S. Bogosavljević-Bošković

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.

Enzymes in broiler diets with special reference to protease

Enzyme supplementation of poultry diets is nutritionally, economically and environmentally justified. Enzymes are used to increase the energy value of feed ingredients and enhance the utilisation of protein, fats, carbohydrates and phytin phosphorus from plant materials, leading to a lower excretion rate of undigested nutrients into the environment and, hence, reduced environmental pollution. This is especially important regarding proteases, as the correct digestion of nitrogenous compounds in feed materials is essential for reducing N excretion – a major pollutant worldwide. Numerous studies have shown no adverse effects of enzyme supplementation in broiler diets on body weight, mortality, health, feed intake, FCR, nutrient digestibility, meat quality and production costs. However, there is still a large amount of uncertainty regarding the use of enzymes.

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.

CARCASS COMPOSITION AND CHEMICAL CHARACTERISTICS OF MEAT FROM BROILER CHICKENS REARED UNDER INTENSIVE AND SEMI- INTENSIVE SYSTEMS

Poultry rearing systems have captured the attention of scientists for many years. A number of attempts have been made to introduce new technologies in rearing poultry for meat and egg production aiming at improving rearing conditions, protecting the environment and enhancing the quality of poultry products. Given the above, the objective of this study was to present the results of an evaluation of the effect of rearing system on major meat quality traits (percent yield of primal cuts in cold carcasses, tissue percentage in major primal cuts and chemical composition of muscle tissue). The experiment involved a total of 400 Hybro broilers reared under two different systems (intensive and semi-intensive systems). The fattening period and slaughter and dressing procedures were followed by measurement and meat sampling for chemical analysis. The results obtained show that broilers reared under the semi-intensive system had a somewhat higher percentage of drumsticks and breasts i.e. first class meat, as well as a higher percentage of breast and thigh muscles. Moreover, the protein content of breast, thigh and drumstick muscles was higher in broilers reared under semi-intensive conditions. As for the fat content of primal cuts, it was found to exhibit higher values in broilers reared under the intensive system. Overall, the results suggest better performance for most traits in free range broilers reared under semi-intensive conditions as compared to those reared intensively.

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).

EFFECT OF NON-GENETIC FACTORS ON STANDARD LACTATION MILK PERFORMANCE TRAITS IN SIMMENTAL COWS* *

Abstract The effect of systematic and continuous environmental factors on milk performance traits over standard lactations in 2805 Simmental cows was evaluated using the general linear model. The systematic factors included the effect of farm or breeding area, calving season, year of birth, season of birth, lactation group and their interactions. The continuous factor analysed was the effect of age at first conception. The effect of farm, lactation group and calving season on standard lactation milk performance was found to be highly significant (P<0.01), excepting the effect of calving season on milk fat percent in standard lactations which showed statistical significance (P<0.05). The interactions between year and season of birth, farm and calving season, and farm and lactation group had a highly significant effect (P<0.01) on all performance traits studied. Age at first conception, as a continuous factor, had a highly significant effect (P<0.01) on milk yield and milk fat percent, and a non-significant effect on milk fat yield. The model used to correct the performance traits over standard lactations for the effect of systematic factors was highly significant (P<0.01). The variance of the model accounted for 20.06 and 37.31% of the total variance of milk fat yield and milk fat percent, respectively. The resulting coefficients of determination (R2) ranged from 0.20 for milk fat yield to 0.37 for milk fat percent.

The effect of protease on productive and slaughter traits in broiler chickens

Carcass conformation is a very important parameter in assessing the overall appearance and meatiness of broilers. This study evaluates the effect of protease supplemented to reduced protein diets on production traits, dressed carcass weight and conformation measures in fast-growing Cobb 500 and slow-growing Master Gris broilers over a fattening period of 49 days. At slaughter, the following measurements were taken: pre-slaughter body weight (BW), conventionally dressed carcass weight and abdominal fat weight. Following carcass dissection into primal cuts, absolute conformation values, including metatarsus length (ML), keel length (KL), breast depth (BD), breast angle (BA) and thigh girth (TG), were determined. For carcass conformation evaluation purposes, index values of carcass conformation measures BW/ML, BW/KL, BW/BD and BW/TG were identified. Genotype and sex had a significant effect on dressed carcass weight and all conformation measures, whereas the effect of different protein levels in protease-supplemented diets was significant only in Master Gris, for metatarsus length and the following indices: BW/ML, BW/KL and BW/TG. Key word: broilers, productive traits, carcass weight, carcass conformation.