Transcript Selection Criteria: Sires

Why is Bull Selection Important?
• The bull contributes 1/2 of the genetic
makeup of his offspring
• He’s the most important individual in herd
• Use a bull to improve the quality and
performance of your herd
• It can be estimated that 87% of the genetics
in your cow herd are a result of the last 3
bulls in your cow’s pedigree.
Name these
three breeds
Selection Criteria: Sires
• Varies depending on the use of the calf and
the age of the cow being bred
• Low BW bulls are an advantage for heifers,
but not necessary or desirable for larger,
mature cows
• Look for more growth and size when
breeding larger framed, mature cows
Genetic Tools - Selection
• Use EPD’s and other estimates of genetic
potential to make permanent improvement
in the genetic level of the herd
• Effective when heritability is moderate to
high
– ex: growth- high heritability
– ex: reproduction- low heritability
Why Is Heritibility Important
• Commercial: sell cattle by weight
^ Weight at various ages is heritable
• WW is estimated to be:
~ 30% heritable
• YW is estimated to be:
~ 45% heritable
Genetic Tools - Crossbreeding
• Breeds can be crossed to improve
heratability traits that are low
Ex: Reproductive Performance
- Crossing Angus bulls on Brahman cows
(Brahman cattle reach sexual maturity later than
other breeds)
What is an EPD
• Expected Progeny Difference
• The difference between EPD’s of two bulls
is the expected difference in progeny
averages when bulls are mated to similar
cows in a herd
• # expressed in pounds & can only be used
as a comparison for animals in the same
breed
Which Bull Would You Select
to use on mature cows when growth is
the most important trait to you?
Bull
BW
YW
WW
Milk
Total Scrotal
Mat.
Frame
A
2.2
16
35
-4
4
.2
7.0
B
.6
12
25
6
12
1.0
6.5
C
-1.8 8
15
3
7
.5
6.0
7.6
.1
2.0 0.0
Avg. .6
3.8
Use of EPD’s
• Use only to compare two or more bulls
• EPD’s allow valid comparisons of all bulls
of the same breed, but they do not allow
you to compare bulls from different breeds
EPD Charts
• Most breed associations provide EPD’s for :
1.
2.
3.
4.
5.
Birth Weight (BW)
Weaning Weight (WW)
Yearling Weight (YW)
Maternal Milk
Carcass
Birth Weights
• High Birth Weight EPD’s
1. Calving Difficulty when bred to first calf
heifers
2. Increased Cost and death loss
• The American Angus Association suggests
that sires with a birth weight EPD in excess
of 3.0 pounds should not be used on first
calf heifers in most cases
Weaning & Yearling Weights
Low WW & YW
Disappointing
Weight of
Calves
Less Pounds
to Sell
Less Dollars
In Pocket
• What is the difference between a sire with a
45 pound EPD for yearling weight versus
one that has an EPD of 5 pounds?
–
–
–
–
A.
B.
C.
D.
Progeny with 20 lbs. difference in YW
Progeny with 30 lbs. difference in YW
Progeny with 40 lbs. difference in YW
Progeny with 50 lbs. difference in YW
Scrotal Circumference
• Yearling bulls with large scrotal
circumference sire daughters that show
estrus at an earlier age
• Be sure to select a bull with a SC of at least
30 cm at one year of age
Milk
• Measured in terms of how it affects
weaning weight of a calf
• Milk EPD on a bull is an estimate of lbs. of
a calf at weaning produced by the bull’s
daughter due to her milking ability
Breeding Plan
Replacement Heifers
• Mate 1st calf heifers to bull with low BW,
calving ease & large scrotal circumference
• Expect to use as many heifers as possible
from these matings as replacements
Breeding Plan
Main Cow Herd
• Mate the remaining cows to bulls which
have EPD’s that meet market criteria
• Look for bulls with higher EPD’s for
growth & carcass yield
How Many Bulls Will I Need
• Age:
1. Yearling (15 mos.) - 20-25 cows per 90
days
2. 2-5 year old- ~ 40 cows per 90 days
• Condition:
1. Poor nutrition - influence semen quality
2. Fat bulls lack stamina to breed a large
number of cows
Factors Affecting A Bull’s Value
• # of calves the bull may sire
• Performance level of the herd on which bull
is to be used
• Type of breeding system you select
• Bull’s Pedigree
Summary
• Look for traits that are economically
important to you
• Demand & buy bulls with total performance
records that will improve your herd
• Selecting and buying a herd bull is the
quickest way to make genetic improvements
in your herd besides using Artificial
Insemination