An increase in the performance of hybrids over that of pure breeds, most notieceably in traits like fertility survivability. Heterosis (Hybrid Vigor)



An increase in the performance of hybrids over that of pure breeds, most notieceably in traits like fertility survivability.

Heterosis (Hybrid Vigor)

Heterosis (Hybrid Vigor)



I. Positive Heterosis



II. Negative Heterosis



Measuring hybrid vigor



Retained hybrid vigor

Measuring Hybrid Vigor



In practice, hybrid vigor is measured as difference

between the average performance of crossbreds and

the average performance of their purebred parent

lines or breeds.



Utilization of heterosis in broiler and laying hen production



Utilization of heterosis in beef production



Utilization of heterosis in lamb production

Hybrid Vigor

GENE FREQUENCY IN POPULATIONS AND POPULATION GENETICS Genetic

Equilibrium

A population in the absence of forces that change gene and genotypic

frequencies A gene frequency : p

a gene frequency : q

p + q = 1

A population:



in the absence of forces that change gene and genotypic frequencies



presence of random mating

Males: A and a genes: pA and qa Females: A and a genes: pA and qa

GENE FREQUENCY IN

POPULATIONS AND

POPULATION GENETICS

Spermatozoon

Ovum pA qa

pA p

AA pq Aa

qa pq Aa q

aa

Genotype Frequencies

p

AA+2pqAa+q

aa=1

Hardy-Weinberg Equilibrium

GENE FREQUENCY IN

POPULATIONS AND

POPULATION GENETICS

Deviations from Hardy–Weinberg equilibrium



Genetic



Genetic



MUTATION



MIGRATION



SELECTION



RANDOM DRIFT



MUTATION



MIGRATION



SELECTION



RANDOM DRIFT

GENE FREQUENCY IN

POPULATIONS AND

POPULATION GENETICS