Consumo e disgestibilidade de pastagem nativa do bioma pampa e inclusões de azevém

Abstract

In order to evaluate the fecal crude protein as intake and digestibility marker of cattle fed with natural pasture from Pampa Biome and annual ryegrass inclusions and evaluate the nutritional quality of these pastures it was conducted two experiments in metabolic cages. In the first experiment, the animals received different native pasture offer levels where treatments consisted of 1.5 and 2.25% of the live weight of dry matter and ad libitum with at least 20% of daily leftovers which were carried out six experimental periods. The second experiment consisted of annual ryegrass inclusion levels in the diet of cattle fed with natural pasture, the treatments were 33%, 66% and 100% of ryegrass to replace the native pasture in two experimental periods. The experiments were carried out in a completely randomized design with 3 treatments and 2 replicates per treatment in each period. The experimental period consisted of 10 days of adaptation and 5 days of collection during the period of the trough collects the forage offered have been sampled, the leftovers and also the total fecal production in each 24 hours. It was measured the fecal productions, concentration of faecal components, nutrient intake and digestibility of diet components. In the Chapter I were study the relationship between digestibility and fecal concentration of crude protein (CPf), being tested exponential and hyperbolic equations generating the digestibility of organic matter (OMD) = 0.709 - 9.506 * exp (- 0.041 * CPf) with R2 = 0.61 and OMD =0.942 - 38.619 / CPf (R2 0.62), respectively. The ratio of organic matter intake (OMI) with the amount of CPf, has a linear relation, it was then carried out stepwise analysis to find out what other variables could explain better the model along with the CPf generating a equation OMI = -6724.30 + 0,998 * CPf + 2.55 * NDFf + 11591.44 * OMD with R2= 0.95. It was determined the ratio of crude protein (CP) of the diet (g/kg of OM) x CPf (g/kg of OM), CPdiet = 1,346*CPf - 47.63 R² = 0.931 (linear model). In the Chapter II were tested two models for all relationships outlined in experiment II, a linear model and a quadratic model, relations were organic matter intake (OMI) x digestibility of neutral detergent fiber (DNDF), OMD x OMI, leaves intake x OMD and OMI x protein/energy ratio. The relationships that were not statistically significant for either model were OMI x protein/energy and leaves intake x OMD. After these relationships, it was found that the CPf has a good potential to estimate intake and digestibility in cattle fed native pastures or associated with annual ryegrass, but these parameters are also affected by different variables.