sheep genetics 4

Question 1

What is lambplan indices?

Answer 1

• 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)

Question 2

what lambplan indices should be -ve and why?

Answer 2

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)

Question 3

how are the indices values used?

Answer 3

• 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

Question 4

what are the 3 major lambplan indices?

Answer 4

lambplan terminal, maternal and dual purpose indices

Question 5

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

Answer 5

-	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.

Question 6

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

Answer 6

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

Question 7

what is the MAT $ index used for?

Answer 7

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

Question 8

what is the DPS $ used for?

Answer 8

 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

Question 9

what is the SRC $ used for?

Answer 9

 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.

Question 10

what are the 4 lambplan terminal indices

Answer 10

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

Question 11

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

Answer 11

 WWT, PWT, PFAT and PEMD

 Designed for high growth and muscle depth with low fat

Question 12

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

Answer 12

 PWT, PFAT and PEMD

 Target 19kg carcass

Question 13

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

Answer 13

 PWT, PFAT and PEMD

 Target 26 kg carcass

Question 14

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

Answer 14

 BWT, WWT, PWT, PFAT, PEMD, PWEC

 Target 22kg carcass lamb from merino or 1st X ewe

Question 15

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

Answer 15

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

Question 16

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

Answer 16

• 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.

Question 17

what is heterosis and what are 2 kinds?

Answer 17

• 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.

Question 18

what is an F1 cross

Answer 18

o Only progeny has hybrid vigour

o A x B

Question 19

what is a 3 breed cross?

Answer 19

• 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

Question 20

what is a 2 breed composite?

Answer 20

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

Question 21

what is a backcross?

Answer 21

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

Question 22

what is an open composite?

Answer 22

• 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

Question 23

what is MAS and when is it used?

Answer 23

• 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)

Question 24

what are the benefits of MAS?

Answer 24

• 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