Impact of rumen-protected glucose on performance, milk composition, and selected blood metabolites of early lactating Holstein Friesian cows

Introduction: High-producing dairy cows often face calving stress and reduced feed intake during the transition period, leading to body fat mobilization to meet production demands. Supplementing rations with energy-dense sources like rumen-protected glucose (RPG) may enhance production performance in early lactation.

Methods: This study evaluated the effects of RPG supplementation on feed intake, body condition score (BCS), production performance, and blood metabolites in 32 early-lactation Holstein Friesian cows (6 ± 1 DIM; milk yield: 30 ± 5 kg/day; body weight: 550 ± 50 kg; BCS: 3.00 ± 0.25). Cows were assigned to four groups (n = 8/group) and fed a basal diet (Control) or supplemented with 150 g (S-150), 300 g (S-300), or 450 g (S-450) of RPG for a 42-day trial after 2 weeks of adaptation.

Results: Results showed significant improvements (p < 0.05) in final body weight, milk yield, energy-corrected milk, and milk-to-feed ratio with RPG supplementation, with the highest effects observed at 450 g/day. Milk components, including solids-not-fat, lactose, and total solids, also increased significantly. While feed intake remained similar (p > 0.05), blood glucose levels rose, and non-esterified fatty acids and β-hydroxybutyric acid concentrations decreased (p < 0.05), indicating reduced ketosis and negative energy balance.

Conclusion: These findings suggest RPG supplementation at 450 g/day improves milk production, quality, and metabolic health in early lactating cows, warranting further exploration of higher dosages like 500-550 g/day.