Plasma concentration of glucose-dependent insulinotropic polypeptide is negatively correlated with respiratory quotient in lactating dairy cows

A. E. RELLING, L. A. CROMPTON, S. C. LOERCH, AND C. K. REYNOLDS

Montreal, Canada

Congreso; 2009 JAM; 2009

In dairy cows, an increase in plasma concentration of GIP was associated with an increase in ME intake (MEI), but the role of GIP in energy partitioning of dairy cattle is not certain. The objective of our study was to examine the relationship between plasma GIP concentrations and energy metabolism. Four mid-lactation, primiparous, rumen-fistulated Holstein-Friesian cows were fed a control diet of 50% forage and 50% concentrate (DM basis) in a 4 X 4 Latin square design with 4-wk periods. The four treatments were: 1) a control diet fed at 1000 and 1600 h; the control diet plus one dose (1.75 kg DM basis at 0955 h) into the rumen of supplemental vegetable proteins (Amino Green, SCA, NuTec) and fed: 2) once (1000 h); 3) twice (1000 and 1600 h); or 4) 4 times (1000, 1600, 2200 and 0400 h). Measurements of respiratory exchange and energy balance were obtained over 4 d during the last week of each period while cows were housed in open-circuit respiration chambers. Blood was collected from the jugular vein every 30 min for 12 h using indwelling catheters and starting at 0800 h on d 20 of each period. Plasma GIP concentration was measured in samples pooled over each 5 consecutive blood samplings. Data were analyzed as repeated measures using mixed models testing random effects of animal and period and fixed effect of treatments, time and their interaction. The relationships between plasma GIP and MEI, heat production (HP), respiratory quotient (RQ) and milk yield (MY) were analyzed using linear correlation procedures, with MEI as partial variant. There was no effect (P> 0.2) of treatment on DMI (18.6 kg/d) and MY (27.6 kg/d). Plasma GIP increased over time during the day (P< 0.01), but it did not change due to treatment (P> 0.7). Plasma GIP concentration was not correlated with MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, increased over time during the day (P< 0.01), but it did not change due to treatment (P> 0.7). Plasma GIP concentration was not correlated with MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, to treatment (P> 0.7). Plasma GIP concentration was not correlated with MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, P< 0.11) and negatively correlated with RQ (r2= -0.72, P< 0.01). The correlations between GIP and RQ or milk yield do not imply causality, but suggest there may be a role for GIP, or associated factors, in the regulation of energy metabolism in dairy cows.< 0.11) and negatively correlated with RQ (r2= -0.72, P< 0.01). The correlations between GIP and RQ or milk yield do not imply causality, but suggest there may be a role for GIP, or associated factors, in the regulation of energy metabolism in dairy cows.P> 0.2) of treatment on DMI (18.6 kg/d) and MY (27.6 kg/d). Plasma GIP increased over time during the day (P< 0.01), but it did not change due to treatment (P> 0.7). Plasma GIP concentration was not correlated with MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, increased over time during the day (P< 0.01), but it did not change due to treatment (P> 0.7). Plasma GIP concentration was not correlated with MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, to treatment (P> 0.7). Plasma GIP concentration was not correlated with MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, MEI or HP (P> 0.4), but was positively correlated with MY (r2= 0.42, P< 0.11) and negatively correlated with RQ (r2= -0.72, P< 0.01). The correlations between GIP and RQ or milk yield do not imply causality, but suggest there may be a role for GIP, or associated factors, in the regulation of energy metabolism in dairy cows.< 0.11) and negatively correlated with RQ (r2= -0.72, P< 0.01). The correlations between GIP and RQ or milk yield do not imply causality, but suggest there may be a role for GIP, or associated factors, in the regulation of energy metabolism in dairy cows.