Desempenho animal e valor nutricional de forrageiras de inverno, sob períodos de pastejo e suplementação

Abstract

The aim of this research was to evaluate the animal performance of weaned heifers submitted to levels of energy supplementation based on whole oat and corn, in a continuous grazing system in a consortium ofhibernal forages. The productive and nutritional characteristics of the forage canopy were also evaluated. At the end of the experiment, the effect of trampling on soil penetration resistance (RP) was evaluated. Twenty-seven Puruna breed (PO) heifers were used, with an average age of 10 months and an initial weight of 180 kg ±24.03 kg. The experimental design used was a randomized block design, composed of three treatments, with three replications per treatment, and with repeated evaluations over time. The treatments consisted of three levels of supplementation: "SS" for no supplementation; "CS0.5" for supplementation of 0.5% of live weight; and "CS1.0" for supplementation of 1.0% of live weight, with repeated evaluations over time (64DAS (days after sowing); 92DAS; 133DAS; and 161DAS). The supplementation used consisted of 70% white oat grain and 30% corn grain. The canopy consisted of three forage species: black oat cv. IAPAR 61, white oat cv. IPR Suprema and rye cv. IPR 89, cultivated in an integrated crop-livestock area. Data were submitted to analysis of variance and means were compared by the Tukey test at 5%. The means of the variables studied, both for animal performance and forage performance in each evaluated period, showed significant effects (Pr>Fc) for the effect of supplementation and period. For average daily gain (ADG), a value of 0.903 kg animai-1.day-1 was obtained, and 372.6 kg LW. ha-1 in 84 days of evaluation. The best results for animal performance were obtained for the CS0.5% and CS1.0% treatments in the 2nd and 3rd grazing cycles (133DAS and 161DAS, respectively). In the evaluation of forage performance, with an average of 2979.6 kg of dry matter (DM).ha-1, the available forage mass (AFM) presented the highest productivity values in the first and second periods; for forage accumulation rate (FAR), with an average of 48.1 kg of DM ha.day-1, the first, second and fourth grazing periods presented the highest rates (56.8, 51.8 and 57.9 kg DM ha.day-1, respectively); for stocking rate (SR), with an average of 745.1 kg LW.ha-1, the first, second and fourth cutting periods (951.8, 831.1 and 765.9 kg LW.ha-1, respectively) showed statistical differences between them. For the production ofDM by species in the forage canopy, IPR Suprema oats had the highest average productivity per period with 775.6 kg DM.ha-1, being the species with the highest average for leaf production, with 500.2 kg.ha-1 per evaluated period. For bromatological evaluations, crude protein (CP), with an average value of 18.47% in the forage canopy, presented higher values in the second, third and fourth periods; for neutral detergent fiber (NDF), The mean value of the forage canopy was 52.90%, with the lowest values found in the third and fourth grazing periods. The hemicellulose (HEM) mean value was 24.14%, with the highest and lowest values occurring in the first and fourth cutting period, respectively. The cellulose (CEL) mean value was 31.39%, with the lowest concentrations presented in the second, third and fourth cutting period. The forage canopy, composed of black oats IAPAR 61, IPR Suprema and rye IPR 89, demonstrated productive potential and suitable bromatological quality for ruminant production, as well as promoting dry matter accumulation for no-tillage, establishing itself as a sustainable and accessible technology for use in systems with annual winter pastures. The evaluation of soil resistance to penetration (RP) indicated an increase in the O to 10 cm range depth layer between the period before the animals entered and after they exited the experimental area.