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In several tulip cultivars propagated in vitro, a high decrease in propagation rate was observed after the 4th - 6th multiplication cycles. In vitro shoot cultures of the model tulip cultivars Blue Parrot and Prominence with relatively stable and high multiplication rate and shoots of new Polish cultivar Fringed Black which revealed a decreased regeneration capacity were used in the experiment. Shoots, multiplied at 8-week subculture period on MS modified medium supplemented with thidiazuron (TDZ) and a-naphthaleneacetic acid (NAA), were treated with low temperature (5°C) for 8, 10 or 12 weeks and with 1 mg·dm⁻³ GA₃ which was added to the medium prior to cooling at the 3rd week of multiplication subculture. The significant enhancement of shoot multiplication by cooling was found for the cultivar Fringed Black only. Low temperature treatment for 10 - 12 weeks markedly increased multiplication rate from 2.5 (non-cooled control) to 5.8 - 6.4 (in the 1st subculture). The effect of increased regeneration capacity was maintained during 8 months of cyclic multiplication. Application of GA₃ decreased affect shoot multiplication rate. It is suggested that the decrease in multiplication rate of cv. Fringed Black could result from dormancy development in shoots because the restoration of regeneration capacity occurred after low temperature treatment.
The aim of this study was the evaluation of the growth of broiler chickens and their slaughter value from 1 to 42 days of age. The research material consisted of the Ross 308 chickens. At 42 days of rearing, the chickens reached the mean final body weight of 2229.9 g. During successive weeks of rearing, the weight of all elements, i.e. giblets, inedible parts and offal, increased with an increasing body weight of birds. At the same time, their percentage in the body weight decreased considerably, and the dressing percentage increased.At 42 days of rearing, the eviscerated carcass weight averaged 1697 g, the percentage of muscles was 46.7%, that of skin and fat was 11.0% and the remainders of the carcass (bones) accounted for 42.5%. During the rearing period, considerable changes in the tissue composition of carcass and their uneven growth were found. Moreover, the effect of age and type of muscle on the chemical composition of muscles was determined.
The aim of this study was to determine an increase in the length of skeletal bones and muscle groups in broiler pullets during the rearing period. The research material consisted of the Ross 308 broiler pullets. The analysis included keel bone, leg bones (tarsometatarsus, femur and tibia), wing bones (humerus and ulna) as well as breast, thigh, drumstick muscles and wing muscles located along humerus and ulna. Day-old chicks weighed 36.5 g on average and during the whole rearing period, i.e. until 6 weeks of age increased their body weight to 2229.2 g. From 1 to 42 days of age, the weight of wing muscles increased from 0.91 to 429.9 g, that of thigh muscles changed from 1.95 to 218.0 g and that of drumstick muscles increased from 1.27 to 140.7 g. At that time, the weight of wing muscles increased from 0.74 to 38.9 g. In day-old chicks, the lengths of tarsometatarsus, tibia, femur, ulna and humerus were 25.6 mm, 32.0 mm, 24.7 mm, 17.5 mm and 17.0 mm, respectively. The respective values for 6-week-old birds were 81.7 mm, 105.8 mm, 78.5 mm, 73.9 mm and 77.8 mm.Adifferent growth rate of the analysed traits as well as a clear decrease in this rate with increasing age of birds were found. For most analysed traits, the rate of increase in muscle weight was three times higher than that in the length of individual skeletal bones. At that time, the keel length increased from 20.4 to 132.6 mm. Positive significant and highly significant relationships were found between most analysed traits such as: body weight of chickens and the weight of their breast and leg muscles.
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