Comparative transcriptomics in adipose tissue of Holstein & Hereford cattle

Improvement in milk production of dairy cows appeared to have led to a significant decline
in fertility. However, beef cattle genetically selected for high growth rates have not been
reported to have compromised fertility. Coincidentally, body conformation of dairy cows is
reportedly lower compared to beef cattle. This may be of importance as adipose tissue (AT)
has been reported to be pertinent in regulation of the hypothalamus-pituitary-gonadal axis,
thus influencing reproductive performances. The current study aimed to establish and
compare transcriptomic signatures ofAT in Holsteins (dairy breed) and Herefords (beef
breed) in order to understanding of the differences in nutritional uptake, fat deposition, and
resource mobilisation between these breeds. Samples from Holsteins (3 and 7 years old)
and Herefords (2 years 7 months and 2 years 10 months old) were used for breed
comparison. Next generation sequencing was utilised to generate transcriptomes of perirenal
AT. RNA was extracted using QiagenRNeasy Mini Kit, followed by quality evaluation
with Agilent 2100 Bioanalyzer. RNA transcription was quantified using RNA-Seq
(IlluminaHiSeq). A total of 73,22,082 (HOL1), 80,156,542 (HOL2), 57,436,770 (HER1) and
56,318,570 (HER2) paired reads were obtained. Differential gene expressions (DGE) were
analysed using edgeR (www.bioconductor.org/packages/release/bioc/html/edgeR.html).
Statistically significant DGE of interest related to functions or influence on nutrition, fat
metabolism, energy expenditure, adipogenesis and lipogenesis (ELOVL5, INSIG1, IRF4, LEPR
LDLR, RAN, RXRα, and SCD)were validated using qRT-PCR.Based on the RNA-seq data, mRNA
expression of ELOVL5, INSIG1, LDLR, RAN, RXRα, and SCD were higher in Herefords as
compared to Holsteins, whereas IRF4 and LEPR were lower. Results reflected that dairy cows
(Holstein) generally have a lower fat mass compared to beef breeds (Hereford). This also
indicated that lipids were heavily mobilised from adipocytes of Holstein to sustain the high
energy demand of milk production, thus affecting the subsequent pregnancy. Outcome of
this study not only contributed to further understanding of differences in reproductive
performance between these breeds, also data may be used to improve management and
productivity of these animals.