Luciana Navajas Rennó

Produção de proteína microbiana e estimativas das excreções de derivados de purinas e de uréia em vacas lactantes alimentadas com rações isoprotéicas contendo diferentes níveis de compostos nitrogenados não-protéicos

The objectives of the present work were to estimate the microbial protein production using the total purine derivatives (PD) excretion, to compare the PD and the urea excretions, obtained from spot urine collection with that observed in the 24 hours collection and to evaluate the plasma and milk N-urea and urea urinary excretion. Sixteen Holstein lactating cows were assigned to four 4X4 Latin Square with 3-wk periods in accordance with the lactation period. The four experimental isoproteic diets were formulated to contain 60% of corn silage and 40% of corn meal, soybean meal, urea and mineral salt mixture as dry matter basis. Crescent levels of urea in the concentrate 0.0, 0.7, 1.4, and 2.1% corresponded to the crude protein of 2.22, 4.18, 5.96 and 8.09% of non protein nitrogen based compounds (NPN), respectively. The urine collection was also estimated with urine samples obtained four hours post fed (spot), by the relation of the daily mean creatinine excretion and the urine spot creatinine concentration. The urinary volume and PD excretion and urea estimated through the urine spot did not differ from that obtained from 24 h urine collection. The N-Microbial production estimated and obtained presenting maximum values of 198.05 and 196.96 g/day with the NPN levels of 5.33 and 4.44%, respectively. The milk allantoin concentration linearly decreased as the NPN increased in the diet and represented 4.5% of total PD excretion. The creatinine excretion was not influenced by the dietary NPN levels (23.41 mg/kg LW), while the estimated and obtained urea excretion, the plasma and milk urea and N-urea concentration linearly increased as the NPN increased in the diet. The plasma and milk N-urea concentration of 19-20 mg/dL and 24-25 mg/dL, respectively, represented the limit values from that would occur nitrogen compounds losses.

Estimativa da produção de proteína microbiana pelos derivados de purinas na urina em novilhos

O trabalho foi realizado para avaliar a determinacao da producao de proteina microbiana com a utilizacao da excrecao urinaria de derivados de purinas; comparar a producao de proteina microbiana por intermedio dos metodos das bases purinas e da excrecao urinaria de derivados de purinas; determinar a producao de proteina microbiana em funcao do consumo de materia seca e da porcentagem de fibra em detergente neutro da racao; e estabelecer a proporcao de alantoina e acido urico, em relacao a xantina e hipoxantina na urina. Foram realizados cinco experimentos com animais fistulados no rumen, abomaso e ileo para estudos simultâneos de consumo, digestoes totais e parciais de nutrientes e eficiencia de sintese de proteina microbiana. Utilizou-se o delineamento experimental em quadrado latino 5x5, a excecao do experimento IV (4x4). Os dados foram agrupados em todos os experimentos, os que envolveram animais mesticos (I, II e III) e zebuinos (IV e V). Utilizou-se, para todos os dados agrupados, o delineamento inteiramente casualizado, em funcao dos niveis de concentrado da dieta. Da urina total coletada em 24 horas, foram analisados os derivados de purinas (alantoina, acido urico, xantina e hipoxantina) para determinar a producao microbiana. Para todos os experimentos agrupados, as excrecoes de derivados de purinas urinarios, representadas pela alantoina e pelas purinas totais, apresentaram comportamento quadratico em funcao dos niveis de concentrado da racao, acompanhando o comportamento do fluxo de compostos nitrogenados microbianos (N mic) estimado pelos derivados de purinas na urina, usando a relacao N purina:N total de 0,116, e o estimado pelas bases purinas no abomaso, encontrando-se valores maximos de 72,07 e 86,08 g N mic/dia, para niveis de 62,91 e 63,60% de concentrado, respectivamente. A relacao alantoina e acido urico:purinas totais foi de, aproximadamente, 98%, indicando que a concentracao de xantina e hipoxantina seria, em torno, de 2%.

Uréia para Vacas em Lactação: 2. Estimativas do Volume Urinário, da Produção Microbiana e da Excreção de Uréia

This research was carried out, using 15 dairy cows (Holstein x Gyr) full fed isoproteic diets with 60% silage and 40% concentrate in the dry matter (DM) basis and 0, 0.7, 1.4, and 2.1% urea correspondent to 2.08, 4.01, 5.76, and 8.07% of crude protein levels in the form of non protein nitrogen compounds (NNP), with the objectives to a non invasive methodology, to estimate the microbial protein production, using the total excretion of purine derivatives (PD); to evaluate the concentrations of creatinine, urea and N-urea in the plasma and in the milk; and to compare the PD and urea excretions obtained from total urine and spot collections. The animals averaging initial live weight of 511.8 kg were randomized allotted to the treatments. The experimental period last 90 days for each cow, starting immediately after calving. The results were interpreted by variance and regression analyses. The urine samples were obtained from 24-h collections or from urine sample obtained, approximately, four hours post feeding (spot urine), while the blood samples were obtained four hours post feeding offer. The urea and N-urea concentrations in the plasma and in the milk, as well as the creatinine excretion, that showed average value of 23.60 mg/kg LW, were not affected by the addition of increasing NNP levels to the diet. The urinary excretions of urea, allantoin, uric acid and PD, the absorbed purines and the microbial N production were not influenced by dietary NNP levels. The daily estimated excretions of urea, allantoin and uric acid followed the same pattern obtained by the 24-h collection. Urine spot sample was satisfactory to estimate the PP excretion and, subsequently, the microbial N production.

Concentração plasmática de uréia e excreções de uréia e creatinina em novilhos

O trabalho foi conduzido com os objetivos de determinar a concentracao plasmatica de N-ureia (NUP), a excrecao fracional de ureia (EFU) e as excrecoes de ureia (EU) e creatinina (EC), para varias condicoes experimentais; estabelecer a relacao entre NUP, excrecao fracional de ureia e excrecao de ureia com a porcentagem de proteina bruta (PB) e fibra em detergente neutro (FDN) da dieta; e avaliar as perdas urinarias endogenas, por meio da determinacao da excrecao de creatinina. Nos experimentos I e II, foram utilizadas racoes constituidas de 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado formuladas para apresentarem niveis variados de proteina de acordo com a energia da dieta e niveis semelhantes de proteina (12% de PB), respectivamente. No experimento III, o nivel de concentrado foi fixo (40%), sendo variavel a idade de corte da graminea. No experimento IV, as racoes foram constituidas de 20,0; 32,5; 45,0; 57,5; e 70,0% de concentrado com, aproximadamente, 12% de PB. Utilizou-se o delineamento experimental em quadrado latino 5 x 5 para todos os experimentos, com excecao do III (4x4). Da urina total coletada em 24 horas, foram determinadas as excrecoes de ureia e creatinina. Para os experimentos I e III, a concentracao de NUP variou linearmente com a porcentagem de PB e FDN da dieta; a excrecao fracional de ureia e a excrecao de ureia tambem variaram da mesma forma para todos os experimentos. A excrecao de ureia aumentou linearmente com a concentracao de NUP. A excrecao de creatinina nao foi influenciada pelo teor de PB dietetico e foi proporcional ao peso corporal para todos os experimentos, com valor medio diario de 27,36 mg/kg PV, podendo ser usada para estimar as perdas endogenas de compostos nitrogenados.

Eficiência de síntese microbiana, pH e concentrações ruminais de amônia em novilhos F1 Limousin x Nelore alimentados com dietas contendo cinco níveis de concentrado

ABSTRACT - A trial was conducted to evaluate the effects of five concentrate levels in the diet on the efficiency of microbial synthesis, balance of nitrogen compounds, ammonia concentrate and pH ruminal fluid. Five rumen, abomasum and ileum fistulated F1 Limousin x Nellore bulls were full fed diets containing 25.0, 37.5, 50.0, 62.5, and 75.0% of concentrate and allotted to a 5 x 5 latin square design. The ammonia concentrations and ruminal pH were determined in ruminal fluid samples collected right after the diets supply and 2, 4, 6, and 8 hours after. The unicompartimental model using chromic oxide as marker determined the passage rate. The efficiency of microbial synthesis, expressed by different forms, was not influenced by the use of concentrate, obtaining average values of 35.17 g Nmic/kg MODR, 33.01 g Nmic/kg CHODR, and 355.66 g MSmic/kg CHODR. The maximum ammonia concentrations, for all treatments, were 2.92 hours after the diet supply. The ruminal pH fluid linearly decreased with the concentrate levels and the collection times. The passage rates of .065, .081, .064, .049, and .046.h-1 were verified for the treatments with 25.0, 37.5, 50.0, 62.5, and 75.0% of concentrate, respectively. The addition of concentrate in the diets reduced the pH and did not alter the microbial efficiency.

Consumos e digestibilidades totais e parciais de matéria seca, matéria orgânica, proteína bruta e extrato etéreo em novilhos submetidos a três níveis de ingestão e duas metodologias de coleta de digestas abomasal e omasal

Six castrated steers fistulated in the rumen and abomasum were randomly assigned to two 3 x3 Latin squares (three animals, three intake levels [1.5 supply, 2.0 and 2.5% LW] and three periods) to compare the collection techniques for abomasal and omasal digesta in order to determine the flow as well as to evaluate the effects of the three offer levels (1.5; 2.0 and 2.5% live weight) on both intakes and total and partial apparent digestibilities of DM, OM, CP, EE and TDN. The chromic oxide was used to estimate the digesta flows and the fecal excretion. DM, OM, CP, EE and TDN intakes showed an increasing linear behavior, according to the ingestion levels. DM total apparent digestibility coefficient decreased linearly, as ingestion levels increased. DM apparent digestibility in the rumen did not differ among treatments and averaged 73.2% for the overall equations. OM total digestibility showed decreasing linear behavior, according to the ingestion levels, whereas the ruminal and total intestinal digestibilities were not affected by the treatments (average of 81.6 and 18.4% for the overall equations, respectively). The model identity test showed some differences among the CP total digestibilities obtained by different methodologies were observed. When ruminal and intestinal digestions were compared, no differences among both methodologies were observed. EE total digestibility was not affected by the treatments, with average value of 76.3%. EE total ruminal and intestinal digestibilities exhibited both increasing and decreasing linear behaviors, respectively, as a function of the ingestion levels, showing an average value of 76.3%. EE total ruminal and intestinal digestibilities showed both increasing and decreasing linear behaviors, respectively, as a function of the ingestion levels. Omasal digesta collection, through ruminal fistula, can be used to replace abomasum fistula, becoming the study of digestion locals a less invasive process. TDN content decreased as feed offer levels increased.

Consumos e digestibilidades totais e parciais de carboidratos totais, fibra em detergente neutro e carboidratos não-fibrosos em novilhos submetidos a três níveis de ingestão e duas metodologias de coleta de digestas abomasal e omasal

Seis novilhos ½ sangue Holandes-Zebu castrados, fistulados no rumen e no abomaso, foram distribuidos em dois quadrados latinos 3x3 (tres animais, tres niveis de oferta - 1,5; 2,0 e 2,5% PV e tres periodos) para determinar os consumos e as digestibilidades totais e parciais dos carboidratos totais (CHO), da fibra em detergente neutro (FDN) e dos carboidratos nao-fibrosos (CNF). As digestibilidades foram determinadas com oxido cromico. Os consumos de CHO, FDN, CNF e NDT (kg/dia) e de CHO, FDN e CNF (% do peso vivo - PV) aumentaram linearmente com os niveis de oferta. O teste de identidade de modelos, realizado para as equacoes de regressao para as digestibilidades total, ruminal e intestinais dos CHO, em funcao dos niveis de oferta, indicou nao existir diferencas entre as metodologias de coleta. As digestibilidades total, ruminal e intestinais dos CHO nao foram influenciadas pelos tratamentos. A digestibilidade total da FDN diminuiu linearmente com o aumento dos niveis de oferta, enquanto as digestoes ruminal e intestinais da FDN nao foram influenciadas pelos tratamentos. Nao foi observado efeito dos niveis de oferta para as digestibilidades totais dos CNF. Utilizando a metodologia de coleta de digesta no omaso, foi observado aumento linear da digestibilidade ruminal dos CNF. Quando foi usada a coleta no abomaso, nao houve efeito do aumento do consumo sobre a digestao ruminal dos CNF. A coleta de digesta abomasal pode ser substituida pela coleta de digesta omasal, via fistula ruminal. A coleta de digesta omasal e vantajosa, tornando o estudo de digestao parcial um processo menos invasivo.

Effects of varying ruminally undegradable protein supplementation on forage digestion, nitrogen metabolism, and urea kinetics in Nellore cattle fed low-quality tropical forage

Effects of supplemental RDP and RUP on nutrient digestion, N metabolism, urea kinetics, and muscle protein degradation were evaluated in Nellore heifers () consuming low-quality signal grass hay (5% CP and 80% NDF, DM basis). Five ruminally and abomasally cannulated Nellore heifers (248 ± 9 kg) were used in a 5 × 5 Latin square. Treatments were the control (no supplement) and RDP supplementation to meet 100% of the RDP requirement plus RUP provision to supply 0, 50, 100, or 150% of the RUP requirement. Supplemental RDP (casein plus NPN) was ruminally dosed twice daily, and RUP supply (casein) was continuously infused abomasally. Jugular infusion of [NN]-urea with measurement of enrichment in urine was used to evaluate urea kinetics. The ratio of urinary 3-methylhistidine to creatinine was used to estimate skeletal muscle protein degradation. Forage NDF intake (2.48 kg/d) was not affected ( ≥ 0.37) by supplementation, but supplementation did increase ruminal NDF digestion ( < 0.01). Total N intake (by design) and N retention increased ( < 0.001) with supplementation and also linearly increased with RUP provision. Urea entry rate and gastrointestinal entry rate of urea were increased by supplementation ( < 0.001). Supplementation with RUP linearly increased ( = 0.02) urea entry rate and tended ( = 0.07) to linearly increase gastrointestinal entry rate of urea. Urea use for anabolic purposes tended ( = 0.07) to be increased by supplementation, and RUP provision also tended ( = 0.08) to linearly increase the amount of urea used for anabolism. The fraction of recycled urea N incorporated into microbial N was greater ( < 0.001) for control (22%) than for supplemented (9%) heifers. Urinary 3-methylhistidine:creatinine of control heifers was more than double that of supplemented heifers ( < 0.001). Control heifers reabsorbed a greater ( < 0.001) fraction of urea from the renal tubule than did supplemented heifers. Overall, unsupplemented heifers had greater mobilization of AA from myofibrillar protein, which provided N for urea synthesis and subsequent recycling. Supplemental RUP, when RDP was supplied, not only increased N retention but also supported increased urea N recycling and increased ruminal microbial protein synthesis.

Níveis de uréia na ração de novilhos de quatro grupos genéticos: consumo e digestibilidades totais

The effects of diet adaptation protocol by steers and of feeding four dietary urea levels (0, 0.65, 1.3, and 1.95%, dry matter - DM basis) on intake and total apparent digestibility of DM, organic matter (OM), crude protein (CP), ether extract (EE), total carbohydrates (CHO), neutral detergent fiber (NDF), nonfiber carbohydrates (NFC) and total digestible nutrients intake (TDN) for Holstein, ½ Holstein-Guzera, ½ Holstein-Gir and Zebu steers were evaluated in this trial. The animals were assigned to four 4x4 latin squares (genetic groups): four animals, four experimental periods and four treatments (diets). The animals were fed diets (12% CP, with increasing urea levels) with 50% tifton-85 bermudagrass hay and concentrate. The first experimental period lasted 19 days, 13 days for adaptation and 6 days for feces collection. The possibility of reducing diet adaptation in the subsequent periods was investigated by evaluating daily DM intake in the adaptation period. The indigestible acid detergent fiber (FDAi) was used as marker of fecal dry matter flow. The adaptation to diets of the subsequent experimental periods was reduced by 10 days, because DM intake means, for each urea level, from 1st to 12th day of adaptation did not differ from the standard mean (13th day). The intake, expressed as kg/day, was higher for Holstein animals, followed by the crossbreds and Zebu. Total DM digestibility was affected nor by the genetic groups, neither by the dietary urea levels.

Balanço de compostos nitrogenados e estimativa das exigências de proteína de mantença de bovinos Nelore de três condições sexuais

The objective of this trial was to investigate the effects of increasing dietary crude protein levels on N balance and metabolizable protein requirements for maintenance in Nellore heifers, bulls and steers averaging 16 months of age and body weight of 254.8, 285.1, and 265.6 kg, respectively. Animals were blocked by sexual category (heifers, bulls and steers) and randomly assigned to treatments in three replicated 4 x 4 Latin squares. Diets contained the following CP levels: 7, 10, 13, and 15%. Estimation of fecal DM output and duodenal DM flow was done using the internal marker indigestible ADF. Total collection of urine was conducted from day 13 to day 14 on each period. Metabolic fecal nitrogen, urinary endogenous losses and total endogenous losses were all estimated using a regression approach. No significant effect of sexual category was observed for any of the studied variables, excepting for N intake that was greater on steers than heifers. N intake, urinary and fecal N excretions, and N balance increased linearly when the dietary CP level varied from 7 to 15%. Fecal metabolic N and urinary endogenous N averaged 6.69 gN/kg of DMI and 0.133 g N/kg0.75 across diets, respectively. The net protein requirement was estimated as 0.431 gN/kg0.75 or 2.69 g of protein/kg0.75. No effect of sexual category on metabolizable protein requirements for maintenance (approximately 4.0 g/kg0.75) was observed in this trial.