Desenvolvimento corporal, idade à puberdade e desenvolvimento da glândula mamária de fêmeas mestiças leiteiras aleitadas com diferentes teores de sólidos totais na dieta líquida

Abstract

The aimof this paper was to determine the effect of increasing total solids (TS) on the liquid diet composed of whole milkwith addition of milk replacer powder in preweaning on performance, age at puberty, age at first insemination, glucose metabolism and mammary fat pad of dairy heifers. Crossbreed Holstein x Gyr heifers (n = 58) were distributed in four different treatments during preweaning period, which consisted of liquid diets with different TS concentrations: 13.5% (n = 15); 16.1% (n = 15); 18.2% (n = 13) and 20.4% (n = 15), provided up to 59 d of age. From 60 to 89 d of age the animals received the same starter from the preweaning period and corn silage was added to the diet at 70 d of age. From 90 to 104 d of age the animals were adapted to the postweaning diet. At 105 d of age, the animals were distributed in 4 collective paddocks, with electronic feed and water bins (Intergado® Ltd., Minas Gerais, Brazil) and received the same total diet ad libitum. Individual evaluations of feed and water intake, body weight and body development were performed until artificial insemination (AI) of heifers at 350 kg BW. Ultrasound mammary gland evaluations were performed from 120 d of age until puberty. Puberty was considered to have occurred when plasma progesterone concentrations of 1 ng/mL were present in 2 consecutive samples. The date of puberty was recorded as the time of the first of these samples were collected.Glucose tolerance test was performed at 280 d of age. The increased TS concentration of liquid feed during the preweaning period did not affect dry matter intake, performance, age at puberty, age at first AI, glucose metabolism and fat pad of the mammary gland. However, measurements of hip width and heart girth linearly increased up to 150 and 240 d of age, respectively.