Effects of feedout strategies and dietary forage inclusions of corn silage on nutritive value mixed ration to lactation cows

The aim of this experiment was evaluate the effects of feedout strategies and dietary forage inclusions of corn silage on nutritive value of total mixed rations to lactation cows. The experiment was carried out at College of Agriculture \"Luiz de Queiroz\" at Piracicaba/SP. Twenty Holstein cows were housed in a tie - stall barn and allocated in a randomly assigned to five replicated 4 x 4 Latin Square design, with 21 d-period, 14 - d to adaptation and the last 7 - d to collected the samples. To compose the treatments, two feedout strategies of corn silage stored in trench silo were employed (silage from the top and silage from the bottom) and the associated two silage levels in the diet (50% or 60% of dry matter). The treatments were: T50)feedout silage from the top, with 50% forage level; T60)feedout silage from the top, with 60% forage level; B50)feedout silage from the bottom, with 50% forage level; B60) feedout silage from the bottom, with 60% forage level. No observed interactions between feedout strategies and forage levels. A smaller proportion of forage in the diet resulted in higher dry matter intake (DMI) and higher milk production. Contrary to expectation, the diets containing silage from the bottom of the silo resulted in lower DMI and lower milk production, probably by higher concentrations of acetic and butyric acids found in this silage. Thus, treatment T50 increased milk production in approximately 2 kg / d compared to treatment B60. Increase of 1 kg / d in DMI, representing an increase of 1.4 kg / d in milk production, when the inclusion of forage was reduced from 60% to 50% dry matter. However, when levels were higher forage, the animals had greater feed efficiency. Under optimal management conditions, which result in well-preserved silages, the differences between the areas of the silo (top and bottom) are negligible. (AU)