This study examined the effects of average daily gain (ADG) during gestation on growth, nutrient digestibility, metabolic response, and subsequent milk yield and composition in dairy heifers. Twenty pregnant Holstein × Gyr heifers (450 ± 5.0 kg; 18 ± 1.1 months) were randomly assigned to moderate (MOD; target 0.35 kg/day) or high (HIG; target 0.70 kg/day) ADG groups, and received a total mixed ration from day 70 of gestation until calving. Body growth, blood metabolites, and lactation performance after birth were measured. At calving, HIG heifers had greater body weight (p 0.05), except for triiodothyronine concentrations, which differed between treatments over time (p 0.10), while milk fat and total solids showed numerical treatment × week interactions (p ≤ 0.10). These results indicate that higher ADG during gestation increases body reserves at calving but does not affect milk yield. The moderate ADG for Holstein × Gyr heifers during gestation may improve milk quality through higher fat and solids content, emphasizing the importance of tailoring growth strategies for heifers during gestation.
Neto et al. (Tue,) studied this question.