Metabolic profile and milk production of cows grazing on ryegrass with crude glycerin supplementation

ABSTRACT: To assess the effect of crude glycerin inclusion on the metabolic profile of lactating cows grazing on ryegrass, an experiment was conducted with eighteen Holstein cows, divided between two treatments: 1) a basal diet without crude glycerin supplementation, 2) a basal diet supplemented with crude glycerin at a rate of 0.3% of the animals’ live weight. A double crossover design was used over a 56-day experiment, divided into four 14-day periods, with the initial period used only to standardize the diet. Data were analyzed blocking for lactation period, including results for milk production (liters per day and corrected to 4% fat content), blood and urine urea and glucose levels, and milk urea nitrogen levels. The inclusion of crude glycerin at 3% of live weight in the diet of lactating Holstein cows grazing on ryegrass was found to reduce urea excretion in milk and increase blood glucose levels, without affecting milk production. Therefore, its inclusion in their diet is recommended.