Suplementação com óleos de amendoim e girassol para vacas leiteiras a pasto no início da lactação

Abstract

This study was performed to evaluate the effect of supplementation with peanut and sunflower oils on milk yield and composition, energy balance and variation in body weight and body condition score, fatty acids profile and oxidative stability of milk, blood metabolites and mRNA abundance of antioxidant and lipogenic-related genes in crossbred Jersey cows fed tropical pasturein the early lactation. Peanut oil was chosen to be a rich source of n-9 fatty acid and sunflower oil as a rich source of n-6. Twenty four cows were used in a completely randomized block design. Animals were assigned to four dietary treatments, (1) concentrated with no oil (CONT), (2) concentrated with 5.6 g/kg DM peanut oil (AME), (3) concentrated with 59.6 g/kg DM sunflower oil (GIR) and (4) concentrated with 59.6 g/kg DM of a 1: 1 mixture (MIX) of peanut oil and sunflower oil simulating an oil with the n-6:n-9 ratio balanced. Milk feed and faces samples were performed at 30 and 60 days in milk (DIM) and the variation in weight and body condition score were performed at 0, 30 and 60 DIM. Milk yield was recorded until 237 DIM. Dry matter, forage and nutrients intakes and nutrients digestibility were similar in all treatments. Cows fed oil increases the intake and digestibility of EE. The oil supplementation decreased the FDN digestibility. The GIR treatment decreased the daily and total milk yield and milk fat percentages. The oil supplementation increase the NEL intake. The GIR treatment decreased NE excreted in milk, the efficiency of use of diet NEL for milk production, the variation in weight and body condition score and improved the EB until 60 DIM. The GIR treatment increase the proportion of PUFAs while AME treatment increases the proportion of MUFA, n-3 PUFA in milk fatty. Higher production of conjugated diene was observed for the GIR treatment. The GIR treatment decreased the gene expression of the enzyme fatty acid synthetase and stearoyl CoA desaturase. For MIX treatment there was increased activity of lipogenic enzymes, except for PPARα. Lower relative abundance of mRNA for SOD1 was observed in GIR and MIX treatments The oil supplementation has a tendency to reduce the relative abundance of mRNA GPX1. Supplementation with oils did not result in better performance in lactating cows kept in tropical pasture. Sunflower oil reduces production and milk fat content and improve the energy balance in early lactation compared to the peanut oil. Supplementation with sunflower oil, rich on n-6 PUFA, increases the proportion of milk fat and reduces the oxidative stability of milk and the gene expression of lipogenic enzymes and antioxidants. Supplementation with peanut oil, rich on n-9 MUFA, increases the health promoter index by increasing the proportion of MUFAs and n-3 PUFin milk without, however, have negative effects on the gene expression of lipogenic enzymes and antioxidants and oxidative stability of fat milk.