Effects of betaine and rumen-protected folic acid supplementation on lactation performance, nutrient digestion, rumen fermentation and blood metabolites in dairy cows

This study evaluated the effects of betaine (BT) and rumen-protected folic acid (RPFA) on lactation performance, nutrient digestion, rumen fermentation and blood metabolites in dairy cows. Thirty-six mid-lactation Holstein dairy cows were assigned to one of four treatments in a 2 × 2 factorial randomized block design. Supplemental RPFA (0 [RPFA-] or 5.2 mg/kg dietary dry matter [DM] of folic acid [FA] from RPFA [RPFA+]) and BT (0 [BT-] or 4.0 g/kg DM of BT [BT+]) was mixed into the daily ration, respectively. The experiment lasted for 105 days with the first 15 days for adaptation and the following 90 days for sample collection. The RPFA × BT interaction was significant for blood folate concentration which decreased with BT addition in RPFA- diet but increased with BT addition in RPFA + diet. Dry matter intake and body weight change were similar among treatments. Dietary RPFA or BT addition increased yield of milk and milk fat but higher milk protein yield was only observed for RPFA addition. Feed efficiency was increased due to RPFA or BT addition. Apparent total-tract digestibility of DM, organic matter, crude protein, neutral detergent fibre and acid detergent fibre increased with RPFA or BT addition. Ruminal pH decreased with RPFA addition but was unchanged with BT addition. Dietary RPFA or BT addition increased ruminal total volatile fatty acids concentration and altered rumen fermentation mode to more acetate production. Ammonia-N concentration was unchanged with RPFA addition but decreased with BT addition. Addition of RPFA or BT increased activity of carboxymethyl-cellulase, xylanase and protease as well as population of total bacteria, protozoa, Ruminococcus (R.) albus and R. flavefaciens. Population of Prevotella ruminicola was higher for RPFA addition but activity of cellobiase and population of total fungi and Ruminobacter amylophilus was higher for BT addition. Blood concentrations of glucose, non-esterified fatty acid, beta-hydroxybutyrate and homocysteine were similar among treatments. Blood total protein and albumin concentrations were increased with RPFA addition but were not affected by BT addition. The data indicated that addition of RPFA or BT had beneficial impacts on lactation performance, nutrient digestion and ruminal fermentation and BT addition might increase FA utilization efficiency in dairy cows receiving diet without RPFA.