In a chicken population of 200 hens with 10 roosters the following measurements
ID: 85871 • Letter: I
Question
In a chicken population of 200 hens with 10 roosters the following measurements refer to breast fat content of the roosters: V_A = 120 V_E = 80 V_NA = 38 a. What is the phenotypic variance in this population? Show all of your working out. b. Estimate narrow heritability (h^2) for breast fat content in this population. Show all of your working out. c. Would you expect an estimate in other chicken populations to be the same? Explain. d. If Harold, a very good lean rooster, has his breast fat estimated at 20g and the total roosters in this population have an average breast fat of 23g, calculate Harold's EBV then estimate the amount of breast fat expected in his progeny if he is mated to a random group of hens. Show all of your working out e. If no new chickens are introduced into this population for 20 years and it is maintained at approximately 200 hens 10 roosters, briefly describe what you would expect to see with respect to variability between the chickens.Explanation / Answer
a) Phenotypic variance is given by the formula,
VP = VG + VE
where VG is genetic variance and VE is environmental variance
Genetic variance VG is composed of additive variance VA and nonadditive variaance VNA
So, VP = VA + VNA + VE
= 120 + 38 + 80
= 238
b) Narrow heritability is calculated by the formula,
h2 = VA / VP
= 120/238
= 0.5042
c) The estimates in other chicken populations will be same if the environmental factors remain unchanged. This is because narrow sense heritability depends only on additive variance and phenotypic variance.
d) Expected breeding value (EBV) is given by the formula,
EBV = h2 x P ( P is average difference between animal and herd)
= 0.5042 x 3
= 1.5126