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Polymorphism of casein genes was studied in half-sib families of artificial insemination bulls of the Finnish Ayrshire dairy breed. Ten grand-sires and 300 of their sons were genotyped for the following polymorphisms : α s1 -casein (B, C), β-casein (A 1 , A 2 ), the microsatellite within the κ-casein gene (ms 5 , ms 4 ) and K-casein (A, B, E). Nine different combinations of these alleles, casein haplotypes, were found. Associations between casein haplotypes and milk production traits (milk and protein yield, fat and protein percentage and milking speed) were studied with ordinary least-squares analysis to find a direct effect of the haplotypes or an association within individual grandsire families using the granddaughter design. Estimated breeding values of sons were obtained from cow evaluation by animal model. No direct effect of the casein haplotypes on the traits was found. Within grandsire families, in one out of four families the chromosomal segment characterized by haplotype 3 (B-A 2 -ms 4 -A) was associated with an increase in milk yield (P

Cattle chromosome 6 was scanned with 11 markers, ten microsatellites and the casein haplotype, to identify quantitative trait loci (QTLs) affecting the following milk production traits: milk yield, fat percentage, fat yield, protein percentage and protein yield. Twelve Finnish Ayrshire half-sib families with a total of 480 sons were genotyped and used in a grand-daughter design. Interval mapping was performed with a multiple-marker regression approach with a one-QTL and a two-QTL model, and the significance threshold values were determined empirically using a permutation test. Across-family analysis with the one-QTL model revealed an effect on protein percentage (P < 0.05) and on milk yield (P < 0.05). The analysis with the two-QTL model identified significant effects (P < 0.05) on protein percentage, milk yield, and fat yield. Comparing these two cases, the results suggest the existence of two QTLs on chromosome 6 with an effect on milk production traits. One of the QTLs was located around the casein genes. As the other QTL was similar in location and effect to a QTL found previously in Holstein-Friesians, an identity-by-descent approach could be applied to fine map this region.

Cattle microsatellite clones (136) were isolated from cosmid (10) and plasmid (126) libraries and sequenced. The dinucleotide repeats were studied in each of these sequences and compared with dinucleotide repeats found in other vertebrate species where information was available. The distribution in cattle was similar to that described for other mammals, such as rat, mouse, pig, or human. A major difference resides in the number of sequences present in the bovine genome, which seemed at best one-third as large as in other species. Oligonucleotide primers (117 pairs) were synthesized, and a PCR product of expected size was obtained for 88 microsatellite sequences (75%). Synteny or chromosome assignment was searched for each locus with PCR amplification on a panel of 36 hamster/bovine somatic cell hybrids. Of our bovine microsatellites, eighty-six could be assigned to synteny groups of chromosomes. In addition, 10 other microsatellites--HEL 5, 6, 9, 11, 12, 13 (Kaukinen and Varvio 1993), HEL 4, 7, 14, 15--as well as the microsatellite found in the kappa-casein gene (Fries et al. 1990) were mapped on the hybrids. Microsatellite polymorphism was checked on at least 30 unrelated animals of different breeds. Almost all the autosomal and X Chr microsatellites displayed polymorphism, with the number of alleles varying between two and 44. We assume that these microsatellites could be very helpful in the construction of a primary public linkage map of the bovine genome, with an aim of finding markers for Economic Trait Loci (ETL) in cattle.

Dairy bulls have been genotyped for K-casein and P-lactoglobulin from semen samples by methodology based on a polymerase chain reaction (PCR), In this study, a previously described method for κ-casein A and B variants was extended to cover also the detection of the E variant. For β-lactoglobulin the variants A and B were genotyped by another PCR-based method. The frequencies of the κ-casein and β-lactoglobulin alleles were determined from 308 and 291 Finnish Ayrshire and 42 and 44 Finnish Friesian bulls, respectively. The bulls had been born between 1973 and 1988. There was no noticeable trend in the differences between allele frequencies over the years, the overall frequencies of κ-casein A, B and E being 0.62, 0.09 and 0.29 in the Finnish Ayrshires and 0.85, 0.14 and 0.01 in Finnish Friesians. The overall frequencies of β-lactoglobulin A and B alleles were 0.25 and 0.75 in Ayrshires and 0.56 and 0.44 in Friesians, Kotieläintuotannon tutkimuslaitoksen eläinjalostusyksikössä on aloitettu tutkimus maitoproteiinivarianttien yhteyksistä eläinten tuotanto-ominaisuuksiin. Tässä julkaisussa esitetään työn ensimmäinen vaihe, jossa molekyyligeneettistä menetelmää sovellettiin keinosiemennyssonnien κ-kaseiinin ja β-laktoglobuliinin genotyypitykseen. Tuloksista laskettiin näiden lokusten alleelifrekvenssit ayrshire- ja friisiläisroduille. DNA-monimuotoisuutta analysoitiin entsymaattisen monistamisen (PCR) ja DNA:ta spesifisesti pilkkovien entsyymien avulla. K-kaseiinin variantit A, B ja E sekä β-laktoglobuliinin variantit A ja B määritettiin spermanäytteistä. Yhteensä 308/291 ayrshire-ja 42/44 friisiläisnäytettä analysoitiin K-kaseiinin/β-laktoglobuliinin suhteen. κ-lokuksen A-, B- ja E-alleelien frekvenssit olivat ayrshire-sonneilla 0,61, 0,10 ja 0,29 ja friisiläissonneilla 0,85, 0,14 ja 0,01. β-laktoglobuliinilokuksessa olivat A- ja B-alleelien frekvenssit ayrshirella 0,25 ja 0,75 ja friisiläisillä vastaavasti 0,56 ja 0,44. Alleelifrekvenssejä tutkittiin ayrshirellä myös ikäryhmittäin sonnien syntymävuosien (1973-88) mukaan. Frekvensseissä ei havaittu systemaattista muutosta tutkittuna ajanjaksona. Näiden rotujen κ-lokuksen alleelifrekvenssit vastasivat hyvin jo aiemmin maidosta proteiinielektroforeesilla määritettyjä frekvenssejä. β-lakloglobuliinin alleelifrekvensseissä havaittiin vähäisiä eroja aikaisempiin tutkimuksiin verrattuna. Erot saattavat johtua analysoidun aineiston koosta. Lisäksi aikaisemmat tutkimukset on tehty lehmillä kun taas tässä tutkimuksessa käytettiin sonneja. Maitoproteiinialleelien ja taloudellisten ominaisuuksien välisistä yhteyksistä tarvitaan yksityiskohtaisempaa analyysiä. Tällaisessa analyysissä κ-kaseiinilokus pitäisi analysoida yhdessä muiden geneettisesti kytkeytyneiden kaseiinilokusten (αs1-, αs2- ja β-kaseiinin) kanssa.

A multiple-marker mapping approach was used to search for quantitative trait loci (QTLs) affecting production, health, and fertility traits in Finnish Ayrshire dairy cattle. As part of a whole-genome scan, altogether 469 bulls were genotyped for six microsatellite loci in 12 families on Chromosome (Chr) 23. Both multiple-marker interval mapping with regression and maximum-likelihood methods were applied with a granddaughter design. Eighteen traits, belonging to 11 trait groups, were included in the analysis. One QTL exceeded experiment level and one QTL genome level significance thresholds. Across-families analysis provided strong evidence (P(experiment) = 0.0314) for a QTL affecting live weight. The QTL for live weight maps between markers BM1258 and BoLA DRBP1. A QTL significant at genome level (P(genome) = 0.0087) was mapped for veterinary treatment, and the putative QTL probably affects susceptibility to milk fever or ketosis. In addition, three traits exceeded the chromosome 5% significance threshold: protein percentage of milk, calf mortality (sire), and milking speed. In within-family analyses, protein percentage was associated with markers in one family (LOD score = 4.5).

A total of 453 bulls belonging to 11 half-sib families of Finnish Ayrshires were genotyped for six microsatellite markers on chromosome 9. The data were used in an attempt to map quantitative trait loci applying regression as a multimarker approach. For association analysis with a granddaughter design, the EBV for 12 traits were used: milk yield, protein yield, fat percentage, protein percentage, daughter weight, bull growth, calf mortality, days open, fertility treatments, nonreturn rate, SCC, and clinical mastitis. The empirical values of significance thresholds were determined using a permutation test on the experimental data. Although no significant effects were found, the results indicate some support for the existence of a locus on chromosome 9 that affects milk and protein yields.

International audience

A cattle genetic linkage map was constructed which covers more than 95 percent of the bovine genome at medium density. Seven hundred and forty six DNA polymorphisms were genotyped in cattle families which comprise 347 individuals in full sibling pedigrees. Seven hundred and three of the loci are linked to at least one other locus. All linkage groups are assigned to chromosomes, and all are orientated with regards to the centromere. There is little overall difference in the lengths of the bull and cow linkage maps although there are individual differences between maps of chromosomes. One hundred and sixty polymorphisms are in or near genes, and the resultant genome-wide comparative analyses indicate that while there is greater conservation of synteny between cattle and humans compared with mice, the conservation of gene order between cattle and humans is much less than would be expected from the conservation of synteny. This map provides a basis for high-resolution mapping of the bovine genome with physical resources such as Yeast and Bacterial Artificial Chromosomes as well as providing the underpinning for the interpolation of information from the Human Genome Project.