Avaliou-se o efeito da suplementação nutricional durante o período pós-parto sobre a eficiência produtiva (desempenho em ganho de peso da matriz e de sua progênie) e reprodutiva (dinâmica folicular, concentração circulante de IGF-1 e taxa de prenhez) de vacas de corte submetidas à IATF. Para isto, foram utilizadas 629 vacas pluríparas lactantes, homogeneamente distribuídas de acordo com a data do parto, grupo genético, idade, peso e ECC. Os animais foram alocados em três grupos experimentais: 1) PNM (Programa Nutricional Mineral; n=208): 0,4 g/Kg de peso vivo (PV) durante 87 dias, 2) PNP (Programa Nutricional Proteico; n=212): 2,0 g/Kg PV durante 87 dias, ambos os programas com início da suplementação 30 dias (D-30) antes da sincronização para IATF e 3) PNPE (Programa Nutricional Proteico-energético; n=209): 3,0 g/Kg/PV durante 57 dias, com início da suplementação no dia zero (D0) do protocolo de IATF. Todos os animais foram sincronizados para IATF utilizando protocolo a base de estradiol e progesterona. As fêmeas não gestantes receberam uma segunda IATF no D42. O diagnóstico de gestação foi realizado 30 dias após a IATF e ao final da estação de monta (após o repasse com touros). Durante o período experimental foram avaliados os parâmetros de consumo de suplemento, ECC e peso corporal das vacas e dos bezerros. A análise estatística foi realizada através do sistema estatístico SAS© . Houve interação tratamento nutricional e tempo para ECC (P=0,008). As vacas do grupo PNP apresentaram ganho superior de ECC somente entre os dias D-30 e D0 (P< 0,0001). Ainda, as fêmeas que ganharam ECC (P< 0,0001) e peso (P=0,0012) no intervalo entre o D0 e D40 apresentaram maior probabilidade de taxa de prenhez à primeira IATF (P=0,0008). Houve interação tratamento∗tempo para o ganho de peso (P=< 0,0001). O grupo PNP apresentou maior ganho de peso somente entre os dias D-30 e D0 quando comparado com aos grupos PNM e PNPE. Verificou-se que as fêmeas que ganham mais peso entre o D0 e o D40 aumentaram a probabilidade de se tornarem gestantes à IATF (P=0,0012). Verificou-se interação tratamento∗tempo para o peso dos bezerros (P< 0,0001). No D40 os bezerros das vacas dos grupos PNP e PNPE apresentaram maior ganho de peso. Entretanto, essa diferença não foi verificada ao final do período de suplementação (D57). A suplementação nutricional não aumentou a taxa de prenhez à primeira (P=0,29) e à segunda IATF (P=0,08). Não foi verificada interação entre tratamento e grupo genético para a taxa de prenhez à IATF (P=0,15). Conclui-se que os animais do grupo PNP apresentaram ECC e peso corporal superior ao grupo PNM somente no período entre o início do tratamento e o início do protocolo de sincronização para IATF. Os animais que ganharam ECC e peso corporal entre o D0 e o D40, independente do tratamento, apresentaram maior probabilidade de prenhez à primeira IATF. Entretanto, não foi verificado efeito dos tratamentos para a taxa de prenhez.

The effect of nutritional supplementation during postpartum period on productive (body condition score BCS was represented as ECC; performance of weight gain of cows and calves) and reproductive (follicular dynamics, circulating concentration of IGF-1 and pregnancy rate) efficiency was evaluated on beef cows submitted to TAI. For this, 629 lactating multiparous cows were used, homogeneously distributed according to calving date, genetic group, age, weight and ECC. Animals were divided into three experimental groups: 1) PNM (Mineral Nutritional Program; n=208): 0,4 g/Kg of body weight (represented as PV) for 87 days; 2) PNP (Protein Nutritional Program; n=212): 2,0 g/Kg PV for 87 days, both programs starting supplementation 30 days (D-30) before synchronization to TAI and 3) PNPE (Protein- Energy Nutritional Program, n=209): 3,0 g/Kg/PV for 57 days, starting on day zero (D0) of TAI protocol. All animals were synchronized to TAI using protocol based on estradiol and progesterone. Blood samples were collected from a subgroup of animals (n=45) on days D-30, D0 and D40 for hormonal analysis of IGF-1. In this same subgroup of animals, ultrasound examinations were performed to evaluate follicular dynamics on D0, D8 and D10. Non- pregnant females received a second TAI on D42. Pregnancy diagnosis was performed 30 days after TAI and at the end of breeding season (after natural service with bulls). During the experimental period, parameters of supplement intake, ECC and body weight of cows and calves were evaluated. Furthermore, pasture bromatological evaluations were carried out during the study period. Statistical analysis was performed using SAS© Statistical System. There was an interaction between nutritional treatment and time to ECC (P=0,008). The cows in the PNP group showed higher ECC gain between days D-30 and D0 (P=<0,0001). The gain of ECC (P<0,0001) and weight (P=0,0012) between D0 and D40 increased the probability of pregnancy rate at the first TAI. There was a treatment∗time interaction for weight gain (P=<0,0001). The PNP group showed greater weight gain between days D-30 and D0 when compared to the PNM and PNPE groups. It was found that females who gain more weight between D0 and D40 increased the probability of becoming pregnant at TAI (P=0,0012). There was an interaction treatment∗time for weight of calves (P<0,0001). On D40, calves from cows from PNP and PNPE groups showed greater weight gain. However, this difference was not verified at the end of supplementation period (D57). There was no effect of treatments on diameter of largest follicle at the time of removal of P4 device and on TAI (P=0,45), but an effect of time was observed (P=<0,0001). Similarly, there was no treatment effect (P=0,84) and treatment∗time interaction (P=0,45) for circulating concentration of IGF-1. However, a time effect was observed for all groups (P=0,0008). Nutritional supplementation did not increase the pregnancy rate at the first (P=0,29) and second TAI (P=0,08). There was no interaction between treatment and genetic group for the TAI pregnancy rate (P=0,15). It is concluded that animals in PNP group had ECC and body weight higher than PNM group only in the period between the start of treatment and the start of synchronization protocol for TAI (D-30 to D0). Animals that gained ECC and body weight between D0 and D40, regardless of the treatment, had a higher probability of pregnancy at first TAI. However, there was no effect of treatments for the variables pregnancy rate, follicular diameter on day of device removal and TAI and circulating concentration of IGF-1.