Short communication: Effects of transition milk and milk replacer supplemented with colostrum replacer on growth and health of dairy calves.

Transition milk (TM, defined here as the second through fourth milkings after calving) supplies additional fat, protein, and immunoglobulins to the calf compared with milk replacer at industry-suggested feeding rates (∼14% solids). Our objective was to determine whether 9 feedings of TM on d 2 through 4 of life increase the growth rate and overall health of calves. Holstein heifer calves on a commercial farm were randomly assigned to 1 of 3 diets (n = 35/diet): milk replacer (MR; Purina Warm Front BOV MOS Medicated Milk Replacer, St. Louis, MO), TM, or a 50:50 blend of MR and colostrum replacer (MCR; Alta HiCal Colostrum Powder Replacer, the Saskatoon Colostrum Company Ltd., Saskatoon, SK, Canada). The TM was harvested from Holstein cows on the farm, pooled, and pasteurized at 71.7°C for 15 s. Nutrient composition on a dry matter basis of TM was 25.9% fat, 41.8% protein, and 14% solids; MR was 10.3% fat, 27.8% protein, and 14% solids; and MCR was 14.6% fat, 38.6% protein, and 15% solids. All calves received IgG-enriched colostrum replacer for the first 2 feedings after birth. Subsequently, calves were fed 1.9 L of MR, TM, or MCR 3 times per day for 3 d (starting on d 2). After initial diets ended, calves were fed and managed similarly. Body weights (d 1, 7, 14, 21, and 56), blood samples (d 1, 7, 14, and 21), and daily health scores (scale of 0 to 3, with 0 representing normal or healthy and 3 representing severe symptoms or ill) were collected through weaning at 56 d. All except 1 calf achieved successful transfer of passive immunity, with serum IgG values greater than 10.0 mg/mL. From birth through weaning, calves fed TM and MCR gained 3 kg more total body weight than those fed MR (34.3, 34.3, and 31.3 kg, respectively). Increased metabolizable energy (using NRC 2001 recommendations) in TM accounts for 0.68 kg of the increased gain compared with MR. Treatment did not alter health scores for ears, eyes, or feces. Haptoglobin concentrations were lower in TM and MCR than in MR calves (4.63, 3.62, and 7.54 µg/mL, respectively), whereas lipopolysaccharide binding protein concentrations were not different. In conclusion, compared with MR alone, feeding TM or MR with colostrum replacer for 3 d increased growth rate of calves throughout the preweaning period.