Transcript Hornlosigkeirt Jesery Presentation

Breeding polled cattle
•Jerseys
• Background and problems
• Wilhelm Wemheuer
• Department of Animal Sciences
• Georg August University Göttingen
Significance
• There is an ongoing discussion in Germany
concerning animal welfare issues in regard to
dehorning calves.
• Dehorning is already prohibited organic farms and
is only permissible with exemptional permissions.
• This has led to a demand for stud bulls
homozygous for polledness.
History
• The first definite description of polled cattle is
to be found in Herodot (460 BCE).
• He states that cattle in Lybia (Africa) sport the
largest horns. Going north, the horns get
successesivly smaller, until they disappear
completely in the Far North.
• His conclusion: The formation of horns is
dependent on the climate: The warmer it is,
the longer the horns are.
History
• This agrees with the fact that the original
polled breeds are to be found in Northern
Europe.
• A. Aberdeen Angus
Scotland
• B. Galloway
Scotland
• C. Fjäll cattle
Northern Sweden
• They are thus one of the origns of polledness.
Genetics
• The gene for hornedness/polledness lies on the
cattle chromosome 1.
• Michel Georges et al. , 1993
• Polledness is a dominant trait.
• Polled breed * horned breed = always polled.
• Known since antiquity.
Genetics
• However, scurs (incompletely developed horns)
occur in European cattle breeds after
crossbreeding with polled bulls.
• The gene for scurs lies on cattle chromosome 19.
M. Asai et al. 2004
• Inheritance is:
a.
recessive
b. independent of cattle chromosome 1
c.
more strongle developed in bulls.
Genetics
• Marker were found for polledness:
• Schmutz et al., 1995 microsatellite
• Harlizius et al., 1997 microsatellite
Charolais
Simmental
• Drögemöller et al., 2005 microsatellite Length of
the gene = 1Mb = 1 million base pairs
• Cargill et al., 2008 Single Nucleotid Polymorphism (SNP)Holstein
First test for Holsteins, did not include all
Genetics
• Medugorac et al. 2012: Bovine polledness - an
autosomal dominant trait with allelic heterogenity
• The lab in Munich found two separate markers for
polledness:
• 85% of one marker set occurs in Holstein
Friesians. The so-called Friesian Mutation.
• One marker set occurs in the naturally polled
breeds (Aberdeen Angus, Galloway, Fjäll cattle).
The so-called Celtic Mutation
Genetics
• Allais- Bonnet et al., 2013 found a mutation
(possibly causal) for the Celtic Type.
• It is a duplication of 202 base pairs.
• Rothammer et al., 2014 reduced the marker set for
the Frisian Type to a duplication of 80.000 (80kb)
base pairs.
• It is still not understood how the duplications
suppress the growth of horns and why one
chromosome is sufficient (i. e., why the trait is
dominant).
Are there several possible origns of
polledness in Jersey cattle?
• Maack Dairy Eclipses-Pp
Celtyc Typ
2005
– Millstream Henery Eta Belle-P
2002
D+E Henery P
1989
–D+E Duncan Brass Bella-P
1987
»D+E Phils Brass Bella-P
1983
• Molly Brook General Bella P
1977
• Molly Brook Norms Belle-P 1975
• Normsland Belle Boy
1960
• Coras Brookside Belle-P 1948
Are there several possible origns of
polledness in Jersey cattle?
• Fairway Mygent Dallas PP
2006
– V. Den Kel Paramount Mygent-P
Friesian Typ 2003
Dutch Hollow Barber Milady-P
1997
– Dutch Hollow S Joe Mistress-P
1990
» Dutch Hollow Pal Madam-P
1988
• Dutch Hollow Silver B Milady-P
1986
• Dutch Hollow Banner Mistress-P 1981
• Jeusaf2993471
1974
• Jeusaf2733605
1967
• Fair-Weather Champion Superb 1952
• Royal Polled Champion
1950
Friesian and Celtic Mutation
• Fairway Mygent Dallas PP
• Dallas has the Friesian Mutation from his dam,
the Celtic on from his sire..
• The two types are also present with appr. 50%
in the remaining polled population of Jerseys.
• Dallas PP is definitely homozygously polled,
but still has a small number of horned
descendants!
Maple Dream Linus PP Friesian/Celtic
Father: Dallas PP Friesian/ Celtic * EclipseP Mother / Celtic
Crossing-over between Friesian
and Celtic mutation
The problem of
cattle chromosome 1
• The cattle chromosome 1 is the longest one. Apart
from the locus for polledness, there are another
600 to 800 loci.
• These loci are coupled to the allele for polledness.
• Chromosome 1 with the allele for polledness can
only be improved via successful crossing over or
recombination with a better selected part of
another Jersey-chromosome 1.
• This only happens in heterozygous bulls or cows.
1: 100? 1:1000?
The problem of inbreeding
• The whole breadth of the global Jersey population
has the be utilised to produce heterozygous cows
in order to prevent inbreeding.
• Polled bulls have to be crossed into the best
female lines.
• The best female polled calves immediately have to
be paired with the best horned bulls.
Conclusion
The creation of new heterozygous lines
• A. prevents inbreeding
• B. increases the chance of successful crossing
over in chromosome 1.