A primary screen of the bovine genome for quantitative trait loci
affecting twinning rate
Dag Inge Våge,
Department of Animal Science, Agricultural University of Norway, Box 5025, N-1432 Aas, Norway
Department of Morphology, Genetics and Aquatic Biology, The Norwegian School of Veterinary Science, N-0033 Oslo, Norway
Received: 14 December 1999 / Accepted: 25 May 2000
Abstract. An autosomal genome scan for quantitative trait loci
(QTL) affecting twinning rate was carried out in the Norwegian
Cattle population. Suggestive QTL were detected on Chromo-
somes (Chr) 5, 7, 12, and 23. Among these, the QTL positions on
both Chr 5 and Chr 23 are strongly supported by literature in the
field. Our results also confirm previous mapping of a QTL for
twinning to Chr 7, but definitely suggest a different location of the
QTL on this chromosome. The most convincing QTL peak was
observed for a region in the middle part of Chr 5 close to the
insulin-like growth factor 1 (IGF1) gene. Since IGF1 plays an
important role in the regulation of folliculogenesis, a mutation
search was performed by sequencing more than 3.5 kb of the gene
in actual families. The sequencing revealed three polymorphisms
in noncoding regions of the gene that will be important in fine
structure mapping and characterization of the QTL.
Higher reproduction capacity has the potential of reducing produc-
tion costs of several livestock species. One way to improve fertility
in cattle is to increase the proportion of the herd producing twins
relative to single calves. Results from experimentation and com-
puter simulation suggest that input costs per unit of beef output
could be reduced by 20–30% in the proportion of a herd that
produces twins (Guerra-Martinez et al. 1990). Twinning rate in
cattle is basically a product of ovulation rate, conception rate, and
embryo survival (Van Vleck and Gregory 1996). Twinning and
ovulation rate in cattle are strongly genetically correlated (0.75–
0.9) (Van Vleck et al. 1991; Gregory et al. 1997), which indicates
that the two traits are influenced by common loci.
Most studies analyzing field data report low heritability of
single-parity twinning rate on the observable scale, generally be-
low 0.04 (Syrstad 1984; Ron et al. 1990; Karlsen et al. 2000).
Despite this, it has been shown that twinning rate can be signifi-
cantly increased by selection. An example is the twinning popu-
lation established at the US Meat Animal Research Center
(MARC), Clay Center, Nebraska, where twinning rate was in-
creased by 25.1% (from 3.4% to 28.5%) over the years 1982 to
1993 (Van Vleck and Gregory 1996). Five of the foundation ani-
mals in this experiment were Norwegian Cattle or Swedish Fri-
esian sires whose daughters had produced twins at a rate of about
10% (Gregory et al. 1990). A recent study by Karlsen et al. (2000),
utilizing field records from the Norwegian Dairy Recording Ser-
vice (NDRS), shows that twinning rate in Norwegian Cattle has
increased during the time period 1978 to 1995, and that some sires
in the population have extremely high or low percentages of mul-
tiple births among their daughters.
Linkage maps in cattle (Barendse et al. 1997; Kappes et al.
1997) have sufficient marker density for genomic scans of popu-
lations for quantitative trait loci (QTL), and much of the mapping
resources are now targeted towards QTL detection of economi-
cally important traits. Previous QTL reports on bovine twinning
and ovulation rate are mainly from the MARC twinning popula-
tion, suggesting QTL for ovulation rate on bovine Chr 5 (Kappes
et al. 1998; Kirkpatrick et al. 2000), Chr 7 (Blattman et al. 1996;
Kirkpatrick et al. 2000), Chr 19 (Kirkpatrick et al. 2000), and Chr
23 (Blattman et al. 1996).
Recently, a male genetic map was developed in six paternal
half-sib families from the Norwegian Cattle population (Våge et al.
2000). The objective of this study was to utilize genotyping in
these families together with field records from the NDRS in order
to identify chromosomal regions with QTL influencing twinning
Materials and methods
Norwegian cattle map (NCM).
Six large paternal half-sib families with
a total of 285 sons of the commercial Norwegian Cattle population were
used in the construction of the map (Våge et al. 2000). The NCM covers
all 29 autosomal chromosomes and summarizes to a total length of 2682
cM. The average length of marker intervals is 12.5 cM, and approximately
82% of the intervals are shorter than 20 cM. More information about the
NCM, including average number of informative sons per marker, is avail-
able on http://www.nlh.no/Institutt/IHF/Genkartstorfe/.
In order to achieve higher marker density in the
middle part of Chr 5, four additional microsatellites (BMS490, CSSM22,
BM1216, and RM29) were genotyped by using primers and PCR condi-
tions as described at USMARC Genome Database (1999). In addition,
parts of the insulin-like growth factor 1 (IGF1) gene were sequenced in
order to detect polymorphisms in addition to a low polymorphic microsat-
ellite in the 5Ј flanking region of the gene (Kirkpatrick 1992). A total of
3670 bp of the gene, including the 5Ј-flanking region, most of the coding
sequence, and parts of introns were sequenced in the six sires by dye primer
sequencing of PCR products (Amersham Pharmacia Biotech, Uppsala,
Sweden). Bovine IGF1 sequences are submitted to GenBank with acces-
sion numbers AF210383, AF210384, AF210385, AF210386 and
AF210387. Oligonucleotides (Table 1) for sequencing were designed from
bovine sequence (Ge et al. 1997) or from homologous ovine and caprine
IGF1 sequences, when bovine sequences were unavailable (Ohlsen et al.
1993; Mikawa et al. 1995).
Polymorphisms in IGF1.
The sequencing of bovine IGF1 revealed
three polymorphisms in non-coding regions. One of these mutations, a
single nucleotide polymorphism (SNP) in the 5Ј-flanking end of the gene
(position 1407 in AF210383), has previously been reported by Ge et al.
(1997). An amplification-created restriction site (ACRS) method (Halias-
sos et al. 1989) was developed for efficient typing of the mutation in the
actual families. Primers IGF1ACRS and IGF5ЈP4 were used to specifically
Correspondence to: S. Lien; E-mail: email@example.com
Mammalian Genome 11, 877–882 (2000).
© Springer-Verlag New York Inc. 2000