The British Ixworth: individual growth and egg production of a purebred dual-purpose chicken

ABSTRACT 1. Killing male one-day-old chicks, especially from layer lines, is banned in some European countries. Therefore, dual-purpose chickens, where each sex is used for meat and egg production, respectively, offer an alternative production solution. This study evaluated the British purebred breed Ixworth as a dual-purpose chicken for meat and egg production. 2. Ixworth chicks (n = 167) were hatched and reared mixed-sex in a floor housing system, with two groups receiving a commercial pullet diet (treatment 1) and two groups receiving a diet composed for males of layer lines (treatment 2). Individual chick performance data were recorded. Males were slaughtered at 12 weeks of age, and their growth rate and carcase variables were analysed. All hens were continuously reared on the pullet diet and kept in a free-range system from 20 weeks old for one laying period (52 weeks). In addition, group-based feed consumption and mortality were recorded. 3. Cockerels in treatment 1 and 2 showed significantly different [T(88) = −2.846, P = 0.003] growth rates (25.3 vs. 27.4 g/day) and average final weights (2166 g vs. 2344 g). The hens in treatment 1 (n = 41) laid an average of 193 eggs per hen housed (mean egg weight: 56.9 g), whereas those in treatment 2 (n = 35) laid 195 eggs per hen housed (mean egg weight: 56.5 g). Nest acceptance was >97.5% and feed consumption was up to 140 g/bird/day. 4. The results showed that the Ixworth may be a suitable breed for dual-purpose use and could be improved through selective breeding, offering potential for preservation of this local breed as well as general biodiversity in poultry farming.


Introduction
Killing day-old male chicks of layer lines was banned in Germany and France in 2022, owing to ethical and consumer concerns, which passed into legislation.Alternative production practices are now necessary, with alternatives including in-ovo sex determination, which enables preselection of female embryos before hatching, or the rearing of the male chicks of layer lines (Krautwald-Junghanns et al. 2018).However, in ovo sex determination may not be acceptable, because the embryos might feel pain during preselection (Corion et al. 2022), and rearing male chicks from layer lines is challenging economically and in terms of growth performance and animal welfare (Reithmayer and Mußhoff 2019;Tiemann et al. 2020;Torres et al. 2019).Another alternative is raising dual-purpose chickens, characterised by breeds suitable for both egg and meat production, which differ from specialised lines by the use of each sex for food production (Siekmann et al. 2018).However, the performance of dual-purpose chickens is typically lower than that of specialised layers or broiler hybrids, with dual-purpose hens usually laying smaller eggs and cockerels yielding less breast meat (Lambertz et al. 2018).
A major advantage of dual-purpose lines is improved behaviour-and health-related welfare.For example, the Lohmann Dual, a commercial dual-purpose hybrid line, showed a lower prevalence of feather pecking relative to the layer hybrid Lohmann Brown (Giersberg et al. 2017).The former was found to be less fearful than the commercial layer hybrid in novel object and avoidance distance tests (Giersberg et al. 2020).Purebred dual-purpose breeds might provide independence from commercial breeding companies for small-scale farmers with extensive production systems, and such breeds preserve valuable genetic resources (Meuser et al. 2021).Lambertz et al. (2018) named Australorps, Bresse Gauloise, New Hampshire, Plymouth Rock, Rhode Island Red, Sulmtaler, Sundheimer, Sussex and the Vorwerk as dual-purpose breeds, but these are traditional and/or local breeds, only a few of which are used commercially.For instance, Bresse Gauloises are produced for Label Rouge systems in France (Muth et al. 2018), whereas Malines are only reared in Mechelen in Belgium (Mueller et al. 2018).The availability of chicks is a limiting factor for many dualpurpose breeds, as many are endangered and maintained only by smaller (hobby) breeders (Gordon 2002).Moreover, research and/or data on the performance and suitability of these breeds for commercial production systems is scarce (Siekmann et al. 2018).
According to Hocking et al. (2003), the Ixworth is a promising dual-purpose breed.It originated in the British village of Ixworth, Suffolk, in the 1930s when Reginald Appleyard aimed to breed economically feasible chickens.The originating breeds of Ixworth are White Orpington, White Sussex, White Minorca, Jubilee and varieties of Indian Game (Barber 2018).Described by the British Poultry Standard as 'excellent table birds with good laying qualities' (Allonby and Wilson 2018), Ixworth chickens are characterised by their white plumage, bright red head appendages with a pea comb, and white-coloured skin, legs and flesh (Allonby and Wilson 2018).The breed has 'critical' status (Wilkinson et al. 2012) and the availability of brooding eggs is limited (Gordon 2002).Adult Ixworth cockerels and hens are relatively heavy at around 4.1 kg (9 lb) and 3.2 kg (7 lb), respectively (Allonby and Wilson 2018), and both sexes mature with a typically deep and well-rounded breast, as shown in Figure 1.Hocking et al. (2003) reported that Ixworth hens laid around 270 eggs per year.Sandercock et al. (2009) and Gordon (2002) found that Ixworth cockerels had a live weight of 1.674 kg on day 70 and 1.910 kg on day 81.Additionally, Gordon (2002) suggested that the Ixworth breed showed potential in terms of breast meat yield and could be an attractive option for niche production systems, provided that premiums cover the cost of its prolonged growing period and high feed conversion ratio (FCR).Allonby and Wilson (2018) described the Ixworth as active, well balanced and a good ranger.Overall, the characteristics of the Ixworth make it a promising dual-purpose breed for extensive husbandry systems.
Typically, performance variables have been analysed using flock rather than individual data.However, for pure breeding lines, often kept in single cages, individual data may be analysed (Tixier-Boichard et al. 2012).Individual data is crucial for further development of breeds, although dualpurpose breeds such as Ixworth have been primarily preserved by small-scale local breeders without intensive breeding programmes aimed at higher performance (Meuser et al. 2021).As a result, these birds often lack uniformity and each breed exhibits genetic substructures (Wilkinson et al. 2012).To improve performance in these genetically variable birds, individual data is essential and can help adapt breeding and housing to the specific needs of each bird.With modern technology and precision livestock farming, it is now possible to automatically detect animal health and welfare on an individual bird basis, potentially creating added value in animal welfare and improving efficiency for farmers and breeders (Li et al. 2020).
The present study evaluated the performance of the British dual-purpose purebred breed Ixworth using individual performance data to reflect variability within the flock.The results provided individual and population-based performance data for the Ixworth breed, with emphasis on its potential use for meat and egg production and to support the preservation of this endangered dual-purpose breed.

Ethical statement
The birds were kept at the Campus Frankenforst of the Agricultural Faculty, University Bonn (53639 Königswinter, Germany).Animal husbandry complied with the order on the protection of animals and the keeping of production animals (Tierschutz-Nutztierhaltungsverordnung, 2006;last revision 2021).The study was approved by the Animal Welfare Officer and responsible commission of the Agricultural Faculty of the University of Bonn (Az 03.20.02_2020.11).

Growth performance
The birds were descendants of an Ixworth strain which were selected and maintained at the Campus Frankenforst of the Agricultural Faculty, University Bonn (53639 Königswinter, Germany).They were incubated and reared at this facility, with a hatching rate of 64.7%; hence, 167 chicks were individually hatched and assigned to their dams.The chicks were divided into four groups, with 41 or 42 chicks per group, and marked with numbered leg bands to record individualspecific data.Wing bands were added at seven days of age.Post-hatched chicks were kept in a confinement ring near infrared spot heaters, food and water.The infrared lamps provided sufficient heat during the rearing period.After 10 days, the chicks were raised in mixed-sexed groups with access to an area of 14.57 m 2 , corresponding to a stocking density of three birds/m 2 .Alfalfa bales and pecking stones were provided from seven days of age onwards, and perches and small bales of straw were provided at six weeks of age.The pen was littered with wood shavings, and birds had ad libitum access to food and water.All groups were fed with a starter diet (Kükenstarter Premium; Mischfutter Werke Mannheim GmbH, Mannheim, Germany; 21.0% crude protein, 0.48% methionine, 1.09% lysine and 12.0 MJ ME/kg; for further information, see supplement material (Table S1)] until they were 14 days old).
Four groups were established with two different treatments (one repetition per treatment).Two groups in treatment 1 received a commercial pullet developer (all-mash A; Deutsche Tiernahrung Cremer GmbH & Co KG, Düsseldorf, Germany; 18.0% crude protein, 0.35% methionine, 0.8% lysine and 11.4 MJ ME/kg) until week 10, whereas two groups in treatment 2 received a commercial diet developed for raising cockerels of layer lines (Junghähne Premium; Mischfutter Werke Mannheim GmbH, Mannheim, Germany; 21.0% crude protein, 0.48% methionine, 1.12% lysine and 12.0 MJ ME/kg) until week 10.At 10 weeks of age, males and females were separated, with males remaining in the barn and females moved to another barn where they were fed with a commercial pullet developer (all-mash R; Deutsche Tiernahrung Cremer GmbH & Co KG, Düsseldorf, Germany; 15.0% crude protein, 0.3% methionine, 0.65% lysine and 11.4 MJ ME/kg) until week 20.During the last two weeks of fattening, the males were fed a conventional finisher diet for broilers (Landkornendmast; Deutsche Tiernahrung Cremer GmbH & Co KG, Düsseldorf, Germany; 20.0% crude protein, 0.5% methionine, 1.05% lysine and 12.4 MJ ME/kg) and were slaughtered at 12 weeks of age (84 days according to ecological standards in Germany).Feed intake was recorded daily, with a weekly weigh-back.All birds were vaccinated against Marek's disease, coccidiosis, infectious bronchitis and Newcastle disease, and were visually inspected twice daily, including feeding and health checks, with mortality recorded as necessary.All birds were weighed individually on a weekly basis from hatching.The feed conversion ratio (FCR) and the European production efficiency factor (EPEF) were calculated using the following formulas: Uniformity was calculated based on the proportion of birds that weighed within 10% above or below the mean weight of all animals.In addition, 32 carcases were weighed and dissected into the most valuable parts after slaughter, including breast, legs and wings.The weight of each part was recorded and its proportion was calculated relative to the whole bird.

Egg production
The hens were reared in sex-mixed groups (as described above) and evaluated for egg production at 20 weeks of age based on onset of lay.The treatment groups were combined based on their feeding regimen during the rearing period.Group 1 included 41 hens (previously in treatment 1) raised with pullet developer and 6 cockerels for breeding.Group 2 included 35 hens and six cockerels (previously in treatment 2) raised with feed formulated for male layer types.
Both groups were housed in conventional floor systems, each with a pen size of 17.6 m 2 (4.0 × 4.4 m).Each pen had one window (1.55 m 2 ) to provide daylight and the barn was equipped with a manual ventilation system.The light programme consisted of 16 h of light and 8 h of dark.Additionally, each group had daily access to an outdoor pasture (108 m 2 ).The stocking densities were 2.33 and 1.98 birds/m 2 for groups 1 and 2, respectively.Each pen was equipped with round feed dispensers and nipple drinkers, perches, laying nests, a dust bath, an alfalfa bale and a pecking stone.The floor was littered with wood shavings and re-littered as needed.The birds were fed ad libitum on a commercial laying diet (all-mash LH; Deutsche Tiernahrung Cremer GmbH & Co KG, Düsseldorf, Germany; 17.5% crude protein, 0.42% methionine, 0.84% lysine and 11.6 MJ ME/kg) and vaccinated every three months against Newcastle disease and infectious bronchitis.
During the study, egg production was monitored over one laying period from 20 to 72 weeks of age at both group and individual bird levels.Individual trap nests were used to confine hens while allowing nest entry until the birds were manually released, allowing for monitoring of egg laying.Nests were checked every 30 min for 5 days a week between 07:00 and 15:30.If a hen was trapped in a nest, an egg check was completed, the bird was identified by wing band, any egg was assigned to that bird and the weight of the egg was recorded.Weekend egg production was recorded at the pen level, with the trap mechanism blocked to allow hens to leave the nest.In total, 54.8% of eggs were assigned to individual hens while the remaining unassignable eggs were distributed evenly among all hens and added to individual egg numbers.Laying maturity was determined when hens reached 50% laying performance.Egg sizes were categorised as S (<53 g), M (53-62 g), L (63-73 g) and XL (>73 g) according to the European marketing standards (EC 589/2008(EC 589/ 2008)).Persistence of lay was calculated in three subperiods across the laying period following Garces et al. (2001), 20-29, 30-50 and 51-72 weeks of age.Egg production variables were calculated using the following formulas:

Statistical analysis
The collected data were analysed using SPSS Statistics 28 (IBM Corporation, Armonk, NY, U.S.A.).Pen-based mean values and standard errors (SE) were reported, with significance attained at P ≤ 0.05.The Levene test was used to check for variance homogeneity before an unpaired t-test for independent groups was conducted to compare the means of the feeding regimes during the growth period based on pen means and pooled SE.Correlations between growth and laying variables and the performance of male and female offspring were calculated with individual bird data using the Shapiro-Wilk test to first determine normal distribution and either Pearson or Spearman-Rho correlation coefficients for normally distributed and non-normally distributed data, respectively.The correlation coefficients |R| = 0.10, |R| = 0.30 and |R| = 0.50 were considered low, medium and high correlations, respectively, according to Cohen (1988).Graphical representation of the results was completed using Sigma Plot 14.0 (Systat Software Inc., Chicago, IL, U.S.A.).

Growth performance of cockerels
The individual growth performance of cockerels was recorded weekly until the twelfth week of age, with separate results reported until weeks 10 and 12.The tenth week of age (70 d) is a comparable slaughter time for other dual-purpose breeds and slow-growing broilers, whereas the twelfth week of age is relevant to European organic production.The cockerels were slaughtered at 12 weeks of age.
Table 1 shows the final weights at weeks 10 and 12, along with the corresponding daily weight gains, FCR, EPEF, mortality and uniformity.The two feeding regimes differed significantly from each other with respect to final weights and daily weight gains (T(88) = −2.846,P = 0.003).Cockerels raised on a pullet diet were, on average, 178.64 g lighter at week 12 than those raised on feed for male layer types, with a lower weight gain of 2.1 g per day.Compared with treatment 1, treatment 2 resulted in a lower FCR and mortality rate and a higher EPEF.Treatment 2 had a higher uniformity at week 10.However, after the diet changed to the finisher, the uniformity of treatment 2 decreased, whereas that of treatment 1 increased until week 12.
The uniformity of the cockerels was 46%-55%, indicating that approximately half of the birds had body weights of ±10% of the mean.After the switch to the finisher diet in weeks 11 and 12, treatment 1 and treatment 2 led to an increase and decrease in uniformity, respectively.Figure 2 shows the weight development of each individual cockerel throughout the growth period, with the grey area indicating birds that were either 10% above or below the mean value of their respective group.The figure highlights the varying weight gains of the birds between the analysed time points, with birds displaying strong weight gain from the sixth week of age.Furthermore, the figure shows a wide range of weights among individual birds, with treatment 2 exhibiting a large range of variation.Notably, individual outliers were observed above and below the mean.
The dressing percentage of the carcases was similar between treatments.Proportion of the carcases (breast, legs, wings) within the different treatments are shown in Table 2.

Correlation of growth performance variables
Correlations were calculated between the individual birdspecific data for growth variables and the proportions of valuable parts in the carcases.The results showed no significant correlation between daily weight gain and the proportions of individual carcase parts.However, a significant negative correlation was found between the proportion of breast and leg (Table 3).

Egg production
The egg production of hens was recorded at both the individual and group level separated by treatment 1 and treatment 2 depending on the feeding regimen used during the rearing period.The first egg was found in both groups on week 20.Table 4 provides an overview of the egg production variables of Ixworth hens.
The egg production of both groups increased rapidly at the beginning of the laying period, with group 1 reaching its peak in week 27 of age (70.03%) and group 2 in week 30 of age (80.00%).A further peak was observed in week 33 of age (75.10%; Figure 3).Laying maturity (50%) was reached in weeks 24 and 25 for group 1 and 2, respectively.Another increase in egg production was observed in week 39 and 44 for group 2 and 1, respectively.From week 51 of age, egg production started to decline and reached 50% from week 54 onwards.
The proportion of S eggs predominated at the beginning of the laying period, but from week 33 of age, most of the eggs were M eggs.Toward the end of the laying period, the proportion of L eggs increased, and some individual birds laid XL eggs.Despite the increase in egg production, the body weight of hens continued to increase throughout the laying period, and the two groups were very similar in terms of egg production or body weight.Two hens, one from each group, were observed to be broody, but as eggs were collected daily, brooding stopped after 1-2 weeks.In group 1, 2 of 41 hens died over the entire laying period, whereas no birds died or had to be culled in group 2. The reasons for deaths remained unclear, as no feather pecking, cannibalism or predator attacks occurred, despite the hens having daily access to the outdoor area.Most of the variables in this study were recorded on an individual bird basis, allowing for conclusions to be drawn about the performance of each hen. Figure 4 shows the individual performance of the hens, revealing marked differences among individuals regarding the total number  12.2 ± .47 12.5 ± 0.17 Carcase (%) 3.4 ± .2629.7 ± 0.34 of eggs laid and the average egg weight in both groups.
The hens showed a high degree of weight heterogeneity (1,910-3,768 g), which was considered in subsequent correlations.
During the study, additional observations were made regarding the behaviour and health of the birds, which can only be reported descriptively.Some individual birds began moulting before the end of the laying period.Additionally, two hens (2.6%) exhibited broody behaviour, during which they stopped laying and lost weight before resuming laying again.Overall, low mortality levels and no instances of disease were observed during the laying period.

Correlation of egg production variables
Based on individual data, correlations between each egg production variable and individual body weights were calculated.The correlation coefficients are presented in Table 5, with significant correlations highlighted.
There were no significant correlations between the total number of eggs, egg weight or age at the onset of laying.However, nest acceptance showed a high positive correlation with the total number of eggs and a moderate positive correlation with egg weight.Correlations between body weight at different ages and production traits revealed that heavier hens laid heavier eggs, with moderate positive correlations between  average egg weight and body weight at weeks 10, 20, 46 and 72.Additionally, hens with higher body weights in weeks 10 and 20 showed a moderate negative correlation with the onset of laying, meaning that heavier hens laid earlier.Furthermore, there was a moderate correlation between body weight at week 46 (mid-term laying period) and the total number of eggs laid per hen, which indicated that heavier hens laid more eggs during the first laying period.Body weight was not correlated with nest acceptance.Finally, heavier hens at 10 weeks of life tended to weight more later in their lifetimes.

Kinship analysis of growth performance and egg production
As all chicks were assigned to their mother hens at hatch, family profiles could be established at least on a half-sibling basis to analyse the correlation between the (laying) performance of single hens' daughters and the (growth) performance of the hens' sons, which is an important correlation for dual-purpose chickens.Although no statistically significant correlation was found (N = 31, r = 0.169, P = 0.363), Figure 5 shows a positive regression, which indicated that hens with daughters exhibiting higher egg production tended to produce sons that grew faster.

Discussion
The Ixworth chicken exhibited final weights comparable to those of other dual-purpose breeds at 12 weeks of age.Cockerels fed a male layer hybrid diet had significantly higher final weights (2345 g) compared with those fed a pullet developer diet (2166 g).In comparison to this data,   However, when compared with young cockerels from laying lines such as Lohmann Brown (Tiemann et al. 2020) and Lohmann Sandy (Baldinger and Bussemas 2021), Ixworth growth performance was increased.Excluding fast-growing broilers and dual-purpose hybrids, the Ixworth outperformed male layer types and other local breeds in terms of growth performance.For an overview and comparison of the Ixworth data and the existing literature, see supplemental material (Table S2).
Feeding is crucial for determining suitability as a dualpurpose breed, as shown in the current study, particularly in terms of growth performance.In this study, commercial diets were used, and the cockerels achieved significantly higher final weights when fed the diet for male layer hybrids compared with pullet developer.Other studies have mostly used broiler diets (Baldinger and Bussemas 2021;Tiemann et al. 2020), but some studies have used a pullet developer (Freick et al. 2022).Dual-purpose breeds typically have higher FCRs than fast-growing broilers, with dual-purpose chickens consuming 1.5 times more feed per kg body weight than conventional broilers (Leenstra et al. (2010).Although fast-growing broilers, like Ross 308, show FCRs of 1.33-1.43(Adler et al. 2020), the FCR of the Ixworth is nearly twice as high, depending on the duration of the growing and finishing period at 2.31-2.63.
Mortality is a performance variable and welfare indicator.Ixworth chickens had low mortality rates in the range of 1.2-2.4%,which was similar to other studies on purebreds (Freick et al. 2022;Nolte et al. 2020).In contrast, other studies on dual-purpose hybrids and purebred breeds reported higher mortality rates of up to 8.8% (Rhinelander; Tiemann et al. 2020) and 11.9% (Bresse Gauloises; Baldinger and Bussemas 2021), which showed that some breeds are not well adapted to commercial settings with larger group sizes, which are typical in birds kept by hobby breeders.However, in this context, the Ixworth appears to be well adapted.In addition to mortality, other animal welfare variables need to be assessed to determine the breed's suitability for practical use.
In addition to weight gain, dual-purpose chickens differ in carcass composition from fast-growing broilers.Almasi et al. (2012) observed that dual-purpose chickens have a higher leg yield than broilers, whereas the latter show a higher breast yield relative to their body weight.Ixworth birds show a higher leg yield than breast yield, with a leg proportion ranging from 31.6-31.8%.This is comparable to the Bresse Gauloises (33%; Nolte et al. 2020) but lower than the Belgian Malines (Mueller et al. 2018).However, the Ixworth has higher breast yield compared to the Vorwerk chicken (11.0%),Bresse Gauloises (13.3%;Nolte et al. 2020) and Belgian Malines (16.5%;Mueller et al. 2018), with a breast yield range of 16.9-17.5%.Owing to differences in carcass composition, the meat from dual-purpose chickens may be more suitable for local marketing and premium products, which would better cover the higher production costs (Damme et al. 2015).The significant negative correlation between breast and leg proportion is interesting from a physiological perspective, especially regarding the growth of breast muscles.
In addition to growth performance, egg production is crucial in assessing breed suitability as a dual-purpose bird.The Ixworth lays an average of 194 eggs in the first laying period, which is 60% of the laying performance of the layer hybrid Lohmann Brown (321 eggs in the first laying period; Lohmann Tierzucht GmbH 2022).Although these results were low relative to those of another study, in which hens were observed from 31 to 55 weeks (Hocking et al. 2003), their egg production was comparable to that of other purebred dual-purpose breeds, such as Bresse Gauloises (54%; Lambertz et al. 2018).Despite not being selected for high egg production (Albentosa et al. 2003), Ixworth achieved unexpectedly impressive laying results comparable to the Bresse Gauloises, which is bred for food production in France.Onset of laying occurs in Ixworth at 20 weeks of age, although laying maturity is not reached until week 24 or 25.In contrast, Bresse Gauloises start laying at 18 weeks of age and reach laying maturity at 22 weeks (Lambertz et al. 2018).Persistence in egg production should be improved to ensure long-term consistency in performance.
Dual-purpose chickens could potentially compensate for lower egg production with longer production lifetime (Lambertz et al. 2018), although this should investigated further in the future.The unsteady egg production curve of the Ixworth might be smoother if more birds were tested, although a breakdown clearly occurred in both treatments before 60 weeks of age.The reason for this was unclear, and is important, especially in terms of dual-purpose genetics, to identify patterns and causes.Egg size distribution in the Ixworth followed a pattern similar to that in other dualpurpose breeds (Nolte et al. 2020;Rizzi 2020), with the majority of eggs in the M category, despite most eggs being in the S category at the start of laying, and only a small percentage (<20%) of larger eggs found towards the end of the production period.
High nest acceptance (>97%) of Ixworth chickens makes their eggs very marketable (>99%), which was comparable to brown layer parental stocks (Farkas et al. 2022).Given that heritability for the choice of egg laying location has been observed in other genetics studies (Sørensen et al. 2017), breeders need to focus on this trait for dual-purpose chickens in general.Compared with hybrid layer types, dual-purpose hens have a higher body weight (2050 g at the end of the laying period; Lohmann Tierzucht GmbH 2022), making them well-suited for use as stewing hens and offering economic benefits at the end of their lifespan.Local breeds cannot compete with commercial laying hybrids, as they were not bred for high egg production and are often rather presented at exhibitions and 'fancier' shows (Nolte et al. 2020).However, the Ixworth breed is competitive with other dual-purpose lines, and is therefore suitable for niche production.
The current egg production results were largely inconsistent with those of Hocking et al. (2003), who extrapolated their data from 31 to 55 weeks of age to a full laying period of 72 weeks, whereas we observed hens for the full period and found a low persistence compared with that of commercial hybrids.Owing to the limited availability of the breed, small sample size and experimental setup, these results may not be practically transferable, and further investigation of how the Ixworth performs under practical and commercial conditions is necessary.
Using individual animal-specific data from this study, correlations were established between a hen's weight and her egg production.The findings showed that body weight was positively correlated with egg production variables in Ixworth hens, which is consistent with results reported by Oke et al. (2004).Heavier hens tend to lay bigger eggs, and there was a weak correlation between the total number of eggs laid and the body weight in the middle of the laying period.Furthermore, the onset of lay was correlated with body weight during rearing, as those that were heavier at 10 weeks of age started laying earlier compared with lighter hens.
In poultry, a negative genetic correlation between reproductive variables and body weight (Barbato 1999) has led to highly specialised lines in the modern industry that excel in either egg production or growth performance (Gangnat et al. 2018).However, dual-purpose chickens have been developed to serve both purposes.Family profile analysis of the Ixworth breed showed no negative correlation between growth performance and egg production, contrary to other studies (Krautwald-Junghanns et al. 2018).Instead, there was a trend indicating that hens with heavier sons produced daughters that laid more eggs, although this was not confirmed statistically.These findings challenge the assumed negative genetic correlation of growth performance and egg production and suggest that the Ixworth is a suitable breed for dual-purpose and selective breeding on both traits.
The Ixworth, like many other purebred dual-purpose breeds, is currently classified as 'critical' (Wilkinson et al. 2012).Purebreds play an important role in conserving biodiversity in poultry farming (Weigend et al. 2014).Integrating dual-purpose breeds into niche production systems can help preserve animal genetic resources and identify breeds that may be more adaptable to future environmental challenges.
Both breed adaptation and individual animal characteristics play important roles in poultry.Collecting animalspecific data is crucial for identifying birds that are best suited to their environment and promoting animal welfare.For example, breeding can affect feather pecking in chickens (Kjaer et al. 2001).To further develop chicken breeding practices and understand the birds' needs, individual observation and data collection are essential.This approach offers insights into how each bird adapts and performs in comparison to the flock average.Beyond measuring performance, recording individual bird data and integrating them into precision poultry farming systems could lead to significant progress in breeding.
In summary, this study demonstrated that the Ixworth is a competitive dual-purpose breed, although its performance falls below that of specialised hybrids or dual-purpose hybrids, such as Lohmann Dual.However, compared with other purebred dual-purpose breeds, the Ixworth exhibits a comparable or superior level of performance.Their growth performance is already promising, but further improvements in egg production could be achieved through breeding management.Collecting animal-specific data provides numerous benefits in the fields of breeding, animal welfare and the recognition of the value of individual animals.
eggs before the project started.Furthermore, the authors would like to thank Dr. Torsten König for his valuable input to the whole project as well as his support in analysing and interpreting the data.

Figure 1 .
Figure 1.Typical appearance of a mature Ixworth hen and rooster at 46 weeks of age.

Figure 2 .
Figure 2. Individual growth development of cockerels at different timepoints during rearing.Body weights in g at hatch in week 2, 4, 6, 8, 10 and 12 are shown in relation to the respective IDs of birds in treatment 1 (pullet developer) and treatment 2 (male layer diet).Grey-shaded area shows the range of uniformity (mean ±10%).

Figure 3 .
Figure 3. Laying performance development of hens from 20-72 weeks of age in treatment groups receiving different feeding regimes during rearing.Hens of group 1 received a commercial pullet developer during rearing, while hens of group 2 received a commercial diet developed for raising cockerels of layer lines for the first 10 weeks, afterwards received a commercial pullet developer as well.

Figure 4 .
Figure 4. Laying performance of individual Ixworth hens, with the corresponding hen ID shown, in treatment groups 1 (top; receiving a commercial pullet developer during rearing) and 2 (bottom; receiving a commercial diet for males of layer lines).Total number of eggs and average egg weight (g) are shown.Eggs that could not be assigned to a specific hen were divided equally among all hens.
Sandercock et al. (2009) andGordon (2002) reported lower live weights of roosters (1674 g at d 70 and 1910 g at d 81, respectively), although weight gains were dependent on feeding.Fast-growing broilers, such as Ross 308, reach final weights of 2196 and 2396 g with daily weight gains of almost 100 g in 34 and 36 d, respectively (Aviagen 2022), whereas Ixworth chickens require 84 days to reach comparable weights and exhibit daily weight gains of 25-27 g.When compared with other dual-purpose local breeds from Germany or Switzerland, the Ixworth achieved higher final weights than the Saxonian chicken(Freick et al. 2022), Vorwerkhuhn(Nolte et al. 2020), Rhinelander(Tiemann et al. 2020) and Schweizerhuhn(Mueller et al. 2018), all with corresponding durations of fattening periods.The Ixworth had a similar final weight as the French breed Bresse Gauloises, and only Belgian Malines, a local meattype breed, attained a comparatively higher body weight.The commercial dual-purpose hybrid Lohmann Dual showed significantly higher growth performance than purebred dualpurpose breeds, including the Ixworth(Tiemann et al. 2020).

Figure 5 .
Figure 5. Kinship analysis of the performance of male and female offspring of individual mother hens.For each mother hen, the average final weight of her male offspring was correlated with the average total number of eggs laid by her female offspring.

Table 1 .
Means ± SE of Ixworth cockerel body weight (BW), daily weight gain (DWG), feed conversion ratio (FCR) and European production efficiency factor (EPEF) when raised on different feeding regimes from 10-12 weeks old.
1 Different superscript letters within a row indicate significantly different mean values (p < 0.05).

Table 2 .
Dressing percentage and meat production traits (proportion of breast, legs and wings) of Ixworth cockerels raised on different feeding regimes.Means ± SE are given.

Table 3 .
Coefficients of correlations among growth performance [daily weight gain (DWG)] and meat production traits (proportion of breast, legs and wings).

Table 4 .
Laying performance (LP) of Ixworth hens during the first laying period (20-72 weeks of age), including egg size categories based on European marketing standards and body weight (BW) at different ages.
1 Data are means (±SEM) at the flock level for both treatment groups.

Table 5 .
Coefficients of correlations among egg production traits and body weight (BW) at different ages (10, 20, 46 and 72 weeks old).