1) Breed A lambs have an average weaning weight of 40 lbs, and breed B lambs have an average weaning weight of 50 lbs. If the average weaning weight of lambs that are AxB crossbreds is 48 lbs, what is the percent individual heterosis of weaning weight in lambs? (2 pts)

2. Assume a trait with the following means: Breed A is 97, Breed B is 103, and Breed C is 107. Individual heterosis for this trait is 5%, and maternal heterosis is 8%. 

a. What performance would you expect from the crossbred progeny of A and B? (2 pts)

b. What performance would you expect from the crossbred progeny of B and C? (2 pts)

c. What performance would you expect from the crossbred progeny of C sires and AB dams? (4 pts)

Q1 Answers:

% Heterosis for Breed A = 16.67%

% Heterosis for Breed B = 4.17%

 

Q2 Answers:

A: Expected Crossbred Performance = 110 lbs

B: Expected Crossbred Performance = 115.50 lbs

C: Expected Crossbred Performance = 174.069 lbs

Step-by-step explanation

Question 1

Breed A lambs have an average weaning weight of 40 lbs, and breed B lambs have an average weaning weight of 50 lbs. If the average weaning weight of lambs that are AxB crossbreds is 48 lbs, what is the percent individual heterosis of weaning weight in lambs? (2 pts)

 

Data:

Breed A = 40 lbs

Breed B = 50 lbs

A x B = 48 lbs

 

Formula:

% Heterosis = (Crossbred average - Purebred average) / Purebred average x 100

 

Computation:

 

Breed A

% Heterosis = (48 - 40) / 48 x 100

% Heterosis = 8 / 48 x 100

% Heterosis = 0.1666667 x 100

% Heterosis for Breed A = 16.67%

 

Breed B

% Heterosis = (|48 - 50|) / 48 x 100

% Heterosis = 2 / 48 x 100

% Heterosis = 0.041666667 x 100

% Heterosis for Breed B = 4.17%

 

============================================

 

Question 2

Assume a trait with the following means: Breed A is 97, Breed B is 103, and Breed C is 107. Individual heterosis for this trait is 5%, and maternal heterosis is 8%. 

 

a. What performance would you expect from the crossbred progeny of A and B? (2 pts)

 

Data:

Breed A = 97 lbs

Breed B = 103 lbs

Individual heterosis = 5% or 0.5

Maternal heterosis = 8% or 0.08

 

Formula:

Purebred Average (PA) = (A + B) / 2

Individual Heterosis (IH) = %Individual Heterosis x Purebred average

Expected Crossbred Average (ECA) = Purebred ave. + Individual Heterosis

Expected Crossbred Performance (ECP) = IH + ECA

 

Computation:

PA = (97+103) / 2

PA = (200) / 2

Purebred Average = 100

 

IH = 0.05 x 100

Individual Heterosis = 5

 

ECA = 100 + 5

Expected Crossbred Average = 105

 

Computation of Expected Crossbred Performance:

ECP = 5 + 105

Expected Crossbred Performance = 110 lbs

 

-----------------------------------------------------------------------------------------------------

 

b. What performance would you expect from the crossbred progeny of B and C? (2 pts)

 

Data:

Breed B = 103 lbs

Breed C = 107 lbs

Individual heterosis = 5% or 0.05

Maternal heterosis = 8% or 0.08

 

Formula:

Purebred Average (PA) = (B + C) / 2

Individual Heterosis (IH) = %Individual Heterosis x Purebred average

Expected Crossbred Average (ECA) = Purebred ave. + Individual Heterosis

Expected Crossbred Performance (ECP) = IH + ECA

 

Computation:

PA = (103+107) / 2

PA = (210) / 2

Purebred Average = 105

 

IH = 0.05 x 105

Individual Heterosis = 5.25

 

ECA = 105 + 5.25

Expected Crossbred Average = 110.25

 

Computation of Expected Crossbred Performance:

ECP = 5.25 + 110.25

Expected Crossbred Performance = 115.50 lbs

 

-----------------------------------------------------------------------------------------------------

 

c. What performance would you expect from the crossbred progeny of C sires and AB dams? (4 pts)

 

Data:

Breed A = 97 lbs

Breed B = 103 lbs

Breed C = 107 lbs

Individual heterosis = 5% or 0.05

Maternal heterosis = 8% or 0.08

 

Formula:

Purebred Average (PA) = (A + B+ C) / 2

Individual Heterosis (IH) = %Individual Heterosis x Purebred Average

Maternal Heterosis (MH) = %Maternal Heterosis x (Purebred Average + Individual Heterosis)

Expected Crossbred Performance (ECP) = (Purebred Average (PA) + Individual Heterosis (IH)) + Maternal Heterosis (MH)

 

Computation:

PA = (97 + 103 + 107) / 2

PA = 307 / 2

Purebred Average = 153.5 lbs

 

IH = 0.05 x 153.5

Individual Heterosis = 7.675 lbs

 

MH = 0.08 x (153.5 + 7.675)

MH = 0.08 x 161.175

Maternal Heterosis = 12.894 lbs

 

Computation of Expected Crossbred Performance

ECP = (153.5 + 7.675) + 12.894

ECP = 161.175 + 12.894

Expected Crossbred Performance = 174.069 lbs