Genome-wide association study identifies QTLs for displacement of abomasum in Chinese Holstein cattle1

Displacement of abomasum (DA) is one of the most common and important disorders in dairy cattle. The objective of the present study was to detect the quantitative trait loci (QTL) for DA in Chinese Holstein using single-step genomic BLUP methodology. A total of 60,556 producer-recorded DA event records from 32,190 cows, together with 2,336 genotyped animals with 40,054 SNP markers, were used for the analysis. Genomic data were incorporated into a threshold model for variance component estimation, and the estimated heritability of DA was 0.108 (SE = 0.086). Results of genome-wide association studies were reported as the proportion of genetic variance explained 20-SNP windows. Eight QTLs covering 129 genes on Bos taurus autosomes 2, 4, 7, 10, 14, 17, 20 showed associations with DA. Ten genes, namely BMP4, SOCS4, GCH1, DDHD1, ATG14, ACBP/DBI, SMO, AHCYL2, CYP7A1, and CACNA1A, involved in insulin metabolism and lipid metabolism pathways may be considered as candidate genes of DA in dairy. The identified QTLs, biological pathways, and associated genes underlying DA identified from the present study will contribute to the understanding of the genetic architecture of this complex disease.

A genome-wide association study for left-sided displacement of the abomasum using a high-density single nucleotide polymorphism array

Left-sided displacement of the abomasum (LDA) is a frequent disease in dairy cattle causing significant financial losses for dairy farmers. Heritability (h²) of this complex disease was estimated at up to 0.5 in German Holstein (GH) cattle. Using the Bovine High Density BeadChip (Illumina Inc., San Diego, CA) comprising 588,753 single nucleotide polymorphisms (SNP) after quality control for 126 LDA cases and 280 population-based controls, we used a mixed linear model analysis in a genome-wide association study (GWAS). We identified 6 genomic regions for LDA on bovine chromosomes 2, 8, 13, 20, 24, and X that were significantly associated with LDA. Each of these regions was covered by 4 to 12 LDA-associated SNP. Single SNP within these regions explained up to 7.3% of the phenotypic variance. An independent sample of 1,554 GH cows, including 539 controls and 1,015 cases, were genotyped for 8 SNP highly associated with LDA on Bos taurus autosomes (BTA) 2, 8, 13, and 24, as well as 6 SNP located in previously identified LDA regions on BTA1, 5, 11, and 27 using competitive allele-specific PCR genotyping technology (KASP). The analysis using the KASP genotypes confirmed LDA-associated loci on BTA2, 8, 13, and 27. These genomic regions may contribute to the susceptibility to LDA in Holstein cows and may harbor functional variants for LDA.

Herd-Level Monitoring and Prevention of Displaced Abomasum in Dairy Cattle

Displaced abomasum (DA) is a postpartum disease that causes significant economic losses in the dairy industry. Abomasal atony and excessive production of gas have been reported as prerequisites for the development of DA. The exact cause of DA is unknown, yet infectious and metabolic disease, diet composition and physical form, cow comfort, and management of dairy cows during the transition period have been associated with the occurrence of this disorder. This review article discusses different factors that lead to the development of DA and strategies for monitoring DA and its comorbidities at the herd level.

Pharmacological evaluation of smooth muscle relaxant and cardiac-modulation potential of Phyla nodiflora in ex-vivo and in-vivo experiments

OBJECTIVE

To investigate the pharmacological basis of its uses of Phyla nodiflora (P. nodiflora) for the treatment of anomalies predominantly by smooth muscle containing tissues such as gastrointestinal/vascular/broncho spasm and cardiovascular modulation.

METHODS

The crude hydroalcoholic extract of P. nodiflora (Pn.Cr) and its fractions were evaluated on isolated rabbit jejunum, rat trachea, aorta and atrium. To access the contractile or relaxant effects of testing materials, the tissues were mounted in isolated organ bath and responses were recorded with transducers coupled with data acquisition system. BALB/c mice were challenged with castor oil for the assessment of in-vivo antidiarrheal activity. Normotensive rats were used for in-vivo hypotensive study.

RESULTS

Hydroalcoholic extract of Pn.Cr at variable concentrations inhibited the natural spontaneous rhythm and 80 mmol/L K⁺ mediated contractions in isolated segment of jejunum with EC₅₀ values of 3.18 and 1.91 mg/mL respectively. Verapamil, a Ca²⁺ channel blocker, demonstrated akin pattern in jejunum and therefore possibly suggesting calcium blocking activity. On isolated rat tracheal tissue, Pn.Cr showed relaxation of high-K⁺ and carbachol mediated contractions (EC₅₀ values: 1.24 and 2.42 mg/mL). Pn.Cr treatment relaxed the rat aortic ring in a cumulative doses with high-K⁺ and phenylephrine-induced contractions (EC₅₀ values 0.25 and 0.92 mg/mL). Activity based fractionation of Pn.Cr showed that dichloromethane fraction was more potent for relaxing the tissues spasm compared to aqueous fraction. In-vivo experiments, significant protection by Pn.Cr (P < 0.05) was observed in castor oil-induced diarrhea (50-500 mg/kg) whereas hypotensive effect in anesthetized rats was seen at the dose range of 1-10 mg/kg of Pn.Cr (P < 0.05).

CONCLUSION

This study suggests the blockage of calcium channel in the smooth muscles as a pharmacological application to make usage of P. nodiflora in the management of diarrhea, asthma and hypotensive effect.

Concentration of Potassium in Plasma, Erythrocytes, and Muscle Tissue in Cows with Decreased Feed Intake and Gastrointestinal Ileus

BACKGROUND

Healthy cows consume large amounts of potassium and a sudden loss in appetite can lead to hypokalemia. The routine method to evaluate potassium homeostasis is the measurement of the extracellular potassium in plasma or serum, but this does not provide information about the intracellular potassium pool.

HYPOTHESIS/OBJECTIVES

To evaluate potassium homeostasis by comparing the extracellular and intracellular potassium concentration in cows with reduced feed intake and gastrointestinal ileus.

ANIMALS

Twenty cows 1-3 days postpartum (group 1) and 20 cows with gastrointestinal ileus (group 2).

METHODS

Observational cross-sectional study. Plasma potassium was measured by using an ion-sensitive electrode. Intracellular potassium was measured in erythrocytes and muscle tissue (muscle biopsy) by using inductively coupled plasma optical emission spectroscopy.

RESULTS

Cows of group 1 did not have hypokalemia. Overall cows with gastrointestinal ileus were hypokalemic (mean ± SD, 2.9 mmol/L ± 0.78), but potassium concentration in erythrocytes and muscle tissue was not lower than in postpartum cows. Intracellular potassium in erythrocytes varied very widely; group 1: 3497-10735 mg/kg (5559 ± 2002 mg/kg), group 2: 4139-21678 mg/kg (7473 ± 4034 mg/kg). Potassium in muscle tissue did not differ between group 1 (3356 ± 735 mg/kg wet weight) and group 2 (3407 ± 1069 mg/kg wet weight). No association between extracellular and intracellular potassium concentrations was detected.

CONCLUSIONS AND CLINICAL IMPORTANCE

That measurement of plasma potassium concentration is not sufficient to evaluate potassium metabolism of cows.

Genome-wide association analysis identifies loci for left-sided displacement of the abomasum in German Holstein cattle

Left-sided displacement of the abomasum (LDA) is one of the most common disorders of the digestive system in many dairy breeds and particularly in Holstein dairy cows. We performed a genome-wide association study for 854 German Holstein cows, including 225 cases and 629 controls. All cows were genotyped using the Illumina Bovine SNP50 BeadChip (Illumina Inc., San Diego, CA). After quality control of genotypes, a total of 36,226 informative single nucleotide polymorphisms (SNP) were left for analysis. We used a mixed linear model approach for a genome-wide association study of LDA. In total, 36 SNP located on 17 bovine (Bos taurus) chromosomes (BTA) showed associations with LDA at nominal -log10P-values >3.0. Two of these SNP, located on BTA11 at 46.70 Mb and BTA20 at 16.67 Mb, showed genome-wide significant associations with LDA at -log10P-values >4.6. Pathway analyses indicated genes involved in calcium metabolism and insulin-dependent diabetes mellitus to be factors in the pathogenesis of LDA in German Holstein cows.