Effect of average daily gain on body size, metabolism, and milk production of Italian Holstein heifers raised on two different planes of nutrition and calving at two different ages

摘要: Abstract The aim of this experiment was to study the effect two average daily gains between 5 and 15 mo age on body measurements, fat deposition, metabolic profile, interaction with at first calving, milk production in lactation. A total 141 Italian Friesian heifers, experimental herds, were allotted 2 feeding regimens formulated for a moderate (M, 0.7 kg/d) or an accelerated (H, 0.9 kg/d) gain diet from age. Half heifers M programmed be bred (ME), half 18 mo (ML) age; H (HE). Every 28 d, weight, withers height, hip length, heart girth, condition score recorded. Also each week one herd −14 70 d post-calving, evaluated. In herd, profile assessed 9 Growth curve parameters estimated measurements heifer. Metabolic profiles both ages (9 15 mo) processed by Principal Components Analysis (PCA). For lactation, composition grew slower (0.73 vs. 0.81 kg/d) than difference reflected also faster girth (0.184 0.169 cm/d). fed increased that 9 mo At age, plasma concentration urea, Ca, Na, albumin, γ-glutamyl transferase activity greater heifers. bilirubin alkaline phosphatase lower 9 mo, urea correlated height parameters. 15 mo, glucose weight Plasma ceruloplasmin ages, 15 mo. results PCA have shown principal component growth functions girth. Experimental calving per se did not affect but peak HE occurred 15 d earlier ML