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Flashcards in sheep genetics 4 Deck (24):
1

What is lambplan indices?

- Gives genetic information on
o terminal, maternal and dual-purpose breeds
- benchmarks
- uses ASBV’s and standard selection indices and accuracy values
- Can customise indices (sheepobject)

2

what lambplan indices should be -ve and why?

Traits that should be small/-ve
o Birth weight (too big = lambing difficulties)
o PFAT- post weaning fat (leaner lamb)
o WEC- worm egg count (more resistant)

3

how are the indices values used?

- ASBV (top) value/2 as sire only provides half
o Bottom value = accuracy
 The higher the accuracy the closer it is to the true breeding value

4

what are the 3 major lambplan indices?

lambplan terminal, maternal and dual purpose indices

5

what is the maternal lambplan indices and what is it used for?

- Lambplan maternal ASBV
o Gives values of progeny
o –ves ok
 FAT and WEC
 breed that excels in maternal traits (e.g. mothering ability and milk production)

o Maternal $ index (MAT $)
 aimed at maternal breeds of specific breeds, doesn’t include FD
 e.g. border and coopworth
 balances the key economic traits relevant to most maternal breeds
o Dual Purpose $ Index (DP$)
 aimed at self-replacing maternal flocks with additional focus on wool quality, such as Corriedales, SAMMs and Dohnes
 same breeding objectives as MAT $ index, and moderate emphasis on improving greasy fleece weight and a small emphasis on reducing micron
o Self-Replacing Carcase $ Index (SRC$)
 self-replacing flocks (+ terminal sires) producing a self-replacing flock with a strong emphasis on carcase traits
 e.g. Dorper, Wiltshire Horn, Wiltipoll and Boer Goats
 same breeding objectives as MAT $ index, except for no economic values for fleece traits = higher gains to be made for growth and carcass traits.

6

what are the does MAT, DPS and SRC stand for?

Maternal $ index (MAT$)
dual purpose $ index (DPS$)
self-replacing carcass $ index (SRC$)

7

what is the MAT $ index used for?

o Maternal $ index (MAT $)
 aimed at maternal breeds of specific breeds, doesn’t include FD
 e.g. border and coopworth
 balances the key economic traits relevant to most maternal breeds

8

what is the DPS $ used for?

 aimed at self-replacing maternal flocks with additional focus on wool quality, such as Corriedales, SAMMs and Dohnes
 same breeding objectives as MAT $ index, and moderate emphasis on improving greasy fleece weight and a small emphasis on reducing micron

9

what is the SRC $ used for?

 self-replacing flocks (+ terminal sires) producing a self-replacing flock with a strong emphasis on carcass traits
 e.g. Dorper, Wiltshire Horn, Wiltipoll and Boer Goats
 same breeding objectives as MAT $ index, except for no economic values for fleece traits = higher gains to be made for growth and carcass traits.

10

what are the 4 lambplan terminal indices

1. carcass plus indices
2. trade $ index
3. export $ index
4. lamb 2020 index

11

what is the carcass plus index and how is it evaluated?

 WWT, PWT, PFAT and PEMD
 Designed for high growth and muscle depth with low fat

12

what is the trade $ index and how is it evaluated?

 PWT, PFAT and PEMD
 Target 19kg carcass

13

what is the export $ index and how is it evaluated?

 PWT, PFAT and PEMD
 Target 26 kg carcass

14

what is the export $ index and how is it evaluated?

 BWT, WWT, PWT, PFAT, PEMD, PWEC
 Target 22kg carcass lamb from merino or 1st X ewe

15

what is the dual purpose $ index and how is it evaluated?

o Dual Purpose $ Index (DP$)
 aimed at self-replacing maternal flocks with additional focus on wool quality, such as Corriedales, SAMMs and Dohnes
 same breeding objectives as MAT $ index, and moderate emphasis on improving greasy fleece weight and a small emphasis on reducing micron

16

what is the self-replacing carcass $ index and how is it evaluated?

- Self-Replacing Carcass $ Index (SRC$)
 self-replacing flocks (+ terminal sires) producing a self-replacing flock with a strong emphasis on carcass traits
 e.g. Dorper, Wiltshire Horn, Wiltipoll and Boer Goats
 same breeding objectives as MAT $ index, except for no economic values for fleece traits = higher gains to be made for growth and carcass traits.

17

what is heterosis and what are 2 kinds?

- hybrid vigour
o wider range of genes= better at coping
o can cross between breeds and within to generate
o maternal
 advantage of the crossbred mother over the average of purebred mothers
 E.g. Hereford x Angus cow is generally a better mother
o Individual
 advantage of the crossbred individual relative to the average of the purebred individuals
 e.g. Limousin x Hereford calf may grow faster than the average of purebred Limousin and Hereford.

18

what is an F1 cross

o Only progeny has hybrid vigour
o A x B

19

what is a 3 breed cross?

- 3 breed cross
o Progeny have both maternal and individual hybrid vigour
o e.g. 1st X ewe x terminal ram (AB x C)
o most common is poll dorest (or similar) x F1 border Leicester x merino ewe

20

what is a 2 breed composite?

- 2 breed composite
o No. of generations after initial F1, considered an even mix of the 2 breeds
o 50% maternal and 50% individual

21

what is a backcross?

- back cross
o full maternal heterosis , 50% individual heterosis
o e.g. 1st X ewe x purebred ram (A x AB)

22

what is an open composite?

- Open composite
o Import any sire based on merit (any breed)
o Heterosis but unpredictable progeny
o E.g. white Suffolk, new genetics to stablise

23

what is MAS and when is it used?

- Marker assisted selection (MAS)
o Single Nucleotide Polymorphisms (SNPs), thousands identified
o Markers for different production traits to estimate EBVs
o First commercial sheep 2009
 Combined with traditional EBVs to increase accuracy
o Boroola and inverdale gene
 Ovulation gene, more present = more ovulation (can get 0,1 or 2)

24

what are the benefits of MAS?

- Greatest benefit for traits of low heritability, difficult/expensive to measure, only measureable in one sex or expressed later in life
o E.g. fertility, disease resistance, longevity etc.

- Potential to increase response to selection substantially
o Breed earlier with increased confidence

allows information nucleus flock
o 500 sires of different breeds progeny tested for a range of traits across different environments – combined with SNP’s