Resumo
Many problems associated with the use of high-grain diets are reported by growers and scientists as the negative effects associated with acidosis. In order to improve the ruminal conditions, studies have been carried out to find an optimal level of fiber to be included in these diets, especially in the so-called non-voluminous diets. Therefore, the objective of this work was to evaluate the effects of the inclusion of physically effective fiber (NDF) from bulks in diets containing whole grains of corn, replacing the pellet, under ingestive, digestive and ruminal parameters. The experiment was carried out at the Animal Science Department of the Federal University of Viçosa. Five rumen fistulated, uncastrated male Nellore cattle with a mean of 393 ± 9 kg and age of 14 months were used. The experimental design was in a 5 x 5 Latin square, consisting of five diets, five animals and five experimental periods. The diets were based on whole corn grain with inclusion of increasing levels of sugarcane in natura, being constituted respectively by: Control (CON) - Diet with 85% of whole grain corn and 15% of a mineral- pore protein; D5 - Diet with 85% of whole grain corn, 5% of sugar cane in natura and 10% of a mineral protein supplement; D15 - Diet with 75% of whole grain corn, 15% of sugar cane in natura and 10% of a mineral protein supplement; D25 - Diet with 65% of whole grain corn, 25% of sugar cane in natura and 10% of a protein mineral supplement; D35 - Diet with 55% of whole grain corn, 35% of sugar cane in natura and 10% of a protein mineral supplement. The experimental periods had a duration of 20 days (14 days for adaptation and six days of collection). The first three days of sampling were used for the sampling of omasal digests, spot collection of feces, and sampling of samples for estimation of concentrations of ammonia and organic acids. Ruminal pH was also measured. On the fourth and sixth day of the collection period, emptying was performed on the full and empty spot of the rumen, respectively. During these days samples were also collected for the isolation of ruminal microorganisms. The physically effective NDF content of each diet was measured at the end of each experimental period with the aid of a set of three sieves called Pen State Particle Sepatator (PSPS), which had 19, 8 and 4 mm sieves. Statistical analyzes were performed using the SAS® MIXED procedure (Version 9.4). The averages were compared using the Dunnett test, assuming 5% for the type I error, and the linear and quadratic effects were tested for inclusion levels of NDF in the diet and the ammonia concentration was evaluated as a repeated measure. The organic matter (OM), neutral detergent insoluble fiber corrected for ash and protein (FDNcp) and neutral detergent insoluble fiber corrected for ash and potentially digestible protein (NDFcpPD), crude protein (CP), ethereal extract , non-fibrous carbohydrates (CNF) and starch responded in a linear decreasing or quadratic manner as a function of the levels of NDF of roughage. The digestibilities of all the constituents reduced with the inclusion of NDF of roughage, with the exception of the potentially digestible NDFcp (PD). The ruminal pH responded in an increasing linear fashion to the addition of voluminous in the diet. The concentration and the pool of propionate linearly reduced and the concentration of butyrate and the acetate pool tended to reduce and elevate, respectively. The concentration of ruminal ammoniacal nitrogen increased linearly. Thus, a level of NDF from volumine of 20.47 g / kg, corresponding to 5% of sugarcane, can be used instead of pellets in whole corn diets, in order to improve the parameters nutritional and metabolic characteristics of this type of food matrix.
One of the problems associated with livestock in Brazil is the emission of greenhouse gases (GHG), responsible for global warming, mainly due to the significant national cattle herd. In addition to enteric methane, animal excreta are sources GHG for atmosphere. This study was conducted with the objective of quantifying N2O, CH4 and NH3 emissions from bovine excreta in pastures of brachiaria grass in silvopastoral (SSP) and monoculture (MONO) systems during the rainy and dry periods of the year. The study was carried out in the Experimental Field José Henrique Bruschi, in the city of Coronel Pacheco, from February to April and from July to October 2017. A randomized complete block design was used, with 3 blocks and 2 replicates per treatment within each block, in a split-plot scheme, considering a factorial 3x2 (3 excreta types and 2 systems) in the plot and period of the year (rainy or dry) as subplot effect. An area within each system was previously isolated from the entrance of animals for 1 year and divided into 18 plots that received the excreta. Dung and urine were obtained from 12 crossbred cows, being 6 cows were kept in grazing in each of the systems for 30 days before excreta collection. At moment of collection, the animals were contained and the dung and urine referring to each of the two systems were homogenized and sampled in triplicate for further analysis of dung and urine total nitrogen and the volatile solids content of dung. Subsequently, 1 L of fresh urine and 1.6 kg of fresh dung were deposited in the respective plots. During the rainy season, urine application increased N2O fluxes in both systems, while dung application increased CH4 fluxes. During the dry period, both N2O and CH4 fluxes were substantially reduced. In general, the fluxes of N2O and CH4 in SSP were higher than the fluxes in Mono. Considering the type of excreta applied in the rainy season, it was observed that the emission factor (EF) of N2O in the area treated with urine was significantly higher than in the area treated with dung (P<0.05) in SSP. Regarding to the effect of the type of system, it was observed that in the rainy period, the EF of N2O for urine and the EF of CH4 for dung in SSP were significantly higher (P<0.05) than in the Mono. The volatilization of NH3 from both dung and urine was higher during the dry period. Regarding to EF of NH3, it was higher (P <0.05) in Mono and in the dry period when urine was applied, there being no difference between systems with dung application. During the period of higher emissions of N2O, there was emission of 0.4% of the N applied in the form of urine in SSP and 0.04% in Mono, with emissions below 0.05% for dung in both systems. Regarding to CH4, there was emission of 0.03% of the volatile solids applied in the form of dung in SSP and 0.01% in Mono, during the period of greatest emission, with no significant emissions with the application of urine. The EF of NH3 for urine ranged from 1.7% to 4.3% in SSP and from 8.3% to 17.1% in Mono, with EF for dung ranging from 1.2% to 5.8% in SSP and from 1.8% to 3.6% in Mono. The present study demonstrates that the emissions of N2O, CH4 and NH3 are influenced by the system of land use, type of excreta and season of the year. In addition, the emission factor of N2O, CH4 and NH3 in both systems, under these conditions, is significantly below that estimated by the IPCC at the global level.