Temporal changes in plasma concentrations of hormones and metabolites in pasture-fed dairy cows during extended lactation
LC Marett, MJ Auldist, C Grainger, WJ Wales, D Blache, KL Macmillan, BJ Leury
JOURNAL OF DAIRY SCIENCE | ELSEVIER SCIENCE INC | Published : 2011
This experiment measured variations in plasma concentrations of metabolic hormones and metabolites in cows undergoing extended lactations of up to 670 d at 2 planes of nutrition. Thirty-seven Holstein-Friesian cows that calved in late winter were selected for varying milk yield and then managed for a lactation of 670 d by delaying breeding until approximately 450 d in milk (DIM). Cows grazed fresh pasture supplemented with pasture silage or hay and crushed wheat or triticale grain. Dietary intake was reduced by approximately 1.8 kg (dry matter) grain/cow per day for 19 of the cows from 300 DIM until the end of lactation to assess the effect of restricted energy intake on the persistency of m..View full abstract
The authors are grateful to D. Mapleson, R. Case, T. Hookey, G. Morris, and staff at the DPI Ellinbank research farm (Department of Primary Industries, Ellinbank, Victoria, Australia) for technical assistance with cow husbandry, grazing management, and sampling procedures. This work was funded by the Department of Primary Industries and the Geoffrey Gardiner Foundation Ltd. (Melbourne, Victoria, Australia).