GENETICS AND LIVESTOCK IMPROVEMENT

| October 16, 2015

SECTION A  Answer ONE (1) question.
1. For an animal industry of your choice, describe and explain the decisions that drive the industry rate of genetic improvement. (5 marks)
2. What is genetic lag, what determines its magnitude and how can farmers manipulate it to their benefit? (5 marks)

1402/117.345 2Hr MAN CP1 Internal
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SECTION B  Answer ALL questions.
3. List THREE (3) things that should be reflected in the relative economic value of a trait included in a selection index and explain why they need to be considered. (2 marks)
4. A pig farmer has a herd of 80 sows. Each sow has one litter per year between 1- and 5-years.  The average litter size is 12.5 piglets.  He is selecting for feed conversion efficiency which is measured once on each individual piglet at 3months-old.  All piglets are weighed at 3-months-old.  He uses four 8-month-old boars for breeding (gestation length of pigs is about four months).
Heritability of feed conversion efficiency is 43% and heritability of live weight at 3-months-old is 24%.  The genetic correlation between feed conversion efficiency and live weight at 3-months is 27%.  Phenotypic variance is 17g2/kg2 for feed conversion efficiency and 890 g2 for live weight at 3-months.
a) Calculate the current rate of genetic gain in feed conversion efficiency being achieved in this herd. (6 marks)
b) What would be the rate of genetic gain in feed conversion efficiency if the farmer decided to select based on the correlated trait live weight at 3 months instead of selecting directly on feed conversion efficiency? (2 marks)
Table for ī up to 10% selected p .000 .001 .002 .003 .004 .005 .006 .007 .008 .009 .00  3.400 3.200 3.033 2.975 2.900 2.850 2.800 2.738 2.706 .01 2.660 2.636 2.600 2.569 2.550 2.527 2.500 2.482 2.456 2.442 .02 2.420 2.400 2.386 2.370 2.363 2.336 2.323 2.311 2.293 2.283 .03 2.270 2.258 2.241 2.230 2.221 2.209 2.200 2.186 2.174 2.164 .04 2.153 2.146 2.136 2.126 2.116 2.107 2.098 2.087 2.079 2.071 .05 2.064 2.057 2.048 2.040 2.031 2.022 2.016 2.009 2.000 1.990 .06 1.985 1.977 1.971 1.965 1.958 1.951 1.944 1.937 1.931 1.925 .07 1.919 1.911 1.906 1.900 1.893 1.888 1.882 1.875 1.871 1.863 .08 1.858 1.852 1.846 1.841 1.837 1.834 1.826 1.820 1.815 1.810 .09 1.806 1.799 1.793 1.788 1.784 1.780 1.775 1.770 1.765 1.760 Table for ī when more than 10% selected p .00 .01 .02 .03 .04 .05 .06 .07 .08 .09 .10 1.755 1.709 1.667 1.628 1.590 1.554 1.521 1.488 1.458 1.428 .20 1.400 1.372 1.346 1.320 1.295 1.271 1.248 1.225 1.202 1.180 .30 1.159 1.138 1.118 1.097 1.078 1.058 1.039 1.021 1.002 .984 .40 .966 .948 .931 .913 .896 .880 .863 .846 .830 .814 .50 .798 .782 .766 .751 .735 .720 .704 .689 .674 .659 .60 .644 .629 .614 .599 .585 .570 .555 .540 .526 .511 .70 .497 .482 .468 .453 .438 .424 .409 .394 .380 .365 .80 .350 .335 .320 .305 .290 .274 .259 .243 .227 .211 .90 .195 .179 .162 .144 .127 .109 .090 .070 .049 .027
1402/117.345 2Hr MAN CP1 Internal
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5. Sharon is a beef cattle farmer with an Angus breeding cow herd.  She has decided to breed her heifers to calve at 2- instead of 3-years of age this year, and realises that she’ll need to purchase a bull especially for this task to avoid calving difficulty in the 2-year-old heifers.  She has a self-replacing cow herd and believes the Self-Replacing Index is a good fit for her breeding objectives.  She will be calving the heifers in a large paddock where providing assistance will be difficult, so she wants to be especially cautious in her bull selection to ensure that the calves will be small at birth.
She has identified the following three bulls as potential purchases, but wants your advice as to the best option.  All three bulls have the same asking price.
Indicate which option is the best bull for Sharon to purchase, justifying your reasoning so that Sharon can make an informed choice herself next year.
(5 marks)

 

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