Cattle and camels (large-sized livestock) are heavy and are long-lived. Once they give birth, they can keep supplying milk for a long period. Goats and sheep (small-sized livestock), by contrast, can grow in population in a short period of time. In a favorable environment, they quickly attain breeding age, and they have short gestation periods and intervals between pregnancies. When people lose their animals due to draught, for example, they sometimes adopt the following strategy: reconstructing their livestock by investing in goats and sheep in the short term, and once reconstruction is finished, shifting the direction of their investment to cattle and camels.

Physiological differences by livestock

		Cattle	Camel		Sheep	Goat
	Age of first pregnancy (years)	3-4	5-6		1-2	1-2
	Gestation period (months)	9-9.5	12-13		5	5
	Interval between pregnancies (months)	14-18	24		8-9	8-9
	Milk production (kg per day)	3-5	3-4		?	0.1-1?
	Available months of milking (months)	7-9	7-18		?	3-5
	Life span (years)	12	25		5-6	5-6
	Weight (kg)	200-250	400-500		25-40	25-40