The effect of crossbreeding with different breeds on slaughter and carcass characteristics and meat quality in Leghorn hens

This study reports slaughter and carcass characteristics and meat quality as a result of crossing Leghorn chickens and five different genotypes. The experiment was carried out in the Prof. Dr. Hümeyra Özgen Research and Application Farm in Selcuk University. The material consisted of 20 leghorn crosses (F2) of each genotype reared under the same feeding and care conditions. The animals were slaughtered at 84 d. In this study, the highest value was determined in the Brahma × Leghorn (BL) genotype, followed by the Cornish × Leghorn (CL), Denizli × Leghorn (DL), and Aracuana × Leghorn (AL) genotypes, respectively, according to slaughter weight and hot and cold carcass performance values. The lowest value was calculated in the Leghorn × Leghorn (LL) genotype, as expected. Slaughter, cold, and carcass weights were found to be similar. A difference was found in colour characteristics (L*,a*,b*) of thigh (b), breast (l), and breast (a) meats of F2 groups. A difference was found in the DM and pH values of the genotypes. CL came into prominence when rearing specific genotypes as free-range broilers. In evaluating the parts of the carcass, it was found that two genotypes were superior to other genotypes in terms of thigh, breast, wing, and back weights. New three-unit and four-unit crossbreeding studies have a potential to add new local commercial genotypes to national economies.


Introduction
Stock performance and carcass quality in broilers may vary depending on several factors, such as breed, sex, age, and the rearing method employed (Santos et al., 2005;Połtowicz and Doktor, 2012).Stock rearing and animal health have grown into a substantial industry, contributing to the budgets of most countries (Almeida et al., 2015).In the 1950s, it took twelve weeks for birds to reach 1.8-2 kg slaughter weight.However, this has been reduced to 40 d by virtue of improvements in animal selection and breeding over the years.Advances in animal rearing techniques taking place in the poultry sector have added to the genetic potential of animals, while positively affecting their capacity of reaching higher live weights (Rémignon et al., 1994).Cross-breeding local chicken populations can augment efficiency in poultry farming (Harikrishnan et al., 2019).By crossing genotypes with a higher capacity for efficiency with local chicken species, the genetic structure of animals can develop, making it possible to create slower-growing lines for poultry farming (Połtowicz and Doktor, 2012).For example, Denizli breed chickens, constituting our local gene pools, may be used in crossbreeding with improved broiler or layer chicken breeds (Garip et al., 2011).
Since local chicken populations are resistant to diseases, thrive on poor quality food, and are preferrred by consumers, they have a potential to constitute one of the alternative sources of income for rural populations (Mengesha, 2012).Organic production supports eco-friendly food production, which can produce quality products by enhancing animal welfare conditions (Sundrum, 2001).Current rearing methods for broilers enable chickens to grow more thigh and breast meat and less abdominal fat in comparison to traditional rearing systems (Castellini et al., 2002).Due to more health-conscious consumers and an increase in demand for alternative products, alternative poultry breeders may be encouraged to rear breeding animals (Franzoni et al., 2021).For that purpose, most researchers seek new genotypes by combining fast-growing commercial hybrids and slow-growing local animals (Rizzi et al., 2013;Cassandro et al., 2015;Wolde et al., 2021).
The Denizli breed represents a substantial local gene pool worthy of preservation because of their peculiar ability to sing for a long time, their feather colour, foot skin colour, and peculiar racial morphological structure (Aksoy et al., 2002).In addition, Atasoy and Gürcan (2000) reported that the Denizli breed chicken had higher live weights than other local Turkish chicken breeds.In the Denizli × Leghorn F2 population, live weights are reported to range from 1814.60-1900.0g in females and males at 32 week (Garip et al., 2011).
In poultry eggs, eggshell colour is an external quality characteristic that affects the shell quality, as well as the egg quality characteristics (Kırıkçı et al., 2005;Drabik et al., 2021).Therefore, chicken breeds like Araucanas which have different eggshell colours draw the attention of breeders and consumers.Researchers have reported on the Araucana, which has different eggshell colours like pheasants, owing to their blue eggshell, which is a dominant character (Punnett 1933;Keneddy and Vevers, 1973).
It is reported that more studies are needed in this context to bring new species from local breeds to future generations and to contribute to the protection of the gene resources of the countries (Keskin et al., 2022).Crossbreeding studies cause some morphological and physiological changes in living things.The hypothesis that there may be a potential for the formation of new, combined, productive breeds by crossing different genotypes with Leghorn females, a commercial layer breed with high yielding characteristics, motivated us to conduct this study.The purpose of this study was to obtain new lines by crossbreeding the Leghorn layer and specific genotype groups from our local chicken breeds with peculiar characteristics, primarily the Denizli breed.In addition, the study examined the evolution of these new genotypes in the genetic potential of F2 crosses and their effects on carcass and meat quality.

Materials and Methods
The eggs from each genotype, including five different chicken breeds of broilers (Brahma, Denizli, Araucana, Leghorn, Cornish) and 20 Leghorn hens produced for crossbreeding were kept in a waiting room at 15 o C and 70% moisture for one week.All daily-collected eggs contained defining information (parent stock, date, group).After seven days of storage, hatching quality eggs were weighed and fumigated.Applying fumigation (14 g formaldehyde, 7 g potassium permanganate, v/w) for 10 mins, the eggs were set into an incubator.Brooder machine was set at 37.7 o C and 65% moisture for incubation and in a hatching machine at 37.2 o C and 70% proportional moisture.The new chicks were recorded by writing down their mother and father record numbers and wing numbers.As a result, the Brahma (B×L), Denizli (D×L), Araucana (A×L), Leghorn (L×L), and Cornish (C×L) crossbreed genotypes were obtained with the Leghorn breed in the female line, respectively.The crossbreed genotypes thus obtained were grown individually in the brooder catch machine where they were kept for one week.
The genotypes were administered 2.5% sugared water solution to reduce their risk of not accessing the feed and reduce the mortality rate and then fed after three to four hours of hunger (McNaughton et al., 1978).A vaccination program (Marek's, Gumboro, Newcastle) aimed at poultry was applied, similar to the one applied at Hümeyra Özgen Research and Application Center Farm Poultry Unit.The animals were revaccinated at appropriate times.
The animals were administered broiler chick mash, which had been previously prepared and weighed, nearly two hours later, ad libitum, using chick feeders.The genotype groups were created with four animals each and five repetitions in such a way that the groups were to have similar environmental conditions.The chick genotypes were individually fed chick starter (I) feed in the brooder catch machine for 0-7 d.Then chick grower feed (II) was used from 8-14 d.In the floor system, sections contained 10-12 birds per square metre, had at least two nipple drinkers, and chicks could not mix.A sawdust material of at least 2.5 cm was used on the floor of the sections as a base.At the end of day 14, the broiler onset feed (III) was used.From days 14-28, all groups were fed under equal conditions.On day 28, the broilers were weighed.After day 28, broiler finishing feed (IV) was administered in the same way and the feed and live weight measurements continued to be done bi-weekly.The broiler groups were fed in the coop sections until day 84.
Five animals from each group, one in each subgroup (repetition), were removed for slaughter.After slaughtering and dressing, the hot carcasses were chilled for 2 h at 4 °C.The carcasses were weighed and refrigerated for 24 h.Carcass weight and proportions were calculated on the basis of the breast (skinless), thighs, wings, back, and neck parts according to a standard procedure (Uijttenboogaart & Gerrits, 1982).In addition, gizzard, liver, and heart weights were calculated using edible parts with economic value.The inedible parts consisted of feathers, feet, head, intestines, kidneys, and urogenital organs.Although the internal organs are not considered as "carcass" in the poultry industry, protein is an essential nutrient source in them (Romero-Garay et al., 2022).
The animals were regularly watered using automatic nipple drinking bowls that were easily accessible.For all experimental stages, a continuous lighting programme was used (23 h of light and one hour of darkness).Nutritional values of the feed supply were determined in a private enterprise and nutritional value analysis of the feed was performed at the Selcuk University, Faculty of Veterinary Science, Animal Feeding and Nutrition Diseases Laboratory (Table 1).For the carcass preparation procedure, wing, thigh, and breast pieces were taken by cutting one bird (five from each group) from each repetition and the pieces were weighed using a balance scale.Feeders were removed eight hours before and birds were weighed prior to slaughter and slaughter weights were determined.After the slaughter, the head and foot weights, as well as consumable (heart, liver, and gizzard) and inedible offal weights of the broilers, which had been defeathered using a wet defeathering method, were individually determined using a balance scale.
The hot performance was determined as the proportion of the weight of hot carcass, which was washed and dried for 10 min, to the slaughter weight.
Hot performance (%) = (hot carcass weight (g) / slaughter weight (g)) × 100 (1) The cold performance was determined from the proportion of the carcass after cold storage room at +4 o C for 24 h to slaughter weight.
Cold performance (%) = ((cold carcass weight (g) / slaughter weight (g)) × 100 (2) Dry matter, pH, water retention capacity, cooking loss, and colour values (L*, a*, b*) of thigh and breast portions of five samples taken from each genotype group were individually determined.Meat colour was measured on the external surface of the breast and thigh muscle after skin removal using a portable colour difference meter based on the lightness (L*), redness (a*), yellowness (b*) system and the external of the removed skin was measured for colour (CIE, 1976).Three measurements were performed per sample and an average value was obtained.Meat pH was measured 24 h after cooling the carcasses.Analysis of the samples was performed at Selçuk University, Faculty of Veterinary Science, Department of Nutritional Hygiene and Technology Laboratory.
The data of the study were evaluated using the IBM SPSS 25 package program licensed by Selcuk University.The normal distribution of the data was analysed using the Shapiro-Wilk test.Multiple analysis of variance (ANOVA) was used for parametric tests and Duncan's test was used for comparisons between groups.In addition, the Kruskal-Wallis-H test was used for non-parametric tests.Intergroup significance was evaluated on the basis of P <0.05.

Results
Table 2 demonstrates the slaughter, hot, and cold carcass performance values of different genotypes.Of the characteristics examined in Table 2, the highest value was in the BL genotype, followed by the CL, DL, and AL genotypes.The lowest value was in the LL genotype, which was expected.Slaughter, cold, and carcass weights were similar.However, the weights were higher in one of the local genotype resources, the DL genotype (related to the CL group, which was crossbred with Brahma, a broiler breed) and in the AL group.Evaluating all slaughter and carcass characteristics, this value was found to be the lowest in the LL group, which is known as a layer genotype (P <0.01).a,b,c : The difference between the groups with different letters in the same column is significant (P <0.05) Table 3 demonstrates the weights of consumable carcass parts related to the F2 genotypes.Accordingly, a difference was found in terms of thigh and wing weights (P <0.001) breast and back weights (P <0.05).
Table 4 demonstrates the weights of inedible carcass parts related to the F2 genotypes.Differences were found in terms of offal and foot weights (P <0.01) and head weight (P <0.05).Evaluating the inedible carcass portion weights in the genotype groups, the highest value was determined in the head and inedible offal in the CL group (P <0.01) and in the head in the Brahma breed.The lowest inedible offal weight was determined in the LL group and the lowest head weight was in the BL group (P <0.05).a,b,c : The difference between the groups with different letters in the same column is significant (P <0.05) Table 5 demonstrates the quality characteristics (L*,a*,b*) defining thigh and breast meats related to the F2 groups.A difference was found in thigh (b) and breast (l) (P <0.01) and breast (a) (P <0.05).7 demonstrates the findings related to dry matter (DM), ash, pH, and water retention in breasts obtained from the F2 genotypes.In the study groups, a difference was found in the DM (P <0.013) and pH values (P <0.003).Tables 5, 6, and 7 demonstrate the findings related to dry matter, pH, water retention capacity, cooking loss, and colour values (L*, a*, b*) in thigh and breast portions.Statistically significant differences were found in the L*, dry matter, and pH values in the breast portions.Differences were found in the b* values of thigh portions of the broilers obtained by crossbreeding (P <0.05).

Discussion
Table 2 demonstrates the preslaughter live, hot carcass, and cold carcass weights related to the Leghorn crossbreeds.Garip et al. (2011) calculated the F1 and F2 crossbreeds of the DL genotypes, respectively, to be 2132.62g and 1856.17g live weight weeks three to 32 in terms of specific efficiency characteristics (P <0.01).Garip et al. (2011) reported the live weight to be 1814.60± 6.58 g in the female Denizli x Leghorn crossbreeds and 1900.0 ± 5.74 g in the males at week 32.Atasoy and Gürcan (2000) reported the live weight of Denizli chicken breeds to be 2597.26g at week 35.However, in the present study, the slaughter weight of the DL genotype was calculated to be 1155.50g on day 84.A study conducted by Castellini et al. (2002) which examined the effect of rearing broiler breed chicken in organic production systems up to 81 days of age on carcass meat quality characteristics reported the live weight, hot carcass, and cold carcass weights to be 4368 g, 3529 g, and 3485 g, respectively.Zanetti et al. (2010) examined the slow-growing, Italian-origin genotypes in terms of carcass and meat efficiency and reported the mean live weight to be 1434-2718 g and the carcass weight to be 879-1726 g.Another study which investigated the Padovana breed chicken obtained 1992, 2571, and 2717 g live weights on days 131, 180, and 201, respectively.It was reported that it was possible to develop the Padovana chicken, a local breed, by crossbreeding (Cassandro et al., 2015).In the slow-growing, Italian-origin chickens, live weight was 1854 g in the Saluzzo breed and 1819 g in the Piemontese breed at the age of 32 weeks (Soglia et al., 2020).In the 18-week Sasso-RIR (SRSR), Sasso crossbreed (LSR), and normal-feathered local chicken breed (LL), the live weights were 1877, 1379, and 1070 g, respectively.The effect of genotype was significant (P <0.05) in this parameter and crossbreeding enhanced the local genotypes in terms of weight.In the present study, the live weights were measured to be 1111.9,1221.9, 1290.4,983.3, and 1155.5 g in AL, CL, BL, LL, and DL, respectively (P <0.05).The discrepancy in values reported by the researchers may be because of the breed, genotype, slaughter age, purpose of rearing, geographical region, and ration content differences.
Table 3 demonstrates the weights of carcass meat portions in relation to the genotype groups.The proportion of the carcass thigh weight to the wing and liver weights was similar, whereas the carcass weight (P <0.001), carcass performance (P =0.029), and breast proportion (P <0.001) were found to be different (Choo et al., 2014).In the present study, it was found that the effect of the genotype on thigh weight (P =0.001), breast weight (P =0.029), and wing weight (P =0.001) was substantial, whereas the effect on the liver weight was not (P =0.509).De Marchi et al. (2005) reported 1084 g hot carcass and 213 g breast weight from the Padovana chicken at 150 days of age.In the present study, higher breast weights were obtained from all Leghorn crossbreeds than the Padovana breed chicken.Evaluating the 306.3, 373.6, and 390.5 g breast weights obtained by Cassandro et al. (2015) from local chicken at 131, 180, and 201 days of age, it was determined that the DL obtained a similar breast efficiency in a shorter period of time.
In addition to an increased population, there has been an increase in the demand for animal products obtained from poultry reared in open-access systems.Considering the environmental adaptation and carcass quality of local breeds, DL can be chosen as a new line for cage-free system rearing.Zanetti et al. (2010) reported that the weights of breasts and thighs obtained from the Italian genotypes were 322-667 g and 140-243 g, respectively, and the genotype determined the weight of both carcass portions (P <0.05).In the present study, it was found that thigh portions were different among genotypes (P =0.001); the highest thigh weight was 332.3 g in the BL genotype, whereas the lowest value was 217.5 g in the LL genotype.This may be due to the differences in the efficiency of the parent stock.The genotypes whose thigh values were examined were superior to the slow-growing Italian-origin genotypes in terms of time and efficiency.The differences between the values reported on local chickens may have been related to the most important factors affecting the carcass, i.e., the genetic factors (breed, sex) and age, care, and feeding practices.
Table 5 demonstrates the L * , a * , and b * values of thighs and breasts related to different genotypes.The L * and a * values of breasts were different (P <0.05), but b * values were similar (P =0.082).The meats obtained from the AL crossbreeds had a yellower carcass content than other genotypes.Free-range production system affect the bright colour of breasts (L * ) and red colour intensity of thighs (b * ) (Sokołowicz et al., 2016) and even the taste of animal products (Fanatico et al., 2007).The AL had a higher b* value than other genotypes, which could cause darker thigh meat than this genotype in an open-access rearing system.Zanetti et al. (2010) reported that a difference in terms of the L * and b * values of slow-growing genotypes in breast meat (P <0.05), whereas the difference between the a * values was negligible.They reported that the L * and a * values of breast meat in slow and fast-growing genotypes were similar, whereas there was a difference in b * value (P <0.05); L * , a * , and b * values of thigh meat were similar (Mikulski et al., 2011).
With increasing consumption of poultry meat and products, it is essential for consumers, retailers, and the poultry industry to achieve consistently high meat quality.The genotypic differences in WHC (water holding capacity), drip loss, and cook loss were found to be inconsequential, which is consistent with the results of Fanatico et al. (2007), Pereira et al. (2013), and Xue et al. (2021).Breast pH was affected by genotype, a finding similar to that of Hailemariam et al. (2022).

Conclusion
In order to improve local chicken breeds, which have a lower productive performance, create disease-resistant local breeds, investigate alternative feeding opportunities, introduce and protect traditional tastes and hand them down the next generations, it is believed that adding new types from local breeds can contribute to the economy, enable them to be handed down the next generation, and contribute to the protection of gene pools of countries.In evaluating the growing performance of layer types, it was concluded that BL and CL came into prominence in rearing specific genotypes as freerange broilers.In evaluating the parts of carcass, it was found that these two genotypes were superior to other genotypes in terms of thigh, breast, wing, and back portion weights.The BL genotype was noted for thigh and back portion weights and the CL genotype for breast and wing portions.No difference was found in terms of inedible weights of carcass portions, which was probably because of morphological breed characteristics.
According to the Hunter calorimetric evaluation results of breasts and thighs, it was determined that the carcass parts obtained from the AL and CL were higher than other genotypes, which could be the reason why consumers prefer them.Evaluating breasts, the LL genotype was found to be lower in terms of DM and the BL was found to be lower in terms of breast pH.Evaluating age at sexual maturity at week eight and the growth measurements including the period until week 84, it was determined that the BL genotype showed the highest performance, which was followed by the DL, CL, and AL genotypes.
In the light of crossbreeding studies between local chicken populations and commercial hybrids, it was concluded that the DL could be considered an efficient, combined breed.With effective crossbreeding between Denizli chicken breeds, which enjoy an economic value owing to their peculiar ability to sing, and commercial hybrids, which have a good adaptation capability as a local gene pool, the genetic potential of the Denizli chicken can be improved to make them more accessible for the general population.This way, it may be possible to create new sources of income for breeders in rural areas.
Since there are a limited number of studies on the crossbreeding of the Araucana breed or meat efficiency, comprehensive studies are needed on this breed.The dominant blue shells may generate a rapid and practical alternative solution to increase the consumer demand through the crossbreeding of this breed with layer-type chicken breeds.
Considering better carcass efficiency and breast portions, the crossbreeding of local chickens with a layer breed may be economically advantageous.Crossbreeds are a good alternative for enhancing the stock and stock systems and protecting the specific meat quality of local chickens.
The findings of the study demonstrate that even dual crossbreeding might be an alternative in poultry rearing, compared to organic systems and free-range systems.Considering the carcass characteristics and organoleptic characteristics of organically-fed chickens, it was concluded that new genotypes suitable for organic production could be obtained.It is known that broilers need to meet the demands of consumers in terms of organic meat.Therefore, in order to have the best broilers to respond better to the organic and free-range feeding systems in Turkey, more and different disciplines must do research.In the light of the findings obtained from the present study, it is concluded that new three-unit and four-unit crossbreeding studies have a potential of adding new commercial local genotypes to national economies.

Table 1
Nutrient content of the phase feeds used in feeding of the genotypes I: Chick starter feed days 1-7, II: Chick grower feed for days 8-28, III: Chick starter feed for days 8-28, IV: Broiler finisher feed for day 28 onward

Table 3
Weights of carcass parts related to different genotype groups at 84 weeks of age

Table 4
Weights (g) of inedible carcass parts in the genotype groups Broiler x Leghorn, DL: Denizli x Leghorn, AL: Aracuana x Leghorn, LL: Leghorn x Leghorn, CL: Cornish x Leghorn L*: Lightness, a*: Redness, b*: Yellowness.The difference between the groups with different letters in the same column is significant <0.05)

Table 6
Specific carcass quality characteristics related to thighs in the genotype groups Broiler x Leghorn, DL: Denizli x Leghorn, AL: Aracuana x Leghorn, LL: Leghorn x Leghorn, CL: Cornish x Leghorn DM: dry matter, WA: water activity, WHC: water holding capacity.The difference between the groups with different letters in the same column is significant (P <0.05)

Table 7
Carcass quality characteristics related to breast in the genotype groups Broiler x Leghorn, DL: Denizli x Leghorn, AL: Aracuana x Leghorn, LL: Leghorn x Leghorn, CL: Cornish x Leghorn.DM: Dry matter, WA: Water activity, WHC: Water holding capacity; the difference between the groups with different letters in the same column is significant (P<0.05)