HEAL ▶▶▶TH
Potential biomarker: Predicting ketosis
Ketosis is one of the major prevalent metabolic disorders in dairy cows, one that is influenced by both genetic and nutritional factors. Studying altered gene expression is a significant move towards determining potential molecular markers for predicting the incidence of ketosis.
BY MATTHEW WEDZERAI R
esearchers at Sichuan Agricultural University carried out a study where they employed a whole blood transcriptome approach to investigate the associat- ed alteration of gene expression with clinical ketosis
in dairy cows. This research was part of a prospective study designed to elucidate molecular mechanisms and identify predictive biomarkers of clinical ketosis. Their results could significantly help us to understand the underlying molecular mechanisms for incidence and progression of ketosis in dairy cows. Previous studies have found significant genetic correc- tions between ketosis and other health parameters, suggest- ing that genetic selection for improved resistance to ketosis is feasible. Nevertheless, the association between difference in gene expression and incidence and progression of ketosis remains unclear. Ketosis is a common metabolic disorder in dairy cows that can lead to enormous economic losses by decreasing milk production, impairing reproductive performance and increas- ing the incidence of other diseases – studies show that eleva- tion of ketone bodies such as β-hydroxybutyrate in the sys- temic circulation contribute to metabolic acidosis. Ketosis can also significantly increase the risk of displaced abomasum, lameness, and metritis. What is usually seen at early lactation is that cows are more prone to suffer from a negative energy balance (NEB) due to milk production and limited feed intake. The NEB in early lactating cows is characterised by a failure of hepatic gluconeogenesis to supply adequate glucose for maintenance and lactation. If the NEB-induced metabolic dis- orders could not be properly adapted and/or combated, cows would finally develop into subclinical or clinical ketosis. Along with NEB, massive fat mobilisation from different adipose depots is seen, leading to fatty acid β-oxidation in hepatic
56 ▶DAIRY GLOBAL | Volume 7, No. 3, 2020
mitochondria to produce energy, but overload fatty acid oc- curs in consequence of the elevated concentrations of ketone bodies and fatty liver syndrome.
The study In their study, researchers used nine Holstein cows diagnosed with clinical ketosis and ten healthy controls, for which whole blood samples were collected at both prepartum and post- partum. Four groups of blood samples were defined: cows with ketosis at prepartum (PCK, N = 9) and postpartum (CK, N = 9), respectively, and controls at prepartum (PHC, N = 10) and postpartum (HC, N = 10). RNA-Seq approach was used for investigating gene expres- sion, by which a total of 27,233 genes were quantified with four billion high-quality reads. They revealed 75, and four dif- ferentially expressed genes (DEGs) between sick and control cows at postpartum and prepartum, respectively, which indi- cated that sick and control cows had similar gene expression patterns at prepartum. There were 95 DEGs between post- partum and prepartum for sick cows, which showed de- pressed changes of gene expression during this transition period in comparison with healthy cows (428 DEGs). The DEGs among different groups were analysed using DESeq2 R package (v1.22.2).
Detecting ketosis Ketosis can be clinically indicated by elevated blood concen- trations of ketone bodies, such as β-hydroxybutyrate (BHBA), acetoacetate and acetone. The standard diagnostic test for ketosis is the concentration of blood BHBA, for which the var- ied cut-point values are used, ranging from 1.0mM to 1.4mM for some studies, while for some studies higher cut-point val- ues of BHBA such as 1.6mM and 1.8mM are used. In the pres- ent study, researchers conservatively employed 2.6mM BHBA as cut-point value for defining the cows with clinical ketosis because of two considerations. First, they tried to avoid false-positive clinical ketosis by increasing the cut-point val- ue. Second, from their former field experiences, it had been observed that cows with blood BHBA ≥ 2.6mM had a clear reduction of dietary intake and milk production.
Differential expression of genes Between postpartum ketotic cows (CK) and postpartum
PHOTO: MARK PASVEER
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
