Effects of Forced Exercise on Two-Year-Old Holstein Heifers

Two trials with 88 two-year-old Holstein heifers measured effects of prepartum exercise on mammary edema, parturition, reproduction, consumption of feed, production and composition of milk, and efficiency of feed utilization. Exercise was in a circular lane; the driving mechanism was powered by an electric motor. Trial I involved three treatments: 1) no exercise; 2) exercise at 5.47km/h for 1.6km/day for 4/wk prepartum; and 3) treatment 2 but continued for 10 days postpartum. Trial II involved two treatments: 1) no exercise; and 2) exercise at 3.54km/h for 1.6km/day for 6 wk prepartum. Intake of feed was measured prepartum and for 50 days postpartum; production and composition of milk were measured for 305-day lactation. In Trial I exercise reduced the number of days prepartum that udder edema was evident, improved ease of calving, and hastened postpartum release of the placenta. Continuing exercise after parturition reduced intake of grain and digestible energy and reduced yield of milk for the first 50 days of lactation. In Trial II exercise increased intake of digestible energy, production of milk, and efficiency of feed utilization for the first 50 days and production for the entire lactation. Composition of milk, changes in body weight, and intake of feed prepartum were not affected by exercise.