Abstract
The purpose of this study was to investigate the effects of increased milk feeding levels or social housing during the preweaning stage of Holstein dairy heifers on subsequent weight gain, health, and reproductive parameters over time. A total of 210 heifers were grouped by calving date in groups of 10 and randomly assigned to one of 3 treatments: low-milk individual housing (LMI; 4 L of milk/d), high-milk individual housing (HMI; 8 L of milk/d), or low-milk social housing (LMS; 4 L of milk/d). Data collected included passive transfer status, disease events, weight gain at different time periods, age at first calving, calving intervals, and milk yield over the first 3 lactations. Passive transfer was successful in 189 calves, and, overall, disease events were low in this herd. The average daily gain for heifers in the HMI group (0.79 ± 0.05 kg/d) was significantly higher (F (2, 9) = 4.76) during the preweaning treatment period compared with the other groups (LMI: 0.59 ± 0.05 kg/d; LMS: 0.68 ± 0.04 kg/d). Although treatment groups did not differ with respect to age at first calving, the LMS and HMI heifers calved (22 and 15 d, respectively) earlier than the LMI heifers. Milk yield over 3 lactations was similar among the treatment groups. This suggests that both nutrition and social dynamics can influence performance of preweaned calves. Further investigation is needed to understand the mechanisms driving increased weight gain in socially housed calves.