AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

HERITABILITY OF SOME IMPORTANT TRAITS

• Approximate heritability value of various traits in various animal species

Species	Trait	h2
Cattle (dairy)	Calving interval	0.10
	Milk yield	0.25
	Fat %	0.55
	Protein %	0.50
Cattle (beef)	Calving interval	0.05
	Birth weight	0.40
	Weaning weight	0.30
	Yearling weight	0.40
	Mature weight	0.65
	Feed conversion	0.40
Pigs	Litter size (number born alive)	0.05
	Little size (number weaned)	0.10
	Weaning weight	0.10
	Feed conversion	0.50
	Loin eye area	0.50
	Back fat thickness	0.70
Sheep	Litter size	0.15
	Birth weight	0.30
	Weaning weight (60-day)	0.20
	Yearling weight	0.40
	Grease fleece weight	0.40
	Staple length	0.50
Horses	Wither height	0.40
	Cannon bone circumference	0.45
	Temperament	0.25
	Walking speed	0.40
	Time to trot one mile	0.45
	Time to run one mile	0.35
	Pulling power	0.25
Poultry	Egg production (to 72 wks)	0.10
	Egg size	0.45
	Egg weight (at 32 wks)	0.50
	Hatchability	0.10
	Viability	0.10
	Body weight (at 32 wks)	0.55

• On the whole, the characters with the lowest heritability are those most closely connected with reproductive fitness.
• Characters with the highest heritability are those that have least importance with regard to natural fitness.
• Heritability can be expressed as percentage from 0 to 100 or in decimal ranging from 0 to 1.
• According to Turner and Young (1969) the estimates of h² values was grouped as
  • 0.3 or more - high
  • 0.3 - 0.1 - intermediate / medium
  • below 0.1 - low
• When we say heritability of a trait is 0.25, it mean that 25 per cent of the differences in performance for the trait in the population are heritable.

  • For example the heritability of milk yield in cattle is 25 % and average of the herd is 2000 kg. This does not mean that 500 kg (25%) is due to heredity and the remaining 1500 kg to environment. It means that of the difference between individual in the herd in milk yield approximately 25 % is due to heredity and 75 % is due to environment.