Banca de QUALIFICAÇÃO: JÚLIA MARA CAMPOS DE SOUZA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: JÚLIA MARA CAMPOS DE SOUZA
DATA: 10/12/2024
HORA: 13:15
LOCAL: Online via GoogleMeet
TÍTULO:

Effects of replacing conventional urea with post-ruminal release urea and interactions with different crude protein levels on nutrient utilization, ruminal fermentation, and nitrogen metabolism of Nellore heifers fed finishing diets

PALAVRAS-CHAVES:

beef cattle nutrition, non-protein nitrogen, protein, recycling

PÁGINAS: 60
GRANDE ÁREA: Ciências Agrárias
ÁREA: Zootecnia
SUBÁREA: Nutrição e Alimentação Animal
ESPECIALIDADE: Avaliação de Alimentos para Animais
RESUMO:

In cattle, the efficiency of nutrient utilization is notably low, as they typically retain only 10–20% of their nutrient intake. Specifically concerning protein, nitrogen assimilation (N) from their diet hovers around 25%. This characteristic not only raises environmental concerns due to nitrogen (N) excretion in manure but also poses financial challenges due to the cost of protein. We hypothesized that the reduction of crude protein (CP) level (11% DM) associated with post-ruminal release urea would increase the efficiency of N utilization in Nellore cattle-fed finishing diets when compared with animals receiving higher levels of CP (14% DM). The objective of this study is to evaluate the interactions between levels of CP (11 vs. 14%) and urea source (feed grade or a post-ruminal release) on digestibility, ruminal parameters, urea N metabolism, and ruminal urea transporters of feedlot finishing Nellore heifers. Eight ruminally cannulated Nellore heifers (525 ± 70 kg of initial weight) will be randomly assigned to 1 of 4 treatment diets in a replicated 4 x 4 Latin square design balanced for residual effects with 2 x 2 factorial arrangement of treatments (2 levels of CP – 11 vs. 14% - and 2 urea sources – feed grade urea (FGU) vs. post-ruminal release urea (PRU)). Four 27-day periods will be conducted with 14d for adaptation to the diet and from day 15 to 27 for sample collection. The sequence of measurements will be d15 to 22, voluntary intake; d16 to 20, total tract digestibility, urinary excretion; d16 to 23, infusion of Co-EDTA; d21 to 23, omasal digesta sampling; d24 for blood and rumen sampling; d25 and 27, ruminal evacuation and 27 for rumen biopsy. Dry matter intake (DMI) will be individually determined by the difference between the amount of feed provided and orts obtained. For the total tract digestibility, the fecal output will be manually collected from each steer immediately after spontaneous defecation on the concrete floor for five days. At the end of 24h, the total fecal output will be weighted and sampled after homogenization. The total tract digestibility will be calculated by the difference between the intake of the diet compounds and their concentration in the fecal material, divided by the intake of the respective dietary compound. Heifers will be fitted with bladder catheters (No. 24, 2-way Foley catheter with a 30-mL balloon) 2h before morning feeding at day 16. This will allow the total urine collected to determine N compounds and purine derivatives excretion. Omasal digesta samples will be collected to assess ruminal and intestinal digestibility at 8 different times, which will represent one day every three hours. Co-EDTA will be used as a fluid phase and small particles indicator, while indigestible neutral detergent fiber (FDNi) will be used as a solid phase indicator. Ruminal fluid and blood will be collected 12 times in 24 hours period. Ruminal fluid samples will be taken from different points in the rumen, and the pH will be immediately measured. The blood samples will be analyzed for glucose, protein metabolites, and enzymes that show liver function. Two rumen evacuations will be conducted 4h after and 1h before the morning feeding to give a representative estimate of the rumen pool size to determine the rumen pool. During the second ruminal evacuation, a sample of rumen epithelium from the ventral sac will be rapidly excised and immediately stored at -80ºC until RNA isolation to access the genic expression of some urea transporter. Data will be analyzed according to a 4 × 4 replicated Latin square design, including the fixed effects of treatments and the random effects of square, animal within Latin square, and experimental period using the SAS MIXED procedure. The results will be considered significant when P ≤ 0.05.

MEMBROS DA BANCA:
Interno - DANIEL RUME CASAGRANDE (Suplente)
Externo à Instituição - EDENIO DETMANN - UFV (Membro)
Interno - MARINA DE ARRUDA CAMARGO DANES (Membro)
Presidente - MATEUS PIES GIONBELLI (Membro)