Effects of fresh‐cow grouping strategy and rumen‐protected glucose on production performance, reproductive variables and risk of culling in Holstein cows

BACKGROUND: The interaction effects of duration of stay in fresh‐cow diet and supplementation with rumen‐protected glucose (RPG) on productivity of dairy cows are largely unknown. We hypothesised that a faster transition from fresh‐cow diet (higher forage:concentrate) to lactation‐cow diet (lower forage:concentrate), combined with supplementation of fresh‐cow diet with RPG will have positive effects on production and health of dairy cows. OBJECTIVES: To investigate the immediate and long‐term effects of length of stay in fresh‐cow diet and supplementation with RPG on productive and reproductive performance of high‐producing dairy cows. METHODS: A total of 264 multiparous Holstein cows (average parity ± standard deviation = 3.2 ± 1.3, ranging from 2 to 6) were used in a 2 × 2 factorially arranged trial. Treatments were the feeding duration of a fresh‐cow diet for 14 or 21 days, each combined by daily supplementation of the fresh‐cow diet with ground corn grain or RPG product top dressed at 500 g/day/head. RESULTS: The earlier transition from fresh‐cow to lactation diet resulted in greater milk production from 15 through 21 days in milk (DIM; by 2.28 kg/day), and also fat‐corrected milk production on 30 and 60 DIM, respectively. Corn grain or RPG supplementation did not affect the average milk production (1 to 21 DIM), as well as milk production and composition on 30 and 60 DIM. Although extent of body condition loss at transition tended to be lesser in cows switching faster to lactation diet, these cows lost more body condition from 30 to 90 DIM. Survival analysis on calving‐to‐conception interval and time to removal from herd did not find any significant difference across treatments. CONCLUSIONS: The positive effects of earlier transition from fresh‐cow to lactation diet were evident by greater milk production from 15 through 21 DIM, and fat‐corrected milk production (30 and 60 DIM), at the expense of body condition in high‐producing dairy cows. A daily topdress of RPG on fresh‐cow diet had no immediate or carryover effects on production of dairy cows.