The age structure of a flock of sheep is shown below. Ages are in years. The num
ID: 146549 • Letter: T
Question
The age structure of a flock of sheep is shown below. Ages are in years. The number of lambs weaned per ewe is 1.2. The breeder selects progeny based on phenotype and wants to increase weaning weight in lambs. The estimated heritability for weaning weight is 0.4 and the phenotypic standard deviation is 4Kg.
a. What are the selected proportions of males and females?
b. What is the expected response to selection per generation?
c. What is the overall generation interval?
d. What is the expected response per year?
e. In this flock if survival rate decreased how would this affect the rate of response to selection? Briefly explain your answer.
age when progeny dropped 2 3 4 5 total number of rams 8 2 10 number of ewes 180 120 80 20 400Explanation / Answer
Ans a) The selected proportions of rams to ewes is that no of females of selected are always greater than the no of females selected. So the proportional of males to females is 8/180 which is 1/22.5 and 2/120 or 1/60. so the no of females selected is greater than the no.of males . In total we have 10/400 or 1/40 or is 2.5%.
Ans b) As mentioned in the question the expected response of the next generation is depending on the weaning weight of the lambs and the higher the heritability of the weaning weight so the higher the weight of the weaning is a positive response of the selection per generation.
Ans c) As per the table we can say that the response of the system is that the no of the sheeps is keeps on decreasing and then the no of males has been down to zero, then we can say that the no have been fallen then we can say the overall generation interval is around every 2 years.
Ans d)The overall expected response of the systems is that the no. of flock of the sheeps have been dcreasing and which can lead to decrease in the weaning weight of the of the sheeps. The heritability is keeps on lowering down because of the less no. of the sheeps.
Ans e) The no. of the flock has been keeps on decreasing as mentioned in the question and we can say that is has an adverse effect on the systems and the weaning weight of the stocks , as the mortality rate has been increased and therefore we can't have the required no.of livestock in the market . So because of this the selection procedure is becames very worse and thats why we have a lower weaning weight.
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