title: Metabolic and endocrine profiles and hepatic gene expression of Holstein cows fed total mixed ration or pasture with different grazing strategies during early lactation.
abstract: BACKGROUND
  In dairy mixed production systems, maximizing pasture intake and total mixed ration (TMR) supplementation are management tools used to increase dry matter and energy intake in early lactation. The objective was to evaluate metabolic and endocrine profiles and hepatic gene expression of Holstein cows fed either TMR ad libitum (without grazing) or diets combining TMR (50 % ad libitum DM intake) and pasture with different grazing strategies (6 h in one grazing session or 9 h in two grazing sessions) in early lactation. Pluriparous cows were grouped by calving date, blocked within group by body weight and body condition score (BCS) and randomly assigned to one of three feeding strategies from calving (day 0) to 60 days postpartum: control cows fed TMR ad libitum (G0; confined cows fed 100 % TMR without access to pasture), pasture grazing with 6 h of access in one session supplemented with 50 % TMR (G1), and 9 h of access in two sessions supplemented with 50 % TMR (G2).
  
  
  RESULTS
  Net energy (NE), but not metabolizable protein (MP), demands for maintenance and/or milk increased in G2 when compared with G1 and G0 cows, respectively. However, NE and MP balances were lower in G1 and G2 than G0 cows. Cow BCS at +55 days was greater in G0 than G2 cows and probability of cows cycling during the first month was greater in G0 and G1 than G2 cows. During the postpartum period, non-esterified fatty acids were greater in G1 than G2 and G0 and β-hydroxybutyrate was greater in G1 and G2 than G0 cows. Plasma insulin was greater and insulin-like growth factor (IGF)-I tended to be greater in G0 than G2 cows, leptin was greater in G2 and G0 and adiponectin were greater in G2 cows. Hepatic expression of growth hormonereceptor-1A and IGF1 mRNA decreased while IGF binding proteins 1,2,4,5 and 6 (IGFBP) mRNA as well as mRNA expression of insulin, leptin (LEPRb) and adiponectin-2 receptors increased from pre to postpartum in all cows. However, only hepatic IGFBP6 and LEPRb mRNA were greater in G2 than G0 and G1 cows, respectively.
  
  
  CONCLUSIONS
  Metabolic-endocrine profiles of cows with different feeding strategies in early lactation reflected not only changes in milk energy output and energy balance but also in walking and grazing activity. Concentrations of insulin and IGF-I were increased in G0 cows whereas plasma adiponectin and both, insulin and leptin sensitivity were improved G2 cows. Increased NE demands in G2 cows when compared to G1 and G0 cows, implied a metabolic stress that impacted negatively on reproductive function.
authors.affiliation: Department of Animal Production and Pastures, School of Agronomy, Universidad de la República (UdelaR), Av. E. Garzón 780, C.P. 12900, Montevideo, Uruguay. lauaste@gmail.com.
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Astessiano
authors.affiliation: Laboratory of Nuclear Techniques, School of Veterinary Medicine, Universidad de la República (UdelaR), C/Lasplaces 1550, C.P. 11600, Montevideo, Uruguay. meikleana@gmail.com.
authors.forename: Ana
authors.initials: A
authors.lastname: Meikle
authors.affiliation: Department of Animal Production and Pastures, School of Agronomy, Universidad de la República (UdelaR), Av. E. Garzón 780, C.P. 12900, Montevideo, Uruguay. maitefs@gmail.com.
authors.forename: Maite
authors.initials: M
authors.lastname: Fajardo
authors.affiliation: Department of Health in Livestock Systems, School of Veterinary Medicine, Universidad de la República (UdelaR), EEMAC, Paysandú, C.P. 6000, Uruguay. jujogil@gmail.com.
authors.forename: Jorge
authors.initials: J
authors.lastname: Gil
authors.affiliation: Department of Animal Production and Pastures, School of Agronomy, Universidad de la República (UdelaR), Av. E. Garzón 780, C.P. 12900, Montevideo, Uruguay. dmattiauda@gmail.com.
authors.forename: Diego Antonio
authors.initials: DA
authors.lastname: Mattiauda
authors.affiliation: Department of Animal Production and Pastures, School of Agronomy, Universidad de la República (UdelaR), Av. E. Garzón 780, C.P. 12900, Montevideo, Uruguay. pablo.chilibroste@gmail.com.
authors.forename: Pablo
authors.initials: P
authors.lastname: Chilibroste
authors.affiliation: Department of Animal Production and Pastures, School of Agronomy, Universidad de la República (UdelaR), Av. E. Garzón 780, C.P. 12900, Montevideo, Uruguay. mariana.carriquiry@gmail.com.
authors.forename: Mariana
authors.initials: M
authors.lastname: Carriquiry
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry / Q000379:methods*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004734:Energy Metabolism; D005260:Female; D005786:Gene Expression Regulation; D006728:Hormones / Q000097:blood*; D008099:Liver
chemical_list: D006728:Hormones