Supplementation strategies for beef heifers in the dry and transition dry-rainy seasons

Esta dissertação foi elaborada a partir de dois experimentos com novilhas de corte submetidas a diferentes estratégias de suplementação a pasto. No primeiro experimento objetivou-se avaliar o efeito da substituição do farelo de soja pelo farelo de algodão em suplementos múltiplos sobre as características nutricionais e desempenho produtivo de novilhas de corte em fase de recria em pastagens de Brachiaria decumbens no período da seca. Foram utilizadas 24 novilhas de corte nelore com idade e peso médio inicial de 8 meses e 210±6 kg, respectivamente. O delineamento foi inteiramente casualizado com quatro tratamentos e seis repetições. Os suplementos continham aproximadamente 30% de proteína bruta (PB) e substituição progressiva do farelo de soja pelo farelo de algodão em 0, 50 e 100%. Aos animais do tratamento controle foi fornecida apenas mistura mineral ad libitum e aos demais tratamentos foram fornecidos 1,0 kg/animal/dia de suplemento. Não houve diferença de GMD entre os animais suplementados e os animais controle (P>0,10). Não foi observado efeito da suplementação (P>0,10) sobre o consumo matéria seca (MS), MS de pasto (MSP), matéria orgânica (MO) extrato etéreo (EE), carboidratos não fibrosos (CNF), fibra em detergente neutro corrigido para cinzas e proteína (FDNcp), fibra em detergente neutro indigestível (FDNi) e nutrientes digestíveis totais (NDT) entre os tratamentos, houve efeito apenas para o consumo de proteína bruta (PB) (P0,10) o consumo nos animais suplementados. A Suplementação ampliou os coeficientes de digestibilidade aparente (P0,10). Observou-se efeito linear positivo (P0,10). Foi verificado efeito linear decrescente (P0.10). No effect of supplementation (P>0.10) was observed on dry matter intake (DM), dry matter on pasture (MSP), organic matter (OM), ether extraction for fat (EE), non-fiber carbohydrates (NFC), neutral detergent fiber corrected for ash and protein (NDF) , indigestible neutral detergent fiber (iNDF) and total digestible nutrients (TDN) between treatments. Only crude protein (CP) showed a difference (P0.10) intake in the supplemented animals. The supplementation increased the digestibility coefficients (P0.10). A positive linear effect was observed (P0.10). Decreasing linear effect was observed (P < 0.10) on the substitution of the relationship microbial nitrogen / nitrogen intake (NMICR). The second experiment aimed to evaluate the nutritional characteristics and productive performance of providing different levels of multiple supplements on heifers grazing Brachiaria decumbens in the transitional period dry-wet season. 24 beef heifers were used aged 11 months and average initial weights of 243±6 kg, respectively. The experiment was completely randomized with four treatments and six repetitions. A supplement with approximately 25 % CP was used. The treatments consisted of four quantities of supplementation of 0; 0.5; 1.0 and 1.5 kg respectively. All treatments received mineral mix ad libitum. A positive linear effect was observed (P<0.10) on ADG and final body weight (PCF) with supplementation quantity. An increasing linear effect (P < 0.10) in intake of DM, OM, CP, EE, NFC and TDN was identified on the increasing quantities of supplements. Opposite effects were observed on consumption of NDF. The quantities of supplements improved linearly (P<0.10) on the digestibility of OM, CP, EE, NFC and TDN. A quadratic effect was observed (P<0.10) on the estimates of digestibility of OM, CP, NDF and TDN between quantities of supplements. A cubic effect (P<0.10) on apparent digestibility of OM, CP, NDF, NFC and TDN levels between supply multiple supplements was clearly detected. A positive linear statistics (P<0.10) on the urinary excretion of urea nitrogen (NUU), serum urea nitrogen (SUN) and flow of microbial nitrogen (NMIC) was found with quantities of supplements. No difference was observed (P<0.10) quantities of supplements on microbial efficiency. The quantities of supplements decreased linearly (P