Slow-release urea, and propolis in dairy cow diets

Using a source of non-protein nitrogen and ionophores can improve microbial efficiency, promoting greater dry matter intake and digestibility, less energy loss, and, consequently, increased milk yield. This study evaluated the performance of crossbred dairy cows receiving diets with different levels of slow-release urea (SRU) with or without propolis extract. Eight multiparous cows (Holstein x Gir) were used, with an initial average body weight of 550 kg in the same lactation period and with an average of 15 kg in milk yield. Cows were distributed into two simultaneous 4 × 4 Latin squares designs. The experiment lasted 84 days and was divided into four 21-day sub-periods. The first 14-d were used to adapt to the diet, while the remaining 7-d were used for data collection. The treatments were: 1) 150 g of SRU (SRU150), 2) 300 g of SRU (SRU300), 3) 150 g of SRU + 20 g of propolis (SRU150P), and 4) 300 g of SRU + 20 g of propolis. The cows were managed on pasture, supplemented with concentrate. The inclusion of propolis extract did not affect dry matter intake, digestibility, milk yield, or composition. The supply of 300 g of slow-release urea promoted an increase in dry matter intake from pasture and reduced concentrate intake without affecting milk yield and composition.