Principles of Dairy Cattle Breeding in Africa

Dairy Cattle Breeding Breeding Globally

1. Principles of Dairy Cattle
Breeding

2. Genetic Control of Milk
Production
•The many genes controlling “milk production”
actually control the expression of:
–Growth hormone (and receptors)
–IGF-1 (and receptors)
–Melatonin (and receptors)
–Blood flow
–Etc., etc., etc.
•COMPLEX set of genes controlling multiple
factors that affect milk synthesis and letdown

3. Genetic Potential
•Determined by combination of genes
encoded by DNA
–Genetic expression –determined by the genes
that are present and affected by methylation
patterns (affect how and when proteins encoded
by genes are produced)
•Methylation patterns affected by environment
–Genetic transmission –only affected by the
genes that are present
•Expression and transmission can be vastly
different in the same animal

4. Imprinting or Programming
•Environmental factors can permanently
alter the ability of a gene to encode proteins
–More dramatic alterations occur during
transition periods (homeorrhetic adjustment
periods)
•Early embryonic development
•Perinatal period (around birth)
•Around puberty
•Transition period around calving

5. Altered Expression
Conception potential (70,000 lbs of milk)
embryo quality uterine conditions
Blastocyst potential (60,000 lbs of milk)
maternal nutrition placental function, dystocia
Birth (45,000 lbs. of milk)
passive immunity early nutrition
Weaning (37,000 lbs. of milk)
nutrition parturition
Lactating Cow (32,000 lbs. of milk)

6. Genetic Expression
•Management decisions and environmental quality
during fetal stages, calfhood, and up UNTIL
calving provide the FOUNDATION for the ability
(or inability) of a lactating cow to produce milk
(determines % of genetic potential that is lost)
•The management of the lactating cow is NOT the
most important factor impacting milk production,
it is simply the part that SHOWS the most
•Even though you can’t always see the foundation,
it determines the “quality of the house” (or
lactational performance) that can be supported…

7. Genetic Progress
50% from sire, 50% from dam
-Sire choices –best in the world
-Dam choices –best in the herd
-after culling and replacement losses
-involuntary culling rate (mastitis, reproduction,
mastitis, death losses) determines potential for
voluntary culling
-voluntary culling rate determines dam side of genetic
progress
Nationally, 94% of genetic progress is from sire
side, 6% is from dam side

8. Population Gene Flow
•76% by bull studs
–Sires to sons –43%
–Cows to sons –33%
•24% by producers
–Sires to daughters –18%
–Cows to daughters –6%
•~ 9 million cows, ~ 600 bulls

9. Genetic Transmission
•Since we don’t harvest our full genetic
potential from cows, should we not worry
about genetic progress (use cheaper bulls)
until management “catches up”????
–Transmission losses are a % of genetic potential
–In well-managed herds, 100 lbs PTA milk
difference provides about 170 lbs actual milk
–In average managed herds, 100 lbs PTA milk
difference provides about 100 lbs actual milk

10. Genetic Progress
•Determinants of genetic progress:
–Accuracy of selection (A)
–Intensity of selection (I)
–Genetic variation (G)
•A x I x G = genetic progress per generation
•A x I x G/GI = genetic gain per year
–If GI is generation interval

11. Genetic Progress
•Genetic variation is beyond control of producer
•Accuracy is determined by breed studs
–Studs select the parents of young sires
•Producer affects genetic change by controlling the
intensity of selection
–Controls rate of this by controlling generation interval
Fast turnover best for genetic progress, not necessarily best for
profitability
Takes 1.5 lactations (on average) to pay off heifer raising costs
-increased longevity makes cows more profitable
-allows more “voluntary” sales of heifers or cows
Average cow leaves the herd after 2.7 lactations nationally (only 1.7
lactations on average in California!!)

12. “Official” Dairy Records
•Dairy Herd Improvement Association (DHIA)
–1/3 of all cows enrolled
–Records production and other performance data
–Forms foundation of genetic evaluations
•Beef is by breed associations
•Swine is by genetic companies like PIC
–Use monthly data to estimate lactation yields
•Standardized to 305-2x-ME
–Adjusts for age at calving, month of calving, times milked per
day, management group, days in milk, region of US, days open
in previous lactation

13. Natural Service vs. AI
•Economic advantages of AI
–Higher producing daughters
–Lower cost per insemination
•Feed, housing costs of bull far exceed AI costs
•Safety issues
•Convenience (often favors natural service)
•Training (favors natural service)

14. Proven vs. Young Sires
•Proven sires are 7-8 years old when first proofs
arrive, have “life expectancy” in service of about
2-3 years
–PTA’s increase in accuracy as Reliability increases
•Young sires first sampled at less than 2 years old
–Pedigree Indexes VERY accurate for the group, can be
inaccurate for any individual
•Select individual, highly reliable proven sires and
groups of young sires to minimize risk
•Requires 10 young sires to produce 1 proven sire
that makes the line-up
–$250,000 investment per proven sire available

15. From USDA-AIPL: http://www.aipl.arsusda.gov/dynamic/trend/current/trndx.html
Fig 9-3. Historic trends for breeding values illustrate the speed of
genetic progress and the value of young sires. (Courtesy of USDA)

16. Breeding Issues in Dairy
•Identification issues
–Estimated 10-12% of all registered animals are
improperly identified
•Inbreeding issues
–Jersey average 6-7%
–Holstein average 7%
•Losses include heifer mortality, health, reproduction,
and milk production
–50-80 lbs of milk per point, 2 lbs fat and protein
•24 distinct genetic lines in Holstein breed
–Fewer available in colored breeds

17. Fig 10-1. Marcus Kehrli tests a calf that has bovine leukocyte
adhesion deficiency (BLAD) (Courtesy of USDA-ARS)

18. Crossbreeding
•Improves milk production, reproduction,
health, heifer mortality (above average of
two breeds crossed)
–Interval from calving to first heat, days open
and calving interval all improved by about a
week
•Greatest heterosis apparent early in life,
decreases with age

19. Fig 10-2. Holstein and Jersey crossbred cows graze in
south-central Pennsylvania. (Courtesy of USDA-ARS)

20. Goal of a Breeding Program
•Make $$$$$$ (where is most income derived?)
•For most herds, production associated traits are
most important
•For some herds, type traits become very important
(marketing cows vs. marketing milk)
•90% of herds derive more than 90% of income
from sale of milk

21. Type vs. Productive Life
Productive Life
Type
Trait

22. Traits of Importance
•Milk
•Health or SCS
•Reproduction
•Type traits
–Udder composite
–Feet and legs composite
–Stature (big or small????)
•Calving ease

23. Factors to Consider
•Economic value
–Does it have a value??
–Will it improve profitability??
•Heritability
–How fast can this trait change?
–Genetic control vs. environmental or management
control
•Heritability is 100% if expression of trait varies solely because
of inheritance
•Genetic variation/(genetics + environment) = h
2
•Reduce management or environmental variation in population,
heritability increases

24. Trait h2 h2
Milk Yield 0.3Fat Yield 0.25
Fat Percentage 0.5Protein Percentage0.5
Reproduction 0.07Milking Rate 0.3
Stature 0.42Feet & Legs Score 0.17
Strength 0.31Fore Attachment 0.29
Body Depth 0.37Rear Udder Height 0.28
Dairy Form 0.29Rear Udder Width 0.23
Rump Angle 0.33Udder Cleft 0.24
Thurl Width 0.26Udder Depth 0.28
Rear Legs-Side View0.21Front Teat Placement0.26
Rear Legs-Rear View0.11Teat Length 0.26
Foot Angle 0.15Final Score 0.29
Heritabilities of various production and type traits
Table 8-1

25. Heritability
•Milk ~30%
•Protein and fat ~ 50%
•Reproduction ~ 10%
•Health ~ 10%
•Type traits between 15 to 40%
–Stature highest
–Feet and legs low

26. Sire Summary Codes
•Name of bull
–bulls registered name
•Registration number
–bulls registration number
•NAAB code
–Indicates breed, stud from which semen can be purchased, bull ID
number
•PTA
–Predicted transmitting ability
–Best estimate of expected extra production per daughter per year
–PTA’s for pounds protein, pounds fat, pounds milk, percent protein,
percent fat

27. Table 9-2. Means (lbs) for calculating PTA% for the May 2004 sire summaries
Breed Milk Fat Protein Protein Milk
1
Ayrshire 16,832 649.2 524.0 16,832
Brown Swiss 19,356 775.9 637.9 19,349
Guernsey 15,427 683.0 506.8 15,438
Holstein 23,382 846.5 691.8 23,378
Jersey 16,053 738.1 568.6 16,055
Milking Shorthorn 16,012 567.9 489.6 16,012
1
Protein Milk = Milk for cows that had protein
Modified from USDA-AIPL: http://www.aipl.arsusda.gov/dynamic/summary/current/yld_mean.htm

28. Sire Summary Codes
•FM$
–Fluid milk dollars
–Weighs PTA milk and fat, reflects the gross income per
lactation the future mature daughters will earn in excess
to herdmates
•CM$
–Predicted transmitting ability cheese merit dollars
–Reflects income per lactation daughters will receive if
milk is priced according to it’s value in cheese

29. Sire Summary Codes
•PTAT
–Predicted Transmitting Ability -Type
–Expected difference in final score between daughters of
the bull and breed average
•TPI
–Type Production Index
–Holsteins
•2 x PTA protein, 2 x PTA fat, 1 x PTA, type, 1 x udder traits
–Other breeds
•3 x PTA$, 3 x CY$, 1 x PTAT

30. Sire Summary Codes
•Calving ease
–Percentage of difficult births in first calf heifers
–Range 5 to 20%
–Median 9%
•Reliability
–Degree of confidence a breeder can place on PTA
–Increases with number of daughters, number of herds
with daughters, number of records per daughter
–Closer number is to 100%, the more reliable PTA

31. Sire Summary Codes
•PPA
–Predicted Producing Ability
–Cow’s ability to produce above or below the average of
other cows
•PI
–Pedigree Index
–Estimate of animal’s genetic transmitting ability based
on pedigree information
•Parent Average
–Estimate of breeding average using sire and dam
information

32. Sire Summary Codes
•PL
–Productive Life
–Predicted herd life for cows remaining in the herd
–Reflects resistance to culling
•SCS
–Somatic Cell Score
–Transmitting ability for somatic cell score
•Lowly heritable
•NM$
–Net merit index
–Uses income and expenses to estimate expected lifetime profit
daughters will provide

33. Sire Summaries
•Type traits expressed in sire summaries
based on linear scoring system
–Scored over a range of 50 points
•No optimum or best score
•Registered and grade
•Type traits expressed as standardized
transmitting abilities (STA’s)
–Scale -3 to +3

34. Calculating Improvements
•Use STA’s
–Based on linear scores
–Scored between 1 and 50 on a biological basis
•Midpoint is zero, each increment represents one
standard deviation
•Score does not indicate “better” or “worse”
•Convert STA’s to actual change in a trait per
generation or per year
–High heritability = rapid change
–Low heritability = slow change
•Allows ranking of importance of selection traits

35. Linear Type TraitMeasurement -3 0 3
Stature Inches - height at hip 55.6 56.6 57.6
Rump Angle Inches - slope from hips to pins0.6 1.3 2.0
Thurl Width Inches - between the pins 4.6 5.0 5.4
Foot Angle Degrees of the angle the front of the
toes make with the ground 41 43 45
Rear Udder HeightInches - between bottom of vulva
and top of milk secreting tissue10.6 10.1 9.6
Rear Udder WidthInches - width of rear udder where
udder attaches to body 5.5 5.8 6.2
Udder Cleft Inches - depth of cleft between rear
quarters at bottom of udder 1.2 1.4 1.6
Udder Depth Inches - between lowest point of
udder floor and point of hock 0.5 1.2 1.9
Teat Length Inches - length of longest teat 2.2 2.4 2.6
Source: Holstein Association
Table 9-3
Average Mature Daughter Measurement Corresponding to Linear Type STA
of Sire When Mated to Breed Average Cows

36. Selection Strategies
•Individual traits -milk, protein, stature, etc.
•Selection Indexes –multitrait indexes
–TPI or PTI –production/type indexes
–Productive Life (PL) –1
st
crop daughters
estimated from type and production traits, 2
nd
crop mostly direct from culling info
–Others include SCS, FL composite, udder
composite, body size composite
–Net Merit $ -additional net profit that a
daughter will produce over her lifetime
•Usually best index for profit of a commercial dairy

37. Corrective Mating Strategies
•Many mating services available
•Can you take your cow with excessive set to
her legs, mate her to a bull with excessively
straight legs, and create a daughter with
perfect legs??
–Corrective mating strategies, over a 30 year
period, did not improve type traits any faster
than randomly selecting bulls from the same
group

38. Fig 9-2. Curt Van Tassell loads a high-capacity DNA
sequencer to find more genetic markers for screening
dairy bulls (Courtesy of USDA-ARS)

39. Summary
•Focus breeding strategies on traits that improve
profitability the most and have the most
opportunity for change
–Net Merit is probably the best selection index currently
available for commercial herds –select bulls that are
above the 90
th
percentile for Net Merit $$
•Registered herds that derive a significant portion of income
from cattle sales are more complicated
–Cull bulls from that group for calving ease issues or
other major “flaws”
•Minimize culling
–Sample groups of young sires on “groups’ of unselected
cows (all 3
rd
service, etc.)
•Restrict young sire use to multiparous cows