EffEct of slaughtEr agE on pErformancE and mEat quality of slow-growing broilEr chickEns* * K a t a r z y n a P o ł t o w i c z , J o a n n a D o k t o r Department of Animal Genetics and Breeding, National Research Institute of Animal Production, 32-083 Balice n. Kraków, Poland abstract the aim of the study was to determine the effect of age of slow-growing broiler chickens on growth performance and meat quality. subjects were hybrids between hubbard meat-type cockerels and yellowleg partridge polish native hens. chickens were raised indoors to 56, 70 or 84 days of age on deep litter under the same environmental conditions and fed ad litibum complete starter, grower and finisher diets containing 20, 18, 15 cp and 2825, 2825 and 2740 mE/kg feed, respectively. at the end of the experiment, 5 cockerels and 5 pullets were selected for slaughter from each age group and subjected to a simplified carcass analysis. breast muscles and leg muscles were evaluated for technological properties such as ph, colour, water holding capacity, drip loss, cooking loss and shear force. the results were analysed statistically using analysis of variance and duncan's multiple range test. the duration of rearing had an effect on carcass and meat quality. the highest, statistically significant differences in the analysed traits were found between chickens slaughtered at 56 and 84 days of age. the highest dressing percentage was obtained in birds raised until 84 days of age. youngest birds were characterized by the poorest muscle content of the carcass and the least favourable technological properties of meat. the highest growth efficiency was obtained when the hybrids were raised to 70 days of age. key words: broiler chickens, slow growing, hybrid, age, meat quality Some of the most important factors affecting the quality of poultry meat are origin and slaughter age. They mainly determine the organoleptic attributes of meat, but also have an effect on its technological properties. In the modern intensive poultry production, age at slaughter depends on whether birds attain the desired body weight, and for many years the duration of rearing has tended to decrease. This course of action is dictated by the desire to improve the economic results of rearing meat chickens, which should be slaughtered immediately after the birds reach the maximum rate of weight gain. On the other hand, the increasingly popular organic production This study was financed from funds for NRIAP statutory activity, project no. 1230.1.

No abstract

the objective of the study was to determine the effect of caponizing Greenleg partridge cockerels on slaughter parameters and meat quality. in total 80 Greenleg partridge cockerels were assigned to two groups with 40 birds per group. Group i (control) consisted of uncastrated cockerels and group ii contained birds that were castrated at 8 weeks of age. Birds were kept until 24 weeks of age and fed the same diet ad libitum. Body weight was recorded at 1, 8, 16 and 24 weeks of age. dressing percentage, proportion of breast and leg muscles, giblets and abdominal fat, and microstructure of the pectoralis superficialis muscle were determined postmortem. physicochemical characteristics of meat (pH, ciE l*a*b* colour, water holding capacity, drip loss, thawing loss, cooking loss, shear force, texture parameters and chemical composition) were determined and sensory evaluation was performed. the castration of Greenleg partridge cockerels contributed to increases in body weight, dressing percentage, and carcass muscle and fat content, and changed the colour of bird skin and muscles. the leg muscles of capons were characterized by higher pH 24h , better water holding capacity, a tendency for higher fat concentration, and better sensory quality. the breast muscles of castrated cockerels lost more water and were tougher than the same muscles from uncastrated cockerels, but received better scores for flavour. In conclusion, the results of this study indicate that the caponized Greenleg partridge cockerels can be used as a valuable material for production of high quality meat.

The aim of the study was to determine slaughter yield and meat quality of native Zatorska ( ZG ) goose and compare them to those of commercial hybrid White Koluda® goose ( WKG ) after fattening in an intensive production system. The experiment was carried out on 500 birds of each group and lasted up to 10 wk of age. The birds were kept on deep litter with access to free range and were fed with the same complete feed mixtures, according to dietary requirements for broiler geese. Body weight, carcass composition, and technological properties of breast and thigh muscles were evaluated (pH 24 , L*a*b* color, water holding capacity, thermal loss, drip loss, and shear force). In addition, chemical composition of breast and thigh muscles, fatty acid profile of muscle lipids, and amino acids of proteins were determined. The body weight, weight of eviscerated carcass, and dressing percentage of ZG were lower ( P < 0.05) than those in WKG. However, breast and thigh muscles of both groups of geese were characterized by similar technological and nutritive values. The differences in meat quality traits concerned only the shear force of breast muscles, with higher values ( P < 0.05) for WKG. Moreover, dry matter content in breast muscles of ZG was higher than that in WKG. The effect of goose genotype on the level of oleic acid and monounsaturated fatty acids in breast muscles was shown. Also, the amino acid proportion of meat protein depended on goose breed. Breast muscles of ZG were characterized by higher ( P < 0.05) content of some nonessential (Glu, Asp, Ala) and essential amino acids (Val, Thr), and thigh muscles contained less ( P < 0.05) Gly, Lys, and Leu and more Pro and Ile than WKG. The present results indicate that the meat of both ZG and WKG broilers showed good technological properties and basic chemical composition and fatty acid profile, and the protein was characterized by high nutritional value. Moreover, the smaller carcasses produced from ZG can better meet the needs of the current market.

the aim of the study was the comparison of the physicochemical and sensory characteristics of capons and cockerels. the experiment involved 80 rhode island red (r-11) cockerels, which were randomly assigned to two groups with 40 birds per group. Group i (control) consisted of uncastrated cockerels, and group ii was comprised of birds subjected to castration at 9 weeks of age. the castration was performed under local anaesthesia by a veterinary surgeon. the birds received the same diets ad libitum and were kept on litter under optimal environmental conditions, at a stocking density of 7 birds/m 2 . at the end of fattening, 8 birds whose body weights were similar to the group average were selected for slaughter from each group. after slaughter, the birds were checked for castration success (removal of the testes), analysed for dressing percentage and technological parameters of the meat and subjected to chemical and sensory evaluation of the breast and leg muscles. in summary, the castration of rhode island red cockerels (r-11) had a favourable effect on body weight, feed conversion ratio, dressing percentage and carcass muscling. the breast and leg muscles of the capons were characterised by better water holding capacity, tenderness and sensory score compared to the uncastrated cockerels. in addition, the castration had a positive effect on the content of crude protein in both the breast and leg muscles which, with a higher crude fat content, were characterised by a more favourable profile of fatty acids, i.e. lower sfa and higher n-6 and n-3 pUfa content.Key words: capon, meat quality, fatty acid, sensorial evaluation, spme-GC-ms, chemometricsAccording to the Codex Alimentarius FAO/WHO, meat quality is defined as a combination of attributes that meet specific demands and make meat desirable for food. Over the last several years there has been an increasing number of consum-*This study was financed from statutory activity, project no. 03-010.01.

In this study, a whole transcriptome analysis of breast muscles was conducted in broiler chicken groups differing in shear force. Shear force is a determinant of tenderness, which in turn is one of the most important parameters of meat quality in chickens. In our analysis, a total of 11,560 transcripts and 9824 genes per sample were identified. In chickens with more tender meat, up-regulation of 19 genes and down-regulation of 49 genes was observed. The up-regulated gene group included the ASB2 gene, which is probably involved in the meat conversion process, as its product results in the degradation of filamins, proteins which form muscle fibres. In the down-regulated gene group, genes which play a role in lipogenesis (THRSP, PLIN1) and in collagen synthesis (P4HA3, LEPREL4, PCOLCE2, COL16A1, COL20A1, VWA1) were detected. Their presence suggests the involvement of the extracellular matrix in the determination of meat tenderness. Thus, our study identified a pool of genes that may participate in the tenderisation process in broiler chickens.

The aim of the study was to determine the effect of caponizing on body weight and physicochemical properties of meat of the capons - hybrids obtained from the crossing of hens of the Yellow-Legged Partridge (Ż-33) breed with meat roosters. The study covered 80 roosters - hybrids, which were randomly assigned to two groups of 40 animals each (8 boxes of 10 pcs in each group). Group I (control) consisted of uncastrated roosters while group II included birds, which were castrated in 8th week of age under local anesthesia by a vet. Birds were fed ad libitum with the same standard diets and kept on litter under optimal environmental conditions with a stocking density of 7 animals/m2. At the end of fattening, i.e. in the 20th week of life, 8 birds with a body weight close to the group average were selected from each group for slaughter. After slaughter, the effectiveness of the procedure was checked (lack of testicles), then the slaughter performance of birds, physicochemical parameters of the pectoral and leg muscles were determined, and sensory evaluation was performed. The procedure of castration of roosters - hybrids had a positive effect on body weight, feed conversion ratio and carcass traits. The pectoral and leg muscles of the capons were characterized by better water absorption, brittleness and sensory evaluation compared to roosters. Among the assessed groups of birds there was also a variation in the coloring of whole carcasses and muscles, which were lighter (L*), more yellow (b*) and less red (a*) in caponized birds. In addition, the castration procedure had a positive effect on the total protein content in both the pectoral and leg muscles, which in turn, with a higher raw fat content, were distinguished by a favorable ratio of n-6/n-3 polyunsaturated fatty acids (PUFA). Based on the results, it can be concluded that the hybrids obtained from the crossbreeding of the Yellow-Legged Partridge (Ż-33) and Ross 308 meat roosters are good choice for capon production. They can complement poultry meat production with a niche product for consumers looking for products of exceptional quality.

This study examined the relationships among physicochemical properties and ultrasonographic image attributes of pectoralis major muscles in broiler chickens. Forty male Ross 308 chicks were randomly assigned to four equinumerous fat-supplementation groups (Group SO: soybean oil; Group FO: flax oil; Group SO + FO: soybean oil + flax oil; and Group BF: beef fat). Ultrasonograms of birds’ pectoral muscles were obtained just before slaughter at 6 weeks of age and were subjected to digital image analyses to determine the mean pixel intensity (MPI) and pixel heterogeneity values (standard deviation of numerical pixel values; MPH). A total of 2, 4, 2, and 6 significant correlations were recorded in Groups SO, FO, SO + FO, and BF, respectively; there were no correlations with the chemical composition of the muscles in Groups SO and SO + FO. The strongest correlations were found between muscle lightness (L*) and MPH in Group BF (physical characteristic; r = −0.82, p = 0.003), and between crude fat/protein content and MPI/MPH of pectoral the major muscles in Groups FO/BF (chemical characteristics; r = 0.72, p = 0.02). There exists a potential application of ultrasonographic imaging and computerized image analysis for predicting certain physicochemical properties of pectoralis major muscles in broiler chickens.