Experiments Local Ethics Committee (Decision No.: 2023/86; Project Approval No.: 2023-86; approval date: 14 December 2023), ensuring compliance with ethical guidelines.

2.2. Experimental Birds and Rearing Conditions

A total of 252 one-day-old Gerze chicks were obtained from a breeder flock maintained at the research farm. At hatch, chicks were randomly allocated to six floor pens, each measuring 3.5 × 3.5 m, with 42 chicks per pen. Each pen was equipped with a round feeder and nipple drinkers. Wood shavings were used as litter material. Heating was provided by infrared heaters, and lighting was supplied by standard white bulbs.
Four of the six pens were provided with access to an outdoor area of 40 m2 per pen from 8 weeks of age onward. At the beginning of outdoor access, the outdoor areas had natural spontaneous herbaceous vegetation; however, no specific forage crops were sown or established for the experiment. Vegetation covers gradually decreased during the rearing period as a result of bird use. Representative images of the outdoor-access areas at the beginning and end of the outdoor period are provided in Supplementary Figure S1. Based on the initial number of birds, this corresponded to approximately 0.95 m2 of outdoor area per bird under the experimental conditions of the study. In the present study, the term “free-range” refers to the experimental groups provided with outdoor access under the spatial conditions described above.

2.3. Rearing and Experimental Design

The lighting program began with 24 h of light for the first 3 days, which was gradually reduced to 20 h by day 14 and subsequently maintained at 14 h of light per day until slaughter. The experimental period was divided into two feeding phases:
  • Starter phase (0–8 weeks): Chicks were fed a commercial starter diet containing 20% crude protein and 3100 kcal/kg metabolizable energy.
  • Grower phase (8–16 weeks): Chicks were fed a commercial broiler grower diet containing 19% crude protein and 3100 kcal/kg metabolizable energy.
The study was arranged as a completely randomized design with three treatment groups, each represented by two replicate pens:
  • Free-Range (FR) group: Two pens, 84 chicks in total, were reared indoors during the first 8 weeks and then provided with outdoor access until slaughter. Feed was provided ad libitum throughout the experiment.
  • Free-Range, Feed-Restricted (FRR) group: Two pens, 84 chicks in total, were reared under the same conditions as the FR group but were subjected to a Skip-a-Day feeding strategy from 8 weeks of age until slaughter. During this period, feeders were manually removed from the pens every other day, resulting in complete feed withdrawal on restriction days, whereas water always remained available ad libitum.
  • Intensive (IN) group: Two pens, 84 chicks in total, were reared indoors throughout the experimental period, with feed provided ad libitum.
The feed-restriction treatment was initiated at 8 weeks of age because this point marked the transition from the starter phase to the grower phase and coincided with the beginning of outdoor access. This timing was selected to avoid feed restriction during the early chick-rearing period and to evaluate the Skip-a-Day strategy during the later growing period, when feed use becomes more relevant for production efficiency in slow-growing genotypes.
All chicks were vaccinated against Newcastle disease, Gumboro disease, and infectious bronchitis according to the farm vaccination program.

2.4. Data Collection and Carcass Analysis

Performance data, including live weight, feed consumption, feed conversion ratio (FCR), and mortality, were collected throughout the experiment. Mortality was recorded daily throughout the experimental period and summarized descriptively at the treatment-group level. Live weights were measured individually at two-week intervals from hatch to 16 weeks of age. Feed consumption was recorded at the pen level by measuring the amount of feed offered and the remaining feed. Accordingly, FCR was calculated at the pen level as feed intake divided by body weight gain for the corresponding period.
At 16 weeks of age, a total of 48 chickens (16 per group) were randomly selected for slaughter. The selection included four males and four females from each of the two replicate pens per group, ensuring a balanced representation. Birds were fasted for 8 h prior to slaughter. The slaughter and processing procedures, including scalding, plucking, evisceration, and chilling, were conducted in a semi-automated facility. The heart, liver, and cleaned gizzard were weighed, and their ratios to the cold carcass weight were recorded as edible giblets. Carcasses were then sectioned according to standard procedures.

2.5. Meat Quality Analysis

Meat quality was assessed on the left thigh and left breast after 12 h of chilling at +4 °C.
  • pH measurement: A Testo 205 pH/temperature measuring instrument (Testo SE & Co. KGaA, Titisee-Neustadt, Germany) equipped with a spear pH probe was used to measure pH at three different points on both breast and thigh meat.
  • Colour measurement: Meat colour parameters (L*, a*, b*) were measured at two points on breast and thigh meat using a Konica Minolta CR-400 chromameter (Konica Minolta, Tokyo, Japan). Mean values were calculated for each pH and colour parameter.

2.6. Statistical Analysis

Statistical analyses were performed using SPSS version 20.0 (IBM Corp., Armonk, NY, USA). The experimental unit was defined according to the level at which each variable was measured. For feed consumption and feed conversion ratio (FCR), the pen was considered the experimental unit because these variables were measured at the pen level [13]. For individually measured traits, including live weight, carcass characteristics, and meat quality parameters, the individual bird was used as the observational unit. However, because birds were housed within pens and each treatment was represented by two replicate pens, the limited level of pen replication was considered when interpreting treatment effects.
Data were checked for normality using the Shapiro–Wilk test and for homogeneity of variances using Levene’s test. For live-weight and pen-level performance traits, the fixed effect of rearing condition was evaluated. For slaughter, carcass, and meat-quality traits, rearing condition, sex, and their interaction were considered where applicable. When a significant main effect was detected, group means were compared using Duncan’s multiple range test. Mortality data, where applicable, were evaluated descriptively because of the low number of events. Statistical significance was declared at p < 0.05.
A sensitivity power analysis was performed using G*Power 3.1.9.7 [14] to estimate the minimum detectable effect size under the available sample structure. The analysis was conducted for one-way ANOVA with three treatment groups, α = 0.05, and 80% statistical power. The minimum detectable effect size was f = 2.274 for pen-level traits, f = 0.463 for slaughter and meat-quality traits, and f = 0.197 for individually measured live-weight data. Therefore, non-significant differences in pen-level traits, particularly feed consumption and FCR, were interpreted cautiously because the limited number of independent pen replicates reduced the ability to detect small or moderate treatment effects.

3. Results

The body weights of the Gerze chickens from hatch to slaughter are detailed in Table 1. The IN group had significantly higher hatch and 2-week live weights than the FR and FRR groups. No significant differences were observed among groups at 4 and 6 weeks of age. From 8 to 14 weeks, the IN and FR groups showed similar live weights and were generally heavier than the FRR group. At 16 weeks, final body weight was significantly higher in the IN group than in the FRR group, whereas the FR group showed an intermediate value and did not differ significantly from either group.
The feed conversion ratio (FCR) and cumulative feed consumption values are presented in Table 2. No significant differences were detected among the treatment groups for FCR or cumulative feed consumption throughout the rearing period. However, because these variables were measured at the pen level, these non-significant results should be interpreted cautiously. Mortality remained low and was identical among treatment groups. In each treatment group, 3 out of 84 birds died during the experimental period, corresponding to a mortality rate of 3.57%. Therefore, no treatment-related mortality pattern was observed.
Carcass and slaughter traits are summarized in Table 3. While the production system had no significant effect on slaughter live weight or carcass weight, a clear influence of sex was observed, with males exhibiting considerably higher live and carcass weights within each group. Chickens in the IN group had a significantly higher dressing percentage (65.3%) compared to those in the free-range groups (FR: 63.5% and FRR: 63.6%). However, sex did not significantly affect the dressing percentage within any of the groups.
Further analysis of carcass traits showed that in all groups, males had significantly higher leg proportions than females, whereas females had significantly higher breast ratios (p < 0.05). No significant differences were found in the breast and leg ratios between the treatment groups. The abdominal fat ratio was highest in the IN group (2.3%), which was significantly greater than the ratios in the FR (1.4%) and FRR (0.4%) groups (p < 0.05). Additionally, the edible giblet ratio was significantly higher in the FR and FRR groups compared to the IN group. The pH and colour characteristics of the leg and breast meat are presented in Table 4. Chickens in the FR group had the highest leg and breast pH values (p < 0.05). Leg L* values were significantly lower in both free-range groups than in the IN group, indicating darker leg meat. Breast L* was lowest in the FR group, whereas the FRR and IN groups showed similar values. In addition, leg a* values were markedly lower in the FR and FRR groups than in the IN group (p < 0.05). No significant differences were detected among treatment groups for leg b*, breast a*, or breast b* values.

4. Discussion

The mean hatch weight of chicks in the IN group was significantly higher than that of the FR and FRR groups. Despite random allocation, a small but significant initial live-weight imbalance was observed among groups. This initial difference should be considered when interpreting subsequent growth responses. The higher hatch weight of the IN group was also reflected in the 2-week live-weight data. However, no statistically significant differences were observed among groups at 4 and 6 weeks of age. From 8 weeks onward, when outdoor access and feed restriction treatments were initiated, differences among groups became more apparent. Chickens reared under IN and FR conditions generally showed similar live weights and were heavier than the FRR group during most of the later growing period. At slaughter, the FR group showed an intermediate final body weight, whereas the IN group had the highest and the FRR group the lowest final body weight. Several previous studies have reported lower body weight or growth performance in birds reared under free-range or outdoor-access conditions than in indoor systems [3,15,16]. In contrast, the difference between the final body weights of birds reared indoors and under free-range conditions was not significant in the present study. This finding may suggest that Gerze chickens were able to adapt to the outdoor-access conditions used in the present experiment. Outdoor area use may differ among genotypes, and slower-growing birds have been reported to use outdoor areas more extensively than fast-growing commercial broilers [17]. Tong et al. [18] reported that outdoor access days influenced growth performance in a local chicken breed, with body weight and daily weight gain at later ages increasing as the duration of outdoor access increased. In the present study, no marked reduction in live weight was observed in the FR group after outdoor access began (Table 1). Thus, the age and duration of outdoor access may influence growth responses and adaptation to free-range conditions [2,18]. Conversely, reduced weight gain was observed in the FRR group after the initiation of outdoor access and feed restriction. Subsequently, the FRR group did not fully compensate for the reduced growth observed after the start of feed restriction. The lower growth of the FRR group may be associated with the combined effect of outdoor access and complete alternate-day feed withdrawal; however, activity level, pasture intake, and behavioural responses were not directly measured in this study. Despite these differences among treatments, the final body weight of Gerze chickens in the current study was consistent with previous reports indicating live weights of approximately 1200–1400 g at 16 weeks of age for this genotype [8]. Recent Gerze-specific growth-curve modelling has shown that growth in this breed follows sex-dependent nonlinear trajectories, supporting the interpretation that changes in growth rate during the later rearing period may partly reflect the biological growth pattern of the genotype [19].
No significant differences in FCR were detected among rearing systems. However, because FCR was calculated at the pen level and the number of independent pen replicates was limited, this result should be interpreted cautiously. This finding is partly consistent with Lase et al. [20], who reported that rearing systems did not consistently affect FCR in indigenous chickens. Vegetation availability in free-range areas may influence feed-seeking behaviour, voluntary feed intake, and FCR [2,4]. However, in the present study, the outdoor area was not established with specific fodder plants. Similarly, Chen et al. used an outdoor-access design without vegetation to reduce the confounding effect of pasture intake when evaluating growth and meat-quality responses [4]. Therefore, any contribution of naturally occurring weeds to feed intake or growth could not be quantified and should be considered only as a possible, unmeasured factor. FCR increased with age and ranged from 3.79 to 3.96 among groups at slaughter age. This was expected because indigenous and slow-growing chickens generally show poorer feed efficiency than fast-growing commercial broilers [20,21,22]. Similarly, cumulative feed consumption per bird did not differ significantly among rearing systems at slaughter age. Nevertheless, as shown in Table 2, the FRR group numerically consumed less feed than the FR and IN groups as a consequence of the complete alternate-day feed withdrawal. This may suggest compensatory feed intake on feeding days; however, daily feed intake patterns were not measured separately, so this interpretation should be considered cautiously. Similar caution has been suggested in slow-growing chickens, where feed restriction may reduce growth without consistently improving overall FCR [22].
At slaughter, four males and four females were randomly selected from each replicate pen to provide a balanced representation of sex within each treatment group. A total of 48 chickens, 16 birds per treatment group, were slaughtered at 16 weeks of age. As expected, sex significantly affected live weight at slaughter and carcass weight across all groups, with males showing higher values than females (Table 3; p < 0.05). However, mean carcass weight did not differ significantly among production systems.
Dressing percentage in chickens varies according to genotype, growth rate, slaughter age, and production system [1,21,23]. Fast-growing broilers generally show higher dressing percentages than slow-growing or indigenous genotypes [1,21]. In indigenous or slow-growing chickens, dressing percentage is commonly reported to range around 62–68% [1,21,23]. In the present study, chickens reared under intensive conditions had a higher dressing percentage than those reared under free-range conditions (p < 0.05). This difference may be partly related to the relatively higher slaughter weight and breast proportion observed in the IN group. Although body weight is an important production trait, breast meat has high economic value in chicken meat production [1,24]. Slow-growing and indigenous genotypes may show lower breast yield and relatively higher leg or thigh yield than fast-growing commercial broilers [1,21,25]. In the present study, leg proportion exceeded breast proportion in all groups, and no significant differences were observed among the FR, FRR, and IN groups for breast or leg proportions. Across all production groups, females had higher breast proportions than males, whereas males had higher leg proportions (p < 0.05). Similar sex-related differences have been reported in Italian [25] and Chinese [26] local chicken genotypes.
This sex-related difference may be associated with differences in growth dynamics and the relative timing of muscle development between males and females [19,24,27]. However, muscle fiber characteristics were not directly measured in the present study; therefore, this explanation should be considered as a possible biological interpretation rather than a measured mechanism. Gizzard development may reflect differences in diet structure and fiber intake. However, the gizzard ratio did not differ among the FR, FRR, and IN groups in the present study. Although the outdoor areas contained natural spontaneous vegetation at the beginning of outdoor access, no specific forage crop was established, and actual forage intake was not quantified. Therefore, the absence of differences in gizzard ratio should be interpreted in relation to the overall rearing system rather than directly attributed to vegetation intake.
Excessive abdominal fat is undesirable in poultry production because it can reduce carcass value and feed-use efficiency. In this study, chickens reared in the IN group had a higher abdominal fat ratio (2.3%) than those reared in the FR and FRR groups. The lower abdominal fat ratio observed in the free-range groups may be associated with greater activity and energy expenditure under outdoor-access conditions [3,16]. This is also consistent with meta-analytic evidence indicating that free-range systems can reduce abdominal fat yield and breast meat fat content [5]. Furthermore, Plavnik and Hurwitz [28] demonstrated that quantitative feed restriction can reduce abdominal fat content. Consistent with this, the FRR group had the lowest abdominal fat ratio (0.4%), followed by the FR group (1.4%), suggesting that feed restriction may have further reduced fat deposition under free-range conditions. The edible giblet ratio, including heart, liver, and gizzard, was higher in the FR and FRR groups than in the IN group. This may be associated with differences in organ development or activity-related physiological adaptation under outdoor-access conditions; however, specific physiological indicators were not measured. The edible giblet ratios observed in the present study were consistent with previous findings for Gerze chickens, in which values ranged between 5.6% and 6.4% [8].
Meat pH is an important indicator of chicken meat quality because it influences tenderness, juiciness, water-holding capacity (WHC), colour, and shelf life. After slaughter, postmortem glycolysis leads to lactic acid accumulation and a decline in pH, which can affect protein functionality, water retention, and meat texture [29]. Lower ultimate pH values in chicken breast meat may be associated with pale, soft, and exudative-like characteristics, reduced water-holding capacity, and altered texture [29]. In the present study, breast pH values were relatively low, depending on the treatment group. Although pre-slaughter stress and postmortem glycolytic rate may influence ultimate pH, these factors were not the primary focus of the present study. Therefore, pH differences were interpreted as meat-quality responses rather than as direct physiological stress indicators.
Regarding meat colour, leg L* values were lower in both free-range groups than in the IN group, indicating darker leg meat. Breast L* was lowest in the FR group, whereas the FRR and IN groups showed similar values. In contrast, leg a* values were higher in the IN group than in the FR and FRR groups, indicating greater redness in leg meat from intensively reared birds. No significant differences were detected among treatment groups for breast a*, leg b*, or breast b* values. Similarly, Almasi et al. [30] reported darker thigh muscle colour in slow-growing chickens reared under free-range conditions than in those raised indoors. Mikulski et al. [31] also reported that meat from chickens with outdoor access was darker and showed differences in selected quality traits compared with meat from indoor-reared birds. These findings should not be interpreted as contradicting the general muscle-type differences described by Barbut [32], because breast and leg muscles differ intrinsically in fiber composition and myoglobin content. Rather, the present results indicate that the rearing system affected some colour parameters within each muscle type. Overall, these findings suggest that rearing condition affected selected meat colour parameters, particularly leg L*, leg a*, and breast L*, but did not uniformly affect all colour traits. As described in the AMSA Meat Colour Measurement Guidelines, meat colour is influenced by multiple factors, including genetics, sex, age, diet, energy density, muscle type, and postmortem conditions [33].
The findings of the present study should be interpreted within a production-oriented sustainability framework. By evaluating growth trajectory, feed use, carcass composition, and meat-quality parameters, this study provides baseline zootechnical evidence for the potential integration of the indigenous Gerze genotype into alternative local poultry production systems [7]. However, broader sustainability dimensions, including life-cycle environmental impacts, economic performance, and social indicators, were beyond the scope of the present experiment. Therefore, the sustainability-related implications of the results should be considered as production-based evidence that can support the design of future multidisciplinary assessments of locally adapted poultry value chains.
Several methodological points should be considered when interpreting the results. First, although the total number of birds was relatively high, each treatment was represented by two replicate pens. This design was sufficient to describe treatment responses under the available experimental conditions, but pen-level variables such as feed consumption and FCR should be interpreted cautiously because the number of independent pen replicates was limited [13]. Second, although the term “free-range” was used to describe the outdoor-access groups, the system evaluated here should be interpreted under the spatial and management conditions of the present experiment. The outdoor area corresponded to approximately 0.95 m2 per bird based on the initial number of birds, which is close to the minimum outdoor area described for some free-range poultry meat production categories. However, certification-based free-range or organic systems may include additional requirements regarding vegetation cover, feed composition, genotype, slaughter age, stocking density, and inspection procedures; therefore, the findings should be interpreted within the experimental outdoor-access conditions of the present study [2]. Future studies including larger pen replication, detailed behavioural and welfare assessments, economic analysis, and environmental indicators would further strengthen the evaluation of Gerze chickens under free-range and feed-restriction strategies.

5. Conclusions

The present study provides production-oriented evidence on the response of indigenous Gerze chickens to intensive indoor, free-range, and free-range feed-restricted rearing strategies. The growth pattern and final body weight of Gerze chickens were consistent with those expected for slow-growing indigenous meat-type chickens. Although the intensive group showed higher live weights at several intermediate ages, final body weight did not differ significantly between the FR and IN groups, while the FRR group had lower final body weight. Therefore, Gerze chickens may show potential for local free-range production under the experimental conditions of the present study.
The Skip-a-Day feed-restriction strategy applied under free-range conditions did not provide a clear advantage in feed conversion and resulted in reduced body weight. Thus, this strategy should not be recommended as a growth-optimizing practice for Gerze chickens without further evaluation of different restriction levels, economic outcomes, and welfare responses. The lower abdominal fat ratio observed in the free-range groups, especially in the FRR group, may be considered a favourable carcass trait; however, this should be interpreted together with the reduced growth performance of feed-restricted birds.
The apparent slowing of body weight gain after 14 weeks suggests that, under similar rearing conditions, extending the production period beyond this age may provide progressively smaller growth gains relative to feed use. Future studies combining growth-curve modelling and economic evaluation could further refine slaughter-age decisions for Gerze chickens under alternative rearing systems. Overall, the findings support the potential use of Gerze chickens in diversified local poultry systems and contribute to the sustainable use and conservation of this indigenous genetic resource. Nevertheless, the limited number of pen replicates and the absence of direct environmental, economic, behavioural, and welfare indicators should be considered when generalizing the results.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/su18126192/s1, Figure S1. Outdoor-access areas used for the free-range groups.

Funding

This research was funded by the Scientific Research Projects Coordination Unit of Ondokuz Mayıs University (Project number: BAP02-2024-4971).

Institutional Review Board Statement

The animal study protocol was approved by the Animal Experiments Local Ethics Committee of Ondokuz Mayıs University (Decision No.: 2023/86; Project Approval No.: 2023-86; approval date: 14 December 2023).

Informed Consent Statement

Not applicable.

Data Availability Statement

Data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The author declares no conflicts of interest. The funders had no role in the design of the study; in the collection. analyses. or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Table 1. The body weights (g) of Gerze chickens during the rearing period in different rearing conditions.
Table 1. The body weights (g) of Gerze chickens during the rearing period in different rearing conditions.
Age (Weeks)
0246810121416
FR35.17 b132.85 b275.40470.32650.83 a876.38 a1075.11 a1282.01 a1279.01 ab
FRR35.26 b131.53 b271.56463.96606.32 b795.35 b996.26 b1182.12 b1231.82 b
IN36.02 a137.53 a280.37454.42652.68 a878.91 a1086.08 a1297.48 a1334.99 a
P0.0480.0130.2040.2170.002<0.0010.0010.0020.009
FR: Free-range group; FRR: Free-range feed-restricted group; IN: Intensive group. a,b: Means with different superscripts within the same column differ significantly (p < 0.05).
Table 2. Feed conversion ratio (FCR) and cumulative feed consumption (g per bird) of Gerze chickens during the rearing period in different rearing conditions.
Table 2. Feed conversion ratio (FCR) and cumulative feed consumption (g per bird) of Gerze chickens during the rearing period in different rearing conditions.
Age (Weeks)Cumulative Feed
Consumption (g per Bird)
246810121416
FR1.602.143.013.673.203.483.573.965059
FRR1.642.253.113.913.003.423.623.934884
IN1.622.173.123.312.693.413.543.795061.5
P0.8280.6560.8690.2870.4680.8910.9160.3310.443
FR: Free-range group; FRR: Free-range feed-restricted group; IN: Intensive group. FCR and cumulative feed consumption were calculated at the pen level.
Table 3. Slaughter and carcass traits of Gerze chickens at 16 weeks of age in different rearing conditions.
Table 3. Slaughter and carcass traits of Gerze chickens at 16 weeks of age in different rearing conditions.
LW (g)Carcass (g)DP (%)Legs (%)Breast (%)Wings (%)Back (%)Neck (%)Gizzard (%)AF (%)Giblets
(%)
FR♂1552.5987.663.631.623.013.322.29.02.21.66.4
♀1115.4707.363.429.326.313.321.98.62.21.26.5
P<0.001<0.0010.8970.0290.0340.8300.6280.2420.9890.3170.948
FRR♂1463.3934.863.931.523.313.223.28.62.30.56.6
♀1101.0696.163.329.726.613.222.48.02.10.36.6
P<0.001<0.0010.3290.0370.0130.9580.2800.1050.3460.4170.810
IN♂1595.41051.365.931.223.713.422.78.51.92.15.6
♀1163.9754.364.829.227.812.822.27.82.32.56.3
P<0.001<0.0010.2080.005<0.0010.2960.4420.0150.0380.5030.079
Effects
FR 1333.9847.463.5 b30.524.613.322.18.8 a2.21.4 b6.4 a
FRR 1282.1815.463.6 b30.624.913.222.88.3 b2.20.4 c6.6 a
IN 1379.6902.865.3 a30.225.713.122.48.2 b2.12.3 a5.9 b
P0.4510.2410.0040.8550.5460.7620.3200.0270.288<0.0010.003
FR: Free-range group; FRR: Free-range feed-restricted group; IN: Intensive group. a,b,c: Means with different superscripts within the same column differ significantly (p < 0.05). ♂: Male. ♀: Female; LW: live weight. DP: dressing percentage. AF: abdominal fat.
Table 4. pH and colour of leg and breast meat of Gerze chickens at 16 weeks of age in different rearing conditions.
Table 4. pH and colour of leg and breast meat of Gerze chickens at 16 weeks of age in different rearing conditions.
Leg pHBreast pHLeg L*Leg a*Leg b*Breast L*Breast a*Breast b*
FR5.95 a5.68 a56.5877 b0.887 b1.93452.42 b4.3461.086
FRR5.90 a5.59 b56.3113 b0.729 b2.46555.54 a4.8110.355
IN5.72 b5.62 b61.6535 a3.856 a1.35858.60 a3.6961.649
P<0.0010.003<0.001<0.0010.1690.0010.2600.228
FR: Free-range group; FRR: Free-range feed-restricted group; IN: Intensive group. a,b: Means with different superscripts within the same column differ significantly (p < 0.05). L*, a*, and b* indicate lightness, redness, and yellowness, respectively.
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Cilavdaroğlu, E. Sustainable Production Potential of Indigenous Gerze Chickens Under Free-Range and Feed-Restriction Strategies. Sustainability 2026, 18, 6192. https://doi.org/10.3390/su18126192

AMA Style

Cilavdaroğlu E. Sustainable Production Potential of Indigenous Gerze Chickens Under Free-Range and Feed-Restriction Strategies. Sustainability. 2026; 18(12):6192. https://doi.org/10.3390/su18126192

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Cilavdaroğlu, Elif. 2026. "Sustainable Production Potential of Indigenous Gerze Chickens Under Free-Range and Feed-Restriction Strategies" Sustainability 18, no. 12: 6192. https://doi.org/10.3390/su18126192

APA Style

Cilavdaroğlu, E. (2026). Sustainable Production Potential of Indigenous Gerze Chickens Under Free-Range and Feed-Restriction Strategies. Sustainability, 18(12), 6192. https://doi.org/10.3390/su18126192

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