Performance and utilization of nutrients in dairy cows fed with sunflower meal

AbstractNon-decorticated sunflower meal (SFM) is a potential protein source for dairy cows with high-fibre content but high ruminal degradability. The effect of replacement of soybean meal (SBM) and wheat middlings (WM) with SFM on the intake, digestibility, microbial protein synthesis, nitrogen utilization and milk production of dairy cows was evaluated. Twelve Holstein cows were blocked by days in milk and distributed in three 4 × 4 Latin squares. Diets were formulated to be isonitrogenous and contained 550 g maize silage/kg dry matter (DM). Treatment diets were no SFM (CON) or 70, 140 and 210 g/kg DM of SFM replacing fixed mixture of SBM and WM (536 and 464 g/kg of the mixture, respectively). The inclusion of SFM in diet did not affect DM intake, but intake of rumen degradable protein increased linearly. Inclusion of SFM reduced or tended to reduce total-tract digestibility of non-fibre carbohydrate, total digestible nutrients and excretion of purine derivatives. Milk production, milk protein content and efficiency of nitrogen use for lactation were reduced with increasing levels of SFM in the diet. The use of non-decorticated SFM as a replacement for SBM–WM mixture in diet reduces performance and efficiency of nutrient use in lactating dairy cows. The outcome of the current study is attributed to reduced fibre digestibility in SFM hulls. Therefore, future studies should evaluate the use of decorticated SFM.