| Abstract | Proizvodnja mesa i jaja na obiteljskim gospodarstvima uobičajeno se odvija u slobodnom načinu držanja koji uključuje manji broj životinja na nekom prostoru, a u takvoj proizvodnji nerijetko se koriste kokoši, koje su svojim fenotipskim i genotipskim obilježjima prilagođene podneblju u kojem se uzgajaju. Iako nisu konkurentne s obzirom na proizvodne rezultate, izvorne ili lokalno adaptirane pasmine peradi imaju važnu ulogu za ruralni sektor i mala seoska gospodarstva. Cilj je ovog istraživanja bio istražiti pasminu kokoš hrvaticu kroz proizvodne pokazatelje (godišnju proizvodnju jaja, prirast tjelesne mase pijetlova do postizanja klaoničkih tjelesnih masa, konverziju krmne smjese po jedinici proizvoda, mortalitet), pokazatelje kvalitete mesa i jaja (osnovni kemijski sastav, pH, sposobnost vezanja vode, teksturu, boju, sastav masnih kiselina i oksidaciju masti, udio osnovnih dijelova u jajetu, visinu bjelanjka, Haughove jedinice, boja žutanjka, čvrstoću i debljinu ljuske) te senzorne karakteristike mesa i jaja (razlikovni i hedonistički testovi). Prikupljena su rasplodna jaja pasmine kokoši hrvatice (350 komada) od 19 registriranih uzgajivača i to 110 jarebičasto-zlatnog soja, 90 crvenog, 60 crnog te 90 crno-zlatnog soja. Jaja su inkubirana i dobiveni rezultati za oplođenost jaja pasmine kokoši hrvatice, kretali su se od 80 % kod crnog do 87 % kod jarebičasto-zlatnog soja, a za valivost od 67 % kod crnog do 77 % kod jarebičasto-zlatnog soja. Nakon valjenja pilići pasmine kokoši hrvatice držani su u ujednačenim uvjetima odvojeni po sojevima kao i pilići hibrida Sasso T44 s kojima je izvorna pasmina uspoređivana. Svi pilići su vagani svaka dva tjedna pri čemu su prosječne vrijednosti mase pilića pasmine kokoši hrvatice bile značajno niže u usporedbi s masama hibrida Sasso T44. Pilići su odvojeni po spolu u dobi od 8 tjedana. Ženske jedinke su držane uz kontrolu svjetlosnog režima radi usklađenosti tjelesnog i spolnog razvoja, a muške jedinke su preseljene u ograđene ispuste i uzgajane slobodnim načinom držanja na zatravnjenim površinama prema tehnološkim zahtjevima za proizvodnju pilećeg mesa u produljenom tovu. Tijekom uzgoja muških jedinki na ispustima do dobi od 112 dana jedinke su vagane svaka dva tjedna, a prirasti tjelesne mase pijetlova pasmine kokoš hrvatica (1662 – 1890 g) bili su niži nego kod hibrida Sasso T44 (3612 g). Konverzija krmne smjese kod pijetlova pasmine kokoš hrvatica kretala od 5,03 do 5,72, a kod Sasso T44 3,76, dok je mortalitet iznosio od 5 do 6,7 %. Vrijednost omjera PUFA n-6/n-3 u prsnom mišiću bila je najmanja kod jarebičasto-zlatnog soja (10,16), a najveća kod hibrida Sasso T44 (11,26). Utvrđen je povoljniji omjer PUFA n-6/n-3 prsnog mišića pijetlova pasmine kokoš hrvatica u odnosu na hibrid Sasso T44. U mišićnom tkivu zabataka omjer PUFA n-6/n-3 bio je najveći kod crno-zlatnog soja kokoši hrvatice (9,88), a najmanji kod hibrida Sasso T44 (8,83). Kod jarebičasto-zlatnog soja pasmine kokoš hrvatica sadržaj esencijelne α-linolenske masne kiseline i ukupnih PUFA n-3 u mišićnom tkivu zabataka bio je značajno veći (p<0,05) u odnosu na hibrid Sasso T44. Usporedbom senzornih odlika prsnog mišića pijetlova pasmine kokoš hrvatica i hibrida Sasso T44, nisu utvrđene statistički značajne razlike. Ženske jedinke odvojene su po sojevima u dobi od 19 tjedana i smještene u uvjete slobodnog uzgoja. Tijekom narednih 52 tjedna evidentiran je broj snesenih jaja po jedinki pasmine kokoši hrvatice (159 – 166,9) i hibrida Sasso T44 (154,1), stopa nesivosti koja je bila najveća u dobi od 7.do 10. mjeseca (od 55,60 do 62,13 %), konverzija krmne smjese kod pasmine kokoši hrvatice (5,25 – 6,01) i hibrida Sasso T44 (4,77) te mortalitet (5 – 20 %). Sadržaj n-6 PUFA jaja bio je najmanji kod hibrida Sasso T44 (9,53 %), a najveći kod crno-zlatnog soja (12,63 %), dok je sadržaj ukupnih n-3 PUFA bio najmanji kod crnog (0,94 %), a najveći kod crvenog soja (1,24 %). Omjer PUFA n-6/n-3 imao je najmanju vrijednost kod crvenog soja (8,12), a najveću kod crnog soja (12,66), dok je kod hibrida Sasso T44 iznosio 8,76. Senzornom analizom kuhanih jaja utvrđena je statistički značajna razlika (p<0,05) između jaja jarebičasto-zlatnog soja pasmine kokoš hrvatica i hibrida Sasso T44, dok razlika između ostalih sojeva i hibrida nije bila statistički potvrđena. Istraživanjem je potvrđeno da je pasmina kokoš hrvatica pogodna za proizvodnju jaja u slobodnom uzgoju te da je masnokiselinski sastav mesa i jaja povoljnog omjera PUFA n-6/n-3 kao i dobrih senzorskih odlika što je preduvjet za veće iskorištavanje ove pasmine u komercijalne svrhe. |
| Abstract (english) | Indigenous chicken breed Hrvatica in the Republic of Croatia is recognized among breeders, who demonstrate a growing interest in the revitalization of this breed for economic reasons and to preserve traditional production in rural areas (Galović et al., 2015). Previous research on the Hrvatica chicken breed was focused mainly on production traits (Janječić et al., 2007a), while the goal of this research was to determine production indicators (annual egg production, increase in body weight of roosters until reaching slaughter body weight, food conversion efficiency per unit of product, mortality), quality indicators of meat and eggs (elementary chemical composition, pH, water binding capacity, texture, colour, composition of fatty acids and fat oxidation, proportion of basic parts in the egg, height of the egg white, Haugh units, colour of the yolk, firmness and shell thickness) as well as sensory characteristics of meat and eggs (differential and hedonic tests). The research was conducted from April 2016 to September 2017. Part of the research took place at the University of Zagreb Faculty of Agriculture, and the part in village Vrbica in the therapeutic community "Ne-ovisnost". Breeding eggs were collected from registered breeders. Chickens of the slow-growing Sasso T44 hybrid were used in the research as a separate, comparable group.
Day-old chicks of Hrvatica chicken separated by strain and Sasso T44 hybrid chicks were kept indoors. Chicks were separated by gender at the age of 8 weeks. Control weighing of chicks in the warm phase was carried out on the 1st, 14th, 28th, 42nd and 56th day of age. Males were moved to a fenced farmyard at the location of the "Ne-Ovisnost" therapeutic community in Vrbica at the age of 56 days and were reared free-range on grassed farmyard according to the technological requirements to produce chicken meat in extended fattening. They were weighed every 2 weeks (70th, 84th, 98th and 112th day of age) until the end of fattening at the age of 112 days. Feed consumption and mortality were monitored during the rearing of male chickens at the farmyard.
Female chickens were delivered to Vrbica at the age of 19 weeks, separated by strains and hybrid Sasso T44 and placed in separate grassy, fenced outdoor areas under free-range conditions. During the research, the consumption was monitored for each group. After start of laying, for the next 52 weeks, the number of eggs laid, the laying rate and the mortality of the hens were monitored.
Phenotypic measurements were performed on male and female chickens of all four strains of the Hrvatica breed and the Sasso T44 hybrid at the age of 16 weeks according to the measurement standards described by Kodinetz (1940). Ten animals of each strain and gender of Hrvatica breed and Sasso T44 hybrids were randomly selected and measured using a calliper for the carcass, while a sliding scale was used for head measurements.
At the age of 112 days, the final weighing of the roosters was carried out, and from each strain of the Hrvatica breed and the Sasso hybrid, males were randomly selected, 7 of them per group were slaughtered and processed. All parts of the carcass were weighed separately. To test meat quality, pH1 value and pH2 value were determined in all breast muscle samples using a Mettler MP120-B digital pH meter, the release of meat water from breast muscle tissue according to the EZ drip loss method, water binding capacity (Sp.v.v) in cm2 by the compression method according to Graü-Hamm (1952), meat colour using the Minolta CR-300 device, muscle resistance using the Warner-Bratzler knife, shrinkage (%) and lipid oxidation according to the modified methods of McDonald and Hultin (1987) and Botsoglou et al (2002). The sensory analysis of heat-treated meat was performed using the hedonic test according to Lawless and Heymann (2010) in controlled conditions in individual boxes by 70 respondents-consumers.
Analysis of egg quality was carried out and included measurement of egg mass with analytical device NABEL - Digital Egg Tester DET–6000 (DET-6000) and elementary parts of the egg (white, yolk and shell) with a Mettler Toledo Jewelry digital scale, determination of width and length for the calculation of egg shape index with a sliding scale, determination of the shell strength, yolk colour, egg white height and Haugh units using the DET-6000 analytical device as well as the yolk colour using the Minolta CR 410 device and the pH
values of the egg white and yolk, measured using a portable pH-meter IQ 150. Sensory analysis of boiled eggs was performed using the triangle test, hedonic test and Just-about-right (JAR) test according to Lawless and Heymann (2010). The analysis was performed under controlled conditions by 29 trained evaluators.
Determination of fatty acid composition was performed on breast, drumstick and egg samples on a Gas chromatography-flame Ionization detection (GC-FID), brand Agilent 7890A system using a Supelco SP 2560 column (100 m, 0.25 mm, 20 um).
After the end of fattening, the average weight of male individuals of the Hrvatica breed at the age of 112 days ranged from 1662.17 g in the red strain to 1890.34 in the black strain, which are lower values than the average weight of the Sasso T44 hybrid, which was 3612.83 g. The conversion efficiency ranged from 5.03 to 5.72 in male chickens of the Hrvatica breed, while it was 3.76 in the Sasso T44 hybrid. Mortality in the observed period was the highest in the hybrid Sasso T44 (6.7 %), followed by the black strain (5 %), while there was no mortality in the other strains of the Hrvatica breed. During the processing of the carcass of roosters, the yield was determined, which in the Hrvatica breed ranged from 78.20 to 79.49 %, depending on the strain, and in the Saasso T44 hybrid it was 80.23 %.
The results of meat quality analysis for water binding capacity, meat texture and meat water release showed that there were no statistically significant differences (p>0.05) neither between the Hrvatica breed strains nor when compared to the Sasso T44 hybrid, and for cooking loss the greatest value was for the black strain (23.76 %) and the lowest for the hybrid Sasso T44 (20.94 %). For the brightness L* of meat colour, the highest value (55.92) was recorded for the red strain, while the lowest (48.82) was recorded for the Sasso T44 hybrid. The highest value (3.05) for the degree of red colour a* was recorded in the black-golden strain and the lowest (1.86) in the hybrid Sasso T44. The highest value (7.24) for the degree of yellow color b* was recorded in the red strain and the lowest (3.75) in the hybrid Sasso T44. The obtained values of lipid oxidation in the fresh muscle tissue of the breast and drumstick did not reveal the influence of the hybrid/strain. However, the hybrid/strain of chickens had a statistically significant (P<0.05) effect on lipid oxidation in the muscle tissue of the breast and drumstick that were frozen.
The average number of eggs laid per year of all strains of the chicken breed Hrvatica was 162.97, and the Sasso T44 hybrid was 154.1, from which we conclude that the Hrvatica breed had better laying capacity than the Sasso T44 hybrid. The Sasso T44 hybrid had a higher egg weight (61.82 g) as well as a harder (65.40 N) and thicker (0.35 cm) shell. The highest (57.19 %) percentage of egg white was found in Sasso T44 eggs, and statistically significant differences (p<0.05) were found in the percentage of egg white in Sasso T44 hybrid eggs compared to all strains of the Hrvatica breed, while the highest percentage of yolk (35.07 %) was determined in the black strain of the Hrvatica breed.
The highest value (59.05) for the brightness L* of the yolk colour was recorded for the black-golden strain, while the lowest (54.62) was recorded for the hybrid Sasso T44. The highest value (15.10) for the degree of red colour a* in the yolk was recorded in the hybrid Sasso T44 and the lowest (12.12) in the black-gold strain. For the degree of yellow colour b* of the yolk, the highest value (45.36) was recorded in the black-golden strain and the lowest (39.57) in the Sasso T44 hybrid. According to the results determined by the DET-6000 analytical device, the highest value (13.02) for yolk colour was recorded in the hybrid Sasso T44 and the lowest (11.51) in the black-gold strain.
The results of the analysis of the fatty acid composition of the muscle tissue of male individuals of the investigated strains of Hrvatica chicken and the Sasso T44 hybrid were dependent on the type of analysed muscle tissue and the strain. In the breast muscle tissue, a higher proportion of MUFA (38.16% and 38.67% compared to 35.25%; p<0.05) was determined in the red strain of the Hrvatica breed and Sasso T44 hybrid compared to the black strain of the Hrvatica breed, while differences in the proportions of other major groups of fatty acids (SFA, PUFA n-6, PUFA n-3) were not found between the groups (p>0.05). A significant difference was not determined in the ratio of PUFA n-6/n-3 in the breast muscle between the examined groups. Significant differences in the proportions of all major groups of fatty acids (SFA, MUFA, PUFA n-6, and PUFA n-3; p<0.05) were found in the thigh
muscle tissue of the investigated strains and hybrid. Differences in the values of the PUFA n-6/n-3 ratio in the thigh muscle tissue were also significant. The highest value (9.88) was determined in the black-gold strain of the Hrvatica breed, while the lowest values were found in the Sasso T44 hybrid (8.58) and the partridge-gold strain (8.83) of the Hrvatica breed. The PUFA n-6/n-3 ratio in the black (9.42) and the red strain (9.32) of the Hrvatica breed were between these values and did not differ statistically from the highest and lowest determined values. Based on the above, we conclude that the muscle tissue of the thigh in the Sasso T44 hybrid and the partridge-gold strain of the Hrvatica breed exhibit a better nutritional balance of long-chain PUFA fatty acids compared to other Hrvatica breed strains. However, the partridge-gold strain also had a significantly higher content (p<0.05) of essential α-linolenic fatty acid and total PUFA n-3 in the thigh muscle tissue compared to the Sasso T44 hybrid.
The fatty acid composition of eggs was the most favourable in the red strain (ratio PUFA n-6/n-3 = 8.12) and the least favourable in the black strain (ratio PUFA n-6/n-3 = 12.66) of the Hrvatica breed.
Sensory analyses of meat and eggs are important in determining the quality of the product, considering the differences that can be significant for the consumer and have an effect on the final selection of the product. In addition to the methods of keeping and feeding, the sensory characteristics of meat and eggs can also be influenced by the genotype, so in this research, the hypothesis that the eggs and meat of Hrvatica chicken breed have better sensory characteristics compared to the eggs and meat of hybrids was set.
Sensory analysis of boiled eggs using the triangle test revealed a statistically significant difference (p<0.05) between the eggs of the partridge-gold strain and the Sasso T44 hybrid, while no statistically significant difference was found between the other strains and the hybrid. Evaluators frequently emphasized the difference in colour and taste of the eggs. In the hedonic test on eggs, no statistically significant difference was found between the examined groups in any of the tested attributes (p>0.05). In the Just-about-right (JAR) test a higher proportion of participants expressed that the colour of the yolk and the smell of boiled eggs from the Hrvatica breed strains were optimally expressed and appropriate when compared to the Sasso hybrid. In the sensory analysis conducted using the hedonic test with 70 participants to determine the likability of breast muscle meat (taste, tenderness, juiciness, richness of aroma, overall liking), no statistically significant differences were found between the meat of the Hrvatica breed strains and the Sasso T44 hybrid. |
