Slaughter Age Research Articles

Discontinuous Economic Growing Quantity Inventory Model

The classical economic growing quantity (EGQ) model is a key concept in the inventory control problems research literature. The EGQ model is commonly employed for the purpose of inventory control in the management of growing items, such as fish and farm animals, within industries such as livestock, seafood, and aviculture. The economic order quantity (EOQ) model assumes that customer demand is satisfied without interruption in each cycle; however, this assumption is not always true for some companies as they do not have continuous operations, except for item storage, during non-working times such as weekends, natural idle periods, or spare time. In this study, we extend the traditional EGQ model by incorporating the concept of working and non-working periods, resulting in the development of a new model called discontinuous economic growing quantity (DEGQ). Unlike the conventional EGQ model, the DEGQ model considers the presence of intermittent operational periods, in which the firm is actively engaged in its activities, and non-working periods, during which only storage-related operations occur. By incorporating this discontinuity, the DEGQ model provides a more accurate representation of real-world scenarios where businesses operate in a non-continuous manner, thus enhancing the effectiveness of inventory control and management strategies. The study aims to obtain the optimal number of periods in each cycle and the optimal slaughter age for the breeding items, and, subsequently, to find the optimal order size to minimize the total cost. Finally, we propose an optimal analytical procedure to determine the optimal solutions. This procedure entails finding the optimal number of periods using a closed-form equation and determining the optimal slaughter age by exhaustively searching the entire range of possible growth times.

Comparison of Nonlinear Growth Models to Estimate Growth Curves in Kivircik Sheep under a Semi-Intensive Production System.

The Kivircik is an indigenous sheep breed from Turkey, and it has superior meat quality compared to other indigenous breeds. Therefore, farmers prioritize Kivircik lamb fattening instead of milk production. Here, we aimed to determine the best nonlinear growth model, i.e., Gompertz, Logistic, Von Bertalanffy, and Brody, to describe the growth curve of Kivircik lambs. The body weight data from birth until 150 days of age belonging to 612 lambs were used as the material of this study. The best fitting model was selected by considering the adjusted coefficient of determination (R2adj), residual mean square, and Akaike's (AIC) and Bayesian information criteria (BIC). Even though the Brody model had a better statistical fit, considering its biological interpretation, the Gompertz model was identified as an appropriate model for describing Kivircik lamb growth. Male lambs, twin lambs, and lambs born in winter had higher mature live weights (44.2 kg, 71.2 kg, and 38.5 kg, respectively) and rate of weight gain (2.1, 2.6, and 2.0, respectively). However, our subgroups revealed a similar rate of maturity (0.01). Growth models are important tools for deciding the optimal slaughter age and they provide valuable information on the management practices of both sexes, birth types, and birth seasons. These results can be applied to breeding programs for early selection, enabling intervention strategies when needed.

Effect of age and sexual condition on the fatty acid profile of intramuscular fat of cattle finished in feedlot

The objective of this study was to evaluate the fatty acid (FA) profile of intramuscular fat of cattle of two categories (16 or 26 months old) and two sexual conditions (Bulls or Steers) finished in feedlot. A total of 32 castrated (n=16) or noncastrated (n=16) animals of the genetic groups ½Purunã + ½Canchim were used. The animals were finished in feedlot, receiving a diet with 50% roughage and 50% concentrated feed. After the slaughter, one Longissimus dorsi sample from each animal was sent to the laboratory for FA profile analyses. The FA content of C17:0 iso and C18:0 was higher for animals slaughtered at 26 months. Lignoceric acid (C24:0) showed a higher content for animals aged 16 months. Animals slaughtered at 16 months showed higher C18:1 cis 11, C18:1 cis 12, C18:1 cis 15, and lower C18:1 trans 16 than those slaughtered at 26 months. The C20:4 and C22:5 were lower as the animals' slaughter age increased. The unsaturated/saturated and polyunsaturated/saturated ratios showed no difference for slaughter age. The concentrations of C24:0, C18:1 trans 10, C18:1 cis 11, C18:1 cis 12, and C22:1 were greater in the meat of bulls than in steers. Bulls had a higher content of polyunsaturated FAs and polyunsaturated/saturated ratio than steers.

Impact of innovative rearing strategies for the Italian heavy pigs: Technological traits and chemical composition of dry–cured hams

To explore the influence of 4 feeding strategies on dry-cured ham quality, 336 barrows and gilts (3 batches, 112 pigs/batch) of 90 kg body weight (BW), were divided into 4 groups and housed in 8 pens with automated feeders. In the control group (C), the pigs were fed restrictively medium-protein feeds and slaughtered at 170 kg BW (SW) and 265 d of slaughter age (SA). With the older age (OA) treatment, the pigs were restrictively fed low protein feeds and slaughtered at 170 kg SW and 278 d SA. The other two groups were fed ad libitum high protein feeds, the younger age (YA) group was slaughtered at 170 kg SW and 237 d SA, the greater weight (GW) at 265 d of SA and 194 kg SW. The hams were dry-cured and seasoned for 607 d, weighed before and after seasoning and deboning. Sixty hams were sampled and sliced. The lean and the fat tissues were separated and analyzed for proximate composition and fatty acid profile. The model of analysis considered sex and treatment as fixed factors. With respect to C: i) OA lowered the ham weight, the lean protein content, increased marbling and decreased the PUFA proportion in intramuscular and subcutaneous fat; ii) YA hams had thicker fat cover with lower PUFA in intramuscular and subcutaneous fat; iii) GW increased the deboned ham weight, fat cover depth and marbling, reduced PUFA in intramuscular and subcutaneous fat, without alteration of the lean moisture content. Sex had a negligible impact.

Investigation of the Effect of Three Commercial Water Acidifiers on the Performance, Gut Health, and Campylobacter jejuni Colonization in Experimentally Challenged Broiler Chicks.

This study investigated the effect of three commercial water acidifiers on the performance, gut health, and C. jejuni colonization in experimentally challenged broiler chicks. A total of 192 one-day-old broiler chicks (Ross 308®) were randomly allocated into 6 treatment groups with 4 replicates according to the following experimental design: group A, birds were not challenged and received tap water; group B, birds were challenged and received tap water; groups C, D, E, and F, birds were challenged and received tap water treated with 0.1% v/v SPECTRON®, with 0.1-0.2% v/v ProPhorce™ SA Exclusive, with 0.1-0.2% v/v Premium acid, and with 0.1-0.2% v/v Salgard® Liquid, respectively. The continuous water acidification evoked undesirable effects on broilers' performance and to an increased number of birds with ulcers and erosions in the oral cavity and the upper esophageal area. ProPhorce™ SA Exclusive and Premium acid significantly reduced the C. jejuni counts in the crop, whereas Salgard® Liquid significantly reduced the C. jejuni counts in the ceca of birds. At slaughter age, only Premium acid significantly reduced C. jejuni counts in the ceca of birds. All the tested products ameliorated the changes induced by C. jejuni infection in the pH in the ceca of birds. It can be concluded that besides the effectiveness of the tested products in controlling C. jejuni in broilers, their continuous application evoked undesirable effects on broilers' performance, leading to the need to modify the dosage scheme in future investigations.

Carcass characteristics and meat quality of Holstein bulls depending on slaughter age and muscle types

Carcass characteristics and meat quality of Holstein bulls depending on slaughter age and muscle types

Economic Growing Quantity Model with Mortality in Newborn Items and Inhibition Cost of Ammonia Production under All-Units Discount Policy

The amount of global ammonia (NH3) emissions is growing continuously, similar to the damage to the environment, particularly humans and animals, caused by those emissions. Various problems derived from pollution by ammonia emissions have attracted increasing attention in recent years. In particular, accumulation of ammonia in poultry farms is a concern for the poultry industry as it can lead to possible damage due to reduced bird performance, damage to the respiratory tract and skin of birds, and thus loss of customers. As birds age, ammonia production increases due to factors such as feeding and mobility, requiring the application of solutions to reduce it such as the use of fans, feed supplements, and temperature adjustments to improve bird health. These solutions impose additional costs on poultry farms to combat ammonia emissions. This study presents a general economic growing quantity (EGQ) model that includes the cost of inhibition of ammonia production during the growing period. In addition, the model is formulated under an all-units discount policy, where the price of newborn items is related to the size of the order purchased from the supplier. Furthermore, the model assumed that some newborn items are dead when the lot is received because of stress experiences and incidents during the catching, loading, transportation, and unloading. Finally, two versions of the proposed general EGQ model are presented: EGQ with no discount and EGQ with known slaughter age.

The Effect of Rearing System on Plumage Quality and Foot-Pad Dermatitis in Guinea Fowls and Pheasants

This study aims to determine welfare parameters such as foot-pad dermatitis (FPD) and plumage quality (PQ) scores at different slaughter ages in barn and free-range rearing systems for guinea fowl and pheasants. The birds randomly distributed with half of 200 Pheasant and 200 guinea fowl chicks were reared in both indoor and free-range systems. Game birds were examined for both FPD score and feather score (PQ) at 6, 12, 14, 16 and 18 weeks of age. The litter moisture content was also measured at 14, 16 and 18 weeks of the growing period. In guinea fowls, litter moisture content differed significantly according to the rearing system (P0.05). In terms of FPD, there was no difference in guinea fowl according to the rearing system, gender and slaughter age, but there was a difference in pheasants according to the slaughter age. In guinea fowl, the head PART feather quality was lower than the barn system (P

Effect of slaughter age and postmortem aging time on tenderness and water-holding capacity of yak (Bos grunniens) longissimus thoracis muscle

The present study investigated the effect of slaughter age (2.43 ± 0.20, 4.15 ± 0.19, 6.62 ± 0.18, 10.59 ± 0.74 years) and postmortem aging time (1, 24, and 72 h) on the tenderness and water-holding capacity (WHC) of yak longissimus thoracis muscles to determine the most suitable age for slaughter to ensure product consistency. Under conventional postmortem aging conditions (4 °C), muscles of each age group exhibited the effect of cold shortening. Once the cold shortening occurred, the age effect on thickening muscle fiber and developing cross-links of collagen, considered to intensify the meat toughness, became less important. Owing to greater carcass weight and intramuscular fat, muscles of the older carcass (over 6-year-old) were less influenced by the cold shortening effect during the chilling process and showed lessened sarcomere contraction, delayed formation of drip loss channels, and increased level of myofibril fragmentation index (MFI) and myofiber structural disintegration, resulting in greater tenderness and WHC, especially 6–7 years group. Aging of 72 h structurally disintegrated the collagen cross-linking and integrity of muscle fibers and elevated the MFI, improving the meat tenderness. Therefore, the suitable slaughter age for yak is 6–7 years old and after 72 h aging, improved quality of yak meat can be obtained.

Modeling growth curves to estimate the suitable slaughter age for the Vietnamese Tap Na pig

Tap Na is an indigenous pig breed which plays an essential role in livestock development in the mountainous Cao Bang province, Vietnam. This study aimed to find the best model to describe the growth of Tap Na pigs, and then predict the live weight, weight gain, and suitable slaughter age by using the best growth model. The body weights of 100 pigs (50 castrated males and 50 females) were measured every month from birth to 10 months of age. The data for growth performance were analyzed in R using eight mathematical functions (von Bertalanffy, Bridges, Janoschek, Gompertz, Logistic, Lopez, Richards, and Weibull). The best models to describe the growth of Tap Na castrated males and females were Gompertz and Richards, respectively. The upper asymptotic body weights (α) were estimated to be 96.00 kg (Logistic) to 192.66 kg (von Bertalanffy) for castrated males, whereas these α values for females were from 102.42 kg (Logistic) to 167.82 kg (von Bertalanffy). The predicted ages at the beginning of the growth acceleration phase were different between castrated males (2.25 to 2.85 months) and females (2.29 to 3.39 months). Consequently, the inflection points and estimated ages at the end of the growth deceleration phase were also different between castrated males and females. The maximum absolute growth rate (monthly gains) occurred at 6 months of age for castrated males and 7 months for females. The maximum average monthly gains were recorded at 8.84 and 10.60 months of age for castrated males and females, respectively. This suggested the suitable slaughter ages are 8.84 months for Tap Na castrated males (82.99 kg) and 10.60 months for females (95.25 kg).

Protected sodium butyrate in chicken diets until 21 days of age improves intestinal development and performance

This study was developed to examine the performance, carcass and cut yields, nutrient digestibility, and intestinal histomorphometry of chickens fed diets supplemented with protected sodium butyrate until 21 days of age. Two experiments were conducted, both of which involved the following treatments: basal diet with inclusion of an antibiotic; basal diet without antibiotic or protected sodium butyrate (PSB; control); basal diet with inclusion of 225 g/t PSB in the pre-starter and starter phases; and basal diet with inclusion of 300 g/t PSB in the pre-starter and starter phases. In the first experiment, 784 male broiler chicks were distributed into the four treatments, with seven replicates of 28 birds, to evaluate performance and carcass and cut yields. In experiment II, 280 male broiler chicks were distributed into the four treatments, with seven replicates of 10 birds, to evaluate intestinal digestibility and histomorphometry. At 42 days of age, the broilers supplemented with 225 g/t PSB had a higher average final weight than the control group. At seven days, the chickens supplemented with 300 g/t PSB exhibited the highest duodenal villus height; those supplemented with 225 or 300g/t PSB or antibiotic showed the greatest jejunal villus height; and those treated with 225 g/t PSB exhibited the highest jejunal villus/crypt ratio. At 21 days of age, the broilers that received 225 g/t PSB showed the highest duodenal and jejunal villus height. The use of protected sodium butyrate in chicken diets up to 21 days of age improves intestinal development and performance until slaughter age.

Effects of bee pollen inclusion on performance and carcass characteristics of broiler chickens

This study was conducted to determine the effect of bee pollen (BP) inclusion on performance and carcass characteristics in broiler chickens. A total of 240 Ross 308 broiler chicks were allocated to 4 treatments (BP inclusion levels of 0, 4, 8, or 12 g/kg DM feed) in a randomized complete block design with sex as a block having 3 replicates with 10 chickens per replicate. After 21 d, the chickens remained in their treatment groups and fed standard grower diet. The results of the current study revealed that BP inclusion had positively improved (P < 0.05) average weekly feed intake (FI), body weight (BW), body weight gain (BWG), and feed conversion ratio (FCR) in both sexes. However, the apparent nutrient digestibility, metabolizable energy (ME), and nutrient digestibility were not affected by the dietary BP. Furthermore, carcass yield in both sexes was improved (P < 0.05) by BP inclusion levels. In contrast, meat pH, shear force, and sensory evaluation in both sexes were not affected (P > 0.05). The results suggest that the broiler chicks can utilize bioactive compounds in BP when supplemented in the starter diets and subsequently improve their growth parameters throughout the growing period as well as carcass yield at slaughter age. These positive improvements could be due to high quality amino acids, essential oils, vitamins, and minerals of BP. Therefore, it is concluded that BP inclusion level of 12 g/kg or more in the starter diets could have positive effects on growth performance and carcass yield at slaughter age without causing adverse effects on meat physico-chemical properties and sensory evaluation in both male and female broiler chickens.

The incidence and associated risk factors affecting myopathies in broiler chickens in Lithuania.

The objectives of this research were to highlight the main factors, which have relevant significance for etiology of myopathies and to assess the incidence of myopathies in a representative population of broilers raised in Lithuania. Eighteen flocks were evaluated to assess the incidence of musculus pectoralis major myopathies (PMM) (total 54,000 broilers) and dorsal cranial myopathy (DCM) (total 124,200 broilers). Thirteen flocks (total 19,500 broilers) were evaluated to find out deep pectoral myopathy (DPM) occurrence in Lithuania. Investigated parameters of each flock were: average broiler live body weight (BW) at slaughter, average slaughter age, treatment and seasons. A correlation analysis was used to measure the strength of the linear relationship between the investigated traits and incidence of these myopathies. Overall, the incidence of PMM in Lithuania was 18.19%. DCM and DPM were 5.16% and 0.27%, respectively. The percentage of PMM in flocks was strongly associated with average broiler live BW at slaughter (r=0.898, p<0.001) and age at slaughter (r=0.693, p<0.001). The percentage of PMM in flocks was negatively related with treatment of broilers (rs=-0.535, p<0.05). The percentage of DCM was positively associated with average broiler live BW at slaughter (r=0.537, p<0.05) and with seasons (rs=0.658, p<0.01). However, our study results revealed, that the analyzed parameters are not so important in DPM etiology. Furthermore, predisposing factors of PMM, DCM and DPM are different. These findings suggest that not only broiler's heavy weight and age at slaughter could have influence for etiology of myopathies.

Influence of cattle category and slaughter age on Charolais-breed carcase and meat traits

The beef consumed worldwide comes from different categories of cattle slaughtered at different ages. The aim of this work was to study the effects of the cattle category (young bulls, heifers, cull cows) and slaughter age on carcase and meat traits, using data on 721 Charolais cattle. At 24h post-mortem in slaughterhouse, 14 carcase traits were measured on each carcase. Then, 2 ribs were collected and aged 14 days. Ten measurements were performed on raw meat (longissimus or rhomboideus muscles) and ten others on longissimus cooked meat. Our results showed that young bulls produced carcases with higher conformation scores, lower fat and meat that had less juiciness, and flavour intensity compared to heifers and cull cows. The carcase traits were more sensitive to variation in the slaughter age than in meat traits. Heifers and cull cows slaughtered at an older age produced heavier carcases. Cull cows slaughtered at above 6 years of age produced carcases with darker muscle and yellower fat. Slaughter age had no effect on the sensory descriptors of cooked meat from all three cattle categories. Heifers slaughtered at earlier than 32 months or later than 36 months produced carcases and meat with similar traits, except for the carcase weight. For cull cows over 6 years old, there was no effect of age at slaughter age on carcase and meat traits. Whatever the cattle category, the slaughter age impacted weakly the traits of raw and cooked meat. Meat from heifers was the most appreciated by trained panellists. HIGHLIGHTS Cooked meat from heifers was better appreciated than cooked meat from young bulls or cull cows. In young bulls, slaughter age had no effect on any carcase and meat traits other than intermuscular fat assessed at the 6th rib. In cull cows, slaughter age affected mostly carcase traits and weakly meat traits.

Beef Nutritional Characteristics, Fat Profile and Blood Metabolic Markers from Purebred Wagyu, Crossbred Wagyu and Crossbred European Steers Raised on a Fattening Farm in Spain.

A high intramuscular fat content characterizes Wagyu (WY) cattle breed. Our objective was to compare beef from WY, WY-by-Angus, or Wangus (WN) steers with European, Angus-by-Charolais-Limousine crossbred steers (ACL), considering metabolic biomarkers pre-slaughtering and nutritional characteristics, including health-related indexes of the lipid fraction. The fattening system with olein-rich diets and no exercise restriction included 82 steers, 24 WY, 29 WN, and 29 ACL. The slaughter ages and weights were (median and interquartile range) 38.4 mo.-old (34.9-40.3 mo.) and 840 kg (785-895 kg) for WY; for WN, 30.6 mo. (26.9-36.5 mo.) and 832 kg (802-875 kg), and for ACL steers, 20.3 mo.-old (19.0-22.7 mo.) and 780 kg (715-852 kg). Blood lipid-related metabolites, except for non-esterified fatty acids (NEFA) and low-density level cholesterol (LDL), were higher in WY and WN than in ACL, while glucose was lower in WY and WN. Leptin was higher in WN than in ACL. Pre-slaughtering values of plasma HDL underscored as a possible metabolic biomarker directly related to beef quality. The amino-acid content in beef did not differ among experimental groups, except for more crude protein in ACL. Compared to ACL, WY steers showed higher intramuscular fat in sirloin (51.5 vs. 21.9%) and entrecote (59.6 vs. 27.6%), more unsaturated fatty acids in entrecote (55.8 vs. 53.0%), and more oleic acid in sirloin (46 vs. 41.3%) and entrecote (47.5 vs. 43.3%). Compared to ACL entrecote, WY and WN showed better atherogenic (0.6 and 0.55 vs. 0.69), thrombogenicity (0.82 and 0.92 vs. 1.1), and hypocholesterolemic/hypercholesterolemic index (1.9 and 2.1 vs. 1.7). Therefore, beef's nutritional characteristics depend on breed/crossbred, slaughtering age and cut, with WY and WN entrecote samples showing a healthier lipid fraction.

Economic Order Quantity for Growing Items with Mortality Function under Sustainable Green Breeding Policy

Determining the optimal slaughter age of fast-growing animals regarding the mortality rates and breeding costs plays an important and major role for companies that benefit from their meat. Additionally, the effects of carbon dioxide (CO2) emissions during the growth cycle of animals are a significant concern for governments. This study proposes an economic order quantity (EOQ) for growing items with a mortality function under a sustainable green breeding policy. It assumes that CO2 production is a practical polynomial function that depends on the age of the animals as well as the mortality function. The aim of the model is to determine the optimal slaughter age and the optimal number of newborn chicks, purchased from the supplier, to minimize the total costs. We propose an analytical approach, with five simple steps, to find the optimal solutions. Finally, we provide a numerical example and some model management insights to help practitioners in this area.

Physicochemical Properties of Black Korean Goat Meat with Various Slaughter Ages

This study was conducted to analyze the physicochemical properties of black goat meat according to the slaughter age (3, 6, 9, 12, 24, 36 months). The moisture content tended to decrease, whereas the fat content, pH, and free amino acid composition tended to increase with increasing slaughter age. The collagen content increased significantly with the increasing slaughter age (p < 0.05). The cooking yield showed a tendency to increase up to 12 months of age, and there was no significant difference after 12 months of age. In all mineral contents, the sample for 12 months of age showed higher values than the others. Considering fatty acid composition, the saturated fatty acid content of the 12-month sample had a lower value than the other samples. However, the unsaturated fatty acid of the 12-month sample had higher values than the other samples. Therefore, the best slaughter age for black goats occurs at 12 months of age when nutrition is excellent.

Effects of Black Cumin Seed (Nigella sativa) and Coconut Meals (Cocos nucifera) on Broiler Performance and Cecal Microbiota.

The objective of this study was to investigate the effect of dietary supplementation with black cumin seed meal (BCSM) and coconut meal (CM) on the performance and cecal microbiota of Cobb 500 hybrid broilers. The study was conducted on 600 chicks on the first day of hatching; the chicks were randomly distributed equally into 12 equal-sized floor pens. Four dietary treatments (C, T1, T2 and T3) were replicated three times (50 chicks/replicate): C was the control group; T1 was supplemented with 10% BCSM; T2 was supplemented with 10% CM; T3 was supplemented with 5% BCSM and 5% CM. At slaughter age on day 35, our findings showed that treatment T2 increased significantly body weight and feed conversion ratio (FCR) compared to C, T1 and T3. In addition, the hot carcass dressing percentages in treatments T1, T2, and T3 were significantly higher than that of the C group. The results of relative normalized comparative gene expression of Clostridioides difficile, Roseburia and Streptococcus were not significantly changed in all treatments (p > 0.05). Treatment T1 resulted in a significant decrease in gene expression of the entire microbiota, while treatment T2 resulted in a significant increase in gene expression of all microbes, leading to an enriched and diverse microbial community. It can be concluded that supplementation with 10% BCSM is beneficial in inhibiting pathogenic microbes during early post-hatch days. In contrast, CM may promote and enhance the diversity of microbial communities during broiler growth. The inclusion of non-conventional feed ingredients in poultry diets may improve growth performance and may reduce the cost of broiler feed.

Performance and Growth Curve Prediction of Crossbred Chickens from Crossing between Local Roosters and Layer Hens

Demand for crossbred chicken (Indonesian native chicken x laying hens) continues to increase. This study aimed to find the best-crossbred chicken resulting from crossing between local/native roosters and laying hens which produce the highest body weight up to eight weeks of age, and its growth prediction using the Gompertz function. Eighteen (18) native roosters (9 Bangkok roosters, 9 Pelung roosters) and 36 laying hens of strains Isa brown, Lohman brown, and Hyline brown (12 each) were used in this study to produce 360 crossbred chickens. Factorial 2x3 (two male local roosters versus three strains of laying hens) using a completely randomized design with 3 replications was applied in this study. The results showed an interaction between native roosters and layer hens on the body weight of crossbred chickens at eight weeks of age. Crossbred chicken from crossing between Pelung rooster and Isa brown layer hen was the best in body weight at eight weeks of age. This crossbred chicken would reach a mature weight of 3026.89 g with an inflection weight of 1113.53 g and an inflection age of 7.40 weeks. In conclusion, crossbred chicken from crossing between Pelung roosters and layer hens of Isa brown strain was the best crossbred with the highest body weight at eight weeks of age. This crossbred chicken could be an alternative for fulfilling the demand for local chicken in Indonesia because the slaughter age could be shortened from 8 months to 8 weeks.

Growth Performance, Carcass Composition and Tenderness of Meat in Male Layer-type Chickens Slaughtered at Different Age

An experiment with male layer-type chickens was carried out in the Institute of Animal Science-Kostinbrod, aiming to investigate their growth performance and carcass composition, as well as the cooking loss and tenderness of the meat at the age of 5 and 9 weeks. The birds were reared in controlled microclimate, with initial stocking density of 22 birds/m2. After 5 weeks of age, fragmentation of the stocking density was applied and it was diminished to 7 birds/m2. Chickens were slaughtered at 5 and 9 weeks of age, and 10 chickens of each age group were subjected to carcass analysis. The average live weight of the birds at 5 weeks was 329 g, while the 9 weeks old chickens reached 1096 g. In order to attain the weight of the first age of slaughter (5 weeks) the chickens gained 294.03 g with a feed conversion ratio of 2.97, whereas for the whole period the feed conversion ratio was 2.91. The dressing percentage of the 5 weeks old chicks was 51.26%. For the 9 weeks old it was 77.62%. The age affected the yield of the main carcass components and the older birds had higher yield of breast (P=0.0035) and thighs (P&lt;0.0001). The cooking loss for both breast and thigh meat was higher in younger chickens (P&lt;0.0001). The tenderness measured as Warner-Bratzler shear force (WBSF) of breast and thigh remained unaffected by the age at slaughter. Its values classified the meat of the male layer-type chickens from this trial as “very tender”.