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 (NE(L)) and low fiber were classified as high NE(L), whereas low NE(L) and higher fiber were defined as low NE(L). Two diets were fed for 3 wk before calving and 2 others fed for 3 wk postpartum resulting in 4 treatment combinations: high NE(L), low NE(L); high NE(L), high NE(L); low NE(L), low NE(L); and low NE(L), high NE(L). Levels of NE(L) (Mcal/kg DM), percentage of acid detergent fiber, and percentage of neutral detergent fiber for low NE(L) vs. high NE(L) 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 NE(L) vs. high NE(L) 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 NE(L), high NE(L) group had less desirable hoof scores than high NE(L), high NE(L), or low NE(L), low NE(L) 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 < or = 5.8) at 8 and 22 DIM were higher for groups fed high NE(L) after calving. No direct relationship between low postpartum rumen pH and hoof scores on individual cows was found. Low NE(L) before calving and high NE(L) right after calving may increase risk of subclinical laminitis if not carefully managed.