Gholamreza Zaboli; mohhamad kameli
Volume 24, Issue 1 , April 2022, , Pages 97-107
Abstract
In order to investigate the effects of different periods of thermal manipulation during embryogenesis on thermotolerance, hatchability and blood parameters of Ross (308) broilers strain, 608 fertile eggs were used in a completely randomized design of 4 treatments with 4 replicates. Experimental groups ...
Read More
In order to investigate the effects of different periods of thermal manipulation during embryogenesis on thermotolerance, hatchability and blood parameters of Ross (308) broilers strain, 608 fertile eggs were used in a completely randomized design of 4 treatments with 4 replicates. Experimental groups with different thermal manipulation (for control (0 h), 6, 12 and 18 hours) where incubated at 65% humidity and 39.5°C from 7 to 16 days of incubation. At 7 d of incubation, the infertile and undeveloped eggs were removed after the candling. The result showed that thyroid hormones and facial surface temperature, as metabolism and thermotolerance index, decreased significantly in 6-, 12- and 18-hour-treated groups compared to the control group (P < 0.05). The hatchability was higher in the eggs exposed to zero (control), six- and 12-hour thermal manipulation than in the other groups (P < 0.05), and a reduction of hatchability was observed in the 18-hour treatment group. Hatching time increased significantly in the thermal-treated groups (P < 0.05), whereas treatments did not have any significant effects on the body weight, body length, and quality of chickens (P > 0.05). Yolk sac percentage was higher in the treated groups than in control (P < 0.05). Increasing the length of thermal treatment increased the female sex ratio (P < 0.05) significantly. The blood concentration of uric acid and total protein significantly decreased in 6-, 12- and 18-hour treatment groups compared to the control group (P < 0.05). In conclusion, based on the results of this study, 6 and 12 hours of thermal manipulation induced thermotolerance without adverse effects on hatchability.
Hassan Shirzadi; Gholamreza Zaboli
Volume 21, Issue 4 , January 2020, , Pages 499-509
Abstract
The aim of this research is to estimate the methionine requirement of Japanese quails (Coturnix coturnix japonica) from 7 to 21 d of age using linear and quadratic broken-line regressions under chronic heat stress. A total of 480 quails were distributed according to a completely randomized ...
Read More
The aim of this research is to estimate the methionine requirement of Japanese quails (Coturnix coturnix japonica) from 7 to 21 d of age using linear and quadratic broken-line regressions under chronic heat stress. A total of 480 quails were distributed according to a completely randomized design in 6 experimental treatments (diets containing 0.40, 0.45, 0.50, 0.55, 0.60 and 0.65% of methionine), with 4 replicates of 20 birds each. The basal diet was based on the corn-soybean meal and was formulated in mash form. Supplemental DL-methionine was added to the basal diet at the expense of corn starch to create experimental diets. The birds were fed a standard diet up to d 7, and then were weighed and randomly allotted to the experimental treatments. Birds exposed to chronic heat stress from 8 d of age for 6 h daily (37 ± 0.8°C from 10 AM to 16 AM). The optimal amounts of methionine for body weight gain, feed conversion ratio, and breast meat yield were obtained with 0.55, 0.57, and 0.60% of the diet as estimated by linear broken-line regression. However, based on the quadratic broken-line regression, the corresponding values were estimated at 0.58, 0.59, and 0.62% of the diet, respectively. According to the findings of this study, It seems that amounts of methionine higher than the usual recommendations are needed for Japanese quails to achieve optimal performance under chronic heat stress.