Exercise 46
What would happen if poultry birds are larger in size and have no summer
adaptation capacity? In order to get small sized poultry birds, having
summer adaptability, what method will be employed?
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NCERT’s answer
Maintenance of temperature is needed for better egg production by poultry birds. Therefore, larger size (increase in surface area of body) and no adaptability of summer may cause decline in egg production. To obtain the smaller size and higher summer adaptability, cross breeding of poultry birds are done. Small size is also needed for better housing and low feed.
In summer: \[\text{large body} + \text{no heat tolerance} \xrightarrow{\text{summer heat}} \text{heat stress} \] \[\text{heat stress} \Rightarrow \text{feed intake}\downarrow,\ \text{growth}\downarrow,\ \text{egg laying}\downarrow,\ \text{mortality}\uparrow \] To combine small body size and summer adaptability with high yield, a high-yielding exotic breed is cross-bred with an indigenous breed that tolerates heat and resists disease, and the progeny is selected for both traits together; small size also means less feed and housing space are needed. Answer: heat stress cuts egg laying and raises mortality; cross-breed a high-yielding exotic breed with a heat-tolerant, disease-resistant indigenous breed, selecting the progeny for both traits.
