Níveis de concentrado na dieta de bovinos Nelore de três condições sexuais: consumo, digestibilidades total e parcial, produção microbiana e parâmetros ruminais

Doze bovinos Nelore de três condições sexuais (CS) – quatro fêmeas, quatro machos castrados e quatro machos não-castrados – com idade aproximada de 15 meses e peso corporal médio de 235, 249 e 239 kg, respectivamente, foram distribuídos em delineamento inteiramente casualizado, em esquema fatorial 2 × 3, composto de dois níveis de concentrado (25 ou 50%) e três CS, objetivando-se estudar o consumo, as digestibilidades total e parcial dos nutrientes, a produção microbiana e os parâmetros ruminais. As coletas de líquido ruminal, para determinação do pH e da concentração de amônia, foram realizadas imediatamente antes do fornecimento da dieta e 2, 4 e 6 horas após a alimentação. Não houve interação significativa de níveis de concentrado e CS para nenhum dos consumos observados. Os consumos de MS, MO, EE, PB, CNF e NDT, em kg/dia, e de MS em % do PC ou em g/kg0,75, não foram influenciados pelos níveis de concentrado ou pela condição sexual. Não houve interação de níveis de concentrados × CS para as digestibilidades totais e parciais dos nutrientes, com exceção do EE. O aumento do nível de concentrado reduziu a digestibilidade da FDN. Os teores médios de N nas bactérias variaram de 7,39 a 6,91%. O fluxo de nutrientes e a eficiência microbiana expressa de diferentes formas, com exceção de gNmic/kgMODR, não foram influenciados pelos níveis de concentrados ou pela condição sexual. A concentração de NH3 máxima de 14,55 mg/dL foi estimada 1,83 hora após a alimentação. O aumento dos níveis de concentrado na dieta não resultou em respostas positivas para os consumos, as digestibilidades parciais e totais da maioria dos nutrientes e a produção microbiana.Twelve Nellore of three sexual categories (four heifers, four bulls and four steers) averaging 15 months of age and body weight of 235, 249, and 239 kg, respectively, were assigned to a completely randomized design with a 2 × 3 factorial arrangement (two levels of concentrate – 25 or 50% and three sexual categories) to evaluate intake, partial and total digestibility of nutrients, microbial protein synthesis and ruminal metabolism. The collection of ruminal fluid was done before and at 2, 4, and 6 hours post-feeding to determine pH and ammonia concentration. With the exception of EE, no other significant effect of concentrate levels and sexual categories was observed on intake and partial or total tract digestibility of nutrients. The intakes of DM, OM, EE, CP, NFC, and TDN (kg/day) and DM (% BW or g/kg0.75) were affected neither by the concentrate levels nor by sexual category. Increasing dietary concentrate levels decreased NDF digestibility. Average bacterial N contents ranged from 6.91 to 7.39. No significant effect of concentrate levels and sexual category was observed on duodenal flow of nutrients and microbial efficiency excepted when expressed as gNmic/kgOMDR. Maximum ruminal NH3 concentration (14.55 mg/dL) was estimated at 1.83 hours after-feeding. It was concluded that increasing dietary concentrate levels did not affect intake, partial and total tract digestibility of most nutrients and microbial protein synthesis

Period of urine and feces collection for evaluation of creatinine excretion, microbial production and nutrients apparent digestibility in Nelore bovines

O presente trabalho foi conduzido com o objetivo de avaliar o efeito da duração do período de coletas de urina e de fezes sobre a excreção urinária de creatinina, de uréia e de derivados de purinas, as purinas absorvidas, a produção de compostos nitrogenados microbianos (Nmic), as digestibilidades aparentes da matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN) e de carboidratos não-fibrosos (CNF) e os teores de nutrientes digestíveis totais (NDT) em Nelores de quatro categorias (novilhas, machos castrados, machos inteiros e vacas em lactação) alimentados com 25 ou 50% de concentrado na base da matéria seca total das dietas. Avaliou-se ainda as concentrações de N-uréia plasmática (NUP) e comparou-se também a produção de Nmic obtida em amostras spot de urina com aquela da coleta total. O experimento foi conduzido em dois períodos experimentais com duração de 28 dias cada, sendo as coletas totais de urina e de fezes efetuadas do 22o ao 28o dias de cada período experimental. As fezes foram retiradas do piso imediatamente após excreção e a urina obtida com sondas em fêmeas e funis nos machos. Utilizou-se dieta com 25% de concentrado no primeiro período e com 50% no segundo experimental. Todas as dietas continham aproximadamente 12% de PB. Utilizaram-se 16 animais da raça Nelore, mantidos em confinamento, alojados em baias individuais, distribuídos em delineamento inteiramente casualizado, em esquema de parcelas subdivididas, tendo nas parcelas os tratamentos em esquema fatorial 2 x 4, sendo dois níveis de concentrado (25 ou 50%) e quatro categorias de Nelores e nas subparcelas os seis dias de coletas de urina. Já para a avaliação das digestibilidades, as comparações foram feitas através de análises de regressão, que foram efetuadas considerando quatro dias de coletas de fezes em cada período, sendo as equações obtidas sempre comparando as digestibilidades dos nutrientes referentes a um dia (24 h), 2 dias (48 h) ou 3 dias (72 h) em relação aos 4 dias (96 h de coleta). Foram feitas também comparações através de equações, utilizando os seis dias de coleta total de fezes, referentes ao segundo período experimental (50% de concentrado), sendo nesse caso utilizado como referência os seis dias de coleta total (144 h de coleta total de fezes). Não houve interação (P>0,05) entre níveis de concentrado, categorias de Nelore e dias de coleta para o volume urinário, a excreção de creatinina e a produção de Nmic. O volume urinário não foi influenciado (P>0,05) pelos níveis de concentrado e dias de coleta, contudo foi significativamente maior (P0,05) pelos tratamentos e dias de coletas, observando-se média de 27,1 mg/kg0,75. As purinas absorvidas e a produção de compostos nitrogenados microbianos também não foram influenciadas (P>0,05) pelos tratamentos e dias de coleta. A produção de Nmic estimada através de amostra spot de urina não diferiu (P>0,05) daquela obtida pela coleta total, nem entre os níveis de concentrados e categorias de Nelore. Não houve diferença significativa (P>0,05) para nenhuma das digestibilidades avaliadas e também para os teores de NDT entre os dias de coleta total de fezes, contudo, observou-se que os coeficientes de variação diminuíram à medida que se aumentou o número de dias de coleta. Concluiu-se considerando as respostas obtidas para excreção de creatinina e a produção de proteína microbiana, que um período de coletas de urina de 24 horas é suficiente para trabalhos com Nelores, independente de serem novilhas, machos castrados ou inteiros e vacas em lactação e que a coleta de amostra spot de urina também pode ser utilizada para estimar a produção de proteína microbiana em novilhas, machos inteiros ou castrados e vacas lactantes da raça Nelore. Concluiu-se também que para avaliar a digestibilidade aparente dos nutrientes, coletas totais de fezes feitas durante um a seis dias são exatas. Contudo, a precisão é melhorada com o aumento dos dias de coleta.This trial was carried out to evaluate the effect of periods of urine and feces collection on urinary excretion of creatinine, urea and purine derivatives, absorbed purine, microbial nitrogen compounds production (Nmic), apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and nonfiber carbohydrates (CNF) and total digestible nutrients contents (TDN) of Nelore bovines four categories (heifers, steers, bulls and lactating cows) fed 25 or 50% concentrate, total dry matter basis. The plasma N-urea concentrations (NUP) were evaluated and the Nmic obtained in urine spot samples was compared with that of total collection. The experiment was divided in two experimental periods of 28 days each, when the feces and urine total collection were performed at 22nd and 28th day of each experimental period. Feces were colleted directly from the floor after excretion and the urine was obtained using catheters in females and funnels in males. A 25% concentrate-based diet was fed to the animals in the first period and a 50% concentrate-based diet in the second one, all of them with 12% CP. Sixteen Nelore bovines, under feedlot, housed in individual pens, were assigned to a completely randomized design, in a split plot scheme, where the treatments were represented by the plots (2 x 4 factorial scheme), with two levels of concentrate (25 or 50%) and four Nelore categories, and the split plots were represented by the urine collections. The comparisons for digestibility evaluation were made by regression analyses, that were performed considering 4 days of feces collection of each period. The equations were obtained by comparing the nutrients digestibility referent to one (24h), two (48h) or three days (72h) compared to four days (96h of collection). Comparison with six days of total feces collection, using equations (second experimental period [50% concentrate]) was considered reference (144h total feces collection). No interaction (P>0.05) among concentrate levels, Nelore categories and collection days for the urinary volume, the creatinine excretion and Nmic production was observed. Urinary volume was not affected (P>0.05) by the concentrate levels and collection days, but significant effect (P0.05) by treatments and collection days, considering average of 27.1 mg/kg0.75. Absorbed purines and microbial nitrogen compounds production were also not influenced (P>005) by the treatments and collection days. Nmic production estimated by the urinary spot collection differed (P>0.05) neither from that obtained by total collection total, nor among the concentrate levels and Nelore categories. No significant difference (P>0.05) was observed for any evaluated digestibility and TDN contents during the total feces collection period. The results suggest that the coefficients of variation decresed as the period of collection days increased. Considering the results of creatinine excretion and of microbial protein production, it was concluded that a 24-h period is enough for researchs with Nelore, independently of the category, and that urinary spot sample collection can be used to estimate microbial protein production in all Nelore bovines (heifers, steers, bulls and lactating cows). Total feces collection from 1 to 6 days to evaluate nutrients apparent digestibility are precise, but better results could be obtained by increasing the collection period

Endogenous fraction and urinary recovery of purine derivatives obtained through different methods in Nelore cattle

Foram realizados dois experimentos utilizando oito novilhas Nelore. No primeiro, objetivou-se avaliar a fração endógena para a excreção urinária de derivados de purinas (DP) em bovinos Nelore alimentados com dieta única em diferentes níveis de oferta de matéria seca (MS), estabelecer a proporção de purinas no abomaso recuperadas na urina como derivados de purinas e verificar o efeito do nível de consumo sobre a produção microbiana (Nmic). As novilhas, com pesos médios de 258 ± 20 kg, fistuladas no rúmen e abomaso, sendo quatro destas fistuladas adicionalmente no íleo, foram alojadas em baias individuais. O experimento foi delineado em dois quadrados latinos 4 x 4, balanceados para efeito residual. Os tratamentos foram constituídos de quatro níveis de oferta da MS 1,2, 1,6, 2,0 e 2,4 % do peso vivo (PV). O experimento foi conduzido em quatro períodos de 14 dias, sendo os primeiros sete dias para adaptação. As perdas endógenas e a recuperação de bases purinas como derivados de purinas foram estimadas por regressão entre a excreção diária dos derivados de purinas na urina (Y) e as bases purinas no abomaso (X), expressas em mmol/kg0,75, representadas, respectivamente, pela intercepta e pelo coeficiente da regressão. As perdas endógenas também foram avaliadas pela regressão entre a excreção de DP, em mmol/kg0,75, e o consumo de MS, em g/kg0,75. Apesar de ter sido obtida uma faixa de variação de consumo de MS de 1,16 até 1,84 % do peso vivo (PV), não foi atingido o máximo planejado de 2,4 % PV. Os coeficientes de digestibilidade aparente total da MS e da MO variaram linearmente (P 0,05) pelos níveis de oferta de MS da dieta, obtendo-se valor médio de 75,63 %. A digestibilidade verdadeira de 92,78 % (P 0.05) with levels of MS offer in diet, with reduction of 2.17 % and 2.21 % to each 1% of live weight respectively. Apparent digestibility coefficient of RNA at small intestine (ID) was not affected (P > 0.05) by the levels of MS offered in diet, obtaining an average value of 75.63%. True digestibility of 92.78% (P > 0.0001), was obtained by the regression between the amount of absorbed RNA (Ŷ) as a function of RNA flux into abomasum (X), expressed in mmol/kg0.75. The mean relation of N-RNA:N- total in isolated ruminal bacteria was 0.1369. Daily flux of RNA (RNA Abo) and microbial production (Nmic Abo) into abomasum as a function of the level of MS offer in diet presented a quadratic behavior, and estimated maximum values of 1.50 mmol/kg0.75 and 55.20 g Nmic respectively to the levels of MS offer 2.43 and 2.45% of PV. Daily urinary excretion of DP, in mmol/kg0.75, increased linearly (P > 0.05) with the level of MS offer in diet. And when it was related to the observed intake of digestible MO, (kg/day), the excretion (P > 0.0001) of 34.415 mmol of DP to each kg of digestible MO ingested was verified. When the excretion of purine derivatives, expressed in mmol/day, was related to the intake of NDT, kg/day, it was observed that there were excretion (P > 0.0001) of 32.15 mmol to each kg of NDT consumed. Considering the intake of MS expressed in g/kg0.75 and the excretion of DP in mmol/kg0.75, a regression was obtained (P > 0.0001): Ŷ= 0.0196x + 0.2421, where 0.2421 mmol/kg0.75 or 0.24 mmol/kg0.75, represents the endogenous excretion of DP. Daily excretion of purine derivatives, mmol/kg0.75, as a function of RNA flux into abomasum, mmol/kg0.75, was adjusted to regression (P > 0.0001) Ŷ = 0.8601x + 0.4603 (R2 = 0.661), where 0,86 represents the recovery of purines as derivatives in urine and the value of 0.4603 mmol/kg0.75 represents the endogenous fraction. Microbial production estimated by purine derivatives in urine, expressed in g N/day, as a function of the levels of MS offer in diet, presented linear regression (P > 0.05), estimating increases of 22.80 g Nmic per 1 % of the MS offered. It was concluded that: different methods resulted in estimates of 0.46 mmol/kg0.75 and 0,24 mmol/kg0.75 to endogenous excretion of purine derivatives in Nelore cattle; the recovery of absorbed purines as derivatives in urine was of 0,86 and the real digestibility of RNA in ID, 0.93, is greater than the value assumed in literature for microbial production calculation. In the second experiment, the objective was to estimate the endogenous contribution in urinary excretion of purine derivatives in Nelore cattle by means of different levels of RNA infusion into abomasum. It was used eight heifers of Nelore breed, with average weight of 296 ± 15 kg, fistulated at rumen and abomasum, accomodated in individual stalls. The experimental design was 2 balanced latin squares 4 x 4, with four animals, four treatments and four experimental periods. Treatments constituted of infusions of RNA into abomasum at dosages of 0, 33, 66 and 100 mmol/day. Every animal received a diet balanced with levels close of their maintenance levels during seven days aiming the adaptation, before beginning of infusions. Following the adaptation to the diet, four experimental periods of nine days each ensued according the scheme: from 1st to 5th day samples of digesta from the abomasum were collected; from 1st to 4th day total collection of urine and feces; from 5th to 9th day infusion of RNA into abomasum; from 6th to 9th day total collection of urine; at the 9th day of the fourth period samples of digesta from the rumen were collected. Therefore, before executing the infusion in each animal, fluxes of microbial protein into abomasum were obtained using purine bases and urinary excretion of purine derivatives. Hence, the flux of purine bases into abomasum was obtained summing up the values of each animal before the infusion with respective infusion quantity. Flux of N total into abomasum, N-RNA and RNA before infusions were, in average, 51.15 g/day; 5.11 and 35.23 g/day, respectively. Daily excretion of purine derivatives (Ŷ) mmol/kg0.75, as a function of RNA flux into abomasum (X), mmol/kg0.75, was adjusted to the regression (P > 0.0001): Ŷ = 0.30127 + 0.74143 X, indicating that 0.30 mmol/kg0.75 correspond to endogenous losses and 0,74 is the purine recovery absorbed in the abomasum as purine derivatives in urine

Levels of mineral mixture and urea in supplementation of crossbred heifers, with Gyr predominance, reared at pasture during the dry season

It was evaluated several levels of mineral mixture and urea for crossbred heifers, with Gyr predominance, in the dry season period in Zona da Mata region in Minas Gerais. The experiment was carried out in a Brachiaria decumbens pasture area, divided in five paddocks of 3.5 hectares. It was used 35 heifers distributed in a 2 õ 2 + 1 factorial scheme, composed of two levels of urea (10 and 25%), two levels of mineral salt (10 and 25%) and a control diet (only mineral salt), totaling five diets, each one evaluated with seven replicates. The supplements were based on ground corn, urea, ammonia sulfate and mineral mixture with 32 to 72% crude protein, and they composed the following diets: MM ( mineral mix), 10:10 (10% mineral mix, 10% urea and 80% corn); 10:25 (10% mineral mix, 25% urea and 65% corn); 25:10 (25% mineral mix, 10% urea and 65% corn), and 25:25 (25% mineral mix, 25% urea and 50% corn). Urea and mineral salt are effective in controlling supplement intake by bovines growing on pastures during dry season because the higher their levels, the lower the intake of supplements. Diets with 25% urea and 10% mineral salt provided higher daily weight gain and higher weight gain:supplemment intake ratio

Variações diárias nas excreções de creatinina e derivados de purinas em novilhos

Objetivou-se estimar as variações nas excreções diárias de creatinina, uréia e derivados de purinas (DP) na urina utilizando coletas durante seis dias consecutivos e avaliar as concentrações de nitrogênio uréico no plasma (NUP) em novilhos. Utilizaram-se quatro animais, machos castrados, de grau de sangue predominantemente Holandês, peso médio de 445 kg, distribuídos em quadrado latino 4 x 4, com os tratamentos definidos em esquema fatorial 2 x 2 (dois níveis de uréia em substituição ao farelo de soja: 0 e 100%; e dois níveis de oferta de concentrado: 0,75 e 1,25% do PV) e a comparação entre dias de avaliação, em esquema de parcelas subdivididas. O volumoso, constituído de silagem de capim-elefante (80%) e silagem de sorgo (20%), foi fornecido à vontade. A síntese de compostos nitrogenados microbianos, estimada a partir da excreção de DP, foi maior quando houve maior oferta de concentrado e menor quando a proteína do farelo de soja foi substituída pela uréia. Não houve efeito da interação níveis de concentrado ´ níveis de uréia nem efeito de níveis de uréia sobre a concentração de NUP e a excreção de N-uréico na urina. As excreções urinárias de uréia, alantoína, ácido úrico e a quantidade estimada de proteína microbiana não foram afetadas pelos dias de coleta de urina. Não houve diferença na excreção de creatinina entre os dias de coleta, sendo obtido valor médio de 25,47 mg/kgPV, 117,92 mg/kg0,75 ou 1,04 mmol/kg0,75. A ausência de efeito de número de dias sobre a excreção de creatinina tem grande aplicação prática. Na estimativa da excreção de creatinina e de derivados de purinas, recomendam-se coletas de urina com duração de 24 horas.The objective of this trial was to investigate the daily variation in the urinary excretions of creatinine, urea and purine derivatives (PD) as well as the plasma concentration of urea-N (PUN) in steers. Four castrated Holstein steers averaging 445 kg of body weight (BW) in the beginning of the trial were used in a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Animals were fed two levels of urea (0 and 100%) and two levels of concentrate (0.75 and 1.25% of BW). Comparisons between collection days were done by a split-plot design. The forage portion of the diet, which was composed by silages of elephant grass (80%) and sorghum (20%) was fed ad libitum. Microbial protein synthesis, estimated by urinary excretion of PD, was increased by feeding the high-concentrate diet while the opposite was observed when urea replaced soybean meal in the diet (high-urea diet). No significant interaction between concentrate versus urea levels was found for NUP and urinary excretion of urea-N. Different levels of dietary urea also had not effect on these same variables. Urinary excretions of urea, allantoin, and uric acid and microbial protein synthesis were not affected by the number of urinary collection days. The same was observed for creatinine excretion, which averaged 25.47 mg/kg BW, 117.92 mg/kg0.75 or 1.04 mmol/ kg0.75. It can be concluded that no more than 24 h (one sampling day) of urine collection was required to accurate determine excretion of nitrogenous compounds, which has important practical applications due to labor and costs reductions

Fatty acid, physicochemical composition and sensory attributes of meat from lambs fed diets containing licuri cake.

The aim of this study was to determine the effect of feeding licuri cake to lambs on the sensory characteristics, physicochemical characteristics and fatty acid (FA) profile of meat from lambs. Forty-four crossbred Santa Ines lambs (21.2 ± 2.70 kg body weight; 6 months old) were housed in individual pens and fed 4 experimental diets, containing 0, 8, 16 or 24% licuri cake (DM basis). The averages concentrations of ash (11.4), pH (5.82), lightness (38.1), cooking loss (26.8) or shear-force resistance (2.48) of lamb meat were not affected by the licuri cake diets. However, there was a linear decrease (P 0.05) the concentrations of SFA C10:0, C15:0, C16:0, C18:0, C14:1, MUFA C18:1 trans, PUFA C18:2 cis, CLA, total sum of ΣSFA and ΣPUFA, desirable fatty acids (DFA), hypocholesterolemic:hypercholesterolemic index, and elongase and Δ9-desaturase C18 enzymes. Licuri cake in the lamb diet improved (P < 0.05) meat aroma, flavor and overall acceptance by consumers. Licuri cake inclusion in the diet of lambs improves sensory attributes of meat and the meat fatty acid profile becomes nutritionally healthier for the human diet because do not affect major FA of meat; however, the growth performance of finishing lambs is reduced