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

Abstract

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&#x202f;&#xb1;&#x202f;1 DIM; milk yield: 30&#x202f;&#xb1;&#x202f;5&#x202f;kg/day; body weight: 550&#x202f;&#xb1;&#x202f;50&#x202f;kg; BCS: 3.00&#x202f;&#xb1;&#x202f;0.25). Cows were assigned to four groups (&#x202f;=&#x202f;8/group) and fed a basal diet (Control) or supplemented with 150&#x202f;g (S-150), 300&#x202f;g (S-300), or 450&#x202f;g (S-450) of RPG for a 42-day trial after 2&#x202f;weeks of adaptation. RESULTS: Results showed significant improvements (&#x202f;<&#x202f;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 (&#x202f;>&#x202f;0.05), blood glucose levels rose, and non-esterified fatty acids and-hydroxybutyric acid concentrations decreased (&#x202f;<&#x202f;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&#x202f;g/day.