COMPARATIVE CHARACTERISTICS OF MORPHOMETRIC INDICATORS OF GROWTH AND DEVELOPMENT OF CHICKEN EMBRYOS OF EGG CROSSES "HISEX BROWN" AND "LOHMANN BROWN" IN DIFFERENT PERIODS OF EMBRYOGENESIS AT VARIABLE TEMPERATURES OF EGG INCUBATION

Abstract

The results of experimental studies on the influence of variable temperatures of egg incubation (37.8°C - 1...14 days; 39.5°C for 2 hours daily - 15-17 days; 37.5°C - 18 days; 37.0 °C - 19-20 days) on the growth and development of chicken embryos of egg crosses "Hisex Brown" and "Lohmann Brown" in different periods of embryogenesis. Under conditions of variable temperature incubation of eggs in the embryos of hens of the Lohmann Brown cross, compared with the Hisex Brown, there was a statistically significant increase in the absolute values of body weight by 12 (p=0.011), 14 (p=0.001), 15 (p= 0.000), 20 (p=0.000) days, body length - on days 6 (p=0.000), 8 (p=0.000), 9 (p=0.025), 13…16 (p=0.000) days. Differences in the rhythm of the growth of chicken embryos were established, accompanied by 5 critical stages of the growth rate of body weight and 6 critical stages of the growth rate of body length in the Haysex Brown cross, and in the embryos of the Lohmann Brown cross - 4 and 1 critical stages, respectively. Throughout the studied period of embryogenesis in the studied crosses, the highest intensity of the growth rate of weight and body length was noted in the embryonic period of development with a decrease towards the hatching period. The highest specific weight growth rate in the embryonic period is typical for embryos of chickens "Hisex Brown" (p=0.000), and body length - for embryos of the cross "Lohmann Brown" (p=0.047). In subsequent periods of embryonic development, the specific rate of growth in body weight and length decreased in both crosses. Differences in the specific rate of body weight growth in embryos of chickens "Hisex Brown" and "Lohmann Brown" in the prefetal (p=0.680) and fetal periods (p=0.477) were not found, and in the specific rate of body length growth - in the prefetal (p= 0.709), fetal periods (p=0.942) and hatching period (p=0.918). By the hatching period, the specific body weight growth rate prevailed in the Lohmann Brown embryos (p=0.000). The effect of exposure to variable incubation temperatures was accompanied by a higher percentage of chick hatchability of the Lohmann Brown cross (94.90%) compared to the Highsex Brown cross (91.90%). The results obtained indicate the feasibility of using the proposed mode of incubation with variable temperatures for cross-country chickens "Lohmann Brown".