Molecular Regulation of Energy Balance in Dairy Cows

Released on by Talia Margaret Grala
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  • Molecular Regulation of Energy Balance in Dairy Cows Book Detail

  • Author : Talia Margaret Grala
  • Release Date : 2014
  • Publisher :
  • Genre : Dairy cattle
  • Pages : 420
  • ISBN 13 :
  • File Size : 46,46 MB
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Molecular Regulation of Energy Balance in Dairy Cows by Talia Margaret Grala PDF Summary

Book Description: The onset of milk production is supported by many metabolic adaptations facilitating nutrient supply to the mammary gland, often at the expense of body tissue reserves. It was hypothesised that alterations to milk production (i.e. energy demand), via changes in milking frequency, or energy supply, through changes in feed intake, may affect these adaptations. Therefore, the aim of this work was to measure hepatic and adipose tissue gene transcription changes during early lactation. Milking cows thrice-daily (3X) resulted in reduced transcription of growth hormone receptor (GHR) at 3 weeks post-calving in the liver, and lower GHR transcription at 6 weeks post-calving in adipose tissue compared with cows milked twice-daily (2X). Reductions in GHR transcription also occurred in the liver during energy restriction, indicating that negative energy balance induced by either increased milking frequency or decreased energy supply may alter the somatotropic axis. Milking cows once-daily (1X) resulted in lower transcription of genes involved in hepatic gluconeogenesis and ketogenesis, and a greater expression of genes involved in lipogenesis in adipose indicating that excess energy is being stored. Lipogenic gene expression in adipose tissue also occurred in adequately-fed cows milked 1X relative to 2X; however, in the liver, there were no effects of reduced milking frequency when energy was restricted. These results indicate 1X milking may be a useful management tool to assist cows transitioning into lactation, but does not modify the hepatic response to a nutritionally-induced energy deficit. Gene expression can be determined by inherited genetic variation and environmental challenges, as described above. Two genes (TMED6 and APOA1) were identified that had altered gene expression during the energy restriction and polymorphisms close by the gene that associated with gene expression. The genotype state of a promoter SNP in TMED6 also associated with insulin concentrations during the recovery from the energy restriction, indicating that there is a link between TMED6 and insulin during periods of nutrient re-supply. To summarise, both changes in energy output and input result in changes to gene transcription in liver and adipose tissue. These changes facilitate the prioritisation of nutrient supply to the mammary gland or elsewhere.

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