No abstract

A comparative slaughter trial was conducted with 36 F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg of BW, to assess the net requirements of protein and energy for growth and maintenance. Three cattle from each group (i.e., steers, bulls, and heifers) were slaughtered at the beginning of the trial to determine the initial body composition. The remaining calves were randomly assigned to 1 of 3 treatments: maintenance (diet containing 70% of DM as corn silage fed at 1.2% of BW daily) or concentrate at 0.75 or 1.5% of BW daily with corn silage available for ad libitum consumption. The diets were isonitrogenous (2% N, DM basis). The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict the maintenance requirements for NE and net protein (MRNE and MRNP, respectively) and the growth requirement for NE and net protein (GRNE and GRNP, respectively). After 84 d of growth, the cattle were slaughtered. The cleaned gastrointestinal tracts, organs, carcasses, heads, hides, tails, feet, blood, and tissues were weighed to measure empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. For each animal within a period, DMI was measured daily and samples of feces were collected to determine diet digestibility. There were no differences in MRNE (P = 0.06) among groups. The combined data indicated a MRNE of 71.2 kcal x kg(-0.75) of EBW x d(-1), with a partial efficiency of use of ME to NE(m) of 0.71. The partial efficiency of use of ME to NE for growth was 0.54 for bulls, 0.47 for steers, and 0.54 for heifers. The GRNE for steers and heifers were similar (P = 0.15) but were 18.7% greater (P = 0.03) for steers and heifers than for bulls. The MRNP did not differ among groups and averaged 2.53 g of CP x kg(-0.75) of EBW x d(-1). Likewise, GRNP was not different among groups. The percentage of retained energy deposited as protein (RE(p)) increased as the content of retained energy in the gain (RE(c), Mcal/kg of empty body gain) decreased. The RE(p) equation of the pooled data was 46.5 x e(-0.2463 x RE(c)). We conclude that the energy requirement of crossbred Bos indicus x Bos taurus for maintenance might be less than that of purebred Bos taurus and that RE(p) is nonlinearly, negatively correlated with RE(c). The GRNE was less for bulls than for steers and heifers. However, we found no differences in MRNE, MRNP, and GRNP for bulls, steers, and heifers of Nellore x Red Angus crossbreds.

Adoption of silvopasture is increasing, but proper design and management of pasture–tree associations is required to sustain pasture productivity. Our objective was to compare agronomic and physiological characteristics of Brachiaria brizantha (Hochst. Ex A.Rich.) Stapf. (palisade grass) cv. Marandu growing in monoculture, or in silvopasture with Eucalyptus urograndis, in the Brazilian Amazon biome. Trees were planted in triple rows (intra-row spacing 3 m, inter-row spacing 3.5 m), referred to as a grove, with three groves per 2-ha silvopasture experimental unit. Space between groves was 30 m, and tree density was 270 ha–1. From October 2015 to September 2016, all experimental units were stocked continuously with cattle by using a variable stocking rate to maintain a Marandu canopy height of 30 cm. In the silvopasture, sampling occurred at 4, 7.5 and 15 m into the non-treed area from the outer tree row in a grove. Photosynthetically active radiation (PAR) reaching the Marandu canopy averaged 21% less for silvopasture than for grass monoculture; however, forage accumulation was not different between systems, nor were Marandu stomatal conductance, water-use efficiency (WUE), transpiration rate, transpiration ratio and leaf temperature. In silvopasture, PAR and forage accumulation were 33% and 29% less, respectively, at the 4-m distance than the 15-m distance from the edge row of trees, associated with lower transpiration rate and transpiration rate and greater WUE. We conclude that Marandu palisade grass can tolerate PAR reduction in silvopasture up to ~20% without reduction in forage accumulation, supporting its potential use in agroforestry systems for cattle production in the Brazilian Amazon Biome.

Objetivou-se avaliar o efeito do nível de produção de leite sobre o consumo e a digestibilidade dos nutrientes (MS, MO, EE, PB, FDNcp e CNF corrigidos), o consumo de NDT, a produção de proteína microbiana e a excreção de compostos nitrogenados na urina. Foram avaliadas as concentrações de N uréico no soro (NUS) e no leite (NUL) de animais de diferentes níveis de produção de leite. Foram comparadas as metodologias de coletas de urina spot e total para quantificação do fluxo de N microbiano. Quinze vacas holandesas foram alocadas em delineamento inteiramente casualizado, com três tratamentos, de acordo com a produção de leite: 5,88 (baixa); 18,54 (média) e 32,6 kg de leite/dia (alta). A dieta foi constituída de silagem de milho fornecida à vontade e 1 kg de concentrado para cada 3 kg de leite produzido. Os consumos de todos os nutrientes, exceto FDNcp, foram maiores nos animais mais produtivos. As digestibilidades de MS e MO e o teor de NDT não diferiram entre os tratamentos, mas as digestibilidades da PB e da FDNcp foram influenciadas pelo nível de produção, sendo maior e menor, respectivamente, nos animais de alta produção. Os teores de NUS e NUL e a excreção de compostos nitrogenados na urina foram altamente correlacionados e superiores nos animais mais produtivos, indicando que a concentração ótima varia com o nível de produção de leite. A produção microbiana não diferiu entre as metodologias de coleta spot e total de urina, sendo inferior nos animais menos produtivos. Assim, a coleta de urina spot pode ser utilizada para estimar a excreção de compostos nitrogenados na urina e a produção de proteína microbiana no rúmen.

RESUMOAvaliaram-se a produção e o valor nutritivo do capim-coastcross (Cynodon dactylon) sob cinco doses de nitrogênio -0, 100, 200, 300 e 400kg/ha.ano -e duas idades de rebrotação -28 e 42 dias. Os tratamentos foram arranjados em esquema fatorial, em blocos ao acaso, com três repetições. A adubação com nitrogênio (N) foi parcelada em três aplicações, realizadas logo após os cortes. A densidade populacional de perfilhos apresentou padrão de resposta quadrático em resposta à aplicação de N. A produção de forragem do capimcoastcross variou de 8,0 a 17,2t/ha.ano para as doses de 0 a 400kg/ha.ano de N, apresentando resposta linear positiva com a adubação nitrogenada. Maiores valores de relação folha:colmo (RFC) foram obtidos em cortes mais tardios, na ausência de aplicação de N. Em geral, as doses crescentes de N diminuíram linearmente a RFC do capim-coastcross. A adubação nitrogenada aumentou linearmente os teores de proteína bruta (PB), observando-se maior eficiência de resposta na idade de 28 dias. Aumentos na digestibilidade in vitro da matéria seca em resposta à aplicação de doses crescentes de N somente ocorreram em plantas mais jovens, aos 28 dias de rebrotação. O teor de fibra em detergente neutro reduziu linearmente com a adubação nitrogenada. O efeito da adubação nitrogenada no valor nutritivo do capim-coastcross depende da idade de rebrotação dessa forrageira. Com a aplicação de maiores doses de N e sob condições favoráveis de crescimento, o pasto de capim-coastcross deve ser manejado com frequência de desfolhação de 28 dias.Palavras-chave: Cynodon dactylon, digestibilidade, fibra em detergente neutro, número de perfilho, proteína bruta ABSTRACTThe production and nutritive value of the bermudagrass cv. coastcross under five different nitrogen doses (0, 100, 200, 300 and 400kg/ha.year)

RESUMO -Objetivou-se avaliar a influência do peso vivo de novilhas sobre o consumo e a digestibilidade da MS, MO, EE, PB, fibra em detergente neutro corrigida para cinzas e proteína (FDNcp) e carboidratos não-fibrosos corrigidos (CNFcp), os consumos de NDT e de proteína degradada no rúmen (PDR), a produção de proteína microbiana e a excreção de compostos nitrogenados na urina e comparar as metodologias de coleta spot e de coleta total de urina. Foram utilizadas 22 novilhas com cinco diferentes pesos (523, 453, 315, 235 e 118 kg), distribuídas em delineamento inteiramente casualizado, com cinco tratamentos (P523, P453, P315, P235 e P118). A alimentação foi constituída de silagem de milho e concentrado, fornecido na proporção de 1,5 kg/dia (tratamentos P523, P453, P315 e P235) ou 2 kg/dia (tratamento P118). Os consumos dos nutrientes em kg/dia e em %PV aumentaram e diminuíram linearmente, respectivamente, com o aumento do peso dos animais. As digestibilidades da MS, MO e o teor de NDT não diferiram entre os tratamentos, enquanto as de PB e FDNcp foram distintas entre os tratamentos, sendo maior e menor, respectivamente, no tratamento P118. A excreção de uréia na urina (em mg/kgPV) foi maior no tratamento P118, variando com o peso vivo e com o consumo de PB e PDR. A produção microbiana, estimada pela excreção urinária de derivados de purinas, não diferiu entre as metodologias de coleta spot e coleta total de urina, sendo menor no tratamento P118. A coleta de urina spot pode ser utilizada para estimativa da excreção de compostos nitrogenados na urina, independentemente do peso vivo. A quantidade de nutrientes ingeridos diariamente aumenta com o peso vivo, entretanto, o consumo desses nutrientes, expresso em %PV, diminui à medida que o peso vivo aumenta.Palavras-chave: FDNcp, Holandês, N-uréico no soro, proteína microbiana, amostra spot Intake, digestibility and urinary excretion of urea and purine derivatives in heifers with different body weights ABSTRACT -The objective of this trial was to evaluate the effect of body weight (BW) of heifers on intake, apparent digestibility of nutrients, microbial protein synthesis, ruminal metabolism, and urinary excretion of nitrogenous compounds. The spot urine sampling and the total collection of urine techniques were used to estimate microbial N flow. Twenty-two heifers with different body weights (523, 453, 315, 235 and 118 kg) were used in a completely randomized design and assigned to the following treatments: BW523, BW453, BW315, BW235 or BW118. Animals were fed corn silage ad libitum plus 1.5 kg/day of concentrate on treatments BW523, BW453, BW315 and BW235 and 2 kg/day on BW118 treatment. Intake of nutrients increased linearly from treatment BW118 to BW523. However, the opposite was observed when DMI was expressed as percentage of BW. Digestibilities of DM and OM and dietary TDN did not differ among treatments but digestibilities of CP and NDF corrected for ash and protein (NDF ap ) were greatest and lowest on BW118 treatment, respectively. The urinary excretion of urea...

The intake and total apparent and partial digestibility of nutrients, ruminal pH and ammonia concentrations and efficiency of microbial synthesis were evaluated in beef cattle fed diets containing sorghum silage and concentrate in the following ratios: 800:200, 650:350, 500:500 and 350:650 g/kg, in a total dry matter basis. Four crossbred Holstein x Zebu rumen and abomasum fistulated steers, 224 ± 23 kg-average initial live weight, were assigned to a 4 × 4 Latin square design. Chromic oxide was used as marker to estimate fecal and abomasal dry matter flows, and microbial efficiency was determined from purine basis. The intakes and total apparent digestibilities of DM, OM, CP and NFC and TDN intakes increased linearly (P b 0.01) with the increase of concentrate in the diet. NDF intake and total apparent digestibility decreased linearly (P b 0.05). The apparent ruminal and intestinal digestibilities of DM, OM, CP, NDF and NFC were not influenced (P N 0.05) by increasing the concentrate in the diet, and the mean values were 619 and 381 (g/kg); 656 and 349; 391 and 498; 902 and 79 and 600 and 399 (g/kg DM), respectively. There was a quadratic effect of collection time (P b 0.01) on the concentration of ruminal NH 3 -N and pH, considering maximum and minimum values of 14.89 mg/dL and 6.16 at 2.39 and 4.28 h after feeding, respectively. The efficiency of microbial synthesis, expressed in different ways was not influenced (P N 0.05) by treatments, with 11.39 g CPmic/100 gTDN on average. Although increasing concentrate levels in the diets resulted in higher intakes of almost all nutrients, this did not result in alterations in the ruminal variables evaluated. Livestock Science 107 (2007) 53 -61 www.elsevier.com/locate/livsciAbbreviations: DM, dry matter; OM, organic matter; CP, crude protein; NFC, non-fibrous carbohydrates; TDN, total digestible nutrients; NDF, neutral detergent fiber assayed with a heat stable amylase and expressed inclusive of residual ash; gCPmic/100 gTDN, grams of crude protein microbial per 100 g of total digestible nutrients; NH 3 -N, ammonia nitrogenous; NDIN, neutral detergent insoluble nitrogen; ADIN, acid detergent insoluble nitrogen; CHODR, total carbohydrates degraded in the rumen; TN, total nitrogen compounds; MicN, microbial nitrogen.

No abstract