Glicerina em substituição ao milho no concentrado de vacas Holandês x Gir em lactação

Evaluated the intake and digestibility of nutrients, production and milk composition and concentration of metabolites in plasma of Holstein x Gir cows fed diets based on corn silage supplemented with concentrates containing crude glycerin or not (GB). The treatments were based on the partial substitution of corn meal in the concentrate supplement by GB of glycerol, about 7% of diet DM. The experiment was conducted in randomized block design, with nine cows per treatment, and three repeated measures, and the cows were distributed in blocks based on milk production and body weight observed in pre-trial period in order and the degree of farrowing blood. The individual consumption were determined by difference between the amounts of diets offered and their leftovers. The individual daily milk production was recorded at each evaluation period, and samples taken for analysis of milk composition in milk urea nitrogen (MUN), fat, protein, lactose, total solids and fat. We also collected blood samples for determination of plasma concentrations of glucose and urea. The determination of apparent digestibility was assessed only in the second collection period using chromic oxide (Cr2O3) as an indicator of fecal excretion. There was no difference (P> 0.05) between treatments for dry matter intake, organic matter, crude protein, neutral detergent fiber and total digestible nutrients. For the consumption of starch and ether extract was no difference between treatments (P <0.05), observed that treatment with the lowest values obtained GB, due to diet composition. The consumption of glycerol was also significant (P <0.05), resulting in higher values for treatment with GB, by the same factor of the foregoing. There was no difference (P> 0.05) among treatments for milk production and composition, except for milk yield corrected for 4% fat and MUN (P <0.05). For plasma concentrations and apparent digestibility were not found differences (P> 0.05) between treatments. In diets of Holstein x Gir supplementation of corn silage with levels of 7% of GB has potential for production of 20 kg / day of milk with high solids content.