Estratégias de intensificação para o sistema de cria em bovinos de corte

Abstract

With global population growth, the demand for food is increasing. The breeding phase of beef cattle production depends on pasture production, which, in turn, is affected by the climate. During the dry season of the year, feed for grazing animals is scarce. Hypotheses: The application of nitrogen will increase the stocking rate. The use of supplements in the form of

concentrates helps in the digestion of forage in the rumen, increasing the consumption of low- nutrient-value pasture. The production of silage maximizes the use of forage in the system.

Objectives: To evaluate two supplementation methods for pregnant cows during the dry season, combined with fertilization and deferred pasture, compared to a system without using any of these technologies. The experiment lasted 24 months, using 36 cows + calves pairs of the Tabapuã breed per year. The pairs were divided into 3 blocks and 3 treatments, with 2 replicates of each treatment in each block. Each treatment had a different paddock size: Control 1.71 ha, Sup1 1.01 ha, and Sup2 0.83 ha. In the control treatment, there was no fertilization on the pastures, and the only supplementation used was commercial mineral salt. In Sup1, the paddocks were fertilized with 165 kg of N/ha/year, divided into 3 applications, and 50% of the area was closed off for deferral at the end of the rainy season. During the dry period, the animals were supplemented with commercial concentrate and had access to the deferred area. For the rest of the year, they were supplemented with mineral salt. Sup2 had the same fertilization as Sup1, but 30% of the area was closed off at the beginning of the rainy season. The accumulated herbage mass in this area was harvested and mixed with dried distiller grains with solubles (DDGS) to make PMR (Partial Mixed Ration) silage. After this process, the area was deferred again. Throughout the year, the cows received commercial mineral salt supplementation and, during the dry season, were supplemented with the silage, while still having access to the deferred pasture. For statistical analysis, the experiment was divided into two periods: pregnancy and lactation (periods 1 and 2, respectively). All 3 treatments showed greater herbage mass in period 1, while herbage accumulation was greater in period 2. The annual average herbage mass was greater for the control and Sup1, with accumulation being greater in Sup1 and Sup2. The average body weight, average daily gain (ADG), and gain per area (GPA) of the cows were greater in period 1. Sup1 and Sup2 treatments showed higher ADG and GPA. The stocking rate was higher in Sup2, followed by Sup1, with the control showing the lowest rate. The GPA of the calves was higher for the Sup1 and Sup2 treatments.