Effect of increasing amounts of milk replacer powder added to whole milk on postweaning performance, reproduction, glucose metabolism, and mammary fat pad in dairy heifers.

The aim of this study was to evaluate the effects of increasing the total solids (TS) content of liquid feed, by adding increasing amounts of milk replacer powder to whole milk, on age at puberty and postweaning performance, glucose metabolism, and mammary fat pad of dairy heifers. Crossbreed Holstein × Gyr heifers (n = 58) were distributed into 4 different treatments during the preweaning period. Treatments consisted of liquid feeds with TS content of 12.5 (actual TS = 13.5 ± 0.53%; n = 15), 15.0 (actual TS = 16.1 ± 0.03%; n = 15), 17.5 (actual TS = 18.2 ± 0.14%; n = 13), or 20.0% (actual TS = 20.4 ± 0.24%; n = 15), which were provided up to 59 d old. From 60 to 89 d old, the animals received the same starter offered during the preweaning period in addition to corn silage ad libitum starting at 70 d old. From 90 to 104 d old, the animals were adapted to a total mixed ration. At 105 d old, the animals were distributed in 4 paddocks equipped with electronic feed and water bins and were fed the same total mixed ration ad libitum. A period of adaptation to the electronic feed bins occurred from 105 to 119 d old. Feed and water intake and body weight and body frame development were assessed until puberty. Mammary gland evaluations were performed monthly by ultrasonography from 120 d of age until puberty onset. Puberty onset was determined as plasma progesterone concentration greater than 1 ng/mL in 2 consecutive samples collected 7 d apart. The date of puberty onset was recorded as the collection day of the first of these samples. A glucose tolerance test was performed at 280 d of age. The increased TS content of the liquid feed fed during the preweaning period did not affect dry matter intake, performance, age at puberty, glucose metabolism, or mammary gland fat pad at later stages of rearing process. Conversely, hip width and heart girth increased linearly up to 150 and 240 d of age, respectively, as a result of the increased TS concentration of the liquid feed during the preweaning period.