Abstract #T100

# T100
Gene expression of hepatic lipid metabolism in primiparous dairy cows with different feeding strategies during early lactation.
A. L. Astessiano*1, A. Jasinsky1, M. Garcia-Roche1, A. Casal1, M. Ceriani1, D. A. Mattiauda1, M. Carriquiry1, 1Udelar, Facultad de Agronomia, Montevideo, Uruguay.

The study objective was to evaluate the effect of grazing in early lactation on changes in triglyceride content and expression of genes related to lipid metabolism in the liver of dairy cows. Primiparous Holstein cows (n = 18, 528 ± 40 kg BW and 3.2 ± 0.2 BCS; fall calving) were used in a randomized block design and assigned, at calving, to 2 nutritional treatments during the first 65 d postpartum (DPP) of lactation: [i] TMR ad libitum (58% forage, 42% concentrate; TMR) or [ii] grazing of Medicago sativa (6-h am grazing in 3-d strips; pasture allowance = 20 kgDM/d) plus TMR (70% of ad libitumTMR; PAS). All cows consumed at each milking, 2.0 kgDM/d of a grain-soybean meal concentrate. Plasma and liver biopsies were collected pre and postpartum (−7 and +42 DPP) to measure plasma NEFA concentrations and hepatic triglyceride (TGA) content and mRNA abundance of genes related to lipid metabolism (SYBR-Green real time RT-PCR). Data were analyzed as repeated measures with a mixed model that included DPP and treatment within DPP as fixed effects. Milk energy output was greater (P = 0.04) for TMR than PAS cows (21.6 vs. 20.0 ± 0.41 Mcal/d) while cow BW did not differ between nutritional treatments. Expression of ACADVL and PPARG mRNA were not affected by nutritional treatments. However, CPT1A mRNA was greater in TMR than PAS cows (2.63 vs.1.99 ± 0.2; P = 0.04), consistent with the greater plasma NEFA concentration in former cows during postpartum (0.63 vs. 0.42 ± 0.03 mmol/L; P < 0.01). In addition, although liver TAG content did not differ between TMR and PAS cows (14 vs. 11 ± 2%), hepatic TAG and plasma NEFA concentrations were negatively correlated only in TMR cows (r = −095, P = 0.01). Results indicated that TMR cows adapted their hepatic metabolism to increase fatty acid oxidation parallel to the increased energy demands of their greater milk production.

Key Words: lipid metabolism, hepatic gene expression, grazing