Circulating insulin-like growth factor I, insulin-like growth factor binding proteins, growth hormone, and resumption of estrus in postpartum cows subjected to dietary energy restriction.

Abstract

The objective of this study was to determine whether serum concentrations of growth hormone (GH), IGF-I, IGF binding proteins (IGFBP), and glucose at wk 2 and 10 postpartum were associated with the ability of postpartum beef cows to resume cycling when maintained on a limited nutrient environment. Cows (n = 29) were individually fed either 130 or 170 kcal ME x BW-75 x d-1 during nonlactation and 170 or 210 kcal ME x BW-75 x d-1 during lactation for an average of 4.1 yr before sample collection. The proportion of cows that resumed estrus within 20 wk after parturition was less (P < .05) at the lower feeding rate (5 of 14) than at the higher feeding rate (11 of 15). Concentrations of IGF-I increased from wk 2 to 10 in cows that resumed cycling but not in cows that remained anestrous and were less (P < .05) at wk 2 and 10 in cows that remained anestrous compared to cows that resumed cycling. Circulating amounts of IGFBP-2 at wk 2 were greater (P < .05) and IGFBP-3 concentrations were lower (P < .05) in cows that remained anestrous compared to cows that resumed cycling. Cows on the lower feeding rate that did not cycle had lower body condition scores and greater concentrations of GH compared (P < .05) to other cows. At the higher feeding rate, body condition score and concentrations of GH did not differ between cows that did or did not resume cycling. Circulating concentrations of IGF-I and IGFBP-2 and -3 at wk 2 postpartum were indicators of the capacity of energy-restricted cattle to resume cycling after parturition.

Effects of herbage allowance of native grasslands in purebred and crossbred beef cows: metabolic, endocrine and hepatic gene expression profiles through the gestation–lactation cycle

“…In agreement with previous reports, commencement of luteal activity was negatively correlated with BCS, circulating IGF-I and insulin concentrations and positively correlated with the hepatic expression of IGFBP2 mRNA (Roberts et al, 1997;Quintans et al, 2010). Indeed, the shorter commencement of luteal activity determined for HI cows was associated with the greater BCS and serum insulin and IGF-I concentrations, and with less IGFBP2 mRNA, in these cows during the gestation-lactation cycle.…”

Effects of parity and body condition at parturition on endocrine and reproductive parameters of the cow

“…Lean cows with lower IGF-I concentrations than fat cows presented a slower decline. IGF-I concentrations are good indicators of the capacity to resume cyclicity after parturition in agreement with Roberts et al (1997): fat cows and multiparous cows had higher IGF-I concentrations and better reproductive performance.…”

“…Although GH concentrations are usually high in early lactating ruminants, the intrahepatic production of its mediator IGF-I is diminished (Chilliard 1999). Circulating concentrations of IGF-I in the peripartum period are good indicators of the capacity of energy-restricted cows to resume cyclicity after parturition (Roberts et al 1997). Cows with ovulatory estrogen-active follicles have higher circulating IGF-I concentrations during the first 2 weeks than cows with anovulatory follicles (Beam & Butler 1997.…”

Insulin-like growth factor and growth hormone receptor in postpartum lactating beef cows

“…This contradiction could be due to the fact that plasmatic concentration of IGF-I is also correlated to the hepatic expression of IGF binding proteins 1-6 and to the IGF acid labile subunit (IGF ALS) (Fenwick et al, 2008), which regulates IGF-I plasma half-life and transport through the vascular endothelium (Thissen et al, 1994). Moreover, the decreased concentration of IGF-I in postpartum beef cows coincided with an increased concentration of circulating IGFBP-2 and decreased IGFBP-3 (Roberts et al, 1997). Therefore, more studies with a higher number of cows and considering the various intermediate steps of the somatotropic axis must be done, in order to explain the source of serum IGF-I reduction in beef cattle.…”