$(a)$ What is lactation period? Name two breeds of cattle which are selected for their long lactation period. Why are they crossed with local breeds?
$(b)$ What are roughage and concentrates?

(N/A) The lactation period is the duration of milk production by a female mammal after the birth of a calf.
Two breeds of cattle selected for their long lactation period are $Jersey$ and $Brown$ $Swiss$.
They are crossed with local breeds because local breeds possess excellent resistance to diseases and environmental stress,while the foreign breeds provide high milk yield. Cross-breeding combines these desirable traits into the offspring.
$(b)$ Roughage: It is a type of animal feed that is largely fibrous and contains a high percentage of cellulose. It provides bulk to the diet.
Concentrates: These are animal feeds that are low in fiber but contain relatively high levels of proteins,carbohydrates,fats,and other essential nutrients to support high productivity.