Resumo

PINTO-SANTINI, Livia V et al. Relationship among energy balance, blood metabolites and hypothalamic expression of orexin receptor type 1 and neuropeptide y  in crossbred dairy cows during postpartum. Rev. Fac. Cienc. Vet. [online]. 2011, vol.52, n.1, pp.25-37. ISSN 0258-6576.

In crossbred dairy cows under tropical conditions, where supply and diet quality may be limited, the relationship among energy status (ES), metabolic and productive status of the animals are still not clear. In this regard, 27 dual purpose (DP) cows (3/4 to 5/8 Bos taurus x 1/4 to 3/8 Bos indicus), were randomly assigned to the following treatments, a combination of body condition (BC) at calving (AC) and feeding level (FL) postpartum (PP): 1) HBCHFL: High BC to PP (BC: ≥ 2.5) and high FL PP (HFL), 2) LBCHFL: Low BC to PP (BC: < 2.5) and HFL, 3) HBCLFL: HBC and low FL PP (LFL) and 4) LBCLFL: LBC and LFL. Energy balance (EB) PP, the concentration of glucose (GLU), cholesterol (COL) and urea nitrogen (UN) and hypothalamic expression of neuropeptide Y (NPY) and orexin receptor type 1  (OX-1R ) by Western Blot, were evaluated. The data was analyzed by ANOVA for repeated time measures, including the effect of BC level of FL and their interaction. No effect of BC x FL on any variable was found. Cows under HFL consumed (kg.anim.d^-1) more feed (10.9 to 12.9 than LFL (8.8 to 10.6) (P<0.01), however, the EB was negative (-7.9 ± 19.4 for HFL and -27.2 ± 13.1 for LFL, (P<0.01). The GLU (mg.dL^-1) concentration was of 61.5 and 56.7 (P<0.05) and COL (mg.dL^-1) of 142.6 and 157.6 (P=0.10) for HBC and LBC, respectively, without effect of FL. The UN (mg.dL-1) was affected by FL (15.9 to 19.2 for LFL and HFL, (P<0.05). A reduction of NPY expression and OX-1R in the 45 d LBCLFL PP was observed and was associated to a diminished central nervous system response caused by marked energetic restriction. The BC to PP is the most important component of ES to consider in DP systems, especially when the diet does not allow high consumption and input of total energy.

Palavras-chave : Energy balance; metabolites; cows; attention; glucose; cholesterol; neuropeptides; blood urea nitrogen.