Microminerais injetáveis para bezerros de corte no pré-desmame

Abstract

The objectives with this work were to evaluate the effects of applying a mixture of trace minerals (Cu, Mn, Se and Zn) 14 prior to weaning on hematological parameters, immune function, antioxidant activity, trace element status and performance of beef calves in the post-weaning period. In the first chapter, literature review was carried out highlighting the role of trace minerals in the animal organism, the obtained results and the potential for using injectable trace mineral mixtures (ITM) at different moments of cattle production cycle. In the remaining chapters, the application effects of a single ITM dose on hematological variables and immune system (chapter 2) and on performance, trace mineral status and parasitic load (chapter 3) of calves maintained in tropical pastures, supplemented with ITM 14 pre-weaning were evaluated. In chapter 2, 64 calves divided in two groups according to birth time were used, being 32 males and 32 females (mean age 208 days at weaning). Females had mena initial BW of 163±19 kg and males 181±23 kg. Study lasted 70 days per group, comprising a period from 14 days prior to weaning (d-14) to 56 days after weaning (d56). Animals were divided based on BW and sex into two treatments: SALINE, saline injection (1 mL/45 kg BW) and ITM, injectable trace minerals (1 mL/45 kg BW) containing Cu, Mn, Se and Zn on its composition. ITM had 15 mg of Cu/mL, 10 mg of Mn/mL, 5 mg of Se/mL and 60 mg of Zn/mL. Animals were Always mantained in a unic group and alternated in diferente paddocks of Urochloa decumbens e Urochloa brizantha cv. Marandu, with access to water and mineral mixture. Similary, in chapter 3 the same calves of chapter 2 and other 56 calves (average age 8 months) were used, being 24 males(initial BW 202 ± 34 kg) and 32 females (initial BW 206 ± 38 kg), submitted to the same experimental protocol. In chapter 2, there was a trend (P = 0.0836) of greater red blood cell concentration at the time of weaning in animals that received ITM. A reduction in mean corpuscular volume (MCV; P = 0.0208) was observed in animals treated with ITM compared to SALINE. There was a tendency (P = 0.0884) to reduce mean corpuscular hemoglobin (MCH) when animals were treated with ITM. There was no treatment effect or treatment x day interaction for the leukogran evaluated variables (P > 0.05), with a day effect (P < 0.05) for these variables. In chapter 3, the application of ITM did not influence BW and ADG of calves (P > 0.05), with no treatment x day interaction (P > 0.05) in the evaluation of the BW in both experiments. Day effect for BW was observed throughout the evaluation (P ≤ 0.05). The application of ITM also did not influence (P > 0.05) the egg count in the feces (eggs/g) between the beginning and the end of the experiment 2. ITM application 14 days before weaning reduced MCV and MCH, increased the concentration of pre-weaning platelets and red blood cells on the day of weaning, with a lower concentration of platelets 14 days after weaning, having no effects on components of immune system, as well as did not influence ADG and the parasitic load of the animals. Despite the greater supply of trace minerals provided by ITM, the macronutrient limitations (mainly CP) reduced performance and limited possible effects of ITM on productive performance.