Influence of transition diets on occurrence of subclinical laminitis in Holstein dairy cows

Pre- and postpartum diets varying in energy and fiber were studied for effects on subclinical laminitis in Holstein cows. Also, ruminal acidosis was examined relative to sole hemorrhages and ulcers. Cows (n = 98) were assigned to a 2 x 2 factorial arrangement of treatments in a randomized complete block. Diets high in net energy of lactation (NEL) and low fiber were classified as high NEL, whereas low NEL and higher fiber were defined as low NEL. Two diets were fed for 3 wk before calving and 2 others fed for 3 wk postpartum resulting in 4 treatment combinations: high NEL, low NEL; high NEL, high NEL; low NEL, low NEL; and low NEL, high NEL. Levels of NEL (Mcal/kg DM), percentage of acid detergent fiber, and percentage of neutral detergent fiber for low NEL vs. high NEL prepartum diets, were 1.51, 30.2, 47.2 vs. 1.65, 23.4, 39.8, respectively, and 1.70, 22.4, 36.8 vs. 1.77, 17.5, 31.4 for low NEL vs. high NEL lactating diets, respectively. A single diet was fed after 21 d in milk (DIM). Measures of hoof discoloration, hemorrhage, and/or ulcer formation were done at about 45 d before calving, and near 28 and 70 DIM. Rumenocentesis was performed 14 d before calving and at 8, 22, and 70 DIM. Hoof scores among treatments were similar at 28 DIM. The low NEL, high NEL group had less desirable hoof scores than high NEL, high NEL, or low NEL, low NEL groups from 55 to 75 DIM. Rumen pH did not differ by treatment before calving. The lowest postpartum rumen pH was significantly lower and rates of ruminal acidosis (pH = 5.8) at 8 and 22 DIM were higher for groups fed high NEL after calving. No direct relationship between low postpartum rumen pH and hoof scores on individual cows was found. Low NEL before calving and high NEL right after calving may increase risk of subclinical laminitis if not carefully managed.