Intensificação do manejo de campo nativo do bioma pampa na interface planta-animal e nutrição de bovinos

Abstract

The objective of this study to identify the parameters that affect the plant-animal interface and the nutrition of cattle due to the different strategies of intensification of the native pasture from Pampa Biome. The experiment started in August 2015 and ended in May 2017. However, the process of intensifying treatments began in March 2015. The area destined for the experiment is approximately 34 ha of natural pasture, average. The following treatments were evaluated: native pasture (NP); NP with liming and fertilization with phosphorus and potassium (NPF); NPF with introduction of annual ryegrass (Lolium multiflorium) (40 kg ha-1 of seeds) and nitrogen fertilization corresponding to 80 kg / ha / year (NPFRN); NPF with introduction of annual ryegrass and legume sowing (NPFRL). The animals were composed of Braford breed with approximate weight at the beginning of the experiment of 136 kg of body weight. The experimental design was completely randomized blocks with two replicates and four treatments totaling eight experimental units (EUs). In Chapter I, the periods used for the evaluations were carried out at two different times; March and October 2016. Were evaluated canopy structures, pasture quality and nutritional aspects. Increasing intake and digestibility were evidenced in October, in the NPFRN and NPFRL treatments, as well as the relation of the intake of degradable protein in the rumen with intake of the digestible organic matter (RDP:DOMI) were higher for this same period, that consequently influenced the average daily gain (ADG), with higher gains in the treatments NPFRN 0.627 kg/day and NPFRL with 0,574 kg/day. In Chapter II, the collections were monthly throughout the experiment. The digestibility of organic matter (DOM) consumed by heifers was higher in treatments NPFRN and NPFRL 0.635 and 0.641 g/kg DMO, respectively. However, during the spring the higher DOM was obtained with a mean of 0.653 g/kg. The crude protein concentration in the diet (CPC) presented similar behavior to DOM. Two models were created using multiple regressions considered stepwise analysis. The first model using the pasture structure and the digestibility allowed explaining 42% of the variability for ADG. In the second model with the variables: RDP:DOMI, DOMI and DMI determined the coefficient of 87%. It was conclude that, as native pasture intensifies, there is an impact on the quality of the food and on the nutritional parameters of ruminants, which are determinant for estimating performance.