# Access to the outdoors during summer affects feed efficiency, carcass composition and meat quality in a slow-growing pure strain of chickens

Salomé Chaumont, Sandrine Mignon-Grasteau, Frédéric Fagnoul, Anne

Collin, Cécile Berri, Elodie Guettier, Elisabeth Le Bihan-Duval

► To cite this version:

Salomé Chaumont, Sandrine Mignon-Grasteau, Frédéric Fagnoul, Anne Collin, Cécile Berri, et al. Access to the outdoors during summer affects feed efficiency, carcass composition and meat quality in a slow-growing pure strain of chickens. Journal of Animal Science, 2025, 103, pp.skaf157. 10.1093/jas/skaf157. hal-05241644

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# Outdoor access and chicken performance

## Access to the outdoors during summer affects feed efficiency, carcass composition and meat quality in a slow-growing pure strain of chickens.

Salomé Chaumont*, Sandrine V Mignon*, Frédéric Fagnoul †, Anne Collin*, Cécile Berri*,
Elodie Guettier*, Elisabeth Le Bihan-Duval*<fnref n="1" />

* BOA, INRAE, Université de Tours, 37380 Nouzilly, France

† Hubbard, Mauguerand, 22800 Le Fœil, France

Scientific section: Housing and Management

<footnote n="1">¹ The authors would like to thank members of the experimental facility for animal care, especially Marine Chahnamian, Patrice Ganier, Lola Guerche, Emmanuel Ledru, and Nathalie Même, as well as Antoine Savoie for the transfer of meteorological data from the Nouzilly station, Pierre Blavy for providing his expertise in the development of the feeder and data extraction, and those who participated in meat quality measurements, especially Thierry Bordeau, Estelle Godet, and Emilie Raynaud. The authors also wish to thank the reviewers for their constructive feedback, which greatly contributed to improve the quality of the manuscript.</footnote>
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## Lay summary

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This study assessed effects of outdoor access, which is required to produce “Label Rouge” slow-growing chickens, compared to indoor rearing, which is used in genetic selection for health reasons. Chickens were reared either indoors or with outdoor access after 28 days of age for two consecutive summers (2022 and 2023), a season when farmers often observe lower performance. Approximately 300 chickens per group were monitored individually each year.

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The chickens reared with outdoor access gained 4% less weight than those reared indoors but had similar feed intake; thus, they used their feed less efficiently. Outdoor access decreased abdominal fat, particularly in females, and had no effect on thigh or breast yield, but it did decrease the quality of meat, which had lower pH, a paler color and more water loss.

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Interactions between housing condition, sex and year indicated that chicken performance and meat quality in free-range systems remained sensitive to environmental challenges, which emphasizes the importance of considering genotype × environment interactions in breeding programs for chicken strains intended to have outdoor access.

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## Teaser text

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By examining effects of outdoor or indoor conditions on slow-growing chickens, the study found that, while access to the outdoors decreases abdominal fat, it also decreases growth, feed-use efficiency and meat quality, which highlighted the strength of genotype × environment interactions.

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## Abstract

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This study assessed effects of outdoor access on growth performance, feed efficiency, carcass composition and meat quality in a slow-growing chicken strain. Chickens were reared either entirely indoors for 78 days or with outdoor access after 28 days of age for 82 days during the summers of 2022 and 2023. Approximately 300 chickens per group were monitored each year.

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Individual growth and feed intake were tracked using radio frequency identification, and feed efficiency was calculated as the gain-to-feed ratio (G:F). Carcass composition, as well as the pH, color, drip loss, cooking loss and firmness of breast meat, of all chickens were measured. The results indicated that the chickens with outdoor access gained 4% less weight than those reared indoors (P < 0.001), with similar feed intake in both environments, except for indoor females in 2023, who consumed more than outdoor-access females in 2023 (P = 0.020). This resulted in a 2% lower G:F for the outdoor-access chickens overall (P < 0.001). Outdoor-access chickens had less abdominal fat yield, particularly females (-19% vs. -12% for males; P < 0.001), but no difference in thigh or breast yield (P > 0.05). Outdoor access influenced the quality of breast meat, which had a more rapid decrease in pH post-mortem, lower ultimate pH, more cooking loss and a paler and less red color (all P < 0.001), although consumers likely could not have detected the differences in color. In 2022, outdoor temperatures reached 36°C, compared to 30°C indoors, which was associated with significantly higher water loss in the meat (P < 0.001). These results highlight trade-offs of outdoor access for slow-growing chickens, particularly during the summer. While providing outdoor access decreases fat accumulation, it also decreases growth, feed efficiency and meat quality. Practical applications include targeted management strategies, such as optimizing the diet to increase nutrient intake, mitigating effects of heat in the summer or rearing the sexes separately to address the differing effects of sex on performance. Future research should explore appropriate behavioral and physiological indicators of chickens' ability to adapt to outdoor access as well as the potential to integrate these indicators into breeding strategies.

**Key words:** feed efficiency, free-range, heat stress, meat quality, slow-growing chicken

List of abbreviation

AFY, abdominal fat yield; BW, body weight; BY, breast yield; CL, cooking loss; DL, drip loss; FI, feed intake; G:F, gain-to-feed ratio; pH15, pH 15 minutes post mortem; pHu, pH 24
64 hours post mortem; RFI, residual feed intake; TY, thigh yield; WB, Warner Bratzler shear force; WG, weight gain

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## INTRODUCTION

68 Poultry meat, which is prized for its nutritional value, affordability and absence of religious restrictions, is the meat produced most worldwide, with more than 126 million tons of chicken meat produced in 2023 (FAOSTAT, 2025). In recent years, consumer attention has shifted toward animal production methods and welfare, which are now key factors in purchasing decisions, along with price and quality attributes such as hygiene, nutritional and sensory characteristics (Delanoue et al., 2018). This change reflects a broader societal concern for ethical production systems. In the French poultry sector, a large percentage of production is dedicated to certified quality labels, particularly the “Label Rouge”, which represents 15% of national chicken production. The Label Rouge national certification mandates using slow-growing genotypes, an extended rearing period of at least 81 days, access to an outdoor area (> 2 m²/chicken), low stocking density when indoors (< 11 chickens/m²) and a diet that includes more than 75% cereals (French Ministry of Agriculture, 1996). These requirements result in chickens that have more flavorful meat than that of standard broilers and improve the image of the product due to the free-range rearing conditions and the chickens’ slower growth rate (Sauveur, 1997). However, due to the longer rearing period and lower feed efficiency of the genotypes used, Label Rouge chickens cost twice as much to produce as conventional fast-growing broilers.

Free-range systems, like those used in Label Rouge production, provide birds access to an outdoor area, which promotes a variety of natural behaviors, such as wing flapping, scratching, foraging and dust bathing, which are associated with higher welfare (Knierim, 2006). However,
these systems also expose chickens to environmental stressors such as predation risks, pathogens and, especially, fluctuating weather conditions (Fanatico et al., 2005). Among these, heat stress is a critical challenge for free-range systems, particularly during the summer. Broilers are highly sensitive to heat, with little ability to thermoregulate, which makes them susceptible to temperature fluctuations (Yahav et al., 2005). Campos et al. (2016) observed that Label Rouge chickens decreased their feed intake (FI) by 5% when ambient temperatures increased from 22°C to 32°C, and Moyle et al. (2014) observed that broilers reared with outdoor access during the summer weighed less than those reared indoors. Heat stress is known to decrease meat quality by influencing key characteristics such as meat pH and water-holding capacity, which increases its water loss and subsequently changes its color, texture and taste (Zhang et al., 2012). Even though this phenomenon is particularly pronounced for fast-growing broiler strains under heat stress, such as Ross 308 or Cobb 500, similar trends have been observed for slow-growing strains used in Label Rouge production (Gonzalez-Rivas et al., 2020), for which maintaining high-quality meat characteristics is crucial to meet consumer demands.

Heat stress also decreases protein synthesis and increases fat accumulation, which results in undesirable changes in carcass composition (Gonzalez-Rivas et al., 2020). These challenges are exacerbated in fast-growing strains, which are often less suited to free-range systems because they are less able to adapt to outdoor access, including lower thermotolerance and little use of the outdoor area for exercise (Gonzalez-Rivas et al., 2020). In contrast, slow-growing strains, such as those used in Label Rouge production, have greater ability to exploit outdoor environments and express more natural behaviors, which could improve welfare and potentially performance (Miao et al., 2005). However, despite their apparent advantages, the extent to which these strains maintain performance and meat quality in outdoor environments, particularly fluctuating weather conditions, remains poorly understood. The difference between
113 indoor and outdoor environments is especially important for breeding companies, since pure
114 strains selected at the top of the breeding pyramid are reared indoors for health reasons, which
115 may result in genotype × environment interactions.

116 To address these concerns, we investigated effects of outdoor access compared to indoor rearing
117 on the production traits, carcass composition and meat quality of a pure naked-neck slow-
118 growing strain commonly used as a sire in the 3-way cross of commercial Label Rouge
119 chickens. Due to birds' sensitivity to heat stress, two experiments were performed during the
120 summer of consecutive years to assess effects of fluctuating weather conditions on these
121 variables. By comparing indoor and outdoor-access chickens, we sought to quantify potential
122 trade-offs between animal-welfare benefits and free-range performance, while considering that
123 chickens with outdoor access may experience fluctuating weather conditions during the growth
124 period and between batches.

125 MATERIALS AND METHODS

126 The project received authorization no. 35627-2022022811529671 v4 from the French Ministry
127 of Higher Education, Research and Innovation after approval by the ethical committee CEEA-
128 018 (CEEA Val de Loire).

129 *Studied Population and Rearing Conditions*

130 The study was conducted on chickens from the S77N meat-type slow-growing strain (Hubbard,
131 France) reared under two different conditions at the INRAE PEAT experimental facility
132 (doi:10.15454/1.5572326250887292E12). In 2022 and 2023, 143 males plus 141 females and
133 129 males plus 140 females, respectively, were housed indoors from day 1 until slaughter at 78
days of age in a 60 m² house (5.0 chickens/m²) with wood chips covering the floor, while 142
134 males plus 151 females and 152 males plus 145 females, respectively, were housed indoors in
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an 84 m² house (3.6 chickens/m²) from day 1 until 28 days of age, then given access to an outdoor area of 2800 m² from day 29 until slaughter at 82 days of age. The difference in slaughter age between the two groups ensured that the chickens reached a similar body weight (BW) at slaughter. The outdoor-access group began its rearing period 18 days before the indoor group in 2022 and 2023, respectively. The outdoor area was equipped with wooden pallets and tarps to provide shaded areas for animals. A thermostat (Digitales thermo-hygrometer, TFA Dostmann, Germany) was used to measure the maximum, mean and minimum temperature (Fig. 1) and relative humidity each day. Regardless of the housing conditions (indoors IN or outdoors OUT), the chickens were fed ad libitum a starter diet from hatching to 27 days of age, followed by a grower-finisher diet from 28 days of age to slaughter (TABLE 1). The feed used in the study contained more energy (1 MJ/kg DM more than the maximum recommended, for the grower-finisher diet) and protein (1% more than the maximum recommended, for both diets) than the feed used under commercial conditions. It was also more similar to the feed used for selection. A small amount of feed was placed on the ground during the first few days to help the chickens become accustomed to an electronic feeding station.

## 151 Measurements

**Growth traits and feed efficiency.** Chicks were identified by a wing band placed at hatching. At 15 days of age, they were also equipped with a radio frequency identification device placed on their neck to continuously monitor individual BW and FI at the feeding station, as described by Guettier et al. (2022) and Berger et al. (2021). These data were used to calculate each chicken's daily FI and weight gain (WG)

To assess the two housing conditions equally, the gain-to-feed ratio (G:F) (WG/FI over a given period) and residual FI (RFI) were calculated from the ages of 15-76 days (Aggrey et al., 2010):

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$$RFI = FI - \hat{FI}$$
$$ \widehat{FI} = \mu + a \times BW^{0.75} + b \times WG \qquad 160 $$

where FI is the total FI measured over the period, $\widehat{FI}$ the estimated FI over the period, μ the mean FI measured over the period, BW<sup>0.75</sup> the metabolic BW at 76 days of age and WG the total WG over the period.

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Based on daily BW, we modeled individual growth curves using the Gompertz function (Laird et al., 1965):

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$$ BW_t = A e^{-\frac{L}{K} \times t} $$

where BW<sub>t</sub> is BW at age t, A the asymptotic BW, L the initial specific growth rate (i.e., growth rate at hatching divided by BW at hatching) and K the maturation factor, which is the rate of decrease in WG after an inflection point (Ti), which was calculated as follows:

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$$ Ti = \frac{1}{K} \times \ln \left| \frac{L}{K} \right| $$

The live BW of chickens was measured immediately before slaughter, after having fasted for 14-17 h.

**Behavior at Slaughter, Carcass Composition and Meat Quality.** Chickens were then hung on the slaughter line and electrically stunned in a water bath before bleeding. Struggling activity between hanging and stunning was assessed using two criteria: whether they attempted to straighten their body up (i.e., place their head over their legs) (0 = no, 1 = yes) and the total duration of wing flapping (TDWF). Carcasses were chilled at 4°C for 24 h and then cut into pieces to assess carcass composition. The right thigh, *pectoralis major*+*pectoralis minor* muscles and abdominal fat were sampled and weighed to calculate thigh, breast and abdominal fat yields, respectively, as a percentage of live BW at slaughter. The pH 15 min post-mortem (pH15) was measured in the left *pectoralis major* by homogenizing 2 g of fresh muscle immediately after slaughter in 18 mL of a 5 mM iodoacetate/15 M KCl solution and then measuring its pH 15 min post-mortem using a portable pH meter (Model ph330i, WTW GmbH,
Vienna, Austria) equipped with a combined glass electrode. At 24 h post-mortem, ultimate pH (pHu) was measured by inserting the electrode into the *pectoralis major*, and the color of the upper ventral side of the skinless breast was measured using a spectrocolorimeter (CM 700 D, Konica Minolta Inc., Tokyo, Japan) and applying the lightness (L*), redness (a*) and yellowness (b*) values of the CIELAB color space. To assess whether consumers could perceive differences between two meat colors (1 and 2, respectively), we calculated the ΔE<sub>1,2</sub> index (Gómez-Polo et al., 2016)):

$$ \Delta E_{1,2} = \sqrt{(L_1 - L_2)^2 + (a_1 - a_2)^2 + (b_1 - b_2)^2} $$

The index's value indicates whether the color difference is not detectable by the human eye (< 1), moderate but detectable (1-3) or strong (> 3).

Drip loss (DL) of breast muscle was measured as the weight of the muscle at 24 h post-mortem minus that after 5 days of storage at 4°C. Breasts were then trimmed to obtain 130-180 g samples and vacuum-packed. One day later for half of the samples and two days later for the other half, trimmed breasts were cooked in a water bath at 85°C for 15-25 min, depending on their weight, wiped dry and weighed to calculate cooking loss (CL) as a percentage of fresh muscle. Three replicate samples, each measuring 1 cm × 1 cm × 3 cm, were used to measure the firmness of the cooked meat. This was done using the Warner-Bratzler (WB) shear test with an Instron Universal Testing Instrument (model 5543, Instron, Norwood, Massachusetts, USA). The compressive-shear force resistance was calculated in Newtons, following the method of Honikel (1998). Breast meat firmness was calculated as the mean of the three replicates per muscle. An effect of the day was added to the models of CL and WB analyzed. Since the day had a significant effect on both parameters, the effects of housing condition, sex and year were corrected for it.

## Statistical Analyses
The distribution of traits was analyzed using the ggplot2 package (Wickham, 2016) of R software (version 4.1.0) (R Core Team, 2021). Feed efficiency, growth and meat-quality traits were analyzed via Type III analysis of variance using the car package (Fox and Weisberg, 2019) with the following model:

$$y_{ijkl} = \mu + H_i + S_j + Y_k + HS_{ij} + HY_{ik} + SY_{jk} + HSY_{ijk} + \varepsilon_{ijkl}$$

where $y_{ijkl}$ is the trait measured for individual l; $\mu$ the overall mean; $H_i$ the fixed effect of the housing condition (i = outdoor-access, indoors); $S_j$ the fixed effect of sex (j = male, female); $Y_k$ the fixed effect of year (k = 2022, 2023); $HS_{ij}$ the interaction between housing condition i and sex j; $HY_{ik}$ the interaction between housing condition i and year k; $SY_{jk}$ the interaction between sex j and year k; $HSY_{ijk}$ the interaction among housing condition i, sex j and year k; and $\varepsilon_{ijkl}$ the random error term for individual l. The analysis was carried out in two steps. First, a model including all effects was run. Second, non-significant effects were removed from the analyses. The results presented below are those from this second step.

Due to a technical problem, WB measurements were overestimated for half of the indoor group in 2023. Therefore, we analyzed only WB data measured in 2022. Multiple comparisons of means were performed using the lsmeans function of the emmeans package (Lenth, 2024). This model provided the ability to highlight effects that occurred every year (no significant interaction with the year) or instead differed between years (significant interaction with the year).

The percentage of chickens that attempted to straighten up was compared between housing conditions, sexes and years using a simple logistic model (glm function of the stats package). Due to the high percentage of zeros in TDWF, a zero-inflation model with gamma distribution was used from the glmmTMB package (Magnusson et al., 2017), which helped to explore the
factors that influenced the probability of wing flapping and, when flapping was observed, those that influenced its duration. Differences were considered significant at P < 0.05.

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# RESULTS AND DISCUSSION

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## Environmental Conditions

Compared to indoor conditions, outdoor conditions had lower chicken density and potentially higher chicken activity due to use of the outdoor area. In addition, since traps to the outdoors were left open all day, the environment in the outdoor-access house was less controlled; thus, the outdoor-access chickens were exposed to more temperature fluctuations even when inside the house. Over the two years, outdoor-access chickens were exposed to more heat peaks, with 8 days over 35°C after opening the trap (vs. 0 days for indoor chickens) (Fig. 1). Weather conditions also differed between the years. For example, the maximum temperature was higher in 2022 than in 2023 (by 3.3°C or 1.6°C from days 28-54 and after day 54, respectively). Days with maximum temperatures > 30°C were also more frequent from days 28-54 in 2022 (14 d vs. 1 d in 2023), but more frequent after day 54 in 2023 (16 d vs. 8 d in 2022). This variable intensity and distribution of hot periods between the two years likely influenced responses of chickens, since heat peaks at a later age, when chickens are heavier, cause more heat stress. This environmental variability resulted in significant differences between years in growth and feed efficiency, carcass composition and meat quality, and to some extent modulated the effects of housing condition or even sex, as discussed below.

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## Growth and Feed Efficiency

As expected, G:F was 2% lower for outdoor-access chickens than for indoor chickens, regardless of sex (TABLE 2). Females had lower G:F than males did. Outdoor access had a significant unfavorable effect on RFI only in 2022, when it was higher for outdoor-access chickens than indoor chickens (-1 ± 30 vs. -114 ± 31 g, respectively), and only for males, for

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which it was again higher for outdoor-access chickens than indoor chickens (26 ± 30 vs. -88 ± 32 g, respectively). The housing condition influenced G:F mainly by influencing growth. For example, outdoor-access chickens had 4% lower WG than indoor chickens did. As shown in supplementary Figure 1, the Gompertz model fitted well with the observed growth curves.

Outdoor-access chickens had a 9% earlier age at the WG inflection point, when the growth rate peaks, which indicated that they had a shorter period of rapid growth. In addition, outdoor-access chickens had a higher maturation rate than indoor chickens did, and more so for females (+9%) than for males (+7%). Thus, the growth rate decreased faster after the inflection point for outdoor-access chickens than for indoor chickens. In contrast, the housing condition influenced FI less, since outdoor access had a significant effect only on females in 2023, which consumed 6% more indoors than with outdoor access (TABLE 2). However, it should be noted that chickens can consume grass and other materials found in the range. Since this was not measured in our study, their feed intake may have been underestimated.

Effects of outdoor access on chicken performance can depend on many factors, such as the strain, nutritional requirements, feed composition, exploratory and foraging behaviors outdoors, characteristics of the outdoor area and environmental conditions (Taylor et al., 2020).

Differences in these factors likely explain those in results in the literature of effects of outdoor access. Nonetheless, studies agree that outdoor access has neutral or negative effects on feed efficiency, whether of Ross 308 males (Castellini et al., 2002), slow-growing females (Wang et al., 2009) or mixed-sex slow-growing chickens (Stadig et al., 2016).

The literature shows no clear indication that negative effects of outdoor access on G:F are due to lower growth, higher FI, or variations of both. For example, Taylor et al. (2020) and Castellini et al. (2016) found that chickens that used an outdoor area the most were less efficient than those that used it less, but this could be due to higher FI with similar WG or to both lower FI and growth rate. In 2023, outdoor-access females had lower FI than indoor females did, which
highlights the importance of considering ingestion capacity when improving chickens' adaptability to outdoor environments, since it may directly influence their ability to compensate for expending more energy in free-range systems. It would also be interesting to quantify ingestion on the range, as some substances as fatty acids or vitamins can improve feed efficiency, whether other substances as fibers in grass can reduce it (Sanz et al., 2000; Sahin and Kucuk, 2001).

Temperatures also significantly influence many components of feed efficiency, including FI and physical activity, since chickens usually decrease these behaviors to produce less heat when ambient temperature is high. This pattern could explain the lower FI and WG observed in the hotter year of 2022 compared to those in 2023.

## Carcass Composition

Housing conditions did not influence thigh or breast yields, but outdoor-access chickens had a lower abdominal fat yield than indoor chickens did, and more so for females (-19%) than males (-12%) (TABLE 3). Other studies confirmed that rearing chickens outdoors did not influence carcass or meat yields (Fanatico et al., 2005; Wang et al., 2009) but was associated with less abdominal fat (Mikulski et al., 2011), likely due to greater activity outdoors (Castellini et al., 2002; Fanatico et al., 2007). Carcass composition differed little between years, with slightly higher thigh and breast yields and a lower abdominal fat yield in 2023 than in 2022. Sex influenced these yields significantly, with females having higher breast and fat yields but a lower thigh yield than males did.

## Meat Quality

Outdoor access influenced all characteristics of meat quality, which varied depending on sex or year (TABLE 4). The pH of the meat of outdoor-access chickens decreased more rapidly immediately after slaughter, as indicated by their lower pH15 (-0.15), especially for females (-0.18 for females and -0.13 for males) and in 2023 (-0.18 in 2023 and -0.12 in 2022), as well as
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by the lower pHu (-0.10) (TABLE 4), which thus increased the risk of pale, soft and exudative meat

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Pre-slaughter hanging is stressful, as indicated by an increase in plasma corticosterone concentration, and intense struggling on the slaughter line results in a rapid decrease in post-mortem pH (Debut et al., 2005). We observed that outdoor-access chickens flapped their wings twice as much as indoor chickens (16% vs. 8%, respectively), which seemed consistent with the lower pH15 of their breast meat. When considering only birds that flapped their wings, the mean duration of flapping was however 28% shorter for outdoor-access chickens than that for indoor chickens (2.41 ± 1.54 vs. 3.31 ± 2.05 sec, respectively), which indicates that outdoor access decreased the magnitude of this behavioral response to stress and suggests that other physiological factors may influence the faster decrease in pH for outdoor-access chickens. In contrast, indoor and outdoor-access chickens did not differ significantly in their attempts to straighten up (4% vs. 5%, respectively). This result is consistent with previous studies that found that chickens' attempts to straighten up were often influenced more by pre-slaughter factors, such as how much time they spent upside down or how they were handled, rather than by environmental factors such as rearing conditions (Jones et al., 2005). Regarding the effect on pHu, some studies found that chickens with outdoor access had the same or higher pHu than indoor chickens (Stadig et al., 2016), while others found the opposite (Castellini et al., 2002; Fanatico et al., 2007). Castellini et al. (2002) hypothesized that the pHu could be lower due to less stress and thus glycogen consumption before slaughter. Outdoor-access chickens had slightly paler meat, which agreed with the effect on meat pH15 and pHu, which occurred only in 2022.

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Outdoor-access chickens had lower redness and yellowness values than indoor chickens. Overall, the color differences between outdoor and indoor conditions were relatively small and not perceptible to the human eye (ΔE = 0.88); the largest difference in color was observed

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between the two years (ΔE = 1.85), and mainly between males and females (ΔE = 3.10), the latter which had paler and less red meat. At the same chronological age, physiological stages differ between males and females, with females generally showing more advanced body development, including higher breast and fat yields. In terms of muscle composition, females tend to have a higher percentage of intramuscular fat (Chabault et al., 2012) and a more pronounced acidity, indicating greater glycogen reserves. Together, these factors contribute to the paler appearance of meat in females. Meat with lower pHu usually has lower water-holding capacity (Mir et al., 2017) and is firmer (Alnahhas et al., 2015). In the present study, this was the case for CL, which was 9% greater for outdoor-access than indoor chickens. In contrast, outdoor access had an opposite effect on DL between 2022 and 2023, but it remained low in both years. Consistent with the differences in pHu, pH15 and CL, outdoor-access chickens had firmer breast meat, and more so for males (+20%) than for females (+7%) (TABLE 4).

The higher temperatures of free-range systems can exacerbate meat-quality defects. At high temperatures, breast meat has lower pHu, more denatured muscle protein and thus greater water loss through exudation, as well as paler and firmer meat (Strasburg and Chiang, 2009; Wang et al., 2018; Zaboli et al., 2019). In the present study, the minimum/maximum temperatures were much higher the day before slaughter for outdoor-access chickens (14/33°C in 2022, 17/33°C in 2023) than those for indoor chickens (8/17°C in 2022, 13/26°C in 2023). One possible mechanism is that, at higher temperatures, chickens may decrease their activity to conserve energy and produce less heat, which decreases glycogen consumption before slaughter, as observed for thigh muscle following acute heat stress (Debut et al., 2005). This increase in glycogen could have caused the lower pHu observed in the meat of outdoor-access chickens.
High temperatures at the end of rearing in 2023 could also explain the effect of the year × sex interaction on pHu. Although high temperatures might be expected to influence males more than females since they weigh more, the opposite occurred. One hypothesis is that males spent
less time outdoors during high temperatures, which may have decreased direct effects of physical activity on glycogen consumption. Field observations during high temperatures in the present study suggested that chickens spent slightly less time outdoors (2.5% fewer chickens outside per degree, data not shown), which supports the hypothesis of less time outdoors under heat stress (Jones et al., 2005), but we did not have detailed data by sex. Future studies should monitor activity levels during high temperatures to better quantify behavioral adaptations of males and females to free-range systems and how they influence performance and meat quality.

Our results highlight the importance for the poultry industry to adapt farming practices according to climatic conditions in order to optimize yields and ensure consistent meat quality.

Better management of hot periods and proper control of outdoor access could minimize the negative effects on meat quality, while enabling producers to better predict the performance of their poultry based on environmental variations. This study was conducted only in the summer because farmers observed that chickens struggled to eat enough to maintain their growth performance during high temperatures. To better distinguish the effects of outdoor activity from those of the response to temperature stress, similar studies should be conducted in other seasons, when chickens have outdoor access but are not exposed to high temperatures.

## CONCLUSIONS

This study showed that outdoor access modified body composition by reducing abdominal fat, and decreased feed efficiency and growth. It also affected meat quality, making it paler, more exudative and firmer. Interactions between housing condition, sex and year showed that chicken performance and meat quality in free-range systems remain sensitive to environmental challenges, such as heat stress in summer. Outdoor enrichment, with the presence of trees and shrubs to increase shaded areas, could serve as a potential mitigation strategy for the future.

The type of vegetation cover in the range, such as protein-rich forage species, should also be considered to increase the nutritional value of the range and maintain animal feed efficiency.
This knowledge is essential to optimize the management of livestock under increasingly variable conditions, particularly in the face of climate change and health challenges, and to better consider genotype × environment interactions in breeding programs of strains intended for free-range systems.

### 386 DISCLOSURES

The authors declare no conflicts of interest. The corresponding author confirms that the manuscript has been read and approved for submission by all authors.

### 389 STUDY FUNDING

This project has been funded by the region Centre-Val de Loire (APR-IR 2021 – n°18) and by Animal Genetics division of INRAE.

### 392 REFERENCES

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**FIGURE 1.** Maximum daily temperature (°C) according to housing condition (IN or OUT) and year (2022 or 2023). Green line: OUT group, year 2022; Blue line: OUT group, year 2023; Orange line: IN group, year 2022; Brown line: IN group, year 2023. Vertical black line: age at which OUT birds had access to the range

<figure><img src="image_2.png" /></figure>
<table><caption>521 TABLE 1. Diet composition and characteristics</caption><thead><tr><th></th><th>Starter<br>(0-27 days)</th><th>Grower-Finisher<br>(28 days-slaughter)</th></tr></thead><tbody><tr><td>Corn</td><td>27.55</td><td>40.46</td></tr><tr><td>Wheat</td><td>20.41</td><td>20.36</td></tr><tr><td>Soybean oil</td><td>5.00</td><td>5.00</td></tr><tr><td>Soybean meal 48</td><td>31.22</td><td>28.80</td></tr><tr><td>Corn gluten 60</td><td>1.79</td><td>1.75</td></tr><tr><td>Pea</td><td>10.00</td><td>0.00</td></tr><tr><td>Calcium carbonate</td><td>1.19</td><td>0.79</td></tr><tr><td>Dicalcium phosphate</td><td>1.85</td><td>1.67</td></tr><tr><td>Salt</td><td>0.40</td><td>0.40</td></tr><tr><td>Vitamins and minerals</td><td>0.40</td><td>0.40</td></tr><tr><td>DL Methionine</td><td>0.132</td><td>0.15</td></tr><tr><td>Lysine</td><td>0.008</td><td>0.17</td></tr><tr><td>Anticoccidial</td><td>0.05</td><td>0.05</td></tr><tr><td>Total Nitrogen content (%)</td><td>21.75</td><td>20.00</td></tr><tr><td>ME (MJ.kg<sup>-1</sup> DM)</td><td>12.5</td><td>13.0</td></tr><tr><td>Lysine (g.kg<sup>-1</sup>)</td><td>11.63</td><td>11.29</td></tr><tr><td>Methionine (g.kg<sup>-1</sup>)</td><td>4.57</td><td>4.62</td></tr><tr><td>Methionine +Cysteine(g.kg<sup>-1</sup>)</td><td>8.22</td><td>8.22</td></tr><tr><td>Tryptophan (g.kg<sup>-1</sup>)</td><td>2.47</td><td>2.27</td></tr><tr><td>Threonine (g.kg<sup>-1</sup>)</td><td>8.13</td><td>7.38</td></tr><tr><td>Calcium (g.kg<sup>-1</sup>)</td><td>12.26</td><td>8.96</td></tr><tr><td>Available phosphorus (g.kg<sup>-1</sup>)</td><td>4.35</td><td>3.79</td></tr></tbody></table>
<table><caption>TABLE 2. Effects of housing condition, sex, year and their interactions for growth and feed efficiency parameters (least square means). 22 = year 2022; 23 = year 2023</caption><thead><tr><th></th><th></th><th>G:F, g.g<sup>-1</sup></th><th>RFI, g</th><th>FI, g.d<sup>-1</sup></th><th>WG, g.d<sup>-1</sup></th><th>K, d<sup>-1</sup></th><th>Ti, d</th><th>BW76, g</th></tr></thead><tbody><tr><td></td><td>N =</td><td>1096</td><td>1056</td><td>1098</td><td>1118</td><td>1118</td><td>1118</td><td>1118</td></tr><tr><td rowspan="4">Housing condition</td><td>IN</td><td>0.445</td><td>-23</td><td>84.4</td><td>36.8</td><td>0.0332</td><td>45.6</td><td>2517</td></tr><tr><td>OUT</td><td>0.434</td><td>20</td><td>83.6</td><td>35.5</td><td>0.0354</td><td>41.5</td><td>2461</td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>0.164</td><td>0.086</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td></tr><tr><td>SE</td><td>0.002</td><td>22</td><td>0.6</td><td>0.1</td><td>0.0001</td><td>0.2</td><td>8</td></tr><tr><td rowspan="4">Sex</td><td>F</td><td>0.415</td><td>28</td><td>75.7</td><td>30.5</td><td>0.0357</td><td>40.4</td><td>2134</td></tr><tr><td>M</td><td>0.464</td><td>-31</td><td>92.2</td><td>41.8</td><td>0.0328</td><td>46.7</td><td>2844</td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>0.055</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td></tr><tr><td>SE</td><td>0.002</td><td>22</td><td>0.4</td><td>0.1</td><td>0.0001</td><td>0.2</td><td>8</td></tr><tr><td rowspan="4">Year</td><td>2022</td><td>0.446</td><td>-57</td><td>81.8</td><td>35.6</td><td>0.0343</td><td>43.5</td><td>2455</td></tr><tr><td>2023</td><td>0.434</td><td>55</td><td>86.2</td><td>36.7</td><td>0.0342</td><td>43.6</td><td>2523</td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>0.293</td><td>0.542</td><td>&lt;0.001</td></tr><tr><td>SE</td><td>0.002</td><td>22</td><td>0.6</td><td>0.1</td><td>0.0001</td><td>0.2</td><td>8</td></tr><tr><td rowspan="6">Housing condition</td><td>IN × F</td><td></td><td>42 <sup>a</sup></td><td>77.0 <sup>b</sup></td><td></td><td>0.0344 <sup>b</sup></td><td></td><td></td></tr><tr><td>IN × M</td><td></td><td>-88 <sup>b</sup></td><td>91.9 <sup>a</sup></td><td></td><td>0.0319 <sup>d</sup></td><td></td><td></td></tr><tr><td>OUT × F</td><td></td><td>14 <sup>ab</sup></td><td>74.5 <sup>c</sup></td><td></td><td>0.0370 <sup>a</sup></td><td></td><td></td></tr><tr><td>OUT × M</td><td></td><td>26 <sup>a</sup></td><td>92.5 <sup>a</sup></td><td></td><td>0.0337 <sup>c</sup></td><td></td><td></td></tr><tr><td><i>P-value</i></td><td></td><td>0.021</td><td>0.013</td><td></td><td>0.001</td><td></td><td></td></tr><tr><td>SE</td><td></td><td>30</td><td>0.6</td><td></td><td>0.001</td><td></td><td></td></tr><tr><td rowspan="6">Sex × Year<sup>1</sup></td><td>IN × 22</td><td></td><td>-114 <sup>b</sup></td><td>82.4</td><td></td><td>0.0337 <sup>c</sup></td><td>44.8 <sup>b</sup></td><td>2496 <sup>b</sup></td></tr><tr><td>IN × 23</td><td></td><td>68 <sup>a</sup></td><td>86.6</td><td></td><td>0.0327 <sup>d</sup></td><td>46.3 <sup>a</sup></td><td>2539 <sup>a</sup></td></tr><tr><td>OUT × 22</td><td></td><td>-1 <sup>a</sup></td><td>81.3</td><td></td><td>0.0350 <sup>b</sup></td><td>42.1 <sup>c</sup></td><td>2414 <sup>c</sup></td></tr><tr><td>OUT × 23</td><td></td><td>41 <sup>a</sup></td><td>85.7</td><td></td><td>0.0357 <sup>a</sup></td><td>41.0 <sup>d</sup></td><td>2507 <sup>ab</sup></td></tr><tr><td><i>P-value</i></td><td></td><td>0.022</td><td>0.791</td><td></td><td>&lt;0.001</td><td>&lt;0.001</td><td>0.022</td></tr><tr><td>SE</td><td></td><td>30</td><td>0.8</td><td></td><td>0.0001</td><td>0.2</td><td>11</td></tr><tr><td rowspan="6">Sex × Year<sup>1</sup></td><td>F × 22</td><td>0.424 <sup>b</sup></td><td>-63 <sup>b</sup></td><td>73.3</td><td>30.2 <sup>d</sup></td><td></td><td></td><td>2112 <sup>d</sup></td></tr><tr><td>F × 23</td><td>0.406 <sup>c</sup></td><td>119 <sup>a</sup></td><td>78.2</td><td>30.9 <sup>c</sup></td><td></td><td></td><td>2156 <sup>c</sup></td></tr><tr><td>M × 22</td><td>0.467 <sup>a</sup></td><td>-52 <sup>b</sup></td><td>90.4</td><td>41.1 <sup>b</sup></td><td></td><td></td><td>2798 <sup>b</sup></td></tr><tr><td>M × 23</td><td>0.462 <sup>a</sup></td><td>-10 <sup>b</sup></td><td>94.0</td><td>42.5 <sup>a</sup></td><td></td><td></td><td>2890 <sup>a</sup></td></tr><tr><td><i>P-value</i></td><td>0.014</td><td>0.022</td><td>0.250</td><td>0.016</td><td></td><td></td><td>0.026</td></tr><tr><td>SE</td><td>0.003</td><td>31</td><td>0.6</td><td>0.2</td><td></td><td></td><td>11</td></tr><tr><td rowspan="8">Housing condition</td><td>IN × 22 × F</td><td></td><td></td><td>73.8 <sup>de</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>IN × 22 × M</td><td></td><td></td><td>90.7 <sup>b</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>IN × 23 × F</td><td></td><td></td><td>80.8 <sup>c</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>IN × 23 × M</td><td></td><td></td><td>93.1 <sup>ab</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 22 × F</td><td></td><td></td><td>71.9 <sup>e</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 22 × M</td><td></td><td></td><td>90.0 <sup>b</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 23 × F</td><td></td><td></td><td>76.2 <sup>d</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 23 × M</td><td></td><td></td><td>94.8 <sup>a</sup></td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="2">Sex<sup>1</sup></td><td><i>P-value</i></td><td></td><td></td><td>0.020</td><td></td><td></td><td></td><td></td></tr><tr><td>SE</td><td></td><td></td><td>0.9</td><td></td><td></td><td></td><td></td></tr></tbody></table>

<footnote n="1">¹ Means within effects with different superscripts are different (P<0.05)</footnote>
<table><caption>TABLE 3. Effects of housing condition, sex, year and their interactions on carcass composition (least square means). 22 = year 2022; 23 = year 2023</caption><thead><tr><th></th><th></th><th>BY, %</th><th>TY, %</th><th>AFY, %</th><th>BW, g</th></tr></thead><tbody><tr><td></td><td>N</td><td>1133</td><td>1135</td><td>1128</td><td>1137</td></tr><tr><td rowspan="4">Housing condition</td><td>IN</td><td>16.9</td><td>25.5</td><td>3.3</td><td>2499</td></tr><tr><td>OUT</td><td>16.9</td><td>25.4</td><td>2.8</td><td>2546</td></tr><tr><td><i>P-value</i></td><td>0.649</td><td>0.411</td><td>&lt;0.001</td><td>&lt;0.001</td></tr><tr><td>SE</td><td>0.1</td><td>0.1</td><td>0.1</td><td>8</td></tr><tr><td rowspan="4">Sex</td><td>F</td><td>17.4</td><td>24.6</td><td>3.8</td><td>2148</td></tr><tr><td>M</td><td>16.4</td><td>26.3</td><td>2.3</td><td>2897</td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td></tr><tr><td>SE</td><td>0.1</td><td>0.1</td><td>0.1</td><td>8</td></tr><tr><td rowspan="4">Year</td><td>22</td><td>16.8</td><td>25.4</td><td>3.1</td><td>2517</td></tr><tr><td>23</td><td>17.0</td><td>25.5</td><td>3.0</td><td>2529</td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>0.032</td><td>0.021</td><td>0.279</td></tr><tr><td>SE</td><td>0.1</td><td>0.1</td><td>0.1</td><td>8</td></tr><tr><td rowspan="6">Housing condition × Sex<sup>1</sup></td><td>IN × F</td><td></td><td></td><td>4.2 <sup>a</sup></td><td>2138 <sup>c</sup></td></tr><tr><td>IN × M</td><td></td><td></td><td>2.5 <sup>d</sup></td><td>2860 <sup>b</sup></td></tr><tr><td>OUT × F</td><td></td><td></td><td>3.4 <sup>b</sup></td><td>2159 <sup>c</sup></td></tr><tr><td>OUT × M</td><td></td><td></td><td>2.2 <sup>c</sup></td><td>2933 <sup>a</sup></td></tr><tr><td><i>P-value</i></td><td></td><td></td><td>&lt;0.001</td><td>0.019</td></tr><tr><td>SE</td><td></td><td></td><td>0.1</td><td>11</td></tr></tbody></table>

<footnote n="1">¹ Means within effects with different superscripts are different (P<0.05)</footnote>
<table><caption>TABLE 4. Effects of housing condition, sex, year and their interactions on meat quality traits (least square means). 22 = year 2022; 23 = year 2023</caption><thead><tr><th></th><th></th><th>pH15</th><th>pHu</th><th>L*</th><th>a*</th><th>b*</th><th>DL, %</th><th>CL, %</th><th>WB, N</th></tr></thead><tbody><tr><td></td><td>N =</td><td>1133</td><td>1141</td><td>1139</td><td>1139</td><td>1139</td><td>1134</td><td>1135</td><td>570</td></tr><tr><td rowspan="3">Housing condition</td><td>IN</td><td>6.66</td><td>5.81</td><td>46.5</td><td>-0.74</td><td>10.10</td><td>1.49</td><td>13.1</td><td>14.3</td></tr><tr><td>OUT</td><td>6.51</td><td>5.71</td><td>47.0</td><td>-1.15</td><td>9.50</td><td>1.35</td><td>14.3</td><td>16.3</td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td></tr><tr><td></td><td>SE</td><td>0.01</td><td>0.01</td><td>0.1</td><td>0.04</td><td>0.07</td><td>0.03</td><td>0.1</td><td>0.1</td></tr><tr><td rowspan="3">Sex</td><td>F</td><td>6.58</td><td>5.72</td><td>48.3</td><td>-1.00</td><td>9.86</td><td>1.78</td><td>13.6</td><td>15.3</td></tr><tr><td>M</td><td>6.59</td><td>5.79</td><td>45.2</td><td>-0.91</td><td>9.71</td><td>1.07</td><td>13.8</td><td>15.2</td></tr><tr><td><i>P-value</i></td><td>0.079</td><td>&lt;0.001</td><td>&lt;0.001</td><td>0.04</td><td>0.083</td><td>&lt;0.001</td><td>0.005</td><td>0.719</td></tr><tr><td></td><td>SE</td><td>0.01</td><td>0.01</td><td>0.1</td><td>0.04</td><td>0.07</td><td>0.03</td><td>0.1</td><td>0.1</td></tr><tr><td rowspan="3">Year</td><td>22</td><td>6.60</td><td>5.73</td><td>45.9</td><td>-1.31</td><td>9.90</td><td>1.34</td><td>13.3</td><td></td></tr><tr><td>23</td><td>6.57</td><td>5.79</td><td>47.6</td><td>-0.61</td><td>9.67</td><td>1.51</td><td>14.1</td><td></td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>&lt;0.001</td><td>0.012</td><td>&lt;0.001</td><td>&lt;0.001</td><td></td></tr><tr><td></td><td>SE</td><td>0.01</td><td>0.01</td><td>0.1</td><td>0.04</td><td>0.07</td><td>0.03</td><td>0.1</td><td></td></tr><tr><td rowspan="5">Housing condition</td><td>IN × F</td><td>6.67 <sup>a</sup></td><td>5.77 <sup>b</sup></td><td></td><td>-0.82</td><td></td><td>1.79 <sup>a</sup></td><td></td><td>14.6 <sup>b</sup></td></tr><tr><td>IN × M</td><td>6.66 <sup>a</sup></td><td>5.85 <sup>a</sup></td><td></td><td>-0.67</td><td></td><td>1.20 <sup>b</sup></td><td></td><td>13.9 <sup>c</sup></td></tr><tr><td>OUT × F</td><td>6.49 <sup>c</sup></td><td>5.68 <sup>d</sup></td><td></td><td>-1.17</td><td></td><td>1.77 <sup>a</sup></td><td></td><td>16.0 <sup>a</sup></td></tr><tr><td>OUT × M</td><td>6.53 <sup>b</sup></td><td>5.74 <sup>c</sup></td><td></td><td>-1.13</td><td></td><td>0.94 <sup>c</sup></td><td></td><td>16.6 <sup>a</sup></td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td>0.032</td><td></td><td>0.097</td><td></td><td>0.001</td><td></td><td>&lt;0.001</td></tr><tr><td></td><td>SE</td><td>0.01</td><td>0.01</td><td></td><td>0.05</td><td></td><td>0.04</td><td></td><td>0.2</td></tr><tr><td rowspan="5">Housing condition × Sex<sup>1</sup></td><td>IN × 22</td><td>6.66 <sup>a</sup></td><td></td><td>45.4 <sup>c</sup></td><td>-1.02 <sup>c</sup></td><td>10.47 <sup>a</sup></td><td>1.25 <sup>c</sup></td><td></td><td></td></tr><tr><td>IN × 23</td><td>6.66 <sup>a</sup></td><td></td><td>47.6 <sup>a</sup></td><td>-0.46 <sup>a</sup></td><td>9.67 <sup>b</sup></td><td>1.73 <sup>a</sup></td><td></td><td></td></tr><tr><td>OUT × 22</td><td>6.54 <sup>b</sup></td><td></td><td>46.4 <sup>b</sup></td><td>-1.58 <sup>d</sup></td><td>9.33 <sup>c</sup></td><td>1.43 <sup>b</sup></td><td></td><td></td></tr><tr><td>OUT × 23</td><td>6.48 <sup>c</sup></td><td></td><td>47.6 <sup>a</sup></td><td>-0.74 <sup>b</sup></td><td>9.68 <sup>b</sup></td><td>1.28 <sup>c</sup></td><td></td><td></td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td></td><td>0.002</td><td>0.002</td><td>&lt;0.001</td><td>&lt;0.001</td><td></td><td></td></tr><tr><td></td><td>SE</td><td>0.01</td><td></td><td>0.1</td><td>0.05</td><td>0.09</td><td>0.04</td><td></td><td></td></tr><tr><td rowspan="5">Sex × Year<sup>1</sup></td><td>F × 22</td><td></td><td>5.71 <sup>c</sup></td><td></td><td>-1.52 <sup>a</sup></td><td>10.13 <sup>a</sup></td><td></td><td>14.2 <sup>b</sup></td><td></td></tr><tr><td>F × 23</td><td></td><td>5.74 <sup>b</sup></td><td></td><td>-0.49 <sup>d</sup></td><td>9.60 <sup>b</sup></td><td></td><td>12.9 <sup>c</sup></td><td></td></tr><tr><td>M × 22</td><td></td><td>5.75 <sup>b</sup></td><td></td><td>-1.08 <sup>b</sup></td><td>9.67 <sup>b</sup></td><td></td><td>12.4 <sup>d</sup></td><td></td></tr><tr><td>M × 23</td><td></td><td>5.84 <sup>a</sup></td><td></td><td>-0.74 <sup>c</sup></td><td>9.75 <sup>b</sup></td><td></td><td>15.3 <sup>a</sup></td><td></td></tr><tr><td><i>P-value</i></td><td>&lt;0.001</td><td></td><td></td><td>&lt;0.001</td><td>&lt;0.001</td><td></td><td>&lt;0.001</td><td></td></tr><tr><td></td><td>SE</td><td>0.01</td><td></td><td></td><td>0.05</td><td>0.09</td><td></td><td>0.1</td><td></td></tr><tr><td rowspan="7">Housing condition</td><td>IN × 22 × F</td><td></td><td></td><td></td><td>-1.22 <sup>d</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>IN × 22 × M</td><td></td><td></td><td></td><td>-0.23 <sup>b</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>IN × 23 × F</td><td></td><td></td><td></td><td>-0.44 <sup>a</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>IN × 23 × M</td><td></td><td></td><td></td><td>-0.50 <sup>ab</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 22 × F</td><td></td><td></td><td></td><td>-1.80 <sup>e</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 22 × M</td><td></td><td></td><td></td><td>-1.35 <sup>d</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>OUT × 23 × F</td><td></td><td></td><td></td><td>-0.53 <sup>a</sup></td><td></td><td></td><td></td><td></td></tr><tr><td></td><td>OUT × 23 × M</td><td></td><td></td><td></td><td>0.94 <sup>a</sup></td><td></td><td></td><td></td><td></td></tr><tr><td></td><td><i>P-value</i></td><td></td><td></td><td></td><td>0.028</td><td></td><td></td><td></td><td></td></tr><tr><td></td><td>SE</td><td></td><td></td><td></td><td>0.06</td><td></td><td></td><td></td><td></td></tr></tbody></table>

<footnote n="1">¹ Means within effects with different superscripts are different (P<0.05)</footnote>