Metabolic adaptations associated with irreversible glucose loss are different to those observed during under-nutrition

Effects of heat stress and nutrition on lactating Holstein cows: II. Aspects of hepatic growth hormone responsiveness

“…If true, it is surprising that WFHS cattle exhibited indices of hepatic GH resistance given that insulin increases or restores hepatic IGF-I production during some periods of positive and negative energy balance, respectively (Butler et al, 2003;Rhoads et al, 2004). Recently, Meier et al (2008) demonstrated that irreversible glucose loss caused by phloridizin treatment resulted in a partial uncoupling of the GH-IGF axis that could not be recapitulated with a similar level of undernutrition. Significantly, the effect of phloridizin treatment on the GH-IGF axis occurred without a change in plasma insulin, indicating that the liver may become insulin insensitive during periods when the interaction between insulin and glucose is weakened.…”

Differences in the expression of genes involved in the somatotropic axis in divergent strains of Holstein-Friesian dairy cows during early and mid lactation

“…Thus the objective of this study was to determine the effect of strain of 26 6 Holstein Friesian cow on the transcriptional regulation of key hepatic genes 1 controlling the somatotropic axis during early-and mid-lactation. 2 …”

“…20 21 Numerous reports have suggested that nutritionally compromised cows have reduced 22 systemic concentrations of insulin and IGF-I (Patton et al, 2006;Lucy, 2008), and 23 Lucy et al (2009) reported that NAHF cows experience an uncoupling of the 24 somatotropic axis in conjunction with reduced BCS. It has been reported that 25 irreversible glucose loss leads to some degree of uncoupling of the somatotropic axis, 26 5 as plasma concentrations of IGF-1 decline concomitant with a reduction in hepatic 1 mRNA abundance of IGF-1 and GH receptor (GHR) (Meier et al, 2008). 2 Furthermore, insulin is also hypothesised to be a key metabolic signal regulating the 3 coupling of the somatotropic axis (Butler et al, 2003).…”

“…It has been reported that 25 irreversible glucose loss leads to some degree of uncoupling of the somatotropic axis, 26 5 as plasma concentrations of IGF-1 decline concomitant with a reduction in hepatic 1 mRNA abundance of IGF-1 and GH receptor (GHR) (Meier et al, 2008). 2 Furthermore, insulin is also hypothesised to be a key metabolic signal regulating the 3 coupling of the somatotropic axis (Butler et al, 2003). 4 5 Current knowledge indicates that the IGF system is composed of: two ligands (IGF-1 6 and IGF-2); two receptors (IGF-1R and IGF-2R); six binding proteins (IGFBP-1-6) 7 and the IGF binding protein-acid labile subunit (IGFBP-ALS).…”

“…Strain comparison studies in New Zealand and Ireland have reported lesser milk 25 volume, greater BCS throughout lactation and superior reproductive performance for 26 4 the New Zealand Holstein Friesian (NZHF) compared to North American Holstein 1 Friesian (NAHF) (Horan et al, 2005b).The NAHF strain has been selected for 2 increased milk yield, body size and angularity in a production system based on year- 3 round calving and greater levels of concentrate supplementation, with little emphasis 4 on traits such as fertility (Hoekstra et al, 1994; Pryce and Veerkamp, 2001; 5 Macdonald et al, 2007). The NZHF strain, on the other hand, has been selected for 6 increased concentrations of milk fat and protein, reduced maintenance energy costs 7 and improved fertility and survival traits under pasture-based systems of production.…”