Physiologic responses to feeding rumen-protected glucose to lactating dairy cows
Journal
Animal reproduction science
Date Issued
2020-04-04
Author(s)
J.A. Sauls-Hiesterman, S. Banuelos, B. Atanasov, B.J. Bradford, J.S. Stevenson
DOI
https:// doi.org/10.1016/j.anireprosci.2020.106346
Abstract
It was hypothesized that rumen-protected glucose (RPG) in diets of dairy cows increases concentrations
of insulin resulting in greater blood progesterone concentrations because elevated
insulin decreases activity of liver enzymes inactivating steroid hormones. Timing of ovulation
was synchronized among 64 postpartum Holstein cows using GnRH and PGF2α (Day 0 = ovulation).
Cows were milked thrice daily and assigned randomly a basal diet supplemented with 0,
1, 2, or 4 kg of an RPG product in place of corn grain, top-dressed in the diet beginning on Day -3.
Blood was collected pre- and post-prandial on Days 0, 2, and 4 to determine plasma glucose and
insulin concentrations and daily from Days 2 through 12. Intake of crude protein and energysoluble
carbohydrates increased linearly with dose, whereas starch intake decreased linearly with
dose. Neither daily milk yield nor dry matter intake (DMI), energy-corrected milk (ECM), somatic
cell count, or percentages of milk fat, protein and lactose on Day 8 differed among dietary
treatments. Neither pre- nor post-prandial changes in plasma glucose differed among treatments.
In contrast, post-prandial glucose decreased from Days 0 through 4. A change in plasma insulin
(post-prandial minus pre-prandial) was detected. Milk urea nitrogen increased linearly with RPG
dose. Concentrations of progesterone were unaffected by RPG dose. It is concluded that insulin
response to RPG was decreased relative to the control and RPG supplementation linearly increased
crude protein intake and milk urea nitrogen with increasing dose, but did not affect
concentrations of progesterone, milk yield, or dry matter intake.
of insulin resulting in greater blood progesterone concentrations because elevated
insulin decreases activity of liver enzymes inactivating steroid hormones. Timing of ovulation
was synchronized among 64 postpartum Holstein cows using GnRH and PGF2α (Day 0 = ovulation).
Cows were milked thrice daily and assigned randomly a basal diet supplemented with 0,
1, 2, or 4 kg of an RPG product in place of corn grain, top-dressed in the diet beginning on Day -3.
Blood was collected pre- and post-prandial on Days 0, 2, and 4 to determine plasma glucose and
insulin concentrations and daily from Days 2 through 12. Intake of crude protein and energysoluble
carbohydrates increased linearly with dose, whereas starch intake decreased linearly with
dose. Neither daily milk yield nor dry matter intake (DMI), energy-corrected milk (ECM), somatic
cell count, or percentages of milk fat, protein and lactose on Day 8 differed among dietary
treatments. Neither pre- nor post-prandial changes in plasma glucose differed among treatments.
In contrast, post-prandial glucose decreased from Days 0 through 4. A change in plasma insulin
(post-prandial minus pre-prandial) was detected. Milk urea nitrogen increased linearly with RPG
dose. Concentrations of progesterone were unaffected by RPG dose. It is concluded that insulin
response to RPG was decreased relative to the control and RPG supplementation linearly increased
crude protein intake and milk urea nitrogen with increasing dose, but did not affect
concentrations of progesterone, milk yield, or dry matter intake.