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ASC 370 > sheep genetics 4 > Flashcards

sheep genetics 4 Flashcards

1
Q

What is lambplan indices?

A
  • 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)
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2
Q

what lambplan indices should be -ve and why?

A

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)

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3
Q

how are the indices values used?

A
  • 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
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4
Q

what are the 3 major lambplan indices?

A

lambplan terminal, maternal and dual purpose indices

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5
Q

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

A 
-	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.

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6
Q

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

A

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

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7
Q

what is the MAT $ index used for?

A

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

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8
Q

what is the DPS $ used for?

A

 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

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9
Q

what is the SRC $ used for?

A

 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.

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10
Q

what are the 4 lambplan terminal indices

A
  1. carcass plus indices
  2. trade $ index
  3. export $ index
  4. lamb 2020 index
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11
Q

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

A

 WWT, PWT, PFAT and PEMD

 Designed for high growth and muscle depth with low fat

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12
Q

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

A

 PWT, PFAT and PEMD

 Target 19kg carcass

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13
Q

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

A

 PWT, PFAT and PEMD

 Target 26 kg carcass

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14
Q

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

A

 BWT, WWT, PWT, PFAT, PEMD, PWEC

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

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15
Q

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

A

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

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16
Q

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

A
  • 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
Q

what is heterosis and what are 2 kinds?

A
  • 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
Q

what is an F1 cross

A

o Only progeny has hybrid vigour

o A x B

19
Q

what is a 3 breed cross?

A
  • 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
Q

what is a 2 breed composite?

A
  • 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
Q

what is a backcross?

A
  • back cross
    o full maternal heterosis , 50% individual heterosis
    o e.g. 1st X ewe x purebred ram (A x AB)
22
Q

what is an open composite?

A
  • 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
Q

what is MAS and when is it used?

A
  • 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
Q

what are the benefits of MAS?

A
  • 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

ASC 370 (21 decks)

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