No abstract

The objective of this study was to evaluate the effect of diets containing different calcium and phytase levels on the nutritional balance of broilers.A total of 108 male AG Ross 308 broilers were used in each of the replicates phases used in the study: starter (1-21 days), grower (29-35 days) and finisher (36-42 days). A completely randomized experimental design in a 3 x 2 factorial arrangement, with three phytase levels (0, 600 or 1200 FTU/kg) and two calcium levels (0.94 and 0.66%; 0.84 and 0.59%; e 0.78 and 0.54% in the starter, grower, and finisher phases, respectively), totaling six treatments with six replicates each.The experimental feeds also contained reduced available phosphorus levels and minimum crude protein level.The method of total excreta collection was applied to determine dry matter, nitrogen, gross energy, calcium, and phosphorus nutritional balance.Reducing dietary calcium levels to 0.66, 0.59, and 0.54%, and using 0.27, 0.22, and 0.20% available phosphorus, 18.50, 17.50, and 16.00% crude protein, and 600 FTU phytase/kg in the diets of the starter, grower, and finisher phases, respectively, allow higher nitrogen, phosphorus, and calcium retention in broilers.During the grower phase, there was positive linear effect of increasing phytase levels in high-calcium diets on AMEn utilization, and the optimal phytase levels for low-calcium diets was 598.71 FTU/kg.In the finisher phase, the best AMEn utilization was obtained with the high-calcium diets.

AGRADECIMENTOSAgradeço a Deus e a Nossa Senhora por me fazerem forte, me manterem firme, segura dos meus objetivos, e persistente. Agradeço toda a proteção e às bênçãos recebidas.À minha família, meu maior tesouro, meu chão, meu mundo. Em especial à minha mãe, Leila, meu porto seguro e meu maior apoio, a quem tanto amo. Ao meu pai que me apresentou outro mundo e a quem tenho aprendido a compreender. Aos meus avós, Maria e Afonso, fontes de inspiração, alicerces da nossa família, exemplos de união e amores da minha vida. À minha avó Estelita, muitas saudades e ao avô Ernesto que não tive oportunidade de conhecer. Aos meus tios e padrinhos, Keila (amiga inseparável e verdadeira), Marciano (incentivador das minhas idéias mais malucas), tio Júnior (pai dos meus amores), Marlon, Sônia, Netinho, Smênia, Valmira, Xandy, Néia, Vanusa, Alípio, Toninho, Mara, eternos cúmplices, amigos, apoios, pessoas que ajudaram a formar minha personalidade e me ajudaram a ser uma pessoa melhor, obrigada por confiarem em mim. Aos meus irmãos Newton, Daniel, Grégory, parceiros eternos de vida, farras, bons momentos e dificuldades e às minhas irmãs Isabela e Lívia, minhas lindas! Amo a todos vocês! Aos meus primos lindos, Neto, Gu, Bia, Arthur, Lorrane, Igor, Fred, Breno, Grazian, Dani (e família), amo vocês demais apesar da distância. Aos meus dois afilhados Arthurzinho e Gu, que me desmontam a cada passagem por Brasília. E o agradecimento mais especial aos novos presentes de Deus que trouxeram vida nova e alegria à família meus sobrinhos Esther, Enzo e Anna.A todos os meus amigos de Brasília, que entendem o motivo da minha distância, mas não menor consideração.À FAPESP pela concessão da bolsa de doutorado e pelo auxílio financeiro à pesquisa, que me possibilitaram ter tranquilidade no desenvolvimento de minhas atividades. À Prefeitura do Campus da USP de Pirassununga por disponibilizar as instalações do abatedouro escola e parte dos animais.Ao professor Luis Felipe Prada e Silva, por todo o apoio, confiança, amizade e estrutura, sem os quais não seria possível o desenvolvimento do trabalho. E por todo o aprendizado e vivência fora do projeto de pesquisa, mas dentro do contexto do LPGC, que só me auxiliam a crescer e me fazem uma melhor profissional a cada dia. The understanding of the molecular mechanisms by which nutrition, genetics and hormonal treatments affect the beginning of puberty is of great importance for developing strategies aiming to reduce the age at first calving, and therefore increase the slaughter rate in Nellore cattle. The effects of progesterone device and of endogenous estradiol on the molecular mechanisms controlling the attainment of puberty in Nellore heifers were investigated.Specifically, the molecular pathways of progesterone and estradiol were studied in the hypothalamus. Thirty five non-pubertal heifers, between 13 and 14 months of age, were divided into four treatment (nine or eight per treatment): P4 device without estradiol (SP), P4 device with estradiol (PE), without P4 device and without estradiol (SS...

SUMMARY Citrus pulp can replace corn in feedlot diets in order to decrease metabolic problems by reducing formation of lactate ruminal. However, while eating, animals can easily select against pelleted citrus pulp due to the greater particle size of the pellet. Therefore, grinding citrus pulp pellet can be an alternative to decrease particle selectivity. This study was realized to evaluate the replacement of ground corn by pelleted citrus pulp and ground citrus pulp on animal performance, sorting index, and feeding behavior of Nellore heifers. Thirty-six Nellore heifers were randomly assigned to three treatments: control diet based on ground corn (GC), partial replacement of GC by ground citrus pulp (GCP), and partial replacement of GC by pelleted citrus pulp (PCP). . Heifers fed with the GC diet had higher final body weight (BW), average daily gain (ADG), and dry matter intake (DMI) compared with heifers fed with citrus pulp (P < 0.05). Ground citrus pulp increased DMI and fiber intake compared with the PCP group (P < 0.05). Heifers fed with PCP and GCP sorted for diet particles from 8 to 19 mm and selected particles with less than 1.18 mm (P < 0.05). Thus, the ground citrus pulp is better than pelleted citrus pulp due to higher feed intake and ADG, in consequence of lower selection index.