Relationship between growth and metabolic parameters of Holstein heifers fed different nutritional regime

In two experimental herds 141 replacement heifers were reared with the aim of investigating the relationships between growth from 5 to 18 mo of age and metabolic parameters. The heifers of both herds were fed on a moderate ADG (MADG: 0.7 kg/d) or on an accelerated ADG (AADG: 0.9 kg/d) diet. Heifers’ BW, BCS, wither height (WH), hip height (HH), body length (BL), and hearth girth (HG) were recorded every 28 days. At 9 and 15 mo of age a blood sample was drawn for analysing metabolic profile. Data from body measurements were processed by analysis of variance and growth curve analysis, using Laird’s form of Gompertz curve. Metabolic profiles were processed by Principal Components Analysis (PCA), followed by Pearson’s correlation analysis between growth curve coefficients and PCs. The AADG heifers had greater actual ADG (0.83 vs 0.74 kg, P<0.001) and greater daily increase of HG (1.76 vs 1.65 mm, P<0.005) than MADG heifers. From 9 to 18 mo of age, BCS of AADG heifers diet was greater than BCS of MADG heifers (P<0.05). From the comparison of growth curve parameters between ADG groups, only the initial growth rate of HG was affected by diet, and no effect was found on maturation rate. The PCA showed a PC1 mainly composed of total protein and albumin (9 and 15 mo), Na and ceruplasmin (9 mo), glucose and Ca (15 mo). This component was positively correlated (P<0.05) with the maturation rate of the growth functions for BW, WH, HH, and HG.