Authors: AHMAD SALAHI, MOZHDEH MOOSANEZHAD KHABISI, ABBAS PAKDEL, ALI BAGHBANZADEH
Abstract: In this experiment 72,000 broiler breeder eggs (Ross 308 strain) collected from 36-week-old flocks were subjected to cold stress during transportation. Eggs were allocated to 4 temperature groups (treatments): 1.2 °C, 1-2 °C, 2.5-3.9 °C, 4-6 °C, and a control group, 21-22 °C. Each treatment had 14,400 eggs, and data were analyzed in a completely randomized design. The results of this study showed that cold stress had a significant effect on percentage of egg weight loss (P < 0.001), and minimal egg weight loss occurred in the control group. The percentage of exploders and early hatched chicks and chick weight were higher in the below zero temperature treatment than the other groups (P < 0.01). Cold stress had a significant effect on chick length, hatchability, and the hatching of fertile eggs (P < 0.001). The effects of cold stress on chick yield and body weight uniformity were significant (P < 0.01). The effect of cold stress on hatchery byproduct efficiency was significant (P < 0.001), but did not affect fertility. Cold stress also had significant effects on early (1-8 days), middle (9-17 days), and late mortality (20-21 days); total embryo mortality; and exposed brain. Ectopic viscera was significant (P < 0.001), and most mortality was observed in below 4 °C treatments. Total percentages of malpositions and deformity (P < 0.001) and egg contamination at 1-9 days (first stage) and 10-21 days (second phase) were affected by cold stress (P < 0.001). Cold stress also had a significant impact on the number of cull chicks; percent of string navel, button navel, total string, and button; omphalitis; full body cavity; red hocks; dehydration; dirty chickens; and stubby down. Cold stress affects performance during incubation and overall chick quality.
Keywords: Cold stress, egg transportation, hatchability, chick quality, malposition and deformity, culls, egg weight loss, embryo mortality and contamination
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