Evaluating the effects of rumen-protected glucose (RPG) on production, metabolism, and inflammation in transitioning dairy cows

Objectives were to evaluate the effects of rumen-protected glucose supplementation on milk production, post-absorptive metabolism, and inflammatory biomarkers in transition dairy cows. Fifty-two multiparous cows were blocked by previous 305 mature equivalent milk yield and randomly assigned to one of two iso-energetic and iso-nitrogenous treatments: 1) control diet (CON; n = 26) or 2) a diet containing RPG (RPG, pre-fresh 8.4% RPG DM basis, post-fresh 9.5% RPG DM basis; n = 26). Cows received their respective dietary treatments from d -21 to 28 relative to calving. Weekly body weight (BW), milk composition, and fecal pH were recorded until 28 d in milk (DIM), whereas milk yield was recorded through 105 DIM. Blood samples were collected on d -7, 3, 7, 14, and 28 relative to calving. Data were analyzed using repeated measures in the MIXED procedure of SAS. Previous 305 mature equivalent milk yield served as a covariate. Fecal pH was similar between treatments and decreased notably post-partum. Dry matter intake pre- and post-partum were unaffected by treatment. Consequently, MY did not differ throughout the experimental period. Milk fat, protein, and lactose were similar amongst treatments. Blood urea nitrogen and plasma glucose concentrations did not differ due to treatment; however, circulating β-hydroxybutyrate post-partum tended to be decreased with a concomitant reduction in concentration of non-esterified fatty acid (NEFA) in the RPG-fed cows compared to CON cows (630 vs. 456 ± 68 μEq/L). Circulating insulin tended to be increased in RPG compared with CON-fed cows. Overall, circulating lipopolysaccharide-binding protein (LBP) and haptoglobin (Hp) did not differ due to treatment, but at 7 DIM, RPG cows had decreased LBP and Hp concentrations by 31% and 27%, respectively compared to CON cows. Supplemental RPG improved some key metrics of post-absorptive bioenergetics and inflammation during the periparturient period, changes primarily characterized by increased insulin and decreased NEFA concentrations and reduced acute phase proteins