Slaughter value and meat quality of Muscovy ducks, Pekin ducks and their crossbreeds, and evaluation of the heterosis effect AbstractThe studies were conducted on 200 Muscovy ducks, 100 Pekin ducks of the A-44 strain and 200 their crossbreeds (sex ratio: 1:1). The ducks were fed complete commercial diets, appropriate for respective species. Slaughter and slaughter value estimation were performed at the age of: 7 weeks -for males and females of the A-44 strain, 10 weeks -for Muscovy females, and 12 weeks -for Muscovy males and crossbreeds (♂ and ♀). Analysis of the chemical composition, physicochemical properties and sensory properties of meat was made on breast muscles. The heterosis effect on the slaughter value and meat quality was additionally estimated in hybrids. The highest live body weights were reported for Mucovy drakes (4450 g), and the lowest -for ducks from this genetic group (ca. 2400 g). The crossbreeds were characterized by average body weights (2980 g), but the highest relative meatiness (ca. 54%) and the lowest fatness (ca. 20%) of carcasses. The best sensory properties were reported for muscles of ducks of the A-44 strain. A favorable heterosis effect was observed in crossbreeds: positive in relation to meatiness and negative in relation to fatness, undesirable in the customers' opinion. No favorable heterosis effect was noted in most meat quality traits.

The objective of this study was to determine age-related changes in the percentage content of edible and non-edible components in broiler chickens. The experimental materials comprised 240 Ross 308 chicks (sex ratio 1:1) raised to 10 weeks of age and fed standard diets ad libitum. Starting from the first week of rearing, every 7 days 10 males and 10 females were selected randomly for slaughter and post-slaughter analysis. The data obtained were verified statistically. The percentage content of edible components increased and the percentage content of non-edible parts decreased as the chicks grew older. In broilers aged 1 week and 10 weeks, edible components accounted for 47.0% and 66.4% total body weight, respectively. The share of muscle tissue increased considerably over this period, from 30.9% total body weight in week 1 to 52.4% in week 10. An increase in the percentage of skin and subcutaneous fat was observed for the first three weeks only, while the percentage content of giblets (in contrast to the remaining edible parts) decreased with age. For non-edible parts, the share of bones diminished by 2.5% and the proportion of slaughter offal reduced by 13.8%. A rising tendency was noted with respect to feathers and abdominal fat, while the content of the remaining offal decreased.

The aim of the present study was to derive multiple regression equations for in vivo estimation of the carcass lean and fat content in Muscovy ducks. The experimental materials consisted of 240 White Muscovy ducklings (120 male and 120 female). One hundred sixteen females aged 10 wk and 112 males aged 12 wk were slaughtered. Before slaughter the ducks were weighed, and the following body measurements were taken: humerus length, drumstick length, chest girth, breast-bone crest length, width between the humeral bones, chest depth, and breast muscle thickness. The coefficients of simple correlation between carcass tissue components and body measurements were calculated. It was found that live body weight was highly correlated with the weights of all tissue components (r = 0.701 to 0.857). In males a significant interrelation was found between breast muscle weight and all body measurements, whereas in females breast muscle weight was correlated with breast-bone crest length, chest girth, width between the humeral bones, chest depth, and breast muscle thickness only. In both males and females the carcass lean content was closely correlated with drumstick length, breast-bone crest length, chest girth, and width between the humeral bones. In drakes the carcass fat content was closely correlated with all body measurements, whereas in hens significant correlations were observed between the carcass fat content and chest girth, width between the humeral bones, and chest depth only. The coefficients of simple correlation between the percentages of carcass tissue components and body measurements were generally low and statistically nonsignificant. Twelve multiple regression equations formulated based on the body measurements of live ducks were verified with respect to the accuracy of estimation of the content of breast muscles, meat, and fat with skin in the carcass. These equations give small SE of the estimate (Sy = 23.3 to 83.8 g), high values of coefficients of multiple correlation between the dependent variable and the set of independent variables, and high values of determination coefficients.

The liver and kidneys of broilers fed during the first two weeks of fattening a fodder containing the addition of 0.025% propolis and/or 0.5% pollen were examined macroscopically and microscopically. Additionally, the effects of these substances on the results of breeding and on pathomorphology of the liver and kidneys in the course of natural, asymptomatic infection with Salmonella Enteritidis were determined. The results demonstrated that propolis has protective effects on the liver of broiler chickens, reducing the intensity of regressive lesions. However, regarding supplementation of the diet with bee pollen, additional research on its effects in animals is needed.

The objective of this study was to determine the effect of diet supplementation with propolis and bee pollen on selected physical, biomechanical and chemical properties of tibial bones in broiler chickens. The experimental materials comprised 384 Ross 308 chickens (four groups, three replications), divided into groups of males and females, and raised to 35 days of age. Control group 1 birds were fed a commercial diet throughout the experiment. Birds of three other experimental groups received for the first two weeks of rearing standard diets with a different content of propolis and/or bee pollen: group 2 -0.025 % propolis, group 3 -0.5 % bee pollen, group 4 -0.5 % bee pollen and 0.025 % propolis. The following parameters of the tibia were determined: weight, length, mid-shaft circumference, vertical and horizontal external diameters, vertical and horizontal internal diameters. The geometric characteristics of the bones were determined based on the above measurements. Mid-shaft shear strength was measured using an Instron universal testing machine 4301 (Instron, Norwood, MA, USA). The crude ash, calcium (Ca) and phosphorus (P) content of the tibia was also determined. Higher values of geometric parameters were noted in the tibial bones of broilers fed a diet supplemented with a combination of propolis and bee pollen, in comparison with birds fed diets containing propolis or bee pollen administered alone. The shear strength values and physical properties of bones were similar in all groups.