Increasing levels of palm kernel cake ( Elaeis guineensis   Jacq.) in diets for feedlot cull cows

Agro-industrial by-products are a great option for ruminant feeding. Alternative feedstuffs in ruminant diets are important to increase diets and reduce production costs. The present study evaluated different levels of palm (Elaeis guineensis Jacq.) kernel cake inclusion in diets for feedlot-finished cull cows and their implications on the intake and digestibility of dry matter (DM) and nutrients, as well as animal performance. The experiment was carried out in Ribeirão do Largo, Bahía, Brazil. Thirty-six Holstein × Zebu crossbred cows were assigned to four treatments at the rate of nine cows per treatment. The animals were fed sugarcane bagasse (roughage 15%) and concentrate (85%). The treatments were no addition of palm kernel cake, 8%, 16%, or 24% palm kernel cake inclusion in the total DM diet. Palm kernel cake inclusion influenced DM and nutrient intakes, which responded quadratically. The digestibility of DM, crude protein, and neutral detergent fiber corrected for ash and protein showed a quadratic response and maximum digestibility at 1.67%, 5.24%, and 3.68% cake inclusion levels, respectively; values decreased thereafter. The total digestible nutrients decreased linearly based on cake inclusion levels. Treatments affected final body weight, mean daily gain, and feed conversion, which showed a quadratic response to increasing levels of the by-product in the diet and maximum values were at 11.98%, 13.07%, and 16.32% inclusion, respectively. Palm kernel cake is a viable alternative ingredient for animal biological efficiency. The 16% inclusion level in the total DM diet was the most appropriate for the finishing of cull cows in the feedlot.