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Embryonic development is a dynamic process that requires a fine balance between several factors in order to achieve an optimum hatchability and chick quality. These factors include the background o...

Commercial Cobb broiler breeders were subjected to molting from 55 to 62 wk of age. Incubating eggs were collected before molting and after molting and were stored for 18, 13, 8, or 3 d. Sample eggs were broken to measure albumen Haugh units (HU) and pH. Two hundred twenty-five eggs per treatment, stored for 18, 13, 8, or 3 d, were incubated for 21 d; the hatched chicks were weighed at the end of incubation and again after Day 7 of rearing. As the storage time increased, albumen HU decreased (P0.001). At all storage times, HU after molting were higher than those before molting (P0.001). Albumen pH increased with storage time (P0.001). A molting x storage interaction on pH was observed after 8 d of storage (P = 0.03). Hatchability of eggs increased after hens were molted, if the eggs were stored for a long time (P0.001). Body weights of 1-d-old chicks from the eggs of hens before molt were heavier than those from eggs after molting (P0.001). Conversely, at 7 d, the chicks from the eggs after molting were significantly heavier than those from eggs before molting (P0.001). We concluded that molting was a procedure to improve hatchability and chick juvenile growth. If eggs need to be stored, we recommended that fresh eggs with high HU value be stored rather than those with low HU values.

Despite thorough selection during the last decade, the incidence of ascites is still high in modern broiler strains. Although ascites occurs mostly at the end of the rearing period, there are indications that the etiology of this problem may have started during embryonic development. Recent studies have shown that the post-hatch performance of the broiler chick might be influenced by changing the environmental conditions in the incubator during embryonic development. This study investigated the effect of increasing incubator CO(2) concentration up to 0.7%, by nonventilation during the first 10 d of incubation, on the embryonic development of 2 commercial broiler strains (Cobb and SAS) differing in their susceptibility for ascites syndrome. The Cobb strain is suspected to be less susceptible than the SAS strain. Overall, the chick embryos of the Cobb strain had a faster development than those of the SAS strain as expressed by their higher BW from embryonic day (ED)10 until ED18. Nonventilation stimulated embryonic development resulting in higher embryonic BW, early hatch, and narrower spread of hatch in both strains. In the SAS strain, nonventilation improved hatchability by more than 10%. Gas composition of the air cell in the egg of the nonventilation groups (both Cobb and SAS) had higher partial pressure of CO(2) and lower partial pressure of O(2) from ED11 until ED14 compared with the ventilation groups. During the entire incubation period, partial pressure of CO(2) was higher in eggs of the Cobb strain compared with the SAS strain. Plasma triiodothyronine, thyroxine, and corticosterone levels were different at the end of the incubation period and during hatching due to nonventilation at the beginning of incubation. It is concluded that nonventilation during the first 10 d of incubation had a stimulatory effect on embryonic development of the 2 broiler strains with no effect of heart weights but with effects on hormone levels, air cell pressures, and hatching parameters.

A non-destructive method to determine the physiological age of Rhipicephalus appendiculatus is described. The ratio of two readily available parameters of the tick was used: body weight over scutal length. Because the latter is constant throughout life and because of the high correlation between body weight and the nutritional status of starving ticks, the ratio between the two provides a biomarker for the physiological condition of the tick in relation to the environmental factors. Two hundred laboratory ticks were followed over a period of one year at two different levels of relative humidity. Three distinct phases of physiological age indices were observed, both in male and female ticks: a steep decline immediately after moulting independent of humidity, a period of constant ratios found only when the ticks were kept at the higher humidity, and a period of gradual decline depending on the humidity. It was shown that the proposed method provides an easy and quick method to evaluate the physiological age of laboratory tick stocks. Preliminary results of the application of this method in the study of the age structure of field populations are discussed.