Suplementação de baixo consumo na recria de bovinos em pastejo durante a seca.

Abstract

Brazil is among the leading producers and exporters of world beef, reaching a record in 2015 of 215.2 million of animals. The objective of this study was to evaluate the effects of low consumption supplementation strategies during cattle rearing on productive performance in the first drought after weaning. The experimental design was a completely randomized block design, with three replications of area, in a subdivided plots scheme, with treatments (mineral mix, additive mineral mix and energy protein supplement) allocated to the plots, and the periods (Transition, Drought start And end of drought) in the subplots. Thirty-six non-castrated steers were used, 12 animals per treatment, with three replicates of each area, using ad alternating grazing system, with a fixed stocking rate of 4 animals.ha-1, providing ad libitum supplements. The total dry herbage mass probably did not restrict consumption, being influenced by the periods, with a higher value of 3,399.82 kg.ha-1 at the end of the drought, while the leaf-stem ratio responded differently according to the strategies of supplementation with values of 0.71; 0.59 and 0.60, respectively, for mineral blend, mineral additive and energy protein. The leaf blade was the most affected component during grazing times and the evaluation period, as well as the pre-grazing leaf-stem ratio (L.S-1), with a significant difference between the beginning of the dry season 1.75 and the end of dryness 0.81. The highest values of total digestible nutrients were from the transition period 57.14% in relation to the beginning of the drought and the end of the drought with 51.40 and 47.89%, respectively. It was observed consumption of 138, 94 and 508 g.day-1.head-1, respectively, for the mineral mixture, mineral mixture and protein-energetic. Both supplementation and the periods of evaluation altered the mean weight gain (ABW) of the grazing animals, and independently. The highest ABW were observed when the post-grazing started with a leaf mass of 2,000 kg.ha-1 or greater and a L.S-1 ratio higher than 1.5. The additional gain of the protein-energy supplement in relation to MM was 34.84 kg, more than one arroba of difference per animal. The variation in ABW of the animals allowed the exploitation of different loads in the pastures, totaling a productivity of 3.5; 4.68 and 7.68 @.ha-1 during the critical period of the year. The daily cost was R$ 0.18; R$ 0.16 and R$ 0.60.head-1, which multiplied by the experimental period had the total cost with supplementation of R$ 35.46; R$ 31.52 and R$ 112.20, respectively, for mineral blend, mineral additive and protein-energy supplement. Therefore, only the additives in the mineral mixture were not sufficient to increase the ABW of grazing animals during the first post-weaning drought.