Perfil metabólico de vacas leiteiras no período de transição em sistema semi-intensivo em Minas Gerais no verão e no inverno

Abstract

In this study, it was evaluated the metabolic profile of dairy cows during the transition period into two seasons, summer and winter. It was used in every season 31 crossbred girolando cowswith two or more calving, totaling 62 cows. During the summer, the animals remained on pasture and were supplemented with corn silage and concentrate in the trough. In winter, corn silage and concentrate was given as much tomeet nutritional requirements. It was made a total of 11 blood samples from each animal according to the following protocol: four samples antepartum spaced weekly, at birth and at 2, 5, 10, 15, 21 and 30 days postpartum. It was evaluated the following parameters: calcium (Ca), phosphorus (P), magnesium (Mg), total protein, albumin, globulin, albumin:globulin ratio (A:G), non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), glutamyl transferase (GGT), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), glucose, triglycerides (TG) and cholesterol. All analyseshas influence of the physiological status. AGNE e BHB was the only not influenced by the season. The mean concentrations of Ca, Mg, TG, total protein and LDH were higher in the summer than in the winter, while glucose was higher in the winter. In both seasons, the lowest average concentrations of calcium occurred close to calving, with 75 % of the animals in winter and 35.48 % of the animals in the summer showed concentrations below the physiological rate. Magnesiums concentrations were lower postpartum than antepartum in both seasons, and phosphorus concentrations suffered great variation over peri-partum. The NEFA concentrations at calving, 2 and 5 days postpartum were the highest of the period. During antepartum 32.26% of the animals in summer and 29.03 % in winter had NEFA concentrations above the cutoff of 0.4 mmol/L. Moreover, 22.58 % of the animals in summer and 19.35 % of the animals during the winter exhibited BHB concentrations above 1.2 mmol/L at any time post-partum, representing the condition of subclinical ketosis. Glucose concentrations were lower postpartum in relation to antepartum and had higher levels at parturition. The cholesterol concentrations in both periods fell continuously until the day of parturition and increased throughout the postpartum period. Triglyceride concentrations had greater values until the week before parturition, decreased to the lowest value at calving and remained at these same levels uo to the end of the collection. The albumin concentration was higher in winter during the pre-partum, but in the week before calving it was equal of the summer season. Albumin concentrations in summer increased in value after calving with concentrations falling in winter. During postpartum albumin concentrations in winter became lower than the concentrations in the summer. The total protein along with globulin, had their lowest concentrations near parturition. The concentrations of GGT, AST and LDH always remained within the reference values. The concentrations of these enzymes were higher postpartum than in the pre-partum. The body condition score during labor was higher in winter than in summer, but equaled the birth, when the body condition declined in both mementos until 21 days postpartum.