A genetic evaluation report for terminal sire breeds for 2007 is shown below. Th
ID: 146543 • Letter: A
Question
A genetic evaluation report for terminal sire breeds for 2007 is shown below. The sires in the report were all born in 2005.
The report shows the estimated breeding values (EBVs) for various traits calculated using BLUP, the accuracy associated with these EBVs and a ‘Carcase Plus’ index value for 5 animals. The objective of the ‘Carcase Plus’ index is to increase post-weaning weight, increase post-weaning eye muscle depth and decrease post-weaning fat depth. The table below also gives the average EBV and index values for all animals born in 2005
5
Animal
Post- weaning weight
Post- weaning fat depth
Post- weaning eye muscle depth
No. of
lambs weaned
Post- weaning faecal egg count
Carcase Plus Index
Sire 1
11.7 -0.5 0.4 3 -23 69% 70% 71% 42% 45%
170
Sire2
7 -1.6 1.7 -10 14 68% 66% 71% 40% 36%
170
Sire 3
10.9 -0.2 0.7 3 -35 65% 63% 68% 38% 56%
163
Sire 4
12.6 -1.9 -0.6 1 10 67% 64% 69% 39% 58%
185
Sire 5
9.6 -0.6 2.2 2 0 39% 37% 41% 10% 28%
176
Mean of 2005 born lambs
7.1 -0.6 0.4 5 0
147
a. Sires 1 and 2 have the same ‘Carcase Plus’ index value of 170 but different values for the component trait EBVs (Post-weaning weight, post-weaning eye muscle depth and post-weaning fat). Explain how this can be the case.
b. Assume a new index was created called ‘Carcase Plus-FEC’. The ‘Carcase Plus- FEC’ index is based on EBVs for post-weaning weight, muscle and fat (as ‘Carcase Plus’ index) but also includes EBVs for post-weaning faecal egg counts. Would you expect a change in the ranking of animals when ranked on this index? Explain your answer commenting on the magnitude of re-ranking for specific index comparisons.
c. What is the expected difference in progeny post-weaning weight if Sire 3 was selected compared to an average 2005 born animal?
d. Give a likely reason why the accuracies associated with post weaning weight EBVs are generally higher than accuracies associated with EBVs for the number of lambs weaned.
e. Briefly explain what information may have been used in calculation of the post weaning weight EBVs for these sires.
Animal
Post- weaning weight
Post- weaning fat depth
Post- weaning eye muscle depth
No. of
lambs weaned
Post- weaning faecal egg count
Carcase Plus Index
Sire 1
11.7 -0.5 0.4 3 -23 69% 70% 71% 42% 45%
170
Sire2
7 -1.6 1.7 -10 14 68% 66% 71% 40% 36%
170
Sire 3
10.9 -0.2 0.7 3 -35 65% 63% 68% 38% 56%
163
Sire 4
12.6 -1.9 -0.6 1 10 67% 64% 69% 39% 58%
185
Sire 5
9.6 -0.6 2.2 2 0 39% 37% 41% 10% 28%
176
Mean of 2005 born lambs
7.1 -0.6 0.4 5 0
147
Explanation / Answer
a) Carcase Plus Index is a value based on the otimal value of EBV s traits like post weaning weight, fat and muscle depth. Carcase plus is an average value of the traits of a group. But EBVs traits are directly related to genetic rrecombination during the production of gamestes and fertilization. Any certain change in the genetic code can change the post weaning fat , wieght muscle depth and other qualities of an animal offspring.
b) Yes there would be a change in the rankings.
The sheeps that are infested with parasites ( with higher FEC value) would have less post weaning weight and fat. The parasites in the intestines of those sheeps feast on the nutrients from the food. The resultant sheep off spring would be thin and disease ridden with a lower Caracase Plus Index.
c) The differnce in post weaning weight of Sire 3 and of 2005 born animal is 3.8.
d) It is easier to calculate the post weaning weight of the progency which are already accustomed to separation from their mother. But for weaning process fing suitable solid feed is difficult and many offsprings dont get accustomed to the sudeen change. So the sucess rate for post weaning is higher.
e) For calculating weanng wight birth weight is required and also the waning age. According to the formula
weaning weight = (pre -weaning weight * weaning age) + weight at birth
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