Inheritance of melanocytic lesions and their association with the white colour phenotype in miniature swine

A line of Munich Miniature Swine (MMS) Troll showing a high incidence of spontaneous benign and malignant cutaneous melanocytic lesions has been developed since 1986. The inheritance of cutaneous melanocytic lesions was studied by establishing the F₁-, F₂- and reciprocal B₁-generations with one melanoma MMS-Troll boar and four unaffected German Landrace sows as founders. A total of 176 animals were available, 27 in the F₁-, 111 in the F₂-, 19 in the B_1-DL-, and 14 in the B_1-Troll-generation. Benign melanocytic lesions were observed in 42% of F₁-, 18% of F₂-, 11% of B_1-DL- and 50% of B_1-Troll-animals. Malignant melanomas developed in 3.6% of F₂- and 7.1% of B_1-Troll-animals, although no animal with white coat colour was affected. A mixed major gene model with arbitrary gene action explained the segregation of benign lesions sufficiently well. For melanomas a mixed major gene model required additional dominant acting suppressor loci to obtain a sufficient fit to the data. An influence of SLA haplotypes on the penetrance of melanocytic lesions was not evident. The association analysis of the white phenotypes strongly indicated that the dominant allele I at the I-locus suppresses malignant melanocytic lesions. A possible explanation is the lack of melanocytes in the skin of dominant white pigs caused by a mutation of the KIT-gene, which leads to a failure of melanoblast migration and development.     

Variance component estimation on the frequency of pathologic changes in the navicular bones of Hanoverian Warmblood horses

The results of a standardized radiological examination of 3748 young Hanoverian Warmblood horses selected for sale at auction as riding horses were used to quantify the influence of systematic effects on and to estimate genetic parameters for the prevalence of pathologic changes in the navicular bones. Radiographic findings in the navicular bones of the front limbs were analyzed as all‐or‐none traits. The pathologic changes were mostly classified as slight [PCN(I); 14.9%], less often as moderate [PCN(II); 5.3%] or severe [PCN(III); 1.8%]. Date and year of auction had a significant influence on the prevalence of documented radiographic findings. The prevalence of PCN(I) was further significantly dependent on the examiner, the type and the quality of auction. PCN(II) was significantly more prevalent in male than in female horses. The age, the anticipated suitability and the region of origin of the horses did not have any significant influence on the prevalence of pathologic changes in navicular bones. A higher percentage of genes of the Hanoverian and the Holstein Warmblood horse increased the probability of PCN(I) classification. A significant influence of the sire was found for PCN(I) and PCN(II), and of the male founder for PCN(II) and PCN(III). The female founder was significant only for PCN(II). In general, radiographic findings of any severity in front left and right navicular bones were significantly correlated with each other. Restricted maximum likelihood (REML) was used for the estimation of genetic parameters. The analyses were performed multivariately in linear animal and sire models including height at withers as a separate trait. Heritability estimates for the prevalence of PCN(I), PCN(II) and PCN(III) of horses of both sexes ranged between h² = 0.09 and 0.21. When distinguishing between findings in males and females, somewhat implausible estimates were obtained for PCN(II) in females, which might have been caused by their low prevalence. The additive genetic correlations between the investigated traits indicated that radiographic findings consistent with navicular syndrome have a uniform genetic pattern in males and in females, and irrespective of their severity. However, their genetic correlation to height at withers was found to be inconsistent and, therefore, not to be utilizable for selection.     

Genetic risk factors for osteochondrosis in various horse breeds

Osteochondrosis (OC) is an injury to cartilage canals with a following necrosis in the growth cartilage, from there it can develop to osteochondrosis dissecans (OCD). Due to its high impact in the equine industry, new insights into predisposing factors and potential high‐risk genetic variants are warranted. This article reviews advancements in quantitative and molecular genetics in refining estimation of genetic parameters and identifying predisposing genetic loci. Heritabilities were highest for hock OC with estimates at 0.29–0.46 in Hanoverian warmblood and Norwegian trotters, whereas in Thoroughbreds only very low genetic variation seemed to be present in hock OC lesions. Whole genome scans using the Illumina Equine SNP50 or SNP70 Beadchip were performed in Thoroughbred, Standardbred, French and Norwegian trotter, Hanoverian and Dutch warmblood. Validation studies in Spanish Purebred and Hanoverian warmblood horses corroborated OC risk loci on ECA 3, 14, 27 and 29. Particularly, a strong association with hock‐OCD was found for a single nucleotide polymorphism (SNP) on horse chromosome (ECA) 3 upstream to the LCORL gene. Gene expression and microRNA analyses may be helpful to understand pathophysiological processes in equine OC and to connect OCD‐associated genomic regions with potential candidate genes. Furthermore progress in elucidating the underlying genetic variants and pathophysiological changes in OC may be expected from whole genome DNA and RNA next‐generation sequencing studies.     

Evaluation of Prolactin Receptor (PRLR) as Candidate Gene for Male Fertility in Hanoverian Warmblood Horses

Stallion fertility has increasing importance as the artificial insemination is employed in horses more intensely. Molecular genetic markers may be useful tools to evaluate the stallion fertility before breeding. The prolactin receptor gene (PRLR) was chosen as a candidate for stallion fertility because of its influence on testicular and accessory sex gland function. Screening the equine PRLR gene for polymorphisms in Hanoverian stallions revealed two single nucleotide polymorphisms (SNPs). Association and haplotype analyses were performed in 162 Hanoverian warmblood stallions for these intragenic SNPs using the least square means (LSM) of the pregnancy rate per oestrus for stallions and the paternal component and embryonic component of the breeding values (BV) of the pregnancy rate per oestrus. The two SNPs (BIEC2‐589441, BIEC2‐560860) showed significant associations using single marker and haplotype analysis with the embryonic and paternal component of BV and one SNP (BIEC2‐560860) was also significantly associated with the LSM of the pregnancy rate per oestrus. This is the first report on an association of PRLR‐associated genetic markers with fertility traits in stallions.     

Implication of FKBP6 for Male Fertility in Horses

In stallions, impaired acrosome reaction (IAR) may often cause subfertility. Single nucleotide polymorphisms (SNPs) within FK506‐binding protein (FKBP6) seem to be associated with IAR in stallions. However, their effect on stallion fertility has not yet been quantified. Using whole‐genome sequence data of seven stallions, we searched FKBP6 for mutations to perform an association study in Hanoverian stallions with estimated breeding values for the paternal component of the pregnancy rate per oestrus cycle (EBV‐PAT) as target trait. Genotyping five exonic mutations within FKBP6 revealed a significant association of the SNP g.11040379C>A (p.167H>N) with EBV‐PAT in 216 Hanoverian stallions. The difference among the two homozygous genotypes was 7.62% in EBV‐PAT, corresponding to one standard deviation of EBV‐PAT. In conclusion, in Hanoverian stallions, the FKBP6‐associated SNP g.11040379C>A confers higher conception rates in A/A homozygous and lower conception rates in C/C homozygous Hanoverian stallions. Thus, an FKBP6‐associated missense mutation is significantly associated with stallion fertility.     

Epidemiologic and genetic analysis of veterinary data of German Brown cattle]

In totally 3740 cows of the breed German Brown Swiss distributed over 115 herds risk factors for the occurrence of diseases were analysed using a threshold model. Disease data were recorded by ten practitioners in southern Bavaria. The most frequent diseases were fertility disorders, followed by metabolic, udder and calving disorders. The influence of the herds could demonstrated clearly for all diseases analysed. The effect of the lactation number contributed significantly to the frequency of milk fever, mastitis, retained placenta, endometritis/metritis and ovary cysts. Heritability estimates vary between h2 = 0.5% and h2 = 4.2% with exception of anestrus/acyclia (h2 = 8.8%). With higher milk yield of cows the disease frequencies increase, especially fertility diseases. However, increasing herd milk yield is associated with decreasing disease frequencies. A depression of A.I.-parameters and an increase of culling rate caused by diseases could be observed. In the case of the occurrence of uterus- and ovary disorders days open are elongated by 58 days in comparison to cows without diseases. Recording of disease data for use in electronic data processing seems necessary, in order to diminish production diseases by breeding and herd control programmes. An important prerequisite in organization of disease data recording is an efficient cooperation between the veterinary practitioner, farmer, inseminator and the official milk recording organisation.     

Influences on the occurrence of abomasal displacements in German Holstein cows]

The objectives of this study were to analyse risk factors for the prevalence of abomasal displacement in German Holstein cows. In the period from 02/01/1999 to 01/31/2000 five veterinary surgeons in Northern Lower Saxony registered all cases of abomasal displacement in German Holstein cows being under the official milk recording scheme. In total, the investigation included 160 farms and 9315 cows. An abomasal displacement was registered in 151 German Holstein cows, corresponding to a frequency of 1.6%. More than 75% of the abomasal displacements appeared during the first 30 days after calving. The left abomasal displacement (74.8%) was recorded more often than the right abomasal displacement (25.2%). Milk recording and pedigree data were supplied by the VIT (Vereinigte Informationssystem Tierhaltung), Verden, and merged with the own recordings. The influences of the calving month, the lactation number, the age at calving, the inbreeding coefficient, calving performance, duration of pregnancy, breed of calf sire, calf sire and the breeding values for the milk performance did not explain a significant part of the variation of the frequency of the abomasal displacement. Significant effects of the sire, birth of twins or even more calves and the herd were obtained for the leftsided abomasal displacement. For the rightsided abomasal displacement and for all abomasal displacements the herd effect was not significant. Heritability estimates using bivariate linear REML models were h2 = 0.043 +/- 0.012 for the leftsided abomasal displacement, and h2 = 0.007 +/- 0.004 for the rightsided abomasal displacement, respectively. Using the threshold model the heritabilities yielded estimates of h2 = 0.51 for the left abomasal displacement, and for the right abomasal displacement of h2 = 0.19, respectively.