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The objective of this experiment was to replace soybean oil with glycerol in feeding mixtures for layers and assess its effect on performance, selected parameters of egg quality and health. Layers were divided into control (C) and experimental (E1, E2) groups of 24 layers each. The experiment was performed from week 20 until week 44 of layers’ age. Soybean oil replacement with glycerol reached 50 and 100 % in experimental feeding mixtures E1 and E2, as compared to the control. Oil replacement with glycerol in experimental groups resulted in a significant decrease (P≤0.01) in weight of eggs, as compared to the control group – C (65.5±5.780 g), E1 (64.53±4.640 g) and E2 (63.66±5.610 g), and egg shell stability (N/cm2) – C 33.79±6.557, E1 31.96±6.995 and E2 31.8±6.621. The difference in the weight of egg shell between groups C (7.13±0.687 g) and E2 (6.85±0.670 g) was highly significant (P≤0.01), the difference between E1 (7.00±0.820 g) and E2 groups for the same parameter was significant (P≤0.05). No significant differences were found between mean values of the weight of egg yolk and white. With regard to feed consumption, 50 % replacement of oil with glycerol did not increase significantly the daily consumption of a feeding mixture per layer (1 egg) – C 122 g (132 g) and E1 123g (136 g), as compared to 100 % replacement in E2 131 g (150 g). The analysis of blood plasma after the prolonged continuous administration of glycerol in a feed did not show any negative effect on layers’ health.

The experiment was performed with a total of 180 day-old, ROSS 308 combination, meat-type hybrid chickens that were divided according to sex into the control group (C1 and C2 with 30♀ and 30♂, respectively) and two experimental groups: GLY-P1 and P2 with pure glycerol (30♀ and 30♂), and GLY-R1 and R2 with raw glycerol (30♀ and 30♂). The chickens received three feeding mixtures during the experiment: the pre-fattening mixture (BR 1) until Day 14, the fattening mixture (BR 2) from Day 15 to Day 30, and the post-fattening mixture from Day 31 to Day 40 (BR 3). 50 % of the soybean oil in feeding mixtures used in the experimental groups (GLY-P and GLY-R) was replaced with pure or raw glycerol at a ratio of 1:2. The feed and water were available ad libitum for consumption. The mean live weight of both male and female chickens in experimental groups on Days 15 and 40 was statistically significantly higher (P≤0.05, P≤0.01) than that in the control group. The consumption of the feeding mixture during the entire 40-day fattening period was higher in female and male chickens in experimental groups. The differences in the mean weight of processed carcass between the control and experimental groups were very significant (P≤0.01). Glycerol obtained during rapeseed processing is a suitable source of energy and can be added in feeds designed for farm animals.

The paper reports on the changes in the chemical composition of breast and thigh muscles in intensively fed chickens of common pheasant, discussing the results obtained from the perspective of the production of high-quality pheasant meat. Young pheasants were fed for 90 days. Unlike breast muscles, thigh muscles showed a significant (P ≤ 0.05) decrease in water content between Day 50 and Day 90 (falling from 757.20 to 728.61 g/kg) which was associated with increasing dry matter content in muscles (from 242.80 to 271.39 g/kg). From a dietetic point of view, one positive finding is that both breast and thigh muscles from young pheasants aged 40 - 90 days contained low levels of fat, ranging from 6.12 g/kg to 8.33 g/kg, and from 20.36 g/kg to 51.37 g/kg, respectively. However, at the end of the monitored period (i.e. between Day 70 and Day 90) fat content in muscles significantly increased (P ≤ 0.01). Differences between average levels of ash (minerals) in breast muscles during the monitored period were not statistically significant. The average levels of ash in thigh muscles decreased statistically very significantly (P ≤ 0.01) on Day 50 (11.75 g/kg). In breast muscles a statistically significant decrease (P ≤ 0.05) was detected on Day 90 (11.67 g/kg). The above-mentioned changes in the chemical composition of muscles in young pheasants may arise due to qualitative age-related changes such as decreasing proteosynthesis and enhanced fat biosynthesis in muscles. This conclusion is supported by profound changes in the parameters of chemical composition related to muscle dry matter which are presented in this paper.

Title of the paper: Cholesterol concentration in yolks and blood plasma in five species of game birds (short communication) Cholesterol concentrations were determined in yolks and blood plasma of five significant species of game birds (common partridge, wild turkey, common pheasant, guinea fowl, and chukar partridge). Two yolk samples and one blood plasma sample were collected from 15 female birds of each species. Dimensions, whole egg weight and weights of sheli, yolk, and white were recorded for each egg. Mean blood plasma concentrations were significantly higher (P < 0.01) in the common partridge (3.44 mmol/1), the wild turkey (3.78 mmol/1), and the common pheasant (3.67 mmol/1) than in the guinea fowl (2.61 mmol/1) and the chukar partridge (2.26 mmol/1). Mean yolk cholesterol concentrations in the wild turkey (1030 mg/100 g), the guinea fowl, and the chukar partridge (both 1010 mg/100 g) were significantly higher (P < 0.01) than in the common pheasant (960 mg/100 g) and the common partridge (930 mg/100 g/1). Mean blood plasma cholesterol concentrations exceeded mean yolk concentrations by a 7- to !2fold. Blood plasma cholesterol concentrations were near the lower limit of the normal range for domestic fowl, while yolk concentrations in the game birds were markedly lower than in the domestic chicken.