Effect of diets with different content of starch and protein fed to dairy cows in early lactation on milk yield and traits

With the aim to study the effect on milk yield and its traits of 2 different levels of fermentable carbohydrates (LS: 25.5%, and HS: 29.5% DM) combined with 2 protein levels (LP: 15.5% and HP: 16.5% DM), 4 Italian Friesian dairy cows in early lactation housed in a tied stall were used. The experimental diets were obtained adjusting in 4 supplements the proportion of high energy fibrous (beet pulp, soybean hull) or starchy (corn meal) feeds and of meal protein more (soybean meal) or less (Soy-Pass : xylose-treated soybean meal) degradable. The highest DMI was observed in HSHP which showed also a low content of NDF. Milk yield resulted over 45 kg/d throughout the study and higher when HSHP diet was fed (46.1 kg). Milk fat was always at high level and the lowest value (3.89%) with HSHP and the highest (4.08%) with LSLP were observed. The diets did not modified milk protein (their average levels resulted of 3.25%) and lactose content. Milk acidity and renneting traits were higher when HSLP was fed, and resulted at adequate levels when all the diets were fed. When the diets for dairy cow are formulated to cover the animal requirements and respect their digestion physiology, it is possible to reach high milk yield level and maintaining, at the same time, a high milk quality .