Milun Petrovic

Broiler rearing systems: a review of major fattening results and meat quality traits

Poultry rearing systems have been the focus of scientific research for many years as a result of consumer demand for high-quality products and legal poultry welfare requirements. Given these requirements, the following study was carried out as a comparative review of the results obtained by different authors on the effect of rearing systems on productive traits (growth, feed conversion and mortality) and meat quality traits (dressing percentage, yield and percentage of primal cuts, and chemical composition of meat) in broilers. Most authors reported a lower final body weight and poorer feed conversion efficiency in free-range systems compared to intensive rearing. Conversely, better meat quality traits, most notably in terms of chemical composition of meat, were observed in non-intensive and organic broilers. The above traits showed differences within the same rearing system, due to the effect of a range of genetic and non-genetic factors. In view of the above, it is hoped that the following review on the use of different rearing systems in broiler meat production can serve as a tool in determining the future direction of research as well as an indicator of its practical applications.

Laying hen rearing systems: a review of major production results and egg quality traits

Laying hen rearing systems have been the focus of scientific research for many years. Over the last few decades, new laying hen rearing systems have been rapidly introduced in an effort to harmonise poultry health and welfare with consumer, producer, industry and environmental demands. Given the above situation, the subject matter of this paper was a comparative review of the results obtained by different authors on the effect of rearing system on productive traits (egg production and mortality) and egg quality characteristics (egg weight, proportions of main egg parts, Haugh units, yolk colour and carotenoids) in laying hens. Although productive performance in alternative systems is often lower compared to conventional, intensive layers, eggs from alternative systems have been proven in numerous studies to have better nutritional properties. Moreover, research results indicate differences within rearing systems. In view of this, this overview of the literature on the use of different rearing systems in table egg production can serve as a tool in determining the future direction of research as well as an indicator of its practical application.

Laying hen rearing systems: a review of chemical composition and hygienic conditions of eggs

Alternative laying hen rearing systems have been rapidly introduced into poultry production in an effort to harmonise poultry health and welfare with consumer, producer, industry and environmental demands. They are an integral part of modern egg production. Husbandry systems for keeping laying hens have an impact on, inter alia, the chemical composition of eggs. The subject matter of this study is a comparative review of the results obtained by different authors on the effect of rearing system on chemical composition (proteins, lipids, cholesterol, vitamins and fatty acids content) and hygienic conditions of eggs from different rearing systems of laying hens. Eggs from these laying hen rearing systems have been proven by a large body of literature data to have better nutritional properties. Moreover, the results analysed also indicate differences within rearing systems. Rearing systems also have an influence on hygienic and microbiological quality of eggs. In view of the above, this comparable overview of the literature on the use of different rearing systems in table egg production can serve as a tool in determining the future direction of research as well as an indicator of its practical application.

THE EFFECT OF THE LEVEL OF MILK YIELD ON THE REPRODUCTION TRAITS IN BLACK AND WHITE COWS

In this study a relationship between the milk yield and following reproduction traits: number of inseminations per conception (AIS), service period (SP), age at calving (AC), calving interval (CI) and birth weight (BW) is studied. The research involved dairy cows of European type of Black and White cattle which are being intensively improved by the genes of Holstein - Friesian breed. Mean values of general average for number of inseminations per conception, service period, age at calving, calving interval and birth weight are: 2.00; 98.78; 1088.08; 376.70 and 36.40, respectively. In general, the estimated phenotypic correlations (rp) between the milk yield over standard lactations and fertility traits were positive and unfavorable, and ranged from 0.24 for the relationship between milk yield and birth weight to 0.70 for relationship between milk yield and age at calving.

Broiler meat quality: The effect of rearing system and length of fattening period

Broiler meat production in recent years has been oriented towards the implementation of non-commercial rearing systems aimed at improving broiler rearing conditions, enhancing meat quality and improving the environment. This study presents productive and slaughter results of broilers reared under two non-commercial systems, including extensive indoor and free-range systems. Length of fattening period was 63 days. On days 49 and 63 of the experiment, male and female broilers were randomly selected from both rearing systems and slaughtered thereafter to be evaluated and compared for the following traits: dressing percentage and percentage yield of primal carcass cuts, as dependent upon rearing system, length of fattening period and broiler sex. The results showed a higher dressing percentage in broilers slaughtered on day 49, regardless of the higher carcass weight of broilers slaughtered on day 63. Broiler sex had a highly significant effect on the percentage yield of breast, thigh and drumstick in the dressed carcass (P<0.01), whereas the percentage yield of thighs was also statistically highly significantly affected by rearing system (P<0.01). Rearing system, length of fattening period and the interaction of these factors had no significant effect (P>0.05) on the percentage yield of primal cuts (breast, thigh, drumstick, wing, back and pelvis), excepting that of pelvis which was significantly affected by rearing system (P<0.05).

EXAMINATION OF THE CERTAIN CHEMICAL CHARACTERISTICS OF DIFFERENT TYPES OF BOILED SAUSAGES PRODUCED IN SERBIA

The objectives of our study were to examine certain chemical quality parameters in samples of various subgroups of boiled sausages and compare obtained values with reference values (Rule book on the quality of minced meat, semi-finished meat and meat products, Official Gazette of RS, no. 31/2012). We used two reference chemical methods: determination of nitrogen and phosphorus content (SRPS ISO 937:1992, SRPS ISO 13730:1999). For determination of hydroxyproline we used M 050 “in house” modified method. We concluded that the total number of tested samples of Fine grounded boiled sausages (n=170), 47 (27.65%) does not match the requirements for the quality provided the above mentioned Rule book, of which 21 samples because lower total protein content (TP) and 33 samples because higher relative protein content of connective tissue (RPC). The most common chemical quality failure of examined Coarsely grounded boiled sausages (n=94) is a higher percent of RPC than allowed (18 - 25 %). We consider in samples of same subgroup lower content of TP in 8 samples (11.11 %). From a total of 8 samples tested Boiled sausages with meat peaces (Sunkarica), all tested samples revealed lower content of TP than allowed (100 %) and 2 samples (25 %) higher relative protein content of connective tissue (RPC). The most common deficiency that reduces the chemical quality of the boiled sausages is higher level of RPC, demonstrated in 53 (19.48 %) of the total (n=272) samples tested. Something minor drawback is the lower percent of TP determined in 37 samples (13.60 %). Total P2O5 content was compatibile with the values permitted by the Rule book in all of 272 examined samples, indicating a strict adherence to regulations when using phosphate as one of the technologically most important additives in the production of boiled sausages.

Regression analysis of milk production traits in Simmental cows.

The relationship between milk production traits over whole lactations was evaluated across three generations of Simmental cows, i.e. between daughters, dams and grand dams, by a phenotypic regression analysis with whole lactation traits in the daughter generation being used as the dependent variables (x1), and those in the dam and grand dam generations being used as the independent variables (x2 and x3). The results were obtained from a sample of 1170 daughters and as many dams and grand dams. The significance of the partial regression coefficients b2 and b3 was separately evaluated by a t-test. An analysis of variance was used to estimate the significance of the simultaneous effect of the production traits of dams and grand dams on the milk production achieved in the daughter generation. The calculated value of the partial regression coefficients for the whole lactation production traits across three generations (grand dams, dams and daughters) and their statistical significances determined by the t and F tests, as well as the regression equations used, suggested that the effect of the grand dam generation on the milk production traits in granddaughters was substantially lower than the effect of dams. The calculated partial regression coefficients (b2 and b3) were positive and statistically very significant (P<0.01), excepting the regression coefficients b3 for lactation length and b2 for milk fat content that were not statistically significant (P>0.05). A very significant change (P<0.01) was observed in all production traits in the daughter generation as simultaneously affected by the traits in the dam and grand dam generations.

Meat quality parameters of broilers from different rearing systems

Bearing in mind certain established European Union regulations on non-industrial poultry meat production, experimental investigations were conducted with the aim to examine the effect of two different rearing systems (free-range rearing and extensive rearing in the chicken pen) on some meat quality characteristics. Investigation results on the shares of muscular tissue, bones and skin in major carcass parts (breasts, thighs and drumsticks) were used as poultry meat quality parameters. Based upon the obtained study results, it could be concluded that a somewhat higher meat share in breasts and drumsticks was recorded with the free-range-reared broilers as compared to the extensively reared ones. A somewhat higher meat share in the drumsticks was registered with the hens whereas other differences from the point of view of the sex effect were small.