Metabolic adaptations in dairy cows of diverging Holstein strains under two feeding strategies

Resumo

The aim of this work was to focus on the molecular mechanisms related to hepatic energy metabolism in Holstein-Friesian dairy cows of different genetic origin subjected to two nutritional strategies throughout lactation. Model 1: Multiparous Holstein-Friesian cows subjected to two feeding strategies. From 0 to 180 days in milk (DIM) the cows were fed a totally mixed ration (TMR) ad libitum (G0, without grazing) or grazed Festuca arundinacea or Medicago sativa and were supplemented with concentrate (G1, with grazing). From 180 to 250 days, all cows grazed Festuca arundinacea and were supplemented with a DTM. Model 2: Holstein cows of New Zealand (NZH) or North American (NAH) genetic origin subjected to two feeding strategies, maximum grazing (MaxP) where forage represented 67 % of the offered dry matter intake (70:30 direct grazing of Medicago sativa and Dactylis glomerata or Festuca arundinacea to conserved forage ratio) and the remaining 33 % of the dry matter intake was offered as concentrate, and the fixed pasture strategy (FixP) where grazing represented 32 % of the DMI offered and the remaining was offered as a TMR. For model 1 plasma and liver biopsies were collected at -14, 35, 60, 110, 180 and 250 DIM and for model 2 liver biopsies were taken at -14, 21, 100 and 180 dry matter intake with the objective to characterize the metabolic-endocrine profiles, gene expression of metabolic pathways, mitochondrial function, protein levels and post-translational modifications by western blot. Our results showed that there was a hepatic mitochondrial dysfunction during early lactation associated with lysine acetylation levels in mitochondrial proteins in cows subjected to grazing strategies which is later reinstated towards late mid-lactation. However, NAH cows in the MaxP strategy failed to recover their mitochondrial function during late mid-lactation and showed higher expression of genes associated with gluconeogenesis suggesting greater persistence than NZH cows.