Review

1
Review

• Fine
• Medium
• Coarse
• Most important breeds?
• Why so many in US?

2
Performance Records

• Purebred Operations
• More records required
• Registration work
• Traits important to breed

3
Genetic Improvement 3 factors

• 1. Selection differential
• 2. Heritability
• 3. Generation interval

4
Selection Differential

• SD is the superiority of replacements compared to
  flock average.
• Example Average adjusted WW 60
• Replacement Ewes - 70
• 70 - 60 10 x .5 x .2
• SD 1.0

5

• Replacement Ram 85 pound adj. ww
• 85 - 60 25 x .5 x .2
• SD 2.5
• Total SD 2.5 1.0 3.5

6
Limits to Selection Differential

• Sires provide more improvement
• SD with only one trait
• More traits - SD per trait decreases
• How many can you keep?

7
Heritability

• of what you see which is due to genetics.
• Traits h2
• Reproduction .1 - .2
• Growth .25 - .40
• Carcass .3 - .5
• Wool .4 - .6

8

• Low h2 traits require multiple records Example
  Lambs born
• h2 - .10 with r lt.20
• Repeatability - likelihood that a ewe twinning in
  2006 will twin in 2007.
• Lamb crop in U.S. has not increased much in 50
  years.

9

• Selection based on one record must account for
  fixed effects.
• Ex 5 year old ewe with twins in 06.
• Individual record not important.
• Perspective buyers
• What has she done relative to flock average each
  of past five years

10

• Wool traits
• highly heritable
• highly repeatable
• one record of performance

11

• Generation Interval
• How fast the flock turns over.
• GI Average Ewe Average Ram Age
• 2
• 4 2 3.0
• 2

12

• GI - Smallest possible 1
• Economic suicide
• Why ??
• Best Solution let ewe age float
• Rams use only one year
• Use older rams from other flocks

13

• Economic Traits
• Ewes
• Pounds Weaned
• Mothering ability
• Milking ability
• Prolificacy
• Growth
• Hardiness and Longevity
• Extended Breeding Season
• Clean Wool

14

• Economic Traits
• Rams
• Offspring Vigor and Livability
• Rate of Gain
• Feed Efficiency
• Breeding Capacity
• Carcass Cutability
• Lambing Ease
• Longevity

15

• Genetic Improvement
• Set Selection Goals
• Identify Superior Individuals
• NSIP - uses all performance records
• - fair comparisons via contemporary groups
• - provides genetic estimates on animals
  without records
• rams and young lambs

16

• NSIP Traits
• Maternal Lambs born
• Pounds Weaned
• Growth 60, 120
• Wool Grease Fleece Weight (GFW)
• Fiber Length
• Fleece Grade

17
Fixed Effects

• Adjust for
• Dam Age
• Type of Birth and Rearing
• Age Adjustment
• Sex
• Homework for lab

18

• Contemporary groups
• What is it?
• When are they needed?

19
Other Sheep Improvement Plans

• Lamb Plan
• Wool Plan
• Ewe Byte
• Group Breeding Schemes
• Great Britain
• SUFFOLK SIRE REFERENCE SCHEME
• Canada
• Western Suffolk Sire Reference program
• Ontario Suffolk Sire Reference program

20

• Why does sheep industry not embrace genetic
  improvement?
• Purebred breeders
• Commercial producers